Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

260353823_Technical Paper 1 final draft

224 views

Published on

  • You can hardly find a student who enjoys writing a college papers. Among all the other tasks they get assigned in college, writing essays is one of the most difficult assignments. Fortunately for students, there are many offers nowadays which help to make this process easier. The best service which can help you is ⇒ www.WritePaper.info ⇐
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
  • Be the first to like this

260353823_Technical Paper 1 final draft

  1. 1. NONTHERMAL TECHNOLOGIES FOR THE PROCESSING OF FOOD AND THE PREVENTION OF INFECTION BY E. COLI O157:H7 Technical Paper I NOVEMBER 25, 2013 MICHAEL GARIBALDI 260353823
  2. 2. 1 ABSTRACT The USDA’s Safety and Inspection Service drafted a report from data collected over multiple years on the contamination level for the human pathogen Escherichia coli O157:H7 in ground beef patties.It was found that in 2000, 0.86% of patties were contaminated, as compared to 0.84% in 2001, 0.78% in 2002, 0.30% in 2003 and 0.17% in 2004. Then, between 2003 and 2006, there were 22 ground beef patty recalls due to the presence of E. coli O157:H7. Efforts to prevent the continuation of such outbreaks including heavier surveillance, hazard analysis and critical control point plans have helped, but not abolished, contamination by E. coli in meat, poultry and other produce. Still, two out of every thousand beefpatties contain traces of E. coli, which is only required in a small dose to induce severe infection in a human. Over the last two decades,the largest produce manufacturers spent billions of dollars fighting E. coli. Even with cleaner handling today, the risk of infection for large-scale producers is astronomical, which is why steps must be taken to block the bacteria’s every chance of infesting consumable goods. This has given rise to a new era of food processing technology.Methods developed overthe last century such as high hydrostatic pressure and irradiation are currently being challenged by potentially better techniques like ozone and antimicrobial films treatment. It is the aim of this paper to select a processing technology for a plant with commercial-scale throughput (on the order of 500 pounds per hour[226.8 kg/hr]) based on multiple acceptance criteria. These criteria include ability to reduce E. coli populations by 5 log10 reductions,preservation of quality, solid food aptitude, induced temperature changes as well as throughput capacity,shelf-life extension, compliance with regulation and public approval rating. The final recommendation is for antimicrobial films, which possessthe ability to prevent outbreak throughout large-scale commercial production of fruits, vegetables,and meats. This is also accompanied by a potential problem analysis and suggestions forfuture work with this technology.
  3. 3. 2 CONTENTS ABSTRACT......................................................................................................................................1 CONTENTS ......................................................................................................................................2 INTRODUCTION..............................................................................................................................4 BACKGROUND................................................................................................................................5 CRITERIA.........................................................................................................................................7 ESSENTIAL..................................................................................................................................7 DESIRABLE..................................................................................................................................9 THE SUBSTITUTES........................................................................................................................11 Ozone Sanitization........................................................................................................................11 Table 1: Ozone Solubility in Water.............................................................................................11 Table 2: Ozone Effectiveness for Selected Food Products............................................................12 Irradiation (IR) .............................................................................................................................13 Table 3: IR Effectiveness for Selected Food Products .................................................................14 High hydrostatic pressure (HHP) ...................................................................................................14 Table 4: HHP Effectiveness for Selected Food Products..............................................................15 Pulsed electric fields .....................................................................................................................16 Table 5: PEF Effectiveness for Selected Food Products...............................................................17 Antimicrobial films and coatings (AF) ...........................................................................................17 Table 6: Antimicrobial Film Effectiveness for Selected Food Products .......................................18 AN ANALYSIS OF SUBSTITUTES.................................................................................................19 Acceptable Alternatives.................................................................................................................19 Desirable Alternatives ...................................................................................................................20 Potential Problem Analysis............................................................................................................21 TABLES OF COMPARISON...........................................................................................................23 Table 8: Comparison of Quality/Shelf-life...................................................................................23 Table 9: Comparison of Inhibition Abilities for E. coli O157:H7.................................................24 Table 10: Comparison of Heating ...............................................................................................24 Table 11: Evaluation of Throughput for HHP.............................................................................24 Table 12: Evaluation of Throughput for IR ................................................................................25 Table 13: Evaluation of Throughput for Ozone ..........................................................................25
  4. 4. 3 Table 14: Evaluation of Throughput for Antimicrobial Films.....................................................26 Table 15: Percent ofUntrained Consumers Who Favor Processed Food over Non-processed (2009)..........................................................................................................................................26 RECOMMENDATION ....................................................................................................................27 FUTURE WORK.............................................................................................................................27 REFERENCES.................................................................................................................................28
  5. 5. 4 INTRODUCTION Consumer’s life habits and an increase in demand for healthier foods are driving a revolution in the food industry to betterpreserve products. With the help of fast transportation and refrigeration, a healthier and more widespread market is developing for suppliers, meaning food will travel hundreds or thousands ofmiles before reaching the consumer. This also presents an opportunity for microorganisms to hitch a ride and spread disease, making preservation techniques all the more relevant. Beginning in the 1970s, health and safety organizations established the role of microbes in food poisoning outbreaks and their ability to grow in adverse environments, such as in refrigerated goods.Species like Escherichia coli,amongst many other pathogens,when present in food are found to propagate and spoil the product. The number of illnesses caused by the consumption of fresh produce is an ongoing concern and there is an emergent need to reduce the incidence of pathogens. Conