Pulsed electric field processing of different fruit juices: Impact of pH and temperature on inactivation of spoilage and pathogenic micro-organisms - International journal of food microbiology 2014 timmermans et al.
This document summarizes a study on using pulsed electric field (PEF) processing to inactivate spoilage and pathogenic microorganisms in different fruit juices. The researchers tested the effect of PEF treatment on the survival of various microbes, including Salmonella, E. coli, Listeria, and yeast, in apple, orange, and watermelon juices. They found that microbial inactivation was influenced by factors like juice pH and temperature. Higher temperatures and lower pH levels enhanced microbial inactivation. The yeast was the most sensitive to PEF, while Listeria was the most resistant. Nonlinear survival curves were successfully modeled using the Weibull model.
Evaluation of quality changes of blueberry juice during refrigerated storage after high-pressure and pulsed electric fields processing.
More information:
www.cwp-bv.nl
www.purepulse.eu
This document summarizes a study examining consumer attitudes towards apple juice produced using two new food processing technologies: high-pressure processing (HPP) and pulsed electric field processing (PEF). Interviews were conducted in Norway, Denmark, Hungary, and Slovakia using a means-end chain approach. The study found that consumers recognized benefits of HPP and PEF juices over conventionally pasteurized juice, such as better taste and nutrition. However, some consumers expressed skepticism about potential risks of PEF. The researchers conclude it is important for producers to provide evidence that new technologies are safe in order to gain consumer acceptance of resulting food products.
Effect of carotenoids levels in PEF treated Orange Juice during storage CoolWave Processing b.v.
This study examined the effects of non-thermal processing (pulsed electric fields and high hydrostatic pressure) and pasteurization on carotenoid levels in orange juice. The results showed that pasteurization significantly decreased total carotenoid concentration compared to fresh orange juice, while decreases were less for pulsed electric field and high pressure processing. During refrigerated storage, carotenoid levels declined more quickly in pasteurized orange juice than juices treated with non-thermal methods. Thus, non-thermal technologies better maintain carotenoid levels in orange juice compared to conventional thermal pasteurization.
General background PEF technology to perform cold pasteurization of juicesCoolWave Processing b.v.
General information about PEF.
PurePulse is the second generation PEF excellent to extend the shelf-life of cold pressed juices or NFC fruit juices.
See also:
www.purepulse.eu
www.topwiki.nl
www.cwp-bv.nl
This document summarizes research demonstrating that high electric fields can kill bacteria and yeasts. The researchers applied direct current pulses up to 25 kV/cm to suspensions of various microorganisms. They found that the electric fields caused death that was not due to electrolysis products or temperature increases. Higher field strengths and longer total pulse times resulted in greater killing of microbes. The sensitivity to electric fields varied between species, with yeasts being more sensitive than bacteria. The research suggests electric fields can kill microbes through a non-thermal mechanism.
Fresh Juice treated with PEF and Pascalisation (HPP)Wouter de Heij
This document describes a study comparing the impact of mild heat pasteurization, high pressure processing, and pulsed electric field processing on orange juice quality. Orange juice was subjected to one of these three processing methods or remained untreated. Samples were then analyzed for microbial levels and quality attributes immediately after processing and during two months of refrigerated storage. The goal was to determine the effect of these alternative pasteurization methods on orange juice quality compared to traditional heat pasteurization.
More information can be found on:
- www.purepulse.eu
- http://www.pinterest.com/toptechtalks/purepulse-pef-20/
- http://en.topwiki.nl/index.php/PurePulse_-_PEF_2.0
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.
Evaluation of quality changes of blueberry juice during refrigerated storage after high-pressure and pulsed electric fields processing.
More information:
www.cwp-bv.nl
www.purepulse.eu
This document summarizes a study examining consumer attitudes towards apple juice produced using two new food processing technologies: high-pressure processing (HPP) and pulsed electric field processing (PEF). Interviews were conducted in Norway, Denmark, Hungary, and Slovakia using a means-end chain approach. The study found that consumers recognized benefits of HPP and PEF juices over conventionally pasteurized juice, such as better taste and nutrition. However, some consumers expressed skepticism about potential risks of PEF. The researchers conclude it is important for producers to provide evidence that new technologies are safe in order to gain consumer acceptance of resulting food products.
Effect of carotenoids levels in PEF treated Orange Juice during storage CoolWave Processing b.v.
This study examined the effects of non-thermal processing (pulsed electric fields and high hydrostatic pressure) and pasteurization on carotenoid levels in orange juice. The results showed that pasteurization significantly decreased total carotenoid concentration compared to fresh orange juice, while decreases were less for pulsed electric field and high pressure processing. During refrigerated storage, carotenoid levels declined more quickly in pasteurized orange juice than juices treated with non-thermal methods. Thus, non-thermal technologies better maintain carotenoid levels in orange juice compared to conventional thermal pasteurization.
General background PEF technology to perform cold pasteurization of juicesCoolWave Processing b.v.
General information about PEF.
PurePulse is the second generation PEF excellent to extend the shelf-life of cold pressed juices or NFC fruit juices.
See also:
www.purepulse.eu
www.topwiki.nl
www.cwp-bv.nl
This document summarizes research demonstrating that high electric fields can kill bacteria and yeasts. The researchers applied direct current pulses up to 25 kV/cm to suspensions of various microorganisms. They found that the electric fields caused death that was not due to electrolysis products or temperature increases. Higher field strengths and longer total pulse times resulted in greater killing of microbes. The sensitivity to electric fields varied between species, with yeasts being more sensitive than bacteria. The research suggests electric fields can kill microbes through a non-thermal mechanism.
Fresh Juice treated with PEF and Pascalisation (HPP)Wouter de Heij
This document describes a study comparing the impact of mild heat pasteurization, high pressure processing, and pulsed electric field processing on orange juice quality. Orange juice was subjected to one of these three processing methods or remained untreated. Samples were then analyzed for microbial levels and quality attributes immediately after processing and during two months of refrigerated storage. The goal was to determine the effect of these alternative pasteurization methods on orange juice quality compared to traditional heat pasteurization.
More information can be found on:
- www.purepulse.eu
- http://www.pinterest.com/toptechtalks/purepulse-pef-20/
- http://en.topwiki.nl/index.php/PurePulse_-_PEF_2.0
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.
DOI: 10.21276/ijlssr.2016.2.4.18
ABSTRACT- The Jambulor jambolan has been used for many years in traditional Indian medicine as treatment for
various diseases for example, diabetes mellitus, as well as bactericide. This study aimed to determine the conductivity in
different samples of a freeze-dried aqueous extract of Syzygium jambolanum. The readings of the electrical voltages of the
samples subjected to different treatment conditions were carried out in a pH meter. Depending on the performed statistical
analysis could be consttar a significant difference (p <0.001) among all samples analyzed groups. In view of the results
obtained, it can be suggested que the behavior related to changes in the electrical voltage values of the samples of an
aqueous extract of Syzygium jambolum, is related to the presence of molecules derived from flavonoids with antioxidant
properties, which can be molecules anthocyanin, which may be present in the samples of said plant extract Studied. Key-words- Syzygium jambolanum, Anthocyanin, Flavonoids, Atioxidant, Natural extract
Thermal stability of two xylanases from Macrotermes subhyalinus little soldie...INNS PUBNET
The knowledge on thermal inactivation kinetics of enzymes is necessary to allow their adequate utilization as natural biopreservatives in the food industry and technology applications. In this work, the kinetics of thermal inactivation was studied for the previously purified and characterized xylanases Xyl1 and Xyl2 from Macrotermes subhyalinus little soldier. Samples of xylanases were treated at different time-temperature combinations in the range of 5-60 min at 50-65°C and the kinetic and thermodynamic parameters for xylanases were calculated. The inactivation kinetic follows a first-order reaction with k-values between 0.0192 ± 0.0002 to 0.0405 ± 0.0003 and 0.0119 ± 0.0005 to 0.0418 ± 0.0004 min-1 for Xyl1 and Xyl2, respectively. Activation energy (Ea) and Z-values were estimated to 48.08 ± 1.84 kJ mol-1 and 43.47 ± 3.02°C for Xyl1, 75.52 ± 3.52 kJ.mol-1 and 27.77 ± 1.87°C for Xyl2. The catalytic reactions of both xylanases are endothermic due to positive enthalpy. The high value obtained for the variation in enthalpy of activation indicates that a high amount of energy is required to initiate denaturation, probably due to the molecular conformation of xylanases. All results suggest that both xylanases are relatively resistant to long heat treatments up to 50°C.
thermal and pulsed electric fields pasteurization of apple juiceGise Hernandez
Thermal and pulsed electric fields pasteurization of apple juice were compared. Both methods effectively reduced spoilage microorganisms like Lactobacillus brevis and Saccharomyces cerevisiae. However, pulsed electric field (PEF) pasteurization had less effect on physicochemical properties and volatile flavor compounds compared to thermal pasteurization. Specifically, pH and total acidity were minimally affected by both methods, but phenolic content and concentrations of volatile compounds showed greater retention after PEF treatment versus thermal treatment. PEF pasteurization is a promising non-thermal alternative for maintaining higher quality attributes in apple juice.
Pulsed electric field (PEF) technology uses short, high voltage electric pulses to induce pores in cell membranes, causing microbial inactivation and cell disintegration without significantly heating the food. This allows for longer shelf life and fresh quality retention compared to thermal pasteurization. PEF works by exceeding the critical transmembrane potential of cells, typically around 10 kV/cm for E. coli. It is effective against vegetative microbes and can reduce microbial loads by 4-6 logs but has limited effectiveness against spores, viruses or enzymes. PEF is suitable for liquid, semi-liquid and some solid foods but requires expensive equipment and refrigeration to extend shelf life.
Pulsed electric field (PEF) technology uses short, intense electric pulses to non-thermally pasteurize liquids and semi-liquid foods. PEF systems generate high voltage pulses between electrodes to irreversibly break down microbial cell membranes. PEF processed foods maintain fresh qualities like flavor, color and nutrients since no heat is used. While PEF can extend shelf-life, products are generally refrigerated for safety or quality. PEF is a promising alternative to thermal pasteurization for heat-sensitive foods.
Non thermal processing of food- Pulsed electric field and visible lightT. Tamilselvan
This document provides information on pulsed electric field (PEF) and pulsed visible light processing of foods. PEF uses short electric pulses to preserve foods through electroporation of microbial cell membranes, while minimizing heat production. PEF has been shown to effectively inactivate various microbes in foods like milk, eggs and juices. Pulsed visible light also uses intense, brief pulses of light to inactivate microbes in foods photochemically and through localized heating. Both techniques are non-thermal alternatives to traditional food processing that reduce degradation of nutritional and sensory qualities compared to heat treatments.
This document discusses several applications of pulsed electric fields (PEF) in food processing, including juice processing, extraction of plant oils and sugars, meat and fish treatment, and microbial decontamination. PEF works by permeabilizing cell membranes through electropermeabilization, allowing for increased mass transfer and extraction of intracellular components. Its applications provide potential to enhance conventional techniques and increase yields while reducing processing times and temperatures.
Hypoglycemic effect of gongronema latifolia extracts in ratsAlexander Decker
This study investigated the hypoglycemic effects of water and ethanolic extracts of Gongronema latifolia leaves in rats. Phytochemical analysis found both extracts contained alkaloids, saponins, tannins, cardiac glycosides, flavonoids and high levels of polyphenols. Rats treated with various doses of both extracts for 21 days had significantly reduced blood glucose levels compared to controls, in a dose-dependent manner. The polyphenol content may cause insulin-like effects by binding insulin receptors or stimulating insulin release, reducing blood glucose similarly to insulin and justifying G. latifolia's traditional use for treating diabetes.
This document summarizes a study that investigated the use of atmospheric cold plasma to decontaminate radicchio (red chicory) leaves. The researchers treated radicchio leaves with cold plasma for 15 or 30 minutes. They then analyzed the effects on microbial reduction, antioxidant activity, and quality attributes over several days of storage. They found that a 15-minute treatment significantly reduced E. coli levels, while a 30-minute treatment was needed to significantly reduce L. monocytogenes. The antioxidant activity and quality of the radicchio were maintained after cold plasma treatment. The study suggests cold plasma may be a promising non-thermal method for decontaminating leafy vegetables while preserving quality and nutritional properties.
Cold Plasma- non thermal technology for food processing.asima shafi
This document provides a seminar report on cold plasma technology for food processing. It discusses:
1. What cold plasma is and how it is generated at near room temperature for food applications.
2. Recent trends in using cold plasma for various food applications beyond microbial decontamination such as functionalization and waste processing.
3. The chemistry involved in cold plasma including homogeneous gas-phase reactions and heterogeneous reactions at surfaces.
4. The different types of cold plasma systems including remote, direct, and atmospheric pressure systems.
Pharmaceutical Biotechnology on Modern Technological PlatformAshikur Rahman
This document discusses how modern biotechnology influences technological platforms. It explains that biotechnology uses living organisms to develop useful products through techniques like recombinant DNA and genetic engineering. These allow genes to be moved between organisms, influencing their traits. The document provides examples of applications in healthcare, agriculture, industry, and the environment. It also describes different branches of biotechnology like bioinformatics, green biotechnology, red biotechnology, and white biotechnology. Finally, it discusses how genetic engineering can help crops gain resistance to diseases and insects, reducing the need for pesticides and helping crops withstand harsh conditions.
Antioxidant activity, photosynthetic rate, and Spectral mass in bean Plants (...IJEABJ
This document summarizes a study that examined the effects of various defense activators (jasmonic acid, salicylic acid, Trichoderma asperellum, and Bacillus pumilus) on antioxidant activity, photosynthetic rate, stomatal conductance, and metabolic profile in bean plants (Phaseolus vulgaris L.). The study found that jasmonic acid and T. asperellum increased antioxidant enzyme activity, photosynthetic rate, and stomatal conductance in the plants. Mass spectrometry analysis also revealed a greater number and quantity of metabolites/masses in the T. asperellum treated plants compared to the other treatments. The results suggest that some defense activators can
Biotechnology, scope, groups of organisms used biotechnology tools, red biotechnology, biologics:products of biotechnology,advantages and limitations of biotechnology, pharmaceuticals vs biologics, rDNA technology, manufacture of biologics, therapeutic biologics, recombinant vaccines, marketed biologics, biosimilars: Indian scenario
Non thermal plasma as a new food preservation methodMaya Sharma
This document discusses the use of non-thermal plasma as a new food preservation method. It introduces plasma and some devices that can generate it, such as dielectric barrier discharges. Plasma contains reactive oxygen and nitrogen species that can damage microbial cell membranes and their DNA. Experiments have shown plasma reducing microorganism populations by up to 5 log after a few seconds of exposure. Plasma technology may help combat biofilms that form on food processing surfaces. The document concludes that non-thermal plasma is an emerging and promising disinfection method for food preservation.
Effects of renewal pattern of recycled nutrient solution on the ion balance i...gugabione
Ion imbalance in recycled nutrient solutions is caused by selective ion uptake of plants, which occurs at different
rates in different growth stages. The objectives of this study were to investigate the ion balances in both recycled nutrient
solutions and rockwool media using different renewal patterns for the nutrient solutions, and to analyze the subsequent effects
on uptake of water and nutrients. Over 12 weeks of paprika cultivation, two different renewal patterns (week units) of 6-4-2
and 8-2-2 weeks were compared with a constant renewal pattern of 4-4-4 weeks (control). The nutrient solution in the reservoir
tank was constantly maintained at EC 2.5 dS・m
-1
and pH 5.5-6.5. The changes in the ion balance with the 4-4-4 week pattern
were smaller than those with the other treatments. In the early growth stage, however, the ion balances similarly changed
among all treatments. Greater changes were subsequently observed for the 6-4-2 week pattern. Although fruit yield and shoot
fresh weight of paprika were the lowest with 6-4-2 renewal pattern, no significant differences were observed. Our results indicate
that renewal intervals can be extended in consideration of growth stage for more efficient and practical operations in closed
soilless cultures.
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.
Bioprocess modeling involves creating mathematical models of biological systems like cell cultures to improve process understanding and performance. Models are developed based on experimental data and can then be used to predict system behavior in different conditions. The modeling approach requires fewer experiments than the empirical approach but takes more time to develop models. Key steps in modeling include problem definition, model formulation, parameter estimation, validation and use of the model for design, optimization and control. Dynamic models are needed to represent transient system behavior important for control applications. Common modeling examples include reaction kinetics, bioreactor systems and sensor models.
Effect of high electric fields on microorganisms_killing bacteria and yeasts ...CoolWave Processing b.v.
This document summarizes research demonstrating that high electric fields can kill bacteria and yeasts. The researchers applied direct current pulses up to 25 kV/cm to suspensions of various microorganisms. They found that the electric fields caused death that was not due to electrolysis products or temperature increases. Higher field strengths and longer total pulse times resulted in greater killing of microbes. The sensitivity to electric fields varied between species, with yeasts being more sensitive than bacteria. The degree of killing depended on the electric field strength rather than current density or energy input. This suggests a non-thermal lethal effect of very high electric fields on microorganisms.
DOI: 10.21276/ijlssr.2016.2.4.18
ABSTRACT- The Jambulor jambolan has been used for many years in traditional Indian medicine as treatment for
various diseases for example, diabetes mellitus, as well as bactericide. This study aimed to determine the conductivity in
different samples of a freeze-dried aqueous extract of Syzygium jambolanum. The readings of the electrical voltages of the
samples subjected to different treatment conditions were carried out in a pH meter. Depending on the performed statistical
analysis could be consttar a significant difference (p <0.001) among all samples analyzed groups. In view of the results
obtained, it can be suggested que the behavior related to changes in the electrical voltage values of the samples of an
aqueous extract of Syzygium jambolum, is related to the presence of molecules derived from flavonoids with antioxidant
properties, which can be molecules anthocyanin, which may be present in the samples of said plant extract Studied. Key-words- Syzygium jambolanum, Anthocyanin, Flavonoids, Atioxidant, Natural extract
Thermal stability of two xylanases from Macrotermes subhyalinus little soldie...INNS PUBNET
The knowledge on thermal inactivation kinetics of enzymes is necessary to allow their adequate utilization as natural biopreservatives in the food industry and technology applications. In this work, the kinetics of thermal inactivation was studied for the previously purified and characterized xylanases Xyl1 and Xyl2 from Macrotermes subhyalinus little soldier. Samples of xylanases were treated at different time-temperature combinations in the range of 5-60 min at 50-65°C and the kinetic and thermodynamic parameters for xylanases were calculated. The inactivation kinetic follows a first-order reaction with k-values between 0.0192 ± 0.0002 to 0.0405 ± 0.0003 and 0.0119 ± 0.0005 to 0.0418 ± 0.0004 min-1 for Xyl1 and Xyl2, respectively. Activation energy (Ea) and Z-values were estimated to 48.08 ± 1.84 kJ mol-1 and 43.47 ± 3.02°C for Xyl1, 75.52 ± 3.52 kJ.mol-1 and 27.77 ± 1.87°C for Xyl2. The catalytic reactions of both xylanases are endothermic due to positive enthalpy. The high value obtained for the variation in enthalpy of activation indicates that a high amount of energy is required to initiate denaturation, probably due to the molecular conformation of xylanases. All results suggest that both xylanases are relatively resistant to long heat treatments up to 50°C.
thermal and pulsed electric fields pasteurization of apple juiceGise Hernandez
Thermal and pulsed electric fields pasteurization of apple juice were compared. Both methods effectively reduced spoilage microorganisms like Lactobacillus brevis and Saccharomyces cerevisiae. However, pulsed electric field (PEF) pasteurization had less effect on physicochemical properties and volatile flavor compounds compared to thermal pasteurization. Specifically, pH and total acidity were minimally affected by both methods, but phenolic content and concentrations of volatile compounds showed greater retention after PEF treatment versus thermal treatment. PEF pasteurization is a promising non-thermal alternative for maintaining higher quality attributes in apple juice.
Pulsed electric field (PEF) technology uses short, high voltage electric pulses to induce pores in cell membranes, causing microbial inactivation and cell disintegration without significantly heating the food. This allows for longer shelf life and fresh quality retention compared to thermal pasteurization. PEF works by exceeding the critical transmembrane potential of cells, typically around 10 kV/cm for E. coli. It is effective against vegetative microbes and can reduce microbial loads by 4-6 logs but has limited effectiveness against spores, viruses or enzymes. PEF is suitable for liquid, semi-liquid and some solid foods but requires expensive equipment and refrigeration to extend shelf life.
Pulsed electric field (PEF) technology uses short, intense electric pulses to non-thermally pasteurize liquids and semi-liquid foods. PEF systems generate high voltage pulses between electrodes to irreversibly break down microbial cell membranes. PEF processed foods maintain fresh qualities like flavor, color and nutrients since no heat is used. While PEF can extend shelf-life, products are generally refrigerated for safety or quality. PEF is a promising alternative to thermal pasteurization for heat-sensitive foods.
Non thermal processing of food- Pulsed electric field and visible lightT. Tamilselvan
This document provides information on pulsed electric field (PEF) and pulsed visible light processing of foods. PEF uses short electric pulses to preserve foods through electroporation of microbial cell membranes, while minimizing heat production. PEF has been shown to effectively inactivate various microbes in foods like milk, eggs and juices. Pulsed visible light also uses intense, brief pulses of light to inactivate microbes in foods photochemically and through localized heating. Both techniques are non-thermal alternatives to traditional food processing that reduce degradation of nutritional and sensory qualities compared to heat treatments.
This document discusses several applications of pulsed electric fields (PEF) in food processing, including juice processing, extraction of plant oils and sugars, meat and fish treatment, and microbial decontamination. PEF works by permeabilizing cell membranes through electropermeabilization, allowing for increased mass transfer and extraction of intracellular components. Its applications provide potential to enhance conventional techniques and increase yields while reducing processing times and temperatures.
Hypoglycemic effect of gongronema latifolia extracts in ratsAlexander Decker
This study investigated the hypoglycemic effects of water and ethanolic extracts of Gongronema latifolia leaves in rats. Phytochemical analysis found both extracts contained alkaloids, saponins, tannins, cardiac glycosides, flavonoids and high levels of polyphenols. Rats treated with various doses of both extracts for 21 days had significantly reduced blood glucose levels compared to controls, in a dose-dependent manner. The polyphenol content may cause insulin-like effects by binding insulin receptors or stimulating insulin release, reducing blood glucose similarly to insulin and justifying G. latifolia's traditional use for treating diabetes.
This document summarizes a study that investigated the use of atmospheric cold plasma to decontaminate radicchio (red chicory) leaves. The researchers treated radicchio leaves with cold plasma for 15 or 30 minutes. They then analyzed the effects on microbial reduction, antioxidant activity, and quality attributes over several days of storage. They found that a 15-minute treatment significantly reduced E. coli levels, while a 30-minute treatment was needed to significantly reduce L. monocytogenes. The antioxidant activity and quality of the radicchio were maintained after cold plasma treatment. The study suggests cold plasma may be a promising non-thermal method for decontaminating leafy vegetables while preserving quality and nutritional properties.
Cold Plasma- non thermal technology for food processing.asima shafi
This document provides a seminar report on cold plasma technology for food processing. It discusses:
1. What cold plasma is and how it is generated at near room temperature for food applications.
2. Recent trends in using cold plasma for various food applications beyond microbial decontamination such as functionalization and waste processing.
3. The chemistry involved in cold plasma including homogeneous gas-phase reactions and heterogeneous reactions at surfaces.
4. The different types of cold plasma systems including remote, direct, and atmospheric pressure systems.
Pharmaceutical Biotechnology on Modern Technological PlatformAshikur Rahman
This document discusses how modern biotechnology influences technological platforms. It explains that biotechnology uses living organisms to develop useful products through techniques like recombinant DNA and genetic engineering. These allow genes to be moved between organisms, influencing their traits. The document provides examples of applications in healthcare, agriculture, industry, and the environment. It also describes different branches of biotechnology like bioinformatics, green biotechnology, red biotechnology, and white biotechnology. Finally, it discusses how genetic engineering can help crops gain resistance to diseases and insects, reducing the need for pesticides and helping crops withstand harsh conditions.
Antioxidant activity, photosynthetic rate, and Spectral mass in bean Plants (...IJEABJ
This document summarizes a study that examined the effects of various defense activators (jasmonic acid, salicylic acid, Trichoderma asperellum, and Bacillus pumilus) on antioxidant activity, photosynthetic rate, stomatal conductance, and metabolic profile in bean plants (Phaseolus vulgaris L.). The study found that jasmonic acid and T. asperellum increased antioxidant enzyme activity, photosynthetic rate, and stomatal conductance in the plants. Mass spectrometry analysis also revealed a greater number and quantity of metabolites/masses in the T. asperellum treated plants compared to the other treatments. The results suggest that some defense activators can
Biotechnology, scope, groups of organisms used biotechnology tools, red biotechnology, biologics:products of biotechnology,advantages and limitations of biotechnology, pharmaceuticals vs biologics, rDNA technology, manufacture of biologics, therapeutic biologics, recombinant vaccines, marketed biologics, biosimilars: Indian scenario
Non thermal plasma as a new food preservation methodMaya Sharma
This document discusses the use of non-thermal plasma as a new food preservation method. It introduces plasma and some devices that can generate it, such as dielectric barrier discharges. Plasma contains reactive oxygen and nitrogen species that can damage microbial cell membranes and their DNA. Experiments have shown plasma reducing microorganism populations by up to 5 log after a few seconds of exposure. Plasma technology may help combat biofilms that form on food processing surfaces. The document concludes that non-thermal plasma is an emerging and promising disinfection method for food preservation.
Effects of renewal pattern of recycled nutrient solution on the ion balance i...gugabione
Ion imbalance in recycled nutrient solutions is caused by selective ion uptake of plants, which occurs at different
rates in different growth stages. The objectives of this study were to investigate the ion balances in both recycled nutrient
solutions and rockwool media using different renewal patterns for the nutrient solutions, and to analyze the subsequent effects
on uptake of water and nutrients. Over 12 weeks of paprika cultivation, two different renewal patterns (week units) of 6-4-2
and 8-2-2 weeks were compared with a constant renewal pattern of 4-4-4 weeks (control). The nutrient solution in the reservoir
tank was constantly maintained at EC 2.5 dS・m
-1
and pH 5.5-6.5. The changes in the ion balance with the 4-4-4 week pattern
were smaller than those with the other treatments. In the early growth stage, however, the ion balances similarly changed
among all treatments. Greater changes were subsequently observed for the 6-4-2 week pattern. Although fruit yield and shoot
fresh weight of paprika were the lowest with 6-4-2 renewal pattern, no significant differences were observed. Our results indicate
that renewal intervals can be extended in consideration of growth stage for more efficient and practical operations in closed
soilless cultures.
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.
Bioprocess modeling involves creating mathematical models of biological systems like cell cultures to improve process understanding and performance. Models are developed based on experimental data and can then be used to predict system behavior in different conditions. The modeling approach requires fewer experiments than the empirical approach but takes more time to develop models. Key steps in modeling include problem definition, model formulation, parameter estimation, validation and use of the model for design, optimization and control. Dynamic models are needed to represent transient system behavior important for control applications. Common modeling examples include reaction kinetics, bioreactor systems and sensor models.
Effect of high electric fields on microorganisms_killing bacteria and yeasts ...CoolWave Processing b.v.
This document summarizes research demonstrating that high electric fields can kill bacteria and yeasts. The researchers applied direct current pulses up to 25 kV/cm to suspensions of various microorganisms. They found that the electric fields caused death that was not due to electrolysis products or temperature increases. Higher field strengths and longer total pulse times resulted in greater killing of microbes. The sensitivity to electric fields varied between species, with yeasts being more sensitive than bacteria. The degree of killing depended on the electric field strength rather than current density or energy input. This suggests a non-thermal lethal effect of very high electric fields on microorganisms.
PurePulse technology allows fresh fruit juices to have a longer shelf life of at least 21 days while preserving their vitamins, aromas, colors, and flavors. This extended shelf life opens up new market opportunities by enabling simplified distribution over a larger sales area with less product loss. The technology has been used successfully in the medical industry for years. It improves upon previous pulse electric field (PEF) preservation methods by employing innovations that achieve the same safety with less capital costs and heating while retaining more of the juices' fresh properties.
Presentación en el Congreso Campings Federación Andaluza: del plan de reposicionamiento de la marca Camping vía CECC. Confederación de Empresarios del Camping y Caravaning.
A condensed version of the presentation given by Gadling Social Media Editor Jessica Marati at the LA Times Travel Show on February 22, 2013. For more information on the subject matter, reach out to @jessmarati on Twitter.
Homo Ludens & Social Gaming: Playing Is A Core Human DesireWooga
Playing is a core human desire, and flow theory suggests that optimal human experiences occur when challenges are balanced with skills. Social games aim to achieve flow for all by being social, having no barriers to entry, allowing for quick sessions, and enabling play anywhere. Social interactions like helping friends and competing further enhance the experience.
This document discusses cell perforation using pulsed electric fields (PEF) to preserve fresh juice. It notes that microbes are naturally present in fresh juice and can exponentially grow, potentially causing foodborne illness outbreaks. The document then explains that applying a pulsed electric field to the juice using PEF technology creates an electric field distribution that perforates microbe cell membranes, immediately eliminating their viability. The result is healthy juice with an extended shelf-life of 21-60 days without refrigeration.
PurePulse es una tecnología que permite conservar zumos frescos por hasta 21 días manteniendo las vitaminas, colorantes, fragancias y aromas mediante el uso de campos eléctricos pulsados. Esto simplifica la distribución, abre nuevos mercados y reduce las pérdidas, permitiendo que los zumos frescos lleguen a 460 millones de consumidores potenciales.
This document provides an overview of information for someone visiting Krakow, Poland. It begins with general information about Poland's climate, geography, history, famous people, politics, economy, religion, sports and holidays. It then provides useful information for visitors about food, currency, time zone, prices, electricity, communication, business hours and useful phrases. The document concludes by providing specific information about Krakow, including how to get there, its location, history, universities, cultural life, nightlife and places to visit in and around the city.
Cool Wave Processing develops and sells PurePulse equipment for pulsed electric field (PEF) pasteurization. PEF uses short electric pulses to pasteurize fresh juices and other products at temperatures below 40°C, preserving fresh taste and quality while extending shelf life to over 21 days. Cool Wave's PurePulse technology provides a commercial-scale industrial PEF solution that can treat 600-1800 liters per hour with lower energy input and better quality outcomes than previous PEF technologies or alternatives like high pressure processing.
This presentation summarizes pulsed electric field (PEF) technology. PEF involves applying high-voltage electric pulses between electrodes to food for less than one second. This minimizes energy loss from heating. PEF induces pores in cell membranes through electroporation, inactivating microbes without detrimental effects to food quality. A square pulse generator uses capacitors, inductors, and solid state switches to produce the high-voltage pulses. Processing factors like electric field strength, temperature, time of exposure, and pulse shape influence microbial inactivation during PEF. PEF improves the shelf life of foods like bread, milk, fruit juices, and more through more efficient microbial inactivation than conventional heat treatment.
Este documento presenta un ejemplo de diseño de mezcla de concreto. Detalla los pasos requeridos como elegir el slump, tamaño máximo del agregado, estimar la cantidad de agua y aire de la mezcla, calcular la relación agua/cemento, y estimar los contenidos de cemento, agregado grueso y fino. Luego muestra un ejemplo numérico aplicando estos pasos para diseñar una mezcla con resistencia requerida de 175 kg/cm2.
This document discusses pulsed electric field (PEF) technology. PEF uses short electric pulses to preserve foods without heat, maintaining fresh qualities and nutrients. It can extend shelf life while ensuring safety. PEF works by applying high-intensity pulses that cause microbial cell membranes to break down without significantly heating the food. PEF has various applications, including pasteurizing juices and milk. It provides advantages like minimal processing, color/flavor retention, and higher nutritional value compared to thermal treatments.
Pulsed Electric Field Processing of FoodStella Mariem
The document discusses various process factors that affect microbial inactivation using pulsed electric fields, including electric field intensity, temperature, pressure, and time of exposure. It explains that increasing any of these factors leads to greater inactivation. It also notes different pulse wave shapes that can be used, and describes how the high voltage electric field pulses cause electroporation, making cell membranes permeable and leading to cell death.
Similar to Pulsed electric field processing of different fruit juices: Impact of pH and temperature on inactivation of spoilage and pathogenic micro-organisms - International journal of food microbiology 2014 timmermans et al.
This study compared the effects of pulsed electric field (PEF) processing and high-temperature short-time (HTST) thermal pasteurization on the shelf life and quality attributes of apple juice. Apple juice treated with both methods was analyzed for microbial growth and quality changes over 168 days of storage. PEF processing was less effective at reducing microbial counts compared to HTST, but maintained better color and sensory qualities closer to fresh juice. While HTST provided greater microbial safety, PEF processing has potential as a non-thermal alternative for maintaining nutritional and sensory qualities of fruit juices if further design improvements can enhance its microbial inactivation effectiveness to meet food safety standards.
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.
More information can be found on:
- www.purepulse.eu
- http://www.pinterest.com/toptechtalks/purepulse-pef-20/
- http://en.topwiki.nl/index.php/PurePulse_-_PEF_2.0
Influence of gongronema latifolium leaf extracts treatment on some hepatic...Alexander Decker
This document summarizes a study on the effects of extracts from the leaves of Gongronema latifolium on hepatic enzyme activity in rats. Rats were treated with various doses of ethanolic and water extracts for 7 days. Blood samples were then analyzed for liver enzyme levels. The results showed that the extracts increased the activity of AST and ALT liver enzymes at doses of 25mg/kg, indicating potential liver cell damage. The extracts also increased serum amylase levels in a dose-dependent manner. However, the extracts did not significantly affect blood urea levels. The conclusion is that while G. latifolium extracts may have some medical benefits, chronic high dose use could adversely impact liver function.
Analysis of some phenolic compounds and free radicalLeozaav
This document analyzes the phenolic compounds and free radical scavenging activity of three strawberry cultivars ('San Andreas', 'Benicia', and 'Albion') during storage. Freshly harvested fruits were stored under refrigerated (4°C) and frozen (-85°C) conditions for 7 days. Total phenolic content, total flavonoid content, and free radical scavenging activity were measured in fresh, refrigerated, and frozen fruits. The 'San Andreas' cultivar had the highest total phenolic content of 0.326 g GAE/100g fresh weight after refrigeration. 'San Andreas' also had the highest levels of total flavonoids after refrigeration. The 'Ben
This document summarizes a seminar presentation on pulsed electric field (PEF) food processing. PEF uses short pulses of electricity to preserve foods without heat, extending shelf life while maintaining quality. It can pasteurize liquids like juice and milk. The document discusses the history of PEF, how it works using electric fields to inactivate microbes, applications in juice and other foods, advantages like minimal nutrient loss, and limitations like only working on liquids. PEF is a promising non-thermal food processing technique still under development.
This document summarizes research optimizing culture conditions for the bacteria Acetobacter aceti TISTR 102 using coconut water supplemented with banana juice. The effects of adding different volumes of banana juice, concentrations of ammonium sulfate and yeast extract, and shaking speeds on bacterial growth were investigated. Coconut water was found to be a suitable base medium, and supplementing it with 50% banana juice by volume resulted in the highest bacterial cell viability. Varying concentrations of ammonium sulfate and yeast extract did not significantly affect growth. Faster shaking speeds of 150 rpm produced higher cell viability than 120 rpm. The goal was to develop a low-cost growth medium utilizing agricultural byproducts for producing bacterial cultures.
This document summarizes research purifying and characterizing a novel antioxidant peptide from the hard-shelled mussel Mytilus coruscus. Enzymatic hydrolysis was used to generate hydrolysates from M. coruscus, which were screened for antioxidant activity. The papain hydrolysate showed the highest free radical scavenging activity. Further purification using chromatography yielded a novel 10 amino acid peptide. In vitro and in vivo assays found the peptide to have potent antioxidant effects, inhibiting oxidative stress markers and enhancing antioxidant enzyme activity in mice. This is the first report of an antioxidant peptide from M. coruscus with potential anti-inflammatory properties.
International Journal of Pharmaceutical Science Invention (IJPSI) is an international journal intended for professionals and researchers in all fields of Pahrmaceutical Science. IJPSI publishes research articles and reviews within the whole field Pharmacy and Pharmaceutical Science, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Effect of agitation speed on the morphology of Aspergillus Niger HFD5A-1 hyph...Haritharan Weloosamy
This document describes a study that investigated the effect of agitation speed on pectinase production and morphology of the fungus Aspergillus niger HFD5A-1 during submerged fermentation. The researchers found that agitation speed influenced pectinase production, with the maximum production achieved at 150 rpm. Higher or lower agitation speeds reduced production. Agitation speed also affected the fungus's morphology, changing from a surface mat at static conditions to spherical pellets at higher speeds. The study provides insight into how physical parameters like agitation impact enzyme production and fungal growth during fermentation.
This study evaluates the transformation dynamics of trenbolone acetate (TBA), an anabolic steroid used in beef cattle production that is a potent endocrine disruptor in aquatic life. Previous research discovered that TBA metabolites can reversibly transform between forms, depending on environmental conditions like temperature and pH. This reversible transformation has implications for the unexpected persistence and transport of TBA and suggests current occurrence data may underestimate bioactive steroid levels. The objectives of this study are to develop analytical methods to detect novel TBA photo-products, evaluate how reversible transformations impact transport risk, detect uncharacterized products in the field, and use modeling to predict impacts on agroecosystems. Key outcomes include optimized analytical methods and findings that reversible transformations
ABSTRACT- The invitro anti-inflammatory activity of various solvent fractions of Parkia biglobosa fruit bark was investigated using human red blood cell membrane stabilization, heat-induced hemolysis and protein denaturation methods. All the extracts of P. biglobosa fruit bark showed a concentration dependent increase in anti-inflammatory activity. The anti-inflammatory activity of the crude extract (60.8%, 58.3%, 78.2%) and last remaining aqueous extract (61.1%, 54.1%, 77.2%) have the maximum membrane stabilization, protection against hemolysis and albumin denatura-tion respectively which was comparable to Diclofenac sodium (61.4%, 60.6%, 100%) at 400μg/ml concentration. This study suggests that P. biglobo-sa fruit bark posses enough potential to reduce inflammation, hence directs the importance of further research and development of novel anti-inflammatory agents. Key words- Invitro anti-inflammatory, fruit bark, HRBC membrane stabilization, hemolysis, protection
Involvement of Physicochemical Parameters on Pectinase Production by Aspergil...Haritharan Weloosamy
This study investigated the effect of physicochemical parameters on pectinase production by Aspergillus niger HFD5A-1 under submerged fermentation. The optimal conditions found were pH 4.5, temperature of 30°C, inoculum size of 2% (v/v) 1 × 106 cell/mL, agitation speed of 150 rpm, 1.80% (w/v) citrus pectin as the carbon source, and 0.40% (w/v) peptone as the nitrogen source. Under these conditions, pectinase production reached 2.51 U/mL after 6 days, representing a 97.6% increase compared to the initial conditions. The
This document describes research to develop mathematical models that predict the time required to inactivate Salmonella in orange juice using high-pressure processing (HPP). Models were developed for both Australian Valencia orange juice (pH 4.3) and navel orange juice (pH 3.7) relating time to inactivation to pressure level (300-600 MPa) and initial Salmonella inoculation level (3-7 log CFU/ml). The models can help juice processors select HPP conditions to achieve at least a 5-log reduction of Salmonella, as required by the FDA. Validation studies showed pressure-treated Salmonella may survive if conditions allow for growth, highlighting the importance of refrigerated storage. These predictive models allow
High voltage pulse technique or High intensity pulsed electric field processing involves the application of electric pulses of high voltage
20-80 kV/cm to the food placed between two electrodes.
The applied electric field create a pores on the cell membrane, thus the phenomenon known as Electroporation or electropermeabilization.
The effect of Electroporation can be divided into four steps:
An increase in the transmembrane potential
Pore formation
Evolution of the number and size of the pores
Pore resealing
This study analyzed G proteins, proteomics, glycomics and metabolomics in plants grown under protected agriculture. Protein profiles showed variation between phenological stages, and western blot detected G protein subunits of 37, 46, and 57 kDa. Two-dimensional electrophoresis identified a 57 kDa protein with a pI of 5.9. Phloem sap proteins also detected G protein subunits of 28, 67 kDa between stages. Sugar analysis found glucose, fructose and sucrose varied between stages, with neutral sugars dominated by glucose, galactose and mannose. The Lightbourn Biochemical Model was applied to integrate results and propose bionanotechnology and biodynamic nutrition for high agricultural competitiveness and sustainability
The study identified and characterized a BAHD family acyltransferase in poplar, PtrPHBMT1, that transfers p-hydoxybenzoate from its thio-ester donor to the sinapyl alcohol monolignol. This results in the conjugate being incorporated into nascent lignin polymers, leading to ester-linked p-hydoxybenzoate pendant groups and altering lignin properties. Genetically manipulating this enzyme controlling lignin p-hydroxybenzoylation could allow accumulating this high-value chemical, p-hydoxybenzoate, in lignocellulosic biomass and improve biofuel production and timber dur
(48)Screening and identifiation of Bacillus sp. isolated from traditional Vie...minhdaovan
Fibrinolytic enzymes produced by microorganisms have been attractive in prevention and
treatment of cardiovascular diseases (CVDs) by their low-cost and safety. This study focused
on screening for the existence of firinolytic enzymes in Vietnamese traditional fermented
soybean paste products and isolation and identifiation of related bacteria. Sixteen fermented
soybean paste samples were collected over three regions of Vietnam in which seven samples
gave the positive results on firinolytic enzyme activity. Miso (MS) and Green Chili (GC)
samples had the highest firinolytic enzyme activities (1.81 and 0.77 FU/g, respectively).
According to morphological features, four strains of bacteria were isolated and all of them
were found to produce firinolytic enzymes. The enzyme activities produced by four isolated
strains were in a range of 29.7 - 77.9 FU/g after culturing on solid state media for 24 h. The
isolated strains were identifid as Bacillus amyloliquefaciens using 16 rRNA sequence and
phylogenetic analysis with 99% similarity
Assessing the Suitability of using Plant Latex as Immobilization Support for ...ijsrd.com
Horseradish peroxidase was immobilized onto latex from three different plants viz. Calotropis procera, Euphorbia royleana and Alstonia scholaris with 0.51 ± 0.01, 0.37 ± 0.01, 0.46 ± 0.01 mg/cm2 conjugation yield and 62.07 ± 0.85, 66.1 ± 0.85, 71.24 ± 0.80 % retention of specific activity respectively. The support, before and after addition of peroxidase was characterized using scanning electron microscopy (SEM) and Fourier transmission infra-red spectroscopy (FTIR). Optimum pH, optimum temperature and changes in kinetic parameters (Ea, Km and Vmax) for immobilized peroxidases were studied and found to differ from that of free peroxidase. Alstonia scholaris latex was most effective in stabilizing the structure of peroxidase during storage at 4°C, whereas thermal stability and reusability of peroxidase was better on Calotropis procera latex. Analytical use of Calotropis procera latex bound peroxidase for determination of phenolic content of fruit juices has also been demonstrated.
Similar to Pulsed electric field processing of different fruit juices: Impact of pH and temperature on inactivation of spoilage and pathogenic micro-organisms - International journal of food microbiology 2014 timmermans et al. (20)
Ang Chong Yi’s Culinary Revolution: Pioneering Plant-Based Meat Alternatives ...Ang Chong Yi Singapore
In the heart of Singapore’s bustling culinary scene, a visionary chef named Ang Chong Yi is quietly revolutionizing the way we think about food. His mission? To create delectable Ang Chong Yi Singapore — Plant-based meat: Next-gen food alternatives that not only tantalize our taste buds but also contribute to a more sustainable future.
Panchkula offers a wide array of dining experiences. From traditional North Indian flavors to global cuisine, the city’s restaurants cater to every taste bud. Let’s dive into some of the best restaurants in Panchkula
The Menu affects everything in a restaurant; as our friend and FCSI consultant Bill Main says, “The Menu is your blueprint for profitability.”
Let’s start with the segment. What will be your marketing and brand positioning? It depends on what menu items you serve. What type of cooking methods and equipment will you use? GUEST EXPERIENCE = FACILITY (Space) DESIGN + MENU + SERVPOINTS™
W.H. Bender & Associates
408-784-7371
whb@whbender.com
www.whbender.com
San Jose, California
FOOD PSYCHOLOGY CHARLA EN INGLES SOBRE PSICOLOGIA NUTRICIONALNataliaLedezma6
Our decisions about what to put on our plate are far more intricate than simply following hunger cues. Food psychology delves into the fascinating world of why we choose the foods we do, revealing a complex interplay of emotions, stress, and even disorders.
A Review on Recent Advances of Packaging in Food IndustryPriyankaKilaniya
Effective food packaging provides number of purposes. It functions as a container to hold and transport the food product, as well as a barrier to protect the food from outside contamination such as water, light, odours, bacteria, dust, and mechanical damage by maintaining the food quality. The package may also include barriers to keep the product's moisture content or gas composition consistent. Furthermore, convenience is vital role in packaging, and the desire for quick opening, dispensing, and resealing packages that maintain product quality until fully consumed is increasing. To facilitate trading, encourage sales, and inform on content and nutritional attributes, the packaging must be communicative. For storage of food there is huge scope for modified atmosphere packaging, intelligent packaging, active packaging, and controlled atmosphere packaging. Active packaging has a variety of uses, including carbon dioxide absorbers and emitters, oxygen scavengers, antimicrobials, and moisture control agents. Smart packaging is another term for intelligent packaging. Edible packaging, self-cooling and self-heating packaging, micro packaging, and water-soluble packaging are some of the advancements in package material.
Cacao, the main component used in the creation of chocolate and other cacao-b...AdelinePdelaCruz
Cacao, the main component used in the creation of chocolate and other cacao-based products is cacao beans, which are produced by the cacao tree in pods. The Maya and Aztecs, two of the earliest Mesoamerican civilizations, valued cacao as a sacred plant and used it in religious rituals, social gatherings, and medical treatments. It has a long and rich cultural history.
Pulsed electric field processing of different fruit juices: Impact of pH and temperature on inactivation of spoilage and pathogenic micro-organisms - International journal of food microbiology 2014 timmermans et al.
2. Martínez et al., 2004a, 2004b; Gómez et al., 2005a, 2005b; Gurtler et al.,
2010; Heinz et al., 2003; Mosqueda-Melgar et al., 2007; Rodrigo et al.,
2001, 2003; Saldaña et al., 2011; Qin et al., 1995), however only a single
micro-organism or one type of juice was selected to evaluate the effect
of PEF. Here, we describe a comparative analysis including species
representing spoilage and pathogenic micro-organisms in varying
juices using treatment conditions based on an existing industrial
scale system for fresh fruit juice processing with a capacity of
1500 L/h and an electrical field strength of 20 kV/cm.
For industrial implementation, it is of paramount importance to de-
termine and validate effective process conditions and constraints in real
food systems with pathogens or realistic surrogates to minimize micro-
bial hazards. Furthermore, it is important to test this on a representative
PEF system, with the same configuration as the industrial system, as the
configuration of the system has a considerable effect on the effective-
ness of inactivation.
The objectives of this study were to investigate inactivation of spoil-
age and pathogenic micro-organisms in fruit juice, to assess the impact
of process parameters and juice composition on the effectiveness of the
PEF process, and to find a suitable model to predict the minimum re-
quired process conditions.
2. Material and methods
2.1. Selection of juice products
Fruit juices used in this study were fresh, non-heated not-from-
concentrate (NFC) juices delivered by a commercial producer of fruit
juices directly after production (orange juice, orange-strawberry juice,
tropical juice) or delivered frozen at −18 °C (lime juice). Watermelon
juice used to evaluate the survival of relevant micro-organisms was ex-
tracted directly from watermelons obtained from a local supermarket,
using a table juice extractor type HR 1861 (Philips) to obtain watermel-
on juice. One single batch of 30 L juice was squeezed, mixed and frozen
in batches of 1 L. Prior to an experiment, the watermelon juice was
thawed and prepared similar as the other juices. Since the matrix com-
position of NFC juices is subject to seasonal variation, apple juice
(Appelsientje Goudappel) and orange juice (Minute Maid) from con-
centrate (FC) were used for inactivation kinetics studies to ensure re-
producibility of experiments over time.
2.2. Preparation and analysis of juices
For all experiments, juices were pasteurized by heating them in glass
bottles filled with 1000 mL of fruit juice for 45 min in a water bath at
85 °C. For inactivation kinetics, orange juice and watermelon juice
were sieved after pasteurization using a sterile sieve (0.225 mm pore
size) to remove pulp, while apple juice did not contain any pulp.
Electric conductivity (Hi 933000, Hanna instruments) and pH
(Metrohm 744, Metrohm, Herisa, Switzerland) were measured of each
juice after inoculation with micro-organisms, and shown in Table 2.
For some experiments, the pH of watermelon juice was changed
from 5.3 to 3.6 by adding HCl.
2.3. Micro-organisms and culture conditions
Pathogenic and spoilage micro-organisms were selected based on
their association with and prevalence in fruit juices, their ability to sur-
vive and to grow in the juice matrices selected in this study and if
known, their resistance towards PEF, as this is inherent to species and
strain level (Gurtler et al., 2010). The micro-organisms were tested in
fresh NFC juices and FC juices with variation in pH, and evaluated
after 1, 4 and 7 days of incubation. Comparable results of survival
were found between both types of juices. The mentioned criteria lead
to the choice for the micro-organisms shown in Table 1. No survival
(i.e., decline in number of micro-organisms) was observed in high acidic
juices (pH 1.8), survival (i.e., a stable number of micro-organisms) was
observed in acid juices (pH 3.6) and growth (i.e., an increase in number
of micro-organisms) was observed for all micro-organisms in weak acid
juices (pH 5.3).
Fresh cultures of the yeast strain Saccharomyces cerevisiae (Table 1)
were prepared by plating from frozen stocks on glucose-peptone-
yeast (GPY) agar plates, containing 40 g glucose, 5 g peptone, 5 g
yeast extract and 15 g agar per 1 L distilled water. Plates were incubated
overnight at 25 °C. One single colony isolate was used for inoculation of
a 50 mL flask containing 10 mL GPY broth and cells were cultivated for
24 h at 25 °C in a shaking air incubator (Innova, 180 rpm). Of this over-
night culture, 0.1 mL was used for inoculation of 9.9 mL fresh GPY me-
dium supplemented with 1% of glucose in a 50 mL flask and incubated
for exactly 24 h at 20 °C and 180 rpm.
Fresh cultures of Salmonella enterica serotype Panama and
Escherichia coli strains (Table 1) were prepared from frozen stock cul-
tures that were plated on TSB (Oxoid) agar plates and incubated over-
night at 37 °C. Listeria monocytogenes strain (Table 1) was cultivated
on BHI (Oxoid) agar plates and incubated overnight at 30 °C. A single
colony isolate was used to inoculate a 50 mL flask with 10 mL TSB
(S. Panama, E. coli) or BHI broth (L. monocytogenes) and cultivated for
24 h at 20 °C in an Innova shaking incubator (180 rpm). Of this culture,
0.1 mL was used to inoculate 9.9 mL fresh TSB or BHI broth supple-
mented with 1% glucose (50 mL flask) and incubated for 24 h at 20 °C
and 180 rpm.
2.4. Determination of PEF inactivation kinetics
Inactivation kinetics of selected spoilage and pathogenic micro-
organisms associated with fruit juice were determined to identify opti-
mal PEF conditions for inactivation of the target organisms in apple juice
and orange juice (FC) and watermelon juice (NFC). Inactivation kinetics
were determined for single strain pathogens (or a pathogen surrogate)
or spoilage micro-organisms rather than for a cocktail of strains.
Table 1
Bacterial strains and yeast strains used in this study.
Species/strains used Culture collection Source of isolation Reference
Saccharomyces cerevisiae CBS 1544 Fermenting fruit juice isolate Zhang et al. (1994)
Salmonella Panama 10908 NA Human outbreak isolate Noël et al. (2010)
Escherichia coli ATCC 35218 PEF resistant surrogate for E. coli O157:H7 Gurtler et al. (2010)
Listeria monocytogenes Scott A Clinical isolate Fleming et al. (1985)
CBS: Centraal Bureau voor Schimmelcultures (Fungal Biodiversity Centre, Utrecht, The Netherlands).
ATCC: American Type Culture Collection, USA.
NA: not applicable.
Table 2
pH and conductivity of juice matrices after inoculation with micro-organisms.
Matrix pH Conductivity [S/m]
Apple juice 3.5 0.26
Orange juice 3.7 0.38
Watermelon juice 5.3 0.30
Watermelon juice 3.6 0.35
106 R.A.H. Timmermans et al. / International Journal of Food Microbiology 173 (2014) 105–111
3. Overnight grown cells of S. cerevisiae (GPY), S. Panama and E. coli
(TSA) or L. monocytogenes (BHI) were pelleted by centrifugation
(4000 rpm, 5 min) at 20 °C, washed with 100 mL PSDF and resuspend-
ed in 100 mL juice. Cells were diluted (1/10 ratio) in 900 mL juice in a
glass bottle to reach approximately 107
cfu/mL (S. cerevisiae) or
108
cfu/mL (E. coli, S. Panama, L. monocytogenes).
Two individual one liter bottles were inoculated with the selected
microbial strain and used to perform duplicate PEF experiments.
All samples, prior to or after PEF treatment were immediately placed
on ice after collection. The number of viable cells was determined by
plating 100 μL of serially diluted PEF-treated juice in sterile peptone
physiological salt diluent (PSDF) in duplicate on suitable agar plates
supplemented with 0.1% sodium pyruvate to enhance outgrowth of
sub-lethally damaged cells (McDonald et al., 1983; Sharma et al.,
2005). Surviving cells were enumerated after 5–7 days at 25 °C
(S. cerevisiae), at 37 °C (S. Panama, E. coli) and 30 °C (L. monocytogenes).
2.5. PEF processing
The PEF system used was a continuous-flow system, where the con-
figuration was a downscaled copy from the pilot-scale PEF equipment
described by Mastwijk, (2006) and Timmermans et al. (2011) and
from an industrial scale system of 1500 L/h capacity. Specific attention
was paid to design criteria, to guarantee the homogeneity of the electri-
cal field when downscaling the treatment device. Higher field strengths
than 20 kV/cm will lead to arcing and the formation of toxic substances
(Mastwijk, 2006), and are therefore not used in this study.
The inoculated juice was pumped by means of a peristaltic pump
(Masterflex L/S pump, Cole-Parmer) through a 6 mm (disposable)
silicone hose (Masterflex 6424-16, Cole-Parmer) at a flow rate of
14–16 mL/min. Before PEF treatment, the juice was preheated, by
heating in continuous flow through a 1 m × 6 mm diameter SS316
heat spiral that was immersed in a water bath at 43 ± 1 °C. Next, the
liquid was pumped through a co-linear PEF treatment device, compris-
ing two vertically positioned treatment chambers with each a diameter
of 1.0 mm and a gap of 2.0 mm, involving a residence time of 13.5 μs in
the treatment chambers at a flow rate of 14 mL/min. The temperature
at the outlet was measured using a 0.3 mm thermocouple type K
(TM-914C, Lutron, Taiwan), and yielded 36 ± 1 °C when juice was
preheated and PEF was turned off. Subsequently, the juice was pumped
through a cooling spiral of 2 mm diameter and 500 cm length cooled on
melting ice. After cooling, the samples of the liquid were collected at the
exit under aseptic conditions. The throughput of the juice in the system
was periodically measured using a digital scale analytical balance (Sar-
torius, Gottingen, Germany) by recording the weight of the collected
juice.
Prior to the experiment, all parts that came into contact with the
juice were sterilized by moist heat in an autoclave for 20 min at
120 °C. The system was started using 1 L of pasteurized juice to fill the
system and to obtain stationary processing conditions of flow in the
range of 14–16 mL/min. A sample of this start-up liquid was taken at
the exit as a negative control. After this, the pasteurized juice at the
inlet was replaced by a bottle of inoculated juice. The start over occurred
at the most intense PEF conditions (i.e. highest repetition rate). A sta-
tionary state was reached before the inoculated juice reached the PEF
treatment chamber. The PEF treated juice was collected every 5 min
after the repetition frequency was set to lower levels. The collected sam-
ples were treated at the following repetition frequencies and number of
pulses are indicated when a flow rate of 14 mL/min was used: 964 Hz
(13 pulses), 785 Hz (10.6 pulses), 650 Hz (8.8 pulses), 560 Hz (7.5
pulses), 390 Hz (5.3 pulses), 270 Hz (3.6 pulses), 220 Hz (3.0 pulses),
180 Hz (2.4 pulses), 140 Hz (1.9 pulses), and 120 Hz (1.6 pulses) and fi-
nalized by sampling of a positive control (no treatment).
Monopolar pulses of 2.0 μs duration at a field strength of 20 kV/cm
were used. Pulse waveform, voltage, and intensity in the treatment cham-
bers were recorded with a digital oscilloscope Tektronix TDS3052B
(Tektronix Inc., Beaverton, USA). Energy balance was made up and correct
for at least 90%, according to Mastwijk et al. (2007).
Specific energy used for each condition was calculated according to
Eq. (1), where w is the specific energy (kJ/kg), Tout is the outlet temper-
ature (°C), Tin is the inlet temperature (°C) and cp is the specific heat ca-
pacity, which is 3.8 kJ/kg·K for fruit juice of 10–12° Brix.
w ¼ Tout–Tinð Þ Á cp ð1Þ
2.6. Experimental design and statistical analysis
Data was collected for each species in two independent PEF experi-
ments, with cleaning and sterilization between the two experiments.
Different inactivation models were evaluated (linearized first order
model, exponential decay, sigmoidal and Weibull). Based on the good-
ness of the fit, evaluated by calculating R2
and RMSE values, it was
found that the empirical model of Weibull was the one that fitted best
to all data.
A mathematical model based on the Weibull distribution was there-
fore used to fit the survival data (log10 survival fraction vs. specific ener-
gy) of all micro-organisms, as shown in Eq. (2) where N is the number of
micro-organisms that survived the treatment, N0 is the initial number of
microbial population, w is the specific energy used (kJ/kg) and α and β
are the two parameters of the distribution; α is called the scale param-
eter (a characteristic of the specific energy used) and β is the shape pa-
rameter (Van Boekel, 2002).
Log
N
N0
¼ À
w
α
β
ð2Þ
Parameters were estimated via nonlinear regression using least-
squares. Individual results were modeled using Gnu-plot.
3. Results and discussion
3.1. Influence of inlet temperature prior to PEF treatment
Initial inactivation experiments were performed in apple juice at an
inlet temperature of 20 °C and an electric field strength of 20 kV/cm.
Under the tested conditions, inactivation of S. Panama was virtually ab-
sent up to an input of specific energy of 60 kJ/kg. Further increase of
specific energy with a concomitant temperature rise did inactivate
cells. To substantiate whether the inactivation resulted from the higher
specific energy input or that cells were more susceptible to PEF at ele-
vated temperature, the experiment was repeated using an inlet temper-
ature of 36 °C. This experiment confirmed that at 36 °C S. Panama cells
were inactivated at lower specific energy input (Fig. 1A). Similar find-
ings were obtained for S. cerevisiae, where the inactivation was en-
hanced by an elevated inlet temperature from 20 °C to 36 °C (Fig. 1B).
Data showed that the initial temperature had a strong influence on
the specific energy required to inactivate the micro-organisms, with
less specific energy required to obtain a similar level of inactivation at
elevated temperatures. Similar observations have been described for
Listeria innocua and E. coli (Heinz et al., 2003; Toepfl et al., 2007;
Wouters et al., 1999).
The effect of the starting temperature on the efficacy of the PEF
treatment may be explained by the temperature dependent character-
istics of the membrane of the micro-organisms. Phase transitions of
the phospholipids from gel to liquid-crystalline phase are temperature
related, which affects the stability of the cell membrane at higher tem-
peratures (Stanley and Parkin, 1991). The critical membrane break-
down potential decreases when the temperature of the solution
increases (Coster and Zimmermann, 1975), and consequently electro-
poration occurs at lower external electrical fields. This suggests, togeth-
er with data shown in Fig. 1, a synergistic effect between temperature
107R.A.H. Timmermans et al. / International Journal of Food Microbiology 173 (2014) 105–111
4. and electrical pulses, implying that every additional PEF pulse is more
effective than the previous one: the temperature increases as a result
of pulsing, leading to a weaker cell and making it more vulnerable to-
wards the next PEF pulse.
For further experiments, an inlet temperature of 36 °C was chosen.
At inlet temperatures exceeding 36 °C, the outlet temperature reaches
critical levels where product quality was compromised.
3.2. PEF effectiveness towards different microbial species in diverse juice
matrices
The inactivation of S. cerevisiae, S. Panama, E. coli and L. monocytogenes
by PEF treatment was investigated in apple juice (Fig. 2A), orange juice
(Fig. 2B) and watermelon juice (Fig. 2C). All species were susceptible
to PEF treatment in apple juice, and inactivation curves obtained
showed a non-linear response (Fig. 2A). With the exception of
L. monocytogenes, similar findings were obtained for orange juice
(Fig. 2B), but a reduced susceptibility was pronounced in watermelon
juice (Fig. 2C). PEF sensitivity followed the order S. cerevisiae N
S. Panama N E. coli N L. monocytogenes, meaning that the energy ex-
pense to inactivate the bacteria is higher than for yeast. Therefore, pro-
cess validation using yeast species can lead to an overestimation of
effectiveness of the process conditions. Validation designs that include
(pathogenic) bacteria on identical small scale equipment are therefore
preferred.
The reduced sensitivity of L. monocytogenes towards electric pulses
compared to that of other micro-organisms might be explained by two
factors. First, the size and shape of the micro-organisms affect the re-
quired electric field to lethally damage the cells, where at smaller cell
sizes, a lower membrane potential is induced by an external field, leading
to a higher microbial resistance to the treatment (Álvarez et al., 2006;
Hülsheger et al., 1983; Zimmermann et al., 1974). Moreover, the shape
of the micro-organism has an influence on the membrane potential,
where a rod-shaped cell requires an electric field more than five times
stronger than that required by a spherical shaped cell with the same
characteristic dimensions (Heinz et al., 2001). As L. monocytogenes is
much smaller (short rods, 0.4–0.5 μm × 0.5–2 μm) than S. Panama
(straight rods, 0.7–1.5 μm × 2–5 μm) and E. coli (straight rods, 1.1–
1.5 μm × 2.0–6.0 μm), it costs more energy to inactivate this micro-
organism, hence it requires less energy to inactivate the large
S. cerevisiae (ellipsoidal shape, 3–15 μm × 2–8 μm) (characteristic di-
mensions taken from Bergey (1986)). A second argument is that
L. monocytogenes is a Gram-positive bacterium with a cell membrane
structure different from the other tested bacteria that are Gram-
negative. Research of Hülsheger et al. (1983), and Toepfl et al. (2007),
also described that this could have an influence on PEF sensitivity.
The reduced sensitivity of L. monocytogenes towards PEF was also
found by Gómez et al. (2005a), and Saldaña et al. (2010), where at
field strengths up to 20 kV/cm inactivation was virtually absent. In-
crease of the field strength up to 35 kV/cm significantly improved sen-
sitivity of L. monocytogenes towards PEF.
The high resistance of L. monocytogenes in orange juice shown in this
study is remarkable, showing virtually no inactivation, where for apple
juice, 3.5 log inactivation at a specific energy input of 87 kJ/kg was
reached. There was a slight difference in the pH of apple juice
56°C 57°C
52°C
48°C
43°C
40°C
46°C
35°C30°C26°C
49°C
-7
-6
-5
-4
-3
-2
-1
0
0 20 40 60 80 100
log(N/N0)[-]
Specific energy [kJ/kg]
A
37°C
35°C
32°C
29°C
25°C
40°C
42°C
41°C
38°C
-7
-6
-5
-4
-3
-2
-1
0
0 20 40 60 80 100
log(N/N0)[-]
Specific energy [kJ/kg]
B
Fig. 1. Reduction of viable counts of A) S. Panama added to apple juice after PEF treatment,
preheated at 20 °C (◊) and 36 °C (♦) and B) S. cerevisiae precultured in apple juice after
PEF treatment, preheated at 20 °C (□) and 36 °C (■).
36 41 46 51 56 61
-7
-6
-5
-4
-3
-2
-1
0
0 20 40 60 80 100
Temperature [°C]
log(N/N0)[-]
Specific energy [kJ/kg]
A
36 41 46 51 56 61
-7
-6
-5
-4
-3
-2
-1
0
0 20 40 60 80 100
Temperature [°C]
log(N/N0)[-] Specific energy [kJ/kg]
B
36 41 46 51 56 61
-7
-6
-5
-4
-3
-2
-1
0
0 20 40 60 80 100
Temperature [°C]
log(N/N0)[-]
Specific energy [kJ/kg]
C
Fig. 2. Reduction of viable counts of S. Panama (◊), E. coli (▲), L. monocytogenes (○) and
S. cerevisiae (□) added to apple juice, pH 3.5 (A), orange juice, pH 3.7 (B), and watermelon
juice, pH 5.3 (C) after PEF treatment, preheated at 36 °C.
108 R.A.H. Timmermans et al. / International Journal of Food Microbiology 173 (2014) 105–111
5. (pH 3.5) and orange juice (pH 3.7) which could have influence on the
observed difference in sensitivity. Similar findings were reported previ-
ously for heat treated E. coli O157:H7 in apple and orange juices with a
higher resistance in orange juice (Mazzotta, 2001). The reduced sensi-
tivity of L. monocytogenes was pronounced even more in the watermel-
on matrix (pH 5.3) (Fig. 2C), and a remarkably higher resistance was
observed for the other tested species as well. To determine if this higher
PEF resistance of the micro-organisms in watermelon juice could (in
part) be explained by a pH effect or, alternatively, induced by the pres-
ence of other components in watermelon juice, experiments were car-
ried out where the pH of watermelon juice was decreased with HCl
from pH 5.3 to 3.6. The results, presented in Fig. 3, show an enhanced
performance of PEF inactivation of micro-organisms when the pH was
reduced. The shape of the inactivation curve of micro-organisms in wa-
termelon juice with an adapted pH is comparable to the curves shown
of apple and orange juices, which suggest that the observed differences
were caused by pH effects.
It is assumed, that the role of pH of the medium in the inactivation of
micro-organisms is related to the fact that most micro-organisms main-
tain the cytoplasmic pH near neutrality (Corlett and Brown, 1980). The
pH of the medium affects the effectivity of weak organic acids, present
in fruits, by influencing the ratio of non-dissociated and dissociated or-
ganic acids. A low pH favors formation of non-dissociated organic acids,
the form that may pass the cell membrane and enter the cytoplasm. In-
side the cell it can dissociate in the cytoplasm and lead to acidification.
Protons may enter the cell by passive influx or via proton dependent
transporters. Reduction of the intracellular pH thereby affects the bio-
chemical processes in the cell including transport processes over the
membrane, redox state, and enzyme activities (Cotter and Hill, 2003).
