This document summarizes research on using pulsed electric fields (PEF) to extract and modify starch properties. PEF involves applying short electric pulses that can improve starch extraction yields and alter starch characteristics like crystallinity, gelatinization temperatures, and viscosity. PEF can decrease starch digestibility based on in-vitro human digestion tests. The document reviews how PEF works, its effects on starch, and potential benefits like providing a physical modification method that is safer and more environmentally friendly than chemical methods.
Pulse electric field processing technologyMusiigeDenis
This document provides information about pulsed electric field (PEF) technology, including:
1. PEF uses short electric pulses to preserve foods while maintaining fresh quality and nutrients. It kills microbes through electroporation without significantly heating the food.
2. The principles of PEF involve applying high-voltage pulses between electrodes to create an electric field that makes microbe cell membranes permeable, causing death. Factors like pulse strength and time affect treatment effectiveness.
3. Studies show PEF effectively kills bacteria, yeasts and molds in orange juice with reductions of 2-6 log, extending its shelf life while retaining quality. It is a promising non-thermal method for food preservation.
Hybrid wind solar energy system : a new rectifier stage topologyPradeep Avanigadda
This document describes a project presenting a new rectifier stage configuration for a hybrid wind/solar energy system. The proposed design fuses a Cuk converter and SEPIC converter, allowing the two intermittent energy sources to power loads separately or simultaneously. This configuration eliminates the need for input filters, reducing harmonics that decrease generator lifespan and increase power losses. Maximum power point tracking can also be implemented for each source to extract optimal power. The objectives are to improve efficiency, reduce harmonics, and enable energy savings compared to existing hybrid energy system rectifier designs.
Dynamic Simulation of a Hybrid Solar and Ocean Thermal Energy Conversion SystemIJRES Journal
Ocean thermal energy conversion (OTEC) is à system in which electricity is produced using small temperature difference of warm surface water and deep cold water in oceans. This paper analyzes the dynamic stability and performance simulation results of a solar and ocean thermal energy conversion (SOTEC) system connected to a power grid through undersea cables. In SOTEC, the temperature of warm sea water was boosted by using a typical low-cost solar thermal collector. The complete system model is established from the dynamics of each subsystem and their interconnections. Specifically, we examine stability and performance of the power system against such disturbance conditions as slow variations of solar radiation and severe three-phase short-circuit fault at the power grid. Simulation results indicate that the design of a power system stabilizer can improve the damping of power system under various disturbance conditions.
Standalone photovoltaic array fed induction motor driven water pumping system IJECEIAES
Due to the absence of energy transmission lines connected to the water pumping sites in remote areas, problems related to the electrical power outages and the environmental degradation caused by fossil fuel. For this one of the most conceived solutions is the photovoltaic water pumping technology which has the advantage of being sustainable and respectful of the environment to supply water to rural areas. To ensure the need of water, especially for domestic use and small communities, in this article, the photovoltaic energy system for autonomous water pumping using the induction motor was presented, particularly adapted to the isolated regions. Pumping system consists of four photovoltaic (PV) panels, boost converter, inverter, induction motor, centrifugal pump and a storage tank. In this study, the output power of a PV solar cell is fully used by proposing the P&O algorithm, where it is used to follow a maximum power point tracking (MPPT) technique. The recommended system is designed, modeled and simulated on the MATLAB / Simulink platform. The efficiency of the proposed algorithm is observed with variable solar sunshine.
Role of power electronics in renewable and non renewable sourcesRayudu Mahesh
The document discusses the role of power electronics in renewable and non-renewable energy sources. It describes several renewable energy systems that use power electronics including wind turbines, photovoltaic solar panels, and wave energy converters. It also discusses some non-renewable systems like internal combustion engines, microturbines, and fuel cells. Power electronics provide flexibility to integrate energy storage, maximize output of renewable sources, and improve the overall efficiency of energy generation and delivery to the electric grid.
a project report on MPPT algorithm for PV panelgauravchitransh
The document discusses renewable energy sources such as solar power. It notes that solar power has the potential to supplement power in cities and rural areas by harnessing the sun's energy through solar collectors. The document then discusses different renewable energy sources in detail, including wind power, hydropower, biomass, geothermal, and solar power. It also reviews literature on increasing the efficiency of solar panels through maximum power point tracking algorithms and circuit modeling of photovoltaic modules.
Eco-Friendly Wastewater Treatment Solution Using Self-Powered Microbial Fuel ...Editor IJMTER
Efficient monitoring and control of Waste Water Treatment Plant (WWTP) has turned
into an important public issue as the cost of electricity continues to grow and the quality requirement
of processed water tightens. A Microbial Fuel Cell (MFC) is a bio-electrochemical system that drives
a current by mimicking bacterial interactions found in nature. Self-powered Wireless Sensor
Networks (WSNs) are more suitable for this application to monitor the status of the waste water. A
novel Wireless Sensor Network (WSN) is proposed in this paper which integrates Microbial Fuel
Cells (MFCs), Field Programmable Analog Array (FPAAs) to design a self-powered, highly flexible
and adaptive system. The profusion of bacteria and chemical ingredients in waste water processing
tanks provides materials for MFCs to convert chemical energy into electrical energy. In wastewater
treatment, water is aerated so bacteria in the liquid break down organic material in a closed series of
containers known as a bioreactor. The simulation of the system is done and the results of which can
also be hardware implemented.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Pulse electric field processing technologyMusiigeDenis
This document provides information about pulsed electric field (PEF) technology, including:
1. PEF uses short electric pulses to preserve foods while maintaining fresh quality and nutrients. It kills microbes through electroporation without significantly heating the food.
2. The principles of PEF involve applying high-voltage pulses between electrodes to create an electric field that makes microbe cell membranes permeable, causing death. Factors like pulse strength and time affect treatment effectiveness.
3. Studies show PEF effectively kills bacteria, yeasts and molds in orange juice with reductions of 2-6 log, extending its shelf life while retaining quality. It is a promising non-thermal method for food preservation.
Hybrid wind solar energy system : a new rectifier stage topologyPradeep Avanigadda
This document describes a project presenting a new rectifier stage configuration for a hybrid wind/solar energy system. The proposed design fuses a Cuk converter and SEPIC converter, allowing the two intermittent energy sources to power loads separately or simultaneously. This configuration eliminates the need for input filters, reducing harmonics that decrease generator lifespan and increase power losses. Maximum power point tracking can also be implemented for each source to extract optimal power. The objectives are to improve efficiency, reduce harmonics, and enable energy savings compared to existing hybrid energy system rectifier designs.
Dynamic Simulation of a Hybrid Solar and Ocean Thermal Energy Conversion SystemIJRES Journal
Ocean thermal energy conversion (OTEC) is à system in which electricity is produced using small temperature difference of warm surface water and deep cold water in oceans. This paper analyzes the dynamic stability and performance simulation results of a solar and ocean thermal energy conversion (SOTEC) system connected to a power grid through undersea cables. In SOTEC, the temperature of warm sea water was boosted by using a typical low-cost solar thermal collector. The complete system model is established from the dynamics of each subsystem and their interconnections. Specifically, we examine stability and performance of the power system against such disturbance conditions as slow variations of solar radiation and severe three-phase short-circuit fault at the power grid. Simulation results indicate that the design of a power system stabilizer can improve the damping of power system under various disturbance conditions.
Standalone photovoltaic array fed induction motor driven water pumping system IJECEIAES
Due to the absence of energy transmission lines connected to the water pumping sites in remote areas, problems related to the electrical power outages and the environmental degradation caused by fossil fuel. For this one of the most conceived solutions is the photovoltaic water pumping technology which has the advantage of being sustainable and respectful of the environment to supply water to rural areas. To ensure the need of water, especially for domestic use and small communities, in this article, the photovoltaic energy system for autonomous water pumping using the induction motor was presented, particularly adapted to the isolated regions. Pumping system consists of four photovoltaic (PV) panels, boost converter, inverter, induction motor, centrifugal pump and a storage tank. In this study, the output power of a PV solar cell is fully used by proposing the P&O algorithm, where it is used to follow a maximum power point tracking (MPPT) technique. The recommended system is designed, modeled and simulated on the MATLAB / Simulink platform. The efficiency of the proposed algorithm is observed with variable solar sunshine.
Role of power electronics in renewable and non renewable sourcesRayudu Mahesh
The document discusses the role of power electronics in renewable and non-renewable energy sources. It describes several renewable energy systems that use power electronics including wind turbines, photovoltaic solar panels, and wave energy converters. It also discusses some non-renewable systems like internal combustion engines, microturbines, and fuel cells. Power electronics provide flexibility to integrate energy storage, maximize output of renewable sources, and improve the overall efficiency of energy generation and delivery to the electric grid.
a project report on MPPT algorithm for PV panelgauravchitransh
The document discusses renewable energy sources such as solar power. It notes that solar power has the potential to supplement power in cities and rural areas by harnessing the sun's energy through solar collectors. The document then discusses different renewable energy sources in detail, including wind power, hydropower, biomass, geothermal, and solar power. It also reviews literature on increasing the efficiency of solar panels through maximum power point tracking algorithms and circuit modeling of photovoltaic modules.
Eco-Friendly Wastewater Treatment Solution Using Self-Powered Microbial Fuel ...Editor IJMTER
Efficient monitoring and control of Waste Water Treatment Plant (WWTP) has turned
into an important public issue as the cost of electricity continues to grow and the quality requirement
of processed water tightens. A Microbial Fuel Cell (MFC) is a bio-electrochemical system that drives
a current by mimicking bacterial interactions found in nature. Self-powered Wireless Sensor
Networks (WSNs) are more suitable for this application to monitor the status of the waste water. A
novel Wireless Sensor Network (WSN) is proposed in this paper which integrates Microbial Fuel
Cells (MFCs), Field Programmable Analog Array (FPAAs) to design a self-powered, highly flexible
and adaptive system. The profusion of bacteria and chemical ingredients in waste water processing
tanks provides materials for MFCs to convert chemical energy into electrical energy. In wastewater
treatment, water is aerated so bacteria in the liquid break down organic material in a closed series of
containers known as a bioreactor. The simulation of the system is done and the results of which can
also be hardware implemented.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document describes a proposed hybrid renewable energy power system that uses multiple energy sources (photovoltaic, wind, fuel cell, battery) along with a motor-generator set and diesel engine for power generation. An energy management and control unit using a programmable logic controller is also proposed to optimize the utilization of the various energy sources. The system is designed to operate in both islanding and grid-connected modes. Modeling and simulation of the system components was performed in MATLAB/Simulink to validate the effectiveness of the proposed system design.
This document summarizes a study that optimized hydrogen production from a photovoltaic-electrolysis system. A proton exchange membrane electrolysis was connected to a photovoltaic array via a DC/DC buck converter with maximum power point tracking control. This allowed maximization of power transfer to the electrolysis and control of injected water flow. Simulation results showed that controlling water flow based on power variations from weather changes and using the DC/DC converter with MPPT control allowed for better adaptation between the PV array and electrolysis, leading to optimal system functioning and maximum hydrogen production.
GENERATION OF POWER THROUGH HYDROGEN – OXYGEN FUEL CELLSinventy
This document summarizes a study that tested the ability of a hydrogen-oxygen fuel cell to generate electricity. The study used a small test rig to run experiments supplying hydrogen and oxygen gases to the fuel cell. The experiments measured voltage, current, power output, and other parameters over time. The results showed that the fuel cell was able to produce up to 13.44W of power at 11.20V by converting the chemical energy of hydrogen into electrical energy. Producing power from hydrogen in a fuel cell is presented as a clean and renewable alternative to fossil fuel-based power generation.
This document provides a summary of maximum power point tracking (MPPT) technology for photovoltaic systems. It discusses modeling of solar cells and how their output is affected by irradiation and temperature. It also describes the basic operation of a boost converter used in MPPT systems. Several common MPPT algorithms are examined, including perturb and observe, incremental conductance, and other methods. Flow charts are provided to illustrate the perturb and observe and incremental conductance algorithms. The conclusion is that the incremental conductance method provides better performance than other methods under varying conditions.
Experimental study on transient response of fuel celljournalBEEI
This research work discusses a control strategy to enhance the transient response of the fuel cell and boost the real and reactive power flow from grid connected to fuel cell. The current output of the fuel cell depends on the availability of hydrogen in the fuel cell stack, a battery bank is implemented to supply the transient current and to prevent it from hydrogen saturation. The battery should only supply when there is a transient. During steady state the total power is produced by the fuel cell by regulating its hydrogen input. A prototype of the system will be created to study a control scheme which regulates the current from an input source and a battery which is connected to a dc motor. The control philosophy is based on d-q transformation and subsequently generating a reference signal that is tracked by an IGBT based inverter. The speed of the motor is controlled using pulse with modulation. The dynamic modeling of the standalone fuel cell that is connected to a dc motor is carried out using MATLAB/SIMULINK platform. The simulation results show that the control scheme works well, although the dynamic response of the system can be improved. The testing carried on the prototype proves that the concept works well, but a hydrogen control scheme should be developed to improve the efficiency of the control scheme.
Kinetics of microbial inactivation for Pulsed Electric Field (PEF, PurePulse)...CoolWave Processing b.v.
Pulsed electric fields (PEF) can be used to non-thermally preserve foods by inactivating microbes. PEF involves applying short pulses of high voltage electricity to food between electrodes. This disrupts microbial cell membranes, killing bacteria while avoiding significant heating and quality changes to foods. The document discusses PEF mechanisms and research on its effectiveness in reducing microbes in various foods like apple juice, orange juice, milk, eggs and pea soup. It also covers factors like pulse waveform, equipment design and limitations of the technology.
Fuzzy Sliding Mode Control for Photovoltaic SystemIJPEDS-IAES
In this study, a fuzzy sliding mode control (FSMC) based maximum power point tracking strategy has been applied for photovoltaic (PV) system. The key idea of the proposed technique is to combine the performances of the fuzzy logic and the sliding mode control in order to improve the generated power for a given set of climatic conditions. Different from traditional sliding mode control, the developed FSMC integrates two parts. The first part uses a fuzzy logic controller with two inputs and 25 rules as an equivalent controller while the second part is designed for an online adjusting of the switching controller’s gain using a fuzzy tuner with one input and one output. Simulation results showed the effectiveness of the proposed approach achieving maximum power point. The fuzzy sliding mode (FSM) controller takes less time to track the maximum power point, reduced the oscillation around the operating point and also removed the chattering phenomena that could lead to decrease the efficiency of the photovoltaic system.
Control of an Autonomous Hybrid Microgrid as Energy Source for a Small Rural ...Yayah Zakaria
Nowadays, the exhaustion of electricity power in rural areas is becoming an important issue for many African Nations. Moreover, challenges include the high cost of extending the power grid to these locations, the economic health of the utilities and lack of revenue in impoverished villages. Numerous new initiatives are being implemented in the countries some of them co-financed by international organizations. In this paper, the hybrid microgrid is carried out as a feasible solution for a small rural village. A model of hybrid microgrid consisting of combination of photovoltaic (PV) panels and battery energy storage (BES) and a control system for managing the components of entire system to feed the village as local load is proposed. The control system must avoid the interruptions of power delivered to the consumers (village) and, therefore, good quality and reliability of the system is required. The PI controllers are used to regulate the voltage and current using three-phase dq transformation, while the parameters are determined using Ziegler-Nichols tuning method. The effectiveness of the proposed method is verified by simulation results given by Matlab / Sim Power Systems R environment.
Control of an Autonomous Hybrid Microgrid as Energy Source for a Small Rural ...IJECEIAES
Nowadays, the exhaustion of electricity power in rural areas is becoming an important issue for many African Nations. Moreover, challenges include the high cost of extending the power grid to these locations, the economic health of the utilities and lack of revenue in impoverished villages. Numerous new initiatives are being implemented in the countries some of them co-financed by international organizations. In this paper, the hybrid microgrid is carried out as a feasible solution for a small rural village. A model of hybrid microgrid consisting of combination of photovoltaic (PV) panels and battery energy storage (BES) and a control system for managing the components of entire system to feed the village as local load is proposed. The control system must avoid the interruptions of power delivered to the consumers (village) and, therefore, good quality and reliability of the system is required. The PI controllers are used to regulate the voltage and current using three-phase dq transformation, while the parameters are determined using Ziegler-Nichols tuning method. The effectiveness of the proposed method is verified by simulation results given by Matlab/SimPowerSystems R environment.
FDA - kinetics of microbial inactivation for alternative food processing tech...Wouter de Heij
This document discusses pulsed electric fields (PEF) technology for non-thermal food preservation. PEF involves applying high-voltage electric pulses to foods placed between electrodes. Studies show PEF can effectively inactivate microbes in foods like apple juice, orange juice, milk, eggs, and pea soup. PEF preserves quality attributes better than thermal processing. However, challenges remain in scaling up equipment and handling issues like air bubbles. Future research is still needed on chemical effects and expanding applications.
The electrical profiles of the renewable polymer graphite (PG) composites upon ultra violet (UV) curing were investigated. Renewable PG films were prepared by mixing with varying weight percent of graphite (with an increment of 5 wt. % of prepared graphite) up to 30 wt.% and crosslinker. Then, the composites solution was slip casted and cured upon stimulated UV irradiation (UV accelerated weathering tester) at different time exposure (up to 1000 hours) was applied. Small changes on the functional groups of the composites were observed due to UV exposure time by Fourier Transform Infrared Spectroscopy (FTIR). Suggesting that chemical crosslink and chain scissions occurred within renewable polymer graphite composites. Further electrical profile through two point probe and four point probe method recorded visibly fluctuating values for both resistivity and conductivity within its composites range. Proposed here that the removal of organic contaminants and weak materials form both renewable polymer and graphite particles through the UV curing may have an effect on the formation of conductive network stability.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
This document discusses using a Loop Power Controller (LPC) and fuel cell system to improve load balancing and reduce power losses in a distribution system. It first provides background on fuel cells and how they can provide continuous power generation. It then discusses how an LPC works by adjusting voltage ratio and phase shift to control real and reactive power flow between two distribution feeders. The document presents a case study where an LPC is used to balance the loads between two feeders that also have intermittent power injection from a fuel cell system. Simulation results show the LPC is able to improve load balancing and reduce overall power losses in the distribution system compared to using only fuel cell generation.
This document reviews performance improvements in microbial fuel cells through the use of suitable electrode materials and bioengineered organisms. Microbial fuel cells directly convert organic matter to electricity using microorganisms. However, their commercial application is limited by low power output. The review discusses how electrode design and selection of optimal microbe species can enhance electricity generation. In particular, Geobacter and Shewanella species have shown promise for direct electron transfer needed for higher performance. Advances in genomic tools may enable engineering of microbes tailored for microbial fuel cells.
This document discusses pulsed electric field (PEF) processing as a non-thermal food preservation technique. PEF uses short, high-voltage electric pulses to induce pores in microbial cell membranes, leading to cell disintegration and microbial inactivation while minimizing negative impacts on sensory and nutritional properties. The document outlines various PEF applications, factors that influence microbial inactivation, commercially available PEF systems, ongoing research needs, and the potential future of PEF processing.
This document outlines a proposed design for a new 20MW geothermal power plant in Savusavu, Fiji. The plant would use a binary cycle system to harness geothermal energy from reservoirs between 70-200 degrees Celsius. The system would include production wells to extract brine, a heat exchanger to transfer heat to a working fluid, turbines turned by the heated fluid, and 80 generators each producing 250kW of power. Electricity would be transmitted through cables to consumers. The plant aims to provide clean, renewable energy to the area at a lower cost than fossil fuels.
This document discusses hybrid renewable energy systems and their suitability for rural regions in India. It notes that about 75% of India's population lives in rural areas that often face electricity shortages, hindering development. Hybrid systems that combine two or more renewable sources like biomass, wind, solar, and hydro could help address this issue by providing a more reliable supply. The document outlines several hybrid system examples and notes their advantages like increased reliability, flexibility, and lower operating costs compared to individual renewable systems. However, hybrid systems also present challenges like complex power conditioning, stochastic resource availability, and coordination with electric grids.
Modeling, Control and Power Management Strategy of a Grid connected Hybrid En...IJECEIAES
This paper presents the detailed modeling of various components of a grid connected hybrid energy system (HES) consisting of a photovoltaic (PV) system, a solid oxide fuel cell (SOFC), an electrolyzer and a hydrogen storage tank with a power flow controller. Also, a valve controlled by the proposed controller decides how much amount of fuel is consumed by fuel cell according to the load demand. In this paper fuel cell is used instead of battery bank because fuel cell is free from pollution. The control and power management strategies are also developed. When the PV power is sufficient then it can fulfill the load demand as well as feeds the extra power to the electrolyzer. By using the electrolyzer, the hydrogen is generated from the water and stored in storage tank and this hydrogen act as a fuel to SOFC. If the availability of the power from the PV system cannot fulfill the load demand, then the fuel cell fulfills the required load demand. The SOFC takes required amount of hydrogen as fuel, which is controlled by the PID controller through a valve. Effectiveness of this technology is verified by the help of computer simulations in MATLAB/SIMULINK environment under various loading conditions and promising results are obtained.
Experiment study of water based photovoltaic-thermal (PV/T) collectorIJECEIAES
Solar radiation can be converted to the electrical energy and thermal energy by photovoltaic panel and solar collector. In this experiment, PV/T collector was designed, fabricated and tested its performance. The experiment conducted on PV/T collector with water flow at mass flow rate 0.012 kg/s to 0.0255 kg/s. The water flow with the stainless stell absorber help the PV/T collector in increasing the convection of thermal heat transfer. The power output increase with increase of radiation. The efficiency of PVT varies with different intensity of radiation which stated in this experiment for 750 W/m2 and 900 W/m2. The analysis of energy and exergy are excuted and results show energy output for water based PV/T collector are 346 W for solar radiation 700 W/m2 and 457 W for solar radiation 900 W/m2. Meanwhile the total exergy output compared to the PV panel without stainless stell absorber, which the exergy increased by 22.48% for 700 W/m2 and 20.87% for 900 W/m2.
High intensity pulsed electric fields applied for food preservationWouter de Heij
This document summarizes research on using high intensity pulsed electric fields (PEF) to preserve liquid foods as an alternative to thermal pasteurization. It investigates how electrical field strength, total pulse energy input, and treatment temperature impact microbial inactivation. Experiments were conducted with bacteria (E. coli, B. megaterium, L. innocua) and yeast (S. cerevisiae) using stainless steel and carbon electrodes. The results indicate that higher field strengths are needed to effectively inactivate smaller cells and cells in aggregates. Temperatures over 40 °C were also found to increase the effectiveness of PEF. An enthalpy balance analysis of a hypothetical PEF process that heats product prior to treatment is
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
This document describes a proposed hybrid renewable energy power system that uses multiple energy sources (photovoltaic, wind, fuel cell, battery) along with a motor-generator set and diesel engine for power generation. An energy management and control unit using a programmable logic controller is also proposed to optimize the utilization of the various energy sources. The system is designed to operate in both islanding and grid-connected modes. Modeling and simulation of the system components was performed in MATLAB/Simulink to validate the effectiveness of the proposed system design.
This document summarizes a study that optimized hydrogen production from a photovoltaic-electrolysis system. A proton exchange membrane electrolysis was connected to a photovoltaic array via a DC/DC buck converter with maximum power point tracking control. This allowed maximization of power transfer to the electrolysis and control of injected water flow. Simulation results showed that controlling water flow based on power variations from weather changes and using the DC/DC converter with MPPT control allowed for better adaptation between the PV array and electrolysis, leading to optimal system functioning and maximum hydrogen production.
GENERATION OF POWER THROUGH HYDROGEN – OXYGEN FUEL CELLSinventy
This document summarizes a study that tested the ability of a hydrogen-oxygen fuel cell to generate electricity. The study used a small test rig to run experiments supplying hydrogen and oxygen gases to the fuel cell. The experiments measured voltage, current, power output, and other parameters over time. The results showed that the fuel cell was able to produce up to 13.44W of power at 11.20V by converting the chemical energy of hydrogen into electrical energy. Producing power from hydrogen in a fuel cell is presented as a clean and renewable alternative to fossil fuel-based power generation.
This document provides a summary of maximum power point tracking (MPPT) technology for photovoltaic systems. It discusses modeling of solar cells and how their output is affected by irradiation and temperature. It also describes the basic operation of a boost converter used in MPPT systems. Several common MPPT algorithms are examined, including perturb and observe, incremental conductance, and other methods. Flow charts are provided to illustrate the perturb and observe and incremental conductance algorithms. The conclusion is that the incremental conductance method provides better performance than other methods under varying conditions.
Experimental study on transient response of fuel celljournalBEEI
This research work discusses a control strategy to enhance the transient response of the fuel cell and boost the real and reactive power flow from grid connected to fuel cell. The current output of the fuel cell depends on the availability of hydrogen in the fuel cell stack, a battery bank is implemented to supply the transient current and to prevent it from hydrogen saturation. The battery should only supply when there is a transient. During steady state the total power is produced by the fuel cell by regulating its hydrogen input. A prototype of the system will be created to study a control scheme which regulates the current from an input source and a battery which is connected to a dc motor. The control philosophy is based on d-q transformation and subsequently generating a reference signal that is tracked by an IGBT based inverter. The speed of the motor is controlled using pulse with modulation. The dynamic modeling of the standalone fuel cell that is connected to a dc motor is carried out using MATLAB/SIMULINK platform. The simulation results show that the control scheme works well, although the dynamic response of the system can be improved. The testing carried on the prototype proves that the concept works well, but a hydrogen control scheme should be developed to improve the efficiency of the control scheme.
Kinetics of microbial inactivation for Pulsed Electric Field (PEF, PurePulse)...CoolWave Processing b.v.
Pulsed electric fields (PEF) can be used to non-thermally preserve foods by inactivating microbes. PEF involves applying short pulses of high voltage electricity to food between electrodes. This disrupts microbial cell membranes, killing bacteria while avoiding significant heating and quality changes to foods. The document discusses PEF mechanisms and research on its effectiveness in reducing microbes in various foods like apple juice, orange juice, milk, eggs and pea soup. It also covers factors like pulse waveform, equipment design and limitations of the technology.
Fuzzy Sliding Mode Control for Photovoltaic SystemIJPEDS-IAES
In this study, a fuzzy sliding mode control (FSMC) based maximum power point tracking strategy has been applied for photovoltaic (PV) system. The key idea of the proposed technique is to combine the performances of the fuzzy logic and the sliding mode control in order to improve the generated power for a given set of climatic conditions. Different from traditional sliding mode control, the developed FSMC integrates two parts. The first part uses a fuzzy logic controller with two inputs and 25 rules as an equivalent controller while the second part is designed for an online adjusting of the switching controller’s gain using a fuzzy tuner with one input and one output. Simulation results showed the effectiveness of the proposed approach achieving maximum power point. The fuzzy sliding mode (FSM) controller takes less time to track the maximum power point, reduced the oscillation around the operating point and also removed the chattering phenomena that could lead to decrease the efficiency of the photovoltaic system.
Control of an Autonomous Hybrid Microgrid as Energy Source for a Small Rural ...Yayah Zakaria
Nowadays, the exhaustion of electricity power in rural areas is becoming an important issue for many African Nations. Moreover, challenges include the high cost of extending the power grid to these locations, the economic health of the utilities and lack of revenue in impoverished villages. Numerous new initiatives are being implemented in the countries some of them co-financed by international organizations. In this paper, the hybrid microgrid is carried out as a feasible solution for a small rural village. A model of hybrid microgrid consisting of combination of photovoltaic (PV) panels and battery energy storage (BES) and a control system for managing the components of entire system to feed the village as local load is proposed. The control system must avoid the interruptions of power delivered to the consumers (village) and, therefore, good quality and reliability of the system is required. The PI controllers are used to regulate the voltage and current using three-phase dq transformation, while the parameters are determined using Ziegler-Nichols tuning method. The effectiveness of the proposed method is verified by simulation results given by Matlab / Sim Power Systems R environment.
Control of an Autonomous Hybrid Microgrid as Energy Source for a Small Rural ...IJECEIAES
Nowadays, the exhaustion of electricity power in rural areas is becoming an important issue for many African Nations. Moreover, challenges include the high cost of extending the power grid to these locations, the economic health of the utilities and lack of revenue in impoverished villages. Numerous new initiatives are being implemented in the countries some of them co-financed by international organizations. In this paper, the hybrid microgrid is carried out as a feasible solution for a small rural village. A model of hybrid microgrid consisting of combination of photovoltaic (PV) panels and battery energy storage (BES) and a control system for managing the components of entire system to feed the village as local load is proposed. The control system must avoid the interruptions of power delivered to the consumers (village) and, therefore, good quality and reliability of the system is required. The PI controllers are used to regulate the voltage and current using three-phase dq transformation, while the parameters are determined using Ziegler-Nichols tuning method. The effectiveness of the proposed method is verified by simulation results given by Matlab/SimPowerSystems R environment.