Similar observations in pH difference were found for Gram-positive
and Gram-negative micro-organisms in buffer solutions (Álvarez et al.,
2002; García et al., 2005; Geveke and Kozempel, 2003; Gómez et al.,
2005a, 2005b; Saldaña et al., 2010; Wouters et al., 1999).
3.3. Mathematical modeling
Microbial inactivation data for the different juice matrices were used
to construct a predictive model for an optimal PEF process. The empirical
model of Weibull (Eq. (2)) was fitted to all inactivation data obtained
from plotting logarithmic inactivation of the survival fraction against spe-
cific energy. The estimated parameters α and β obtained from the differ-
ent micro-organisms in the tested juices are shown in Table 3. The
goodness of the fit was evaluated by calculating R2
and RMSE values.
The determination coefficient R2
for each model of micro-organism in
varying medium was higher than 0.93, which means that less than 7%
of the total response variation remained unexplained by the Weibull
equation. The values for parameter RMSE were in the range of 0.01 to
0.56, and can be assumed close to the observed data (Saldaña et al., 2011).
Another test for judging the applicability of the Weibull model is by
plotting the observed data to the model calculations, as shown in Fig. 4.
The difference between a point in the graph and the line of equivalence
is a measure of the inaccuracy of the corresponding estimation. Since
the data points of all micro-organisms are randomly distributed above
and below the equivalence line, no systematic tendency is found, and
therefore the Weibull model studied was satisfactory in terms of de-
scribing all data being analyzed.
As an indication for the quality of the estimated model, the statistical
correlation between the parameters α and β (expressed in the correla-
tion coefficient) has been calculated. If this correlation coefficient is
N0.99, it signals that the parameter estimates could not be well estimat-
ed in the regression procedure (van Boekel., 2002). The results show
that there is no such problem with the current dataset. Modeling of
the data where the pH of watermelon juice was decreased showed an
increase in the statistical correlation.
The shape factor β in Table 3 indicates that the survival curves of
S. Panama, E. coli, S. cerevisiae and L. monocytogenes fitted with the
Weibull model were all concave downward (β N 1), which was also ob-
vious from Figs. 1, 2 and 3. Downward concavity (β N 1) indicates that
36 41 46 51 56 61
-7
-6
-5
-4
-3
-2
-1
0
0 20 40 60 80 100
Temperature [°C]
log(N/N0)[-]
Specific energy [kJ/kg]
Fig. 3. Reduction of viable counts of S. Panama (◊) and S. cerevisiae (□) in watermelon juice
after addition of HCl to pH 3.6 and PEF treatment, preheated at 36 °C.
Table 3
α and β values estimated from the fitting of the mathematical model based on the Weibull distribution to experimental data for different micro-organisms in varying juices and the cal-
culated specific energy based necessary for a 5 log reduction.
Micro-organism Medium pH α (kJ/kg) (95% CI)a
β (95% CI)a
R2b
RMSEc
Correlation
between α and β
Calculated specific
energy necessary for 5 log
reduction [kJ/kg]d
Salmonella Panama Apple juice 3.5 20.52 (18.39–22.65) 1.40 (1.29–1.51) 0.96 0.19 0.98 65
Orange juice 3.7 23.63 (21.79–25.47) 1.38 (1.25–1.51) 0.99 0.20 0.96 76
Watermelon juice 5.3 70.15 (67.36–72.95) 2.60 (1.86–3.34) 0.96 0.10 0.39 130
Watermelon juice 3.6 41.12 (38.76–43.47) 3.05 (2.37–3.73) 0.99 0.19 0.86 70
E. coli Apple juice 3.5 15.15 (8.65–21.65) 1.08 (0.72–1.44) 0.93 0.56 0.97 67
Orange juice 3.7 16.39 (13.16–19.62) 1.27 (0.99–1.55) 0.97 0.26 0.95 58
Watermelon juice 5.3 71.29 (65.89–76.68) 1.58 (1.16–2.01) 0.94 0.09 0.62 197
Saccharomyces
cerevisiae
Apple juice 3.5 29.56 (24.36–34.75) 2.19 (1.64–2.74) 0.96 0.53 0.96 62
Orange juice 3.7 24.85 (22.63–27.08) 1.90 (1.71–2.09) 0.99 0.24 0.98 60
Watermelon juice 5.3 51.28 (48.52–54.04) 2.92 (2.35–3.50) 0.97 0.16 0.89 89
Watermelon juice 3.6 38.43 (33.78–43.07) 3.22 (2.27–4.17) 0.93 0.44 0.95 63
Listeria
monocytogenes
Apple juice 3.5 28.88 (27.66–30.09) 1.18 (1.09–1.27) 0.97 0.05 0.89 113
Orange juice 3.7 88.46 (73.05–103.87) 1.51 (1.05–1.97) 0.91 0.07 0.91 257
Watermelon juice 5.3 187.07 (146.81–227.33) 1.61 (1.31–1.92) 0.97 0.01 0.98 508
a
95% CI: confidence interval.
b
R2
: determination coefficient.
c
RMSE: root mean square error.
d
Calculation based on estimated α and β parameters and the Weibull model (Eq. (2)).
109R.A.H. Timmermans et al. / International Journal of Food Microbiology 173 (2014) 105–111
6. remaining cells become increasingly damaged, whereas upward
concavity (β b 1) indicates that remaining cells have the ability to
adapt to the applied stress (van Boekel, 2002). Therefore, concave
downward (β N 1) survival curves of all micro-organisms tested
in this research can be interpreted as evidence that the microbial
cells show the tendency to become weaker when specific energy
and temperature increase, indicating that accumulated damage
due to synergy occurs. This synergistic effect between temperature
and pulses is in line with the results of the experiments on the in-
fluence of inlet temperature on PEF inactivation, as described in
Section 3.1. Contradicting, in literature concave upward (β b 1)
survival curves of E. coli (Álvarez et al., 2003a; Rodrigo et al.,
2003; Saldaña et al., 2010), Lactobacillus plantarum (Gómez et al.,
2005b; Rodrigo et al., 2001), Yersinia enterocolitica (Álvarez et al.,
2003c), S. enterica serovars (Álvarez et al., 2003d; Saldaña et al.,
2010) and L. monocytogenes by Álvarez et al. (2003b) and Gómez
et al. (2005a) were reported. It is difficult to compare these studies
with our results, since different PEF equipment with varying treatment
chambers and settings were used. All these studies with an upward con-
cavity had in common that they operated at a maximum temperature of
35 °C and used square-wave pulses. If we consider the data up to 35 °C,
we observe the same findings: survival of S. Panama up to 35 °C as
shown in Fig. 1A (open symbols) gave comparable inactivation curves
as described by the abovementioned studies with concave upward pa-
rameters (α = 124.95, β = 0.34, R2
: 0.96, RMSE: 0.05), and when
more pulses were given, PEF showed to be more effective in inactivation,
leading to concave downward parameters when Weibull fit was per-
formed over data up to 49 °C (α = 50.43, β = 1.56, R2
: 0.92, RMSE:
0.32). This suggests that the synergistic effect between temperature and
pulses is apparent at temperatures above 35 °C, and was therefore not
observed in the other studies.
Evaluation of the Weibull parameters α and β in the aforementioned
studies with respect to the variable electric field strengths, showed no
influence on the β parameters when higher or lower electric field
strengths were used. Nevertheless, increase of the electric field strength
greatly affects the α parameter, showing a more efficient PEF process,
what is expressed by a lower energy use or shorter treatment time.
When the parameters α and β are compared for all different micro-
organisms, it can be seen that the β-value for the S. cerevisiae dataset
was higher compared to that for other micro-organisms, confirming
that S. cerevisiae is more susceptible to the PEF treatment than other
micro-organisms. To facilitate the comparison among micro-organisms
and matrices the energy needed to inactivate 5 log cycles is calculated.
Based on the estimated α and β parameters, a calculation is made to es-
timate the amount of specific energy necessary to have a 5 log reduction
of a certain micro-organism in a specific fruit juice (Table 3). Most energy
is necessary to inactivate the micro-organism L. monocytogenes in water-
melon juice.
The dependence of the parameters α and β on the pH of the different
juices is shown in Fig. 5. Although limited experiments with a variable
pH were carried out, it can be concluded from Fig. 5A that the β param-
eter does not depend on pH in a systematic way. Contrary, the α param-
eter, depicted in Fig. 5B, seems to be dependent on the pH of the fruit
juice for all micro-organisms tested. In low-acid fruit juices, more spe-
cific energy is needed to inactivate micro-organisms than in more acid
fruit juices. The effect of acidification of the low-acid watermelon juice
of pH 5.3 to pH 3.6 is indicated with the filled symbols in Fig. 5, showing
no effect on the β parameter, but a reduction of the α parameter. Similar
results for the shape independency and scale dependency towards pH
were found for PEF treatment of L. monocytogenes and L. plantarum in
media with varying pH (Gómez et al., 2005a, 2005b).
4. Conclusion
PEF processing conditions for fruit juices were assessed and inactiva-
tion of micro-organisms was dependent on pH, the type of microbial
species and inlet temperature of the matrix.
A synergistic effect between temperature and PEF treatment was
demonstrated and suggests that optimization of the PEF conditions to
reduce the energy input should aim for processing at higher inlet tem-
perature to allow more effective inactivation per pulse.
The diversity in PEF resistance across the different microbial species
shows the importance to validate industrial processes with relevant
micro-organisms (spoilage and pathogens) for the food products. Test-
ing of pathogens has to be done in the food matrix desired to be PEF pas-
teurized, as intrinsic factors such as pH and conductivity, influence the
amount of energy required to reach the required reduction of micro-
organisms.
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-7
-6
-5
-4
-3
-2
-1
0
-7-6-5-4-3-2-10
Calculateddata(LogN/N0)
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