FDA - kinetics of microbial inactivation for alternative food processing tech...Wouter de Heij
This document discusses pulsed electric fields (PEF) technology for non-thermal food preservation. PEF involves applying high-voltage electric pulses to foods placed between electrodes. Studies show PEF can effectively inactivate microbes in foods like apple juice, orange juice, milk, eggs, and pea soup. PEF preserves quality attributes better than thermal processing. However, challenges remain in scaling up equipment and handling issues like air bubbles. Future research is still needed on chemical effects and expanding applications.
The electrical profiles of the renewable polymer graphite (PG) composites upon ultra violet (UV) curing were investigated. Renewable PG films were prepared by mixing with varying weight percent of graphite (with an increment of 5 wt. % of prepared graphite) up to 30 wt.% and crosslinker. Then, the composites solution was slip casted and cured upon stimulated UV irradiation (UV accelerated weathering tester) at different time exposure (up to 1000 hours) was applied. Small changes on the functional groups of the composites were observed due to UV exposure time by Fourier Transform Infrared Spectroscopy (FTIR). Suggesting that chemical crosslink and chain scissions occurred within renewable polymer graphite composites. Further electrical profile through two point probe and four point probe method recorded visibly fluctuating values for both resistivity and conductivity within its composites range. Proposed here that the removal of organic contaminants and weak materials form both renewable polymer and graphite particles through the UV curing may have an effect on the formation of conductive network stability.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
Biotechnology and Bio Engineering,
Environmental Engineering,
Petroleum and Mining Engineering,
Marine and Agriculture engineering,
Aerospace Engineering.
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https://www.tandfonline.com/action/journalInformation?journalCode=lfri20
Food Reviews International
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lfri20
Starch Extraction and Modification by Pulsed
Electric Fields
Luís M. G. Castro, Elisabete M. C. Alexandre, Jorge A. Saraiva & Manuela
Pintado
To cite this article: Luís M. G. Castro, Elisabete M. C. Alexandre, Jorge A. Saraiva & Manuela
Pintado (2021): Starch Extraction and Modification by Pulsed Electric Fields, Food Reviews
International, DOI: 10.1080/87559129.2021.1945620
To link to this article: https://doi.org/10.1080/87559129.2021.1945620
Published online: 10 Jul 2021.
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3. increased potential of their functionality. [3,10–13]
However, the physical modification technologies are
gaining more and more attention by the food industry since chemical reagents are not used to change
starch properties and there is no alteration of α-D-glucose residues. In this way, these new starches do
not need to be called modified and as they are intended for human consumption, physical modifica
tion techniques are preferred by consumers over chemical modification. Besides, these techniques are
simple to execute, safer, easier to operate, sustainable and environmental-friendly. [7,14–16]
Several
emergent technologies can be used for physical modification of starch, such as high pressure,
ultrasound and pulsed electric fields. [14,17]
Pulsed electric fields (PEF) technique is defined as a non-
thermal food processing technology that consists in the application of short-duration electric pulses
(nano to milliseconds) with electric fields intensities up to 80 kV/cm. It is a very versatile technique
that has shown potential to physically modify the native properties of starch from different sources.
[18–26]
In addition, when the intensity of the electric fields used is greater than 20 kV/cm, this technique
has the potential to be a substitute for the conventional thermal processing to inactivate pathogenic
and spoilage organisms at lower temperatures, while maintaining the sensorial and nutritional
characteristics of food products. [27,28]
The purpose of this review is to provide a more detailed and correct understanding of the
application of PEF technology to extract and modify starch properties. The PEF principles, funda
mentals, and working systems will be firstly explained and then the potential of PEF to extract starch
will be discussed. Next, the starch modification will be detailed and explored. After this, it will be
discussed how the properties of starch are changed by PEF. Finally, the economic feasibility of PEF will
be exploited and, the main conclusions and some future perspectives will be described.
2. Principles, fundamentals, and working systems
The essential components of a PEF system are the pulse generator and the treatment chamber
(Figure 1). High-voltage alternating current is converted into direct high-voltage energy (electrical
current that propagates in a single direction) by a pulse generator to be used by a PEF system. Once
converted, this energy is stored in the condenser from which electrical pulses are produced through
rapid discharges of electrical energy in the treatment chamber between the two electrodes. The
discharges are controlled by a switch, which is the most critical component since it must turn on/off
the circuit at high voltages and current in a fraction of microseconds. A pulse transformer is used to set
up the condenser when the voltage is insufficient. The discharges create an electric potential
Switch
Chamber
Condenser
Pulse Generator
Battery
a b
Figure 1. PEF system (A) and a simplified representation of the PEF electrical circuit (B).
2 L. M. G. CASTRO ET AL.
4. V
(A)
V
(A)
t
(μs)
t
(μs)
t
(μs)
t
(μs)
a b
c d
Figure 2. Different PEF pulses shapes: (A) Monopolar square-wave; (B) Monopolar exponential; (C) Bipolar square-wave; (B) Bipolar
exponential.
a
b
c
PRODUCT FLOW
Figure 3. Schematic representation of the electric field of the parallel (A), co-axial (B), and colinear (C) configurations.
FOOD REVIEWS INTERNATIONAL 3
5. differential, leading to the formation of the electrical pulses and, consequently, of the electrical pulse
fields. The material to be processed is also placed in the treatment chamber between the electrodes.
[29,30]
The generated pulses by the PEF system can be unipolar or bipolar if one or two pairs of electrodes
are used during treatment, respectively, but they are also classified according to the shape as square-
wave, where the applied voltage is kept constant at the maximum value for a certain time (the pulse
width) after which the voltage suddenly decreases, or as exponential, where the maximum voltage
initially applied decays exponentially over time. In this case, the pulse width is defined as the time
required for the voltage to drop to 37% (Figure 2). This difference in geometry makes square wave
pulses more advantageous, as they deliver more energy than exponential ones. For this reason, bipolar
square wave pulses are the most used in food processing. [24,31,32]
Depending on the configuration of the electrodes, the chamber will have different geometries. In
the parallel configuration, the chamber is parallelepipedal and the electrodes are on opposite sides
(Figure 3A). This allows the electric field to be uniform and the product flow has a direction
perpendicular to the electric field. To achieve an acceptable uniform electric field, the chamber length
should be superior to the one between the electrode due to the decrease of impedance (the measure
ment of the opposition that the circuit has to the current when the voltage is applied) with the chamber
length. However, the large electrode surface and low electrical resistance may lead to electrode
corrosion in the electrode-flow interface at high currents. It is advantageous to operate symmetrically
to the ground to prevent current leak. The coaxial configuration consists of two cylindrical electrodes,
being the positive pole surrounded by the negative (Figure 3B). As in the parallel configuration, the
product flow has a perpendicular direction to the electric field. Despite being easy to build and
allowing for greater homogenization, the electric field is not uniform along the column. This can be
standardized by manipulating the diameters, but this could decrease the impedance by increasing the
surface area of the electrodes, making this configuration only suitable for low-conductivity loads. In
the collinear configuration, the chamber has a tubular shape with the electrodes adjacent to each other
and separated by an insulating material (Figure 3C). This facilitates the dynamic of fluids, is very
desired for food processing, it is easy to clean and has a high resistance due to the reduced cross-
section area. When compared to the parallel configuration, multiple co-linear unities can be connected
and operated at a lower current, which limits the reaction of the electrodes. However, the electric field
and temperature are unevenly spread in the chamber.[32–34]
Treatments can be done in batch or
continuous mode. Batch treatments can be considered static and allow the use of reduced volumes of
solid and/or semi-solid samples. For this reason, they are more commonly found in experimental
studies and are more advantageous in the laboratory environment since allows to have strict control of
the parameters. However, systems that do not provide agitation can result in a certain portion of the
volume not being treated properly. In the case of continuous treatments, which are more suitable for
processing liquids and are easily integrated into industrial processes, the lack of agitation can be
avoided through multiple treatment zones inline or flow channels. Generally, the parallel chambers are
used in batch systems, whereas the coaxial and collinear chambers are more used in continuous
systems, where the sample is pumped at a known flow rate and the pulses are applied at a known
frequency. [35,36]
The phenomenon that governs PEF is called electro-pulsation, i.e., the exposure of cells to electric
pulses, which lead to alterations on the cell membranes, increasing the permeability and/or conduc
tivity. When a cell senses an external electric pulsed field, a variation in the difference between the
electric voltage of the intra and extracellular media in normal physiological conditions (basal trans
membrane potential) is induced, being its effects dependent on the duration and intensity of the
electric field. The most common effect is characterized by the formation of unstable metastable
hydrophilic pores in the bi-phospholipid membranes by water molecules, thus leading to an induced
increase permeability for molecules without mechanisms of transmembrane transport. [37]
However,
the membrane conductivity and permeability only increase considerably when a minimum value of
transmembrane potential (non-universal value and dependent on multiple factors) is reached. As long
4 L. M. G. CASTRO ET AL.
6. this value is maintained, the changes in permeability and conductivity are maintained. When the
electric field is removed, the value of the transmembrane potential is less than the minimum
previously reached, both conductivity and permeability decrease to a stable and detectable level
allowing diffusion of ions and small molecules. Some alterations on the physiological cellular processes
and reactions to stressors can still be exhibited after resealing of the membrane before the cell returns
to the native state. Then, the membrane recovers gradually to its native conditions if no damages were
created and the cellular viability should be preserved. [37–39]
3. Potential to obtain starches
Starch and proteins are naturally formed simultaneously in the endosperm or cotyledons, with the
starch granules involved in a continuous proteinaceous matrix. These proteins can be classified into
storage proteins, which are the proteins that are adsorbed on the surface of the starch granules after the
extraction of the granules, and in granule-associated proteins. These are biologically different from
storage proteins, have a large amount of basic and hydrophobic amino acids, and are strongly linked to
the surface and/or integral components of starch granules. However, “true” granule-associated
proteins are defined as those proteins that are found on the surface or inside the granules or in both
places and can be classified according to the molecular weight in surface or internal granule-associated
proteins. [40,41]
Because surface proteins are inefficiently removed with saline solutions and the
extraction of internal proteins requires gelatinization of starch granules. However, to guarantee that
extracted starch maintain economic value, it must be isolated without significant alterations of the
starch granule. Prabhu et al. [42]
studied the use of PEF to extract starch from the macroalga Ulva ohnoi
coupled with biomass fractionation into protein and ash. An alga suspension was treated by PEF and
then the thalli were resuspended in water, agitated, and filtered to collect the starch-containing
biomass. The starch was further collected and dried. The conductivity of the PEF supernatant was
69.84% higher than the control, indicating that treatment affected membrane permeability allowing
the removal of salts and ions from the algae cytosol (p<0.05). After PEF treatment, more protein and
ash (14.94 and 68.52%, respectively) was effectively extracted out of the initial biomass to the super
natant in relation to the control (3.16 and 46.67%, respectively) (p<0.05). Duque et al. [20]
studied the
effect of PEF treatment on the physical and functional properties of oat flour. The raw oat flour used
consisted of milled intact raw oat groats, while the thermally processed oat flour was composed of
kilned (115ºC for 30 min), steam-cooked (18 min at 100-104ºC), rolled, and milled raw oat groats as
performed in the industry. It was verified that the PEF treatment altered the secondary structure of
proteins by converting the α-helixes into β-sheets, promoting the unfolding and/or re-assembly of the
proteins. The absence of starch in the supernatant of all samples could be explained by the size of the
pores created, witch difficulted the release of starch from the matrix but allowed the passage of other
components such as protein, minerals, and ions. The PEF treated biomass had less ash than the
control, while the protein and starch contents were significantly higher than the control and original
biomass. Furthermore, the starch extraction yield and starch purity on PEF-treated biomass were
59.54 and 53.05%, respectively, while in the control were 52.31 and 59.40%, respectively. Therefore, the
usage of PEF can lead to the increase of starch yield by removing other cellular constituents such as
proteins and ash. Such a decrease in purity could have been caused by damages induced to the
cellulose of cell walls and cytoskeleton. These results show a new potential to use PEF as an emerging
pre-treatment technique to improve starch extraction. However, more research needs to be carried out
to evaluate its potential applied to other matrices such as vegetables, fruits, roots and tubers, and
cereals rich in starch and optimize the treatment conditions to obtain starches with higher purity.
4. Ability to modify starch properties
The native starch properties can be modified by PEF. Initially, a starch suspension is prepared with
deionized water at 25ºC and the electric conductivity is adjusted between 50 and 200 μS usually with
FOOD REVIEWS INTERNATIONAL 5
7. Table 1. Treatment conditions by pulsed electric fields.
Suspension (w/
w) PEF system
EFI (kV/
cm)
SEI (kJ/
kg)
σ (μS/
cm)
τ
(μs) P (nº) t (μs) f (Hz) T (ºC) Reference
Wheat starch
(-)
Potato
starch (-)
Pea starch (-)
— 2.86-
8.57
2.86-
8.57
2.86-
8.57
— — 6
6
6
— — 600
600
600
— Li et al. [25]
Li et al.
[25]
Li et al.
[25]
Rice starch (40
g)
- 2.86-
8.57
- - 6 - - 600 - Wu et al.
[19]
Potato starch
(8%)
Bench-scale continuous
Unipolar square-wave
pulse
Two parallel copper
electrodes
Pumping flow: 60 mL/
min
30-50 - 200 40 20.16 806 1008 <50 Han et al.
[22]
Corn starch
(8%)
Bench-scale continuous
Bipolar square-wave
pulse
Two parallel copper
electrodes
Pumping flow: 60 mL/
min
30-50 - 200 40 - - 1008 <50 Han et al.
[24]
Tapioca starch
(8%)
Bench-scale continuous
Bipolar square-wave
pulse
Two parallel copper
electrodes
Pumping flow: 60 mL/
min
30-50 - 150 10 21.37 214 1000 <50 Han et al.
[21]
Waxy rice
starch (10%)
Bench-scale continuous
Bipolar square-wave
pulse
Two parallel copper
electrodes
Pumping flow: 60 mL/
min
30-50 - 50 40 - - 1000 40-
45
Zeng et al.
[26]
Maize starch
(8%)
Bench-scale continuous
Bipolar square-wave
pulse
Pumping flow: 60 mL/
min
30-50 - 150 10 20.16 424- 1272
1000 <50 Han
et al.
[23]
Potato (1:1) Batch treatment
Two parallel stainless-
steal electrodes
0.5
0.7
0.9
1.1
0.7
0.9
58.48
49.25
49.63
50.10
151.81
153.09
1610 20 900-
6250
- 100 - Abduh
et al. [18]
Oat flour (8%)
(Raw)
Batch treatment
Two parallel stainless-
steel electrodes
Bipolar square-wave
pulse
2.2
2.1
2.1
4.4
4.3
4.1
53
249
484
51
220
441
305
303
309
308
305
307
20 1458
5000
7778
307
1029
1628
- 100 - Duque
et al. [20]
Oat flour (8%)
(Thermally
treated)
Batch treatment
Two parallel stainless-
steel electrodes
Bipolar square-wave
pulse
2.2
2.1
2.1
4.4
4.3
4.1
49
233
434
48
200
418
348.25
355.70
355.30
355.10
358.22
358.00
20 1250
4118
6364
261
854
1400
- 100 - Duque
et al. [20]
Abbreviations: EFI: Electric field intensity; SEI: Specific energy input; σ: conductivity; τ: Pulse width; P: pulse number; t: treatment
time; f: frequency; T: Temperature.
6 L. M. G. CASTRO ET AL.
8. a KCl solution. Next, the suspension is mixed and pumped into the PEF chamber to be treated at the
desired conditions (Table 1). Despite the treatment conditions change significantly according to the
starch modification property desired and according the starch source, the intensity of the electric field
usually range between 2.86 and 50 kV/cm, the treatment time range between 214 and 1272 μs and the
frequency used varies between 600 and 1008 Hz. The pulse duration ranges change between 6 and 40
μs and the pulses applied are usually between 20.16 and 21.37 μs. After treatment, the suspensions are
cooled to the room temperature, vacuum filtered, dried at 40ºC and stored. According to the Joule
effect, the passage of an electric current through a conductive material generates heat, which is directly
proportional to the square of the intensity of the electric current, causing the temperature to increase
during the treatment.[32,43,44]
When the temperature reaches 60ºC or more, the starch may gelatinize
and a water bath is usually used to keep the temperature below 50ºC preventing gelatinization
process.[22–24,45]
On the other hand, the increase in temperature leads to an increase in conductivity,
which is influenced by the ionic strength of the suspension. If the conductivity is very low (non-
conductive suspension medium), the induced transmembrane potential will be too low. However, high
conductivities are not desirable for PEF treatment since only small electric fields can be created.
[32,46,47]
According to the literature, conductivity is maintained between 50 and 200 μS/cm. If the
conductivity is too low, it must be corrected with a KCl solution, a reference certificate material in the
conductivity calibration. [47]
If the conductivity is too high, sludge can be washed and centrifuged. [26]
4.1. Granule morphology and particle size
The different arrangements of the amylopectin chains in the granule cause starch to have different
polymorphisms. The type A polymorphism is formed by six double amylopectin chains, while type
B has seven chains. Type C is a mix between type A and B. [48]
Li et al. [25]
evaluated the effect of PEF on
the granular morphology of starches with different polymorphisms and reported that the morphology
of wheat (type A), potato (type B), and pea (type C) starch granules were not damaged by PEF
treatment from 2.86 to 8.57 kV/cm. However, Wu et al. [19]
observed sunken areas on the PEF-treated
rice starch granules (type-A) subjected to the same electric field intensities, and fractures were also
seen at the highest intensity used (8.57 kV/cm). These results may indicate that the damage caused by
using low electric field strengths may be dependent on the botanical origin of the starch. The damages
on granular morphology appear to be more evident when a higher electric field intensity order is used
independently of the starch polymorphism. Zeng et al. [26]
treated waxy rice (type A) starch using
intensities from 30 to 50 kV/cm and verified that the damages to the granules increased with the field’s
intensity. Native starch granules had an irregular shape and the surface of some granules was rough
when treated at 30 kV/cm. At 40 kV/cm, some pits were observed, as well as aggregation due to surface
adhesion between the starch granules. After the 50 kV/cm treatment, some starch granules were
twisted and flocked. Similar results were reported for corn (type A), potato (type B), and tapioca (type
A) starches.[21,22,24]
Such alterations of morphology suggest that the granules structure was altered
after the PEF treatment.
Regarding the particle size (Table 2), Han et al. [24]
evaluated the effect of PEF on the particle size
distribution of corn starch granules and observed an increase of the mean volume diameter of the PEF
treated granules, when compared to the native. However, the granular particle size at which 90% of
granules were smaller by volume (D90) increased significantly at 40 and 50 kV/cm, i.e., the granular
size increased. These results indicate that the treatment damaged the granule outer part and the inner
part could have absorbed more water and swells after treatment. Consequently, occurs granular
aggregation due to the strengthening of the van der Waal’s and electrostatic forces between the
granules. Similar results were reported for potato starch. [22]
Recently, Duque et al. [20]
also verified
a significant increase on the particle size of the raw oat flour at D10 and D50 and for the thermally
processed flour at a D10 due to the aggregation of the starch granules regardless the electric field
intensity used (~2 or ~4 kV/cm) at the highest specific energy input, indicating that the thermally
processed flour was less susceptible than raw flour due to the thermal pretreatment. It was also verified
FOOD REVIEWS INTERNATIONAL 7
9. that the secondary structure of the protein associated with the oat starch granules was altered during
the PEF treatment, indicating that the changes on these proteins during the treatment could have been
partially responsible for such aggregation.[49]
4.2. Birefringence and X-ray diffractometry
The amylopectin present in the crystalline regions have a radial arrangement from the helium of the
starch granule to its surface. The Maltese crosses appear when polarized light crosses this arrangement,
being this phenomenon named birefringence. [50]
Li et al. [25]
evaluated the effect of the electric field
intensity from 2.86 to 8.57 kV/cm on wheat, pea, and potato starches with different polymorphisms.
Under polarized light, the birefringence did not vary significantly at lower electric fields (2.86 to 5.71
kV/cm), indicating that the arrangement of amylose and amylopectin was not significantly disturbed.
Abduh et al. [18]
also did not report changes on the birefringence of potato starch granules treated in
the range of 0.5 to 1.1 kV/cm at the specific energy input of 50 and 150 kJ/kg. However, when Li et al.
[25]
applied higher electric field intensities (7.14 and 8.57 kV/cm), the Maltese crosses of the wheat
Table 2. Particle size distribution results of the PEF-treated starches.
Suspension
EFI
(kV/
cm)
SEI
(kJ/
kg)
D4,3 (μm)
PEF/Native
D3,2 (μm)
PEF/
Native
D10 (μm)
PEF/Native
D50 (μm)
PEF/Native
D90 (μm)
PEF/Native
SSA (m2
/
g)
PEF/
Native Reference
Corn 30
40
50
— 23.65/15.22
27.74/
15.22
29.68/
15.22
9.46/7.37
10.15/
7.37
10.47/
7.37
8.18/7.40
9.28/
7.40
10.47/
7.40
18.54/14.89
22.77/
14.89
23.60/
14.89
44.29/24.22
53.80/24.22
58.81/24.22
0.63/0.81
0.59/
0.81
0.57/
0.81
Han et al.
[24]
Potato 30
40
50
— 56.11/37.93
85.16/
37.93
113.8/4/
37.93
16.80/
16.67
22.95/
16.67
24.91/
16.67
16.93/
16.12
19.16/
16.12
21.79/
16.12
38.14/35.76
46.17/
35.76
51.14/
35.76
89.74/63.68
231.41/
63.68
341.96/
63.68
0.36/0.36
0.26/
0.36
0.24/
0.36
Han et al.
[22]
Oat flour
(Raw)
2.2
2.1
2.1
4.4
4.3
4.1
53
249
484
51
220
441
———— ———— 6-7/7-8
7-8/7-8
24-30/
7-8
7-8/7-8
7-8/7-8
22-27/
7-8
23-30/23-33
22-31/23-
33
93-108/23-
33
29-34/23-
33
32-34/23-
33
85-123/23-
33
64-298/331-
451
43-370/331-
451
244-403/
331-451
234-365/
331-451
341-358/
331-451
295-412/
331-451
———— Duque
et al. [20]
Oat flour
(Thermal
treated)
2.2
2.1
2.1
4.4
4.3
4.1
49
233
434
48
200
418
———— ———— 14-15/12-
14
16-20/
12-14
33-46/
12-14
13-15/
12-14
11-18/
12-14
30-57/
12-14
150-192/82-
257
106-238/
82-257
146-213/
82-257
151-213/
82-257
91-206/82-
257
102-255/
82-257
889-914/565-
1299
871-955/
565-1299
213-931/
565-1299
904-939/
565-1299
639-918/
565-1299
226-925/
565-1299
———— Duque
et al. [20]
Abbreviations: EFI: Electric field intensity; SEI: Specific energy input; D4,3: Volume mean diameter (De Brouckere diameter); D3,2: Area
mean diameter (Sauter diameter); D10: size of the particle below which 10% of the sample lies; D50: size of the particle which 50% of
the sample is smaller and 50% is larger; D90: he size of the particle below which 90% of the sample lies; SSA: Special surface area;
PEF/native: PEF treated vs native starch.
8 L. M. G. CASTRO ET AL.
11. (type A) and potato (type B) starch granules faded, while no alterations were observed on pea starch
(type C). This suggests that starches from type A and B can be more susceptible to PEF treatment than
type C. PEF treatment can cause changes in the radial arrangement of amylopectin in the crystalline
zones, leading to losses of the Maltese crosses and consequently birefringence, depending on the
polymorphism of the starch but also on the intensity of the applied electric fields. Wu et al. [19]
used
intensities from 2.86 to 8.57 kV/cm to treat rice starch (type A) granules, but possible changes on the
Maltese crosses were not possible to observe due to the very small diameter of rice granules (3-8 μm).
The diffraction methods such as X-ray diffractometry (XRD) are the only method available to
quantify the long-range crystalline order,[51,52,53]
and some studies have been applied on starch as
depicted in Table 3. Li et al. [25]
evaluated the effect of PEF treatment from 2.86 to 8.57 kV/cm on
starches with different polymorphisms, namely wheat (type A), potato (type B), and pea (type C)
starches. No significant changes were observed on the diffraction peaks, indicating that crystalline
morphology variations caused by PEF treatment were small. In general, the relative crystallinity values
of starches treated with lower electric field intensities (2.86 to 5.71 kV/cm) appear to be slightly higher
than those treated at higher intensities (7.14 and 8.57 kV/cm) when compared to the native starch,
which correlates with the differences in birefringence observed previously. These results indicate that
during treatment the amylose chains could have been reorganized at lower field intensities, leading to
an increase of relative crystallinity. At higher field intensities, the treatment could have disrupted the
starch chain arrangements, namely hydrogen bonds between the amylopectin chains in the crystalline
regions. Once these bonds are disrupted, the relative crystallinity decreases and consequently occurs
a loss of birefringence (Maltese crosses) under polarized light. [50]
These results are similar to the
findings obtained by Wu et al. [19]
for rice starch treated from 2.86 to 8.57 kV/cm. For higher electric
field intensities, Zeng et al. [26]
treated native waxy rice starch verifying that the relative crystallinity
decreased with the increase of the electric field intensity from 30 to 50 kV/cm. Additionally, the
diffraction peaks intensity at 15.3, 17.1, 18.2, and 23.5° also decreased with the increase of the field
intensity. These results are in agreement with the findings reported for tapioca, corn, and potato
starches. [21,22,24]
The higher the electric field intensity is, the more energy is provided during the PEF
treatment to disrupt the non-covalent bonds between the starch chains and, at the same time, promote
the interaction between the water molecules and the hydroxyl groups of the starch molecular chains.
This leads to a transformation of starch granules from crystal into non-crystal. [23]
The decrease of
crystallinity can be a consequence of the disruption of the amylopectin crystallites that form it. [53]
During the literature revision, it was noticed that the percentage of amylose of the analyzed starches
was never reported. Knowing that the amylose content can have a significant effect on starch
polymorphism,[54]
it is suggested that such information should be included and reported from now
on. [50]
4.3. Small-angle X-ray scattering, Fourier transform infrared spectra, and nuclear magnetic
resonance
The lamellar architecture of starch can be characterized and studied by small-angle X-ray scattering
(SAXS) (Table 3). Starch granules are formed by amorphous rings alternating with semi-crystalline
rings. While the amorphous rings are made up of disorganized amylose and amylopectin, the semi-
crystalline rings are formed by an alternating lamellar structure of crystalline regions and amorphous
regions with a regular repetition distance between 9 and 10 nm. [48]
Li et al. [25]
studied the effect of the
PEF treatment on the semi-crystalline lamellae thickness of starches with different polymorphism,
namely wheat (type A), potato (type B), and pea (type C) starches. No significant differences were
found for wheat, indicating that no changes were induced in the semi-crystalline lamellae thickness.
However, significant differences were found for pea and potato starches at 2.86 and 5.71 kV/cm
treatments, respectively. The scattering peak position for pea decreased from 0.912 to 0.597 nm−1
and
for potato increased from 0.669 to 0.683 nm−1
. These alterations led to an increase of 0.285 nm of pea
lamella repeating distance and a decrease of 0.193 nm of potato when compared to the corresponding
10 L. M. G. CASTRO ET AL.
12. native starches. For waxy rice starch (type A), Zeng et al. [26]
reported that the lamella repeating
distance of starches treated by PEF increased with the PEF intensity. The native starch had a lamella
repeating distance of 8.89 nm, but when the 30, 40, and 50 kV/cm electric field intensities were applied,
the distance increased to 8.93, 9.56, and 9.63 nm, respectively. Contrarily, Wu et al. [19]
verified that the
treated lamella repeating distance of the PEF treated rice starches (type A) decreased significantly with
the increased PEF intensity from 2.86 to 8.57 kV/cm. These results indicate that the PEF treatment can
differently affect the lamella repeating distance of starches from different botanical origins.
The bands of the Fourier transform infrared spectra (FTIR) spectra at ~1047 and ~1022 cm−1
can
be used to detect changes in the crystallinity and amorphous regions of starch granules. For this
reason, the intensity ratio A1047/1022 has been extensively used to acquire information on the crystal
linity of short-range molecular order and the double-helix packing within the inner granule structure.
Nuclear magnetic resonance (NMR) has been used for direct quantification of the proportion of
double-helices of the short-range order based on the C1 and C4 positions. [52]
In Table 3 are presented
the studies about the measurement of the short-range double-helical order of native and PEF treated
starches using FTIR spectra and NMR analysis. Han et al. [23]
reported no significant effects on the
maize starch chemical structure when treated at 50 kV/cm using 1
H and 13
C NMR spectra. Li et al. [25]
analyzed the infrared spectra of the wheat, potato, and pea starches treated from 2.86 to 8.75 kV/cm
and verified that the A1047/1022 intensity of the potato starch had a bigger variation than the pea and
wheat starches. The 13
C NMR spectra revealed that the order structure of the wheat (type A) and
potato (type B) starches decreased 0.7 and 1.6%, respectively, when treated at 8.75 kV/cm compared to
the native starch, while an increase of 4.5% was observed for pea starch (type C). Such a decrease
indicates that the ordered (crystalline) structures were disrupted, which may have been due to the
break of hydrogen bonds. Wu et al. [19]
also reported a significant decrease in the A1047/1022 intensity of
the waxy rice (type A) treated at 8.75 kV/cm. It can be inferred that PEF treatment changes the order
structure of all starch polymorphisms, but the changes are more severe for the type B. Duque et al. [20]
treated raw and thermally processed oat flour with PEF and reported that the A1047/1022 intensity of the
oat raw flour decreased significantly when compared to the control after being treated at 4.1 kV/cm
and 441 kJ/kg. These results indicate that PEF induced disruption of the short-range crystallinity, thus
altering the starch structure. In the case of the thermally processed oat flour, no significant changes on
the A1047/1022 intensity were found after PEF treatment.
It can be seen that the relative crystallinity values determined by X-ray diffraction are substantially
lower than the proportion of double-helices determined by RMN analysis (RMN structure order).
These differences indicate that there is a percentage of double chains of amylopectin that is not
quantified by the X-ray diffraction. [55]
4.4. In-vitro digestibility and molecular weight
In-vitro digestibility starch studies have great importance since they can predict the glycemic response
in in-vivo systems. The most used and reliable technique is still the Englyst method. [56]
In Table 4 are
presented the studies about the in-vitro digestibility of native and PEF treated starches. Li et al. [25]
evaluated the effect of PEF treatment from 2.86 to 8.57 kV/cm on the digestibility of starch with
different polymorphisms, namely wheat (type A), potato (type B) and pea (type C) starches. In general,
the treated starches had a significant increase in rapidly digestible starch and a decrease in slowly
digestible starch, while the resistant starch content remained unchanged when compared to the native
starches. These results are in agreement with those reported by Wu et al. ,[19]
who treated rice (type A)
starch from 2.86 to 8.57 kV/cm. Zeng et al. [26]
also documented similar results for waxy rice starch,
despite the decrease in the resistant starch content. The different types of polymorphism do not appear
to be a possible explanation for such results. However, it remains plausible to think that due to the
damage and morphological changes that PEF can cause in starch granules, the digestible enzyme will
have easier access to new and/or greater number of glycosidic linkages in regions that initially would
be inaccessible. As previously observed, the PEF treatment can lead to a decrease of the starch relative
FOOD REVIEWS INTERNATIONAL 11
14. crystallinity and alter the starch granules morphology, which indicated that the starch structure can be
more susceptible to enzymatic activity. Thus, a greater number of degraded glycosidic bonds should
translate into greater hydrolysis of the starch, i.e., an increase in the rapidly hydrolyzed starch, and
consequently less will be the slowly digestible starch content. These results indicate that the molecular
weight of starch chains’ could have been altered after the PEF treatment (Table 4). Han et al. [23]
reported that the molecular weight of maize treated starch decreased significantly with the increase of
the electric field intensity from 30 to 50 kV/cm and with the treatment time from 424 to 1272 μs
(r2
>0.95). The decrease in molecular weight increased with the increase of the electric field intensity.
Additionally, the electric field intensity had more effect on the decrease of molecular weight than time.
Therefore, the decrease of the molecular weight could have been due destabilization of the amylo
pectin. However, Zeng et al. [26]
found that PEF treatment did not cause significant variations in the
molecular weight of waxy rice starch chain. Li et al. [25]
hypothesized that changes in the molecular
weight of starch molecules could have been responsible for the starch digestible capacity. More
recently, Wu et al. [19]
noticed an increase in the relative molecular weight of short amylopectin
chains and an increase of the relative molecular weight of long amylopectin chains when the intensity
of the electric field was superior to 5.71 kV/cm after treatment, despite did not found significant
changes in the molecular weight. Such a result indicates a breakdown of the molecular chain as
supposed by Li et al. [25]
Furthermore, the ratio of the chain length ratio of amylose to amylopectin was
less than one and the amylose content did not vary significantly when compared to the control. [19]
These results point in the direction of changes in the amylopectin chains during PEF treatment. Future
analyzes of the detailed structure of amylopectin may provide new data to explain the variations in
starch digestibility. Another relevant question is the behavior of these modified starches in in-vitro
simulation systems of the human digestive tract and their impacts on human health as well as the
potential benefits. Abduh et al. [18]
evaluated the glucose release per volume digest of the in-vitro
human intestine digestion and observed that the digestibility of the starch leached from the potato
shreds into the processing medium after PEF treatment was reduced (lower amount of glucose
released) after 120 min of digestion when compared to the earlier digestion times. Such reduction
was prevalent in the starch treated at 1.1 kV/cm and 50 kJ/kg in relation to the untreated starch
(p<0.05), which could have been due to starch disruption as indicated by the changes in the
gelatinization range temperature. This result is an initial evidence of the health benefits that the
starches treated by PEF starch treatment can have, since a reduction of starch digestibility is normally
associated to resistant starch, which has several benefits such as the diabetes management and decrease
the glycemic indexes. [57]
4.5. Differential scanning calorimetry and pasting properties
Table 5 depicts the most recent studies about the effect of PEF on the gelatinization temperatures and
enthalpy of the modified starches. Han et al. [23]
reported that for maize starch, gelatinization
temperatures and enthalpy decreased with the increase of the electrical field strength from 30 to 50
kV/cm and treatment time from 424 to 1272 μs due to the breaking of amylopectin chains, decreasing
the molecular weight and consequently leading to their degradation. But this result also shows that
there is an interactive effect between the electrical field strength and the treatment time. Zeng et al. [26]
reported that the gelatinization temperatures and enthalpies also decreased significantly for waxy rice
starch for the same range of electric field strength. The PEF-treated starches had lower gelatinization
temperatures and enthalpies when compared to the native ones (p<0.05). These results are similar to
the ones found for tapioca, corn and potato starches. [21,22,24]
PEF treatment leads to the breaking of
hydrogen bonds and therefore less energy is needed to disrupt the remaining ones, as evidenced by the
decrease in the gelatinization temperatures and enthalpies, especially the onset temperature, which
corresponds to the temperature at which the starch gelatinizes. The onset temperature can also be
found through the pasting property graphs when there is an initial increase in the viscosity, i.e., the
pasting temperature. [6,45]
The difference can rely on the fact that differential scanning calorimetry is
FOOD REVIEWS INTERNATIONAL 13
17. based on temperature sweeps and heat flow variations, whereas its determination by the graphs of
pasting properties is based on the measurement of viscosity changes. [58]
Abduh et al. [18]
processed
shredded potato using electric field intensities from 0.5 to 1.1 kV/cm and specific energy inputs at 50
and 150 kJ/kg and reported that the leached granules leached during the treatment and using higher
specific energy inputs had a narrower gelatinization range than those performed at a lower total
specific energy, which indicates that the crystallites had a stronger cohesion. The gelatinization
temperatures were inferior to those reported for potato starch treated between 30 to 50 kV/cm, but
Table 6. Pasting properties results of the PEF-treated starches.
Suspension
EFI
(kV/
cm)
SEI
(kJ/
kg)
PT
(ºC)
PEF/
Native
Peak
(BU)
PEF/
Native
SH (BU)
PEF/
Native
SC (BU)
PEF/
Native
EC (BU)
PEF/
Native
FV (BU)
PEF/
Native
BD (BU)
PEF/
Native
SB (BU)
PEF/
Native Reference
Tapioca 30
40
50
— — 921/982
889/
982
820/
982
517/496
505/
496
469/
496
295/279
281/
279
260/
279
572/557
546/
557
493/
557
512/505
489/
505
444/
505
626/703
608/
703
560/
703
— Han et al.
[21]
Corn 30
40
50
— — 291/335
282/
335
250/
335
280/320
271/
320
243/
320
220/253
215/
253
201/
253
528/568
469/
568
470/
568
482/537
442/
537
426/
537
71/82
67/82
49/82
— Han et al.
[24]
Potato 30
40
50
— — 2771/
2961
2705/
2961
2641/
2961
1074/
1060
1063/
1060
1022/
1060
555/524
535/
524
523/
524
955/913
917/
913
910/
913
922/907
862/
907
877/
907
2216/
2437
2170/
2437
2119/
2437
— Han et al.
[22]
Rice 2.86
5.71
8.57
— — 637.0/
632.2a
639.0/
632.2a
629.3/
632.2a
— — 587.0/
583.0ab
589.0/
583.0ab
581.0/
583.0ab
803.3/
805.0a
805.7/
805.0a
799.7/
805.0a
50.0/
49.2a
50.0/
49.2a
48.3/
49.2a
216.3/
222.0a
216.7/
222.0a
218.7/
222.0a
Wu et al.
[19]
Oat flour
(Raw)
2.2
2.1
2.1
4.4
4.3
4.1
53
249
484
51
220
441
83/84
84/
84
75/
84
83/
84
83/
84
72/
84
3334/
3451a
3154/
3451a
2081/
3451a
3122/
3451a
3135/
3451a
1761/
3451a
———— ———— 1592/
1624ab
1518/
1624ab
909/
1624ab
1378/
1624ab
1432/
1624ab
761/
1624ab
3692/
3711a
3297/
3711a
2439/
3711a
3403/
3711a
3395/
3711a
2223/
3711a
1742/
1826a
1636/
1826a
1172/
1826a
1744/
1826a
1703/
1826a
999/
1826a
2100/
2086a
1779/
2086a
1529/
2086a
2025/
2086a
1963/
2086a
1461/
2086a
Duque
et al.
[20]
Oat flour
(Thermal
treated)
2.2
2.1
2.1
4.4
4.3
4.1
49
233
434
48
200
418
67/68
66/
68
67/
68
68/
68
66/
68
73/
68
4268/
4385a
4148/
4385a
3923/
4385a
4159/
4385a
4070/
4385a
4087/
4385a
———— ———— 3094/
3075ab
3075/
3075ab
3029/
3075ab
3021/
3075ab
3053/
3075ab
3213/
3075ab
5227/
5292a
5223/
5292a
5156/
5292a
5149/
5292a
5219/
5292a
5310/
5292a
1173/
1235a
1073/
1235a
893/
1235a
1138/
1235a
1017/
1235a
873/
1235a
2133/
2142a
2148/
2142a
2127/
2142a
2127/
2142a
2166/
2142a
2097/
2142a
Duque
et al.
[20]
Notes: a) Results reported in cp; b) Trough viscosity.
Abbreviations: EFI: Electric field intensity; SEI: Specific energy input; SH: Start holding; SC: Start of cooling; EC: End of cooling; FV: Final
viscosity; BD: Breakdown; SB: Setback; PEF/native: PEF treated vs native starch.
16 L. M. G. CASTRO ET AL.
18. the gelatinization enthalpies were superior. [22]
These differences could have been due to differences in
potato variety and/or differences in the electric field intensity conditions. Furthermore, no effects were
observed on the unleached starch granules, indicating that these granules were less subjected to
treatment than those that were leached since they were protected in the original matrix. According
to Duque et al.,[20]
who treated raw and thermally processed oat flour using electric field strengths
from 2.1 to 2.2 kV/cm at 53-484 kJ/kg and from 4.1 to 4.4 kV/cm at 51-441 kJ/kg, the narrowing of the
range of the gelatinization temperature indicated that fusion of the crystallites of less cohesion was
favored and may have been strengthened, thus leading to the increase of the gelatinization
temperatures.
In Table 6 are presented the studies concerning the effect of PEF on the pasting temperature and
viscosity of starch when compared to the native starches. Wu et al. [19]
treated rice (type A) starch
using electric field intensities from 2.86 to 8.57 kV/cm and reported that treatment did not have
a significant impact on rice starch peak, trough, breakdown viscosities, and pasting temperature with
a small decrease in the setback viscosity. At higher intensities, Han et al. [21]
studied the effect of PEF
processing on tapioca (type C) starch and observed that the viscosity peak decreased when the electric
field increment from 30 to 50 kV/cm, indicating that granules swell less before they burst. After
treatment, both granules’ surface and crystalline structure were destroyed, leading to a decrease in
peak viscosity. Breakdown viscosity also decreased with increasing electric field strength, indicating
that the stability of the hot paste increased. Setback and final viscosities also decreased with increasing
electric field strength, thus indicating less retrogradation tendency. These results were similar to the
findings for corn (type A) and potato starches (type B). [22,24]
Duque et al [20]
recently treated raw and
thermally treated oat flour at 2.1-2.2 kV/cm at 53-484 kJ/kg and 4.1-4.4 kV/cm at 51-441 kJ/kg.
Overall, the PEF treatment caused a significant decrease in the viscosity and pasting temperatures
treated at higher specific energy inputs. The decrease in pasting temperatures relative to the control
indicated that the starch granules of the oat flour started swelling earlier than the control flour. The
peak viscosity of the raw oat flour decreased when compared to the control, but the treatment did not
cause significant changes in the case of the thermally processed flour. These results indicate that raw
oat flour had higher susceptibility than thermally processed flour due to the effect of thermal pre-
treatment, which may have led to aggregation and partial gelatinization before treatment. The break
down viscosity decreased in both flours compared to the control and the lowest values were seen for
the thermally treated flour. The decrease in breakdown viscosity indicated an improvement in the
paste stability, i.e., the swollen starch granules may have a lower degree of collapse and less extension
of the solubilized starch capable of retrograding. Additionally, only the raw oat flour had significantly
lower setback viscosity when compared to the control, indicating a decreased tendency to retrograde.
However, no analysis was made of how swelling and solubility were affected by the treatment, nor were
tests carried out to understand the impact of PEF treatment on starch retrogradation despite evidence
of lower retrogradation of treated starches.
5. Benefits and limitations
Besides being used to physically modify starch, the PEF technique has also been recently used to
chemically modify starches and further compared with the traditional chemical acetylation methods.
[55,59,60–63]
Results show that the traditional acetylation of starch by PEF reduces costs, saves reagent,
reduces the modification time, and promotes reaction efficiency (higher degrees of acetylation. [60–
62,64]
Figure 4 compares step by step both traditional acetylation and starch physical modification by
PEF. According to the literature, traditional acetylation requires the use of acetic anhydride as an
acetylating agent, which leads to increased costs and entails additional risks for the environment.
Regarding the modification step itself, this procedure requires extra care that does not occur in
physical modification such as pH adjustment (so that acetylation conditions are promoted). This
adjustment is made with NaOH, which implies the use of a second chemical reagent. In addition,
FOOD REVIEWS INTERNATIONAL 17
19. traditional acetylation is a time-consuming process, much more than physical modification. After
modification, it is necessary to use ethanol to stop the acetylation reaction and wash the starches to
remove unused acetic anhydride during acetylation. Until this stage, chemical acetylation requires the
use of different chemical solvents, whereas physical modification only requires the use of water as
a solvent. Then the starches are dried, sieved and stored. Thus, PEF technology is much faster, safer,
greener, and more environmentally friendly. In the physical modification, it is only necessary to filter
the cooled starches after modification and then dry, sieve, and store.
Overall, the physical modification has several advantages over the chemical methods, namely: 1)
simplification/reduction of the number of steps and consequently a reduction of the time spent from
the preparation of the starch suspension to the storage of the modified starch; 2) a significant reduction
in modification time; 3) non-usage of chemical solvents and the exclusive use of water, which leads to
a decrease in waste produced (greener and more environmentally friendly); 4) more ease of use; 5)
easier control of experimental conditions, having already created guidelines for the application of PEF
in food and biotechnological processes with the parameters that are necessary to control; and 6) the
possibility to carry out in batch or continuous mode (automation).
Some of the major disadvantages of PEF are 1) the high initial cost of the PEF equipment, 2) the
maintenance costs and 3) the need for specialized workers. [30,65]
However, the initial investment
becomes more advantageous in the long run and with the equipment full depreciation after five years.
Using orange juice as a case study it was estimated that the cost per PEF would be around $0.037/L
using a commercial equipment worth $988,000. The total capital cost of $2,100,000 with an annual
Suspension (35%)
Acetic anhydride addition
(dropwise within 30 min)
Modification
(30 ºC at 300 rpm for 60 min and pH
8.0-8.5 adjusted with NaOH 3%)
Ethanol addition
(stop reaction)
Washing (with ethanol)
Drying (45 ºC)
Sieving and storage
Suspension (8%)
Conductivity adjustment
(50-200 μS/cm)
Stirring
Modification
(< 50 ºC at 2.86-50 kV/cm for 214-
1272 μs and 600-1008 Hz)
Sample cooling
(water bath)
Filtration
Drying (45 ºC)
Sieving and storage
Chemical modification
Physical modification
Conductivity adjustment
(11 mS/cm)
Figure 4. Flowcharts of the physical and starch modification.
18 L. M. G. CASTRO ET AL.
20. depreciation of $210,000/year. Utility and labor costs were estimated to be around $69,000/year and
$220,000/year, respectively. [65]
6. Conclusions
PEF has shown the potential to aid the extraction of starch from algae, but more studies are needed
to evaluate its potential in other matrices such as vegetables, fruits, roots and tubers, and cereals rich
in starch and to optimize the operating conditions to increase protein removal and increase starch
purity. The PEF treatment induces significant changes in granular morphology and the changes on
the Maltese crosses do not seem to be affected at lower intensity fields, but the crosses seem to
disappear according to the starch polymorphism at higher electric fields, being the type A and
B starches more susceptible than the type C. The PEF treatment also leads to the decrease of relative
crystallinity, can change the starches lamellar repeating distance depending on the botanical origin
of starch, decrease the gelatinization temperatures and enthalpies, viscosity, and pasting tempera
ture. Regarding the in-vitro digestibility, it seems to lead to an increase of the rapidly digestible
starch content and a consequent decrease in the slowly digestible starch, while maintaining the
resistant starch content. These can be related to changes in the starch chains and future analyzes of
the detailed structure of amylopectin may provide new data to explain the variations in starch
digestibility. The lower digestibility of starch treated by PEF in in-vitro human simulated digestion
conditions seems promising for the incorporation of these starches in the human diet. The PEF
modification technology is a safer technique as it does not require the use of chemical solvents,
therefore it is a more environmentally friendly technique, presenting a lower processing cost
compared to traditional acetylation.
Acknowledgments
Thanks are due to the Universidade Católica Portuguesa by the financial support of the CBQF Associate Laboratory
under the FCT project UID/Multi/50016/2019 and to the University of Aveiro and FCT/MCT for the financial support
for the QOPNA research Unit (FCT UID/QUI/00062/2019) and to Laboratório Associado LAQV-REQUIMTE (UIDB/
50006/2020) through national funds and, where applicable, co-financed by the FEDER, within the PT2020 Partnership
Agreement. Author Luís M. G. Castro is also grateful for the financial support of this work from FCT through the
Doctoral Grant SFRH/BD/136882/2018.
Funding
This work was supported by the Fundação para a Ciência e a Tecnologia [SFRH/BD/136882/2018,UID/Multi/50016/
2019,UID/QUI/00062/2019,UIDB/50006/2020].
ORCID
Luís M. G. Castro http://orcid.org/0000-0002-4082-9679
Elisabete M. C. Alexandre http://orcid.org/0000-0003-4175-2498
Jorge A. Saraiva http://orcid.org/0000-0002-5536-6056
Manuela Pintado http://orcid.org/0000-0002-0760-3184
Author contributions
Luís M. G. Castro searched, reviewed the available literature, and created the first version of the manuscript. Elisabete
M. C. Alexandre, Jorge A. Saraiva, and Manuela Pintado conceptualize the idea, provided scientific supervision,
performed a critical revision, and provided the necessary conditions to produce the paper.
FOOD REVIEWS INTERNATIONAL 19
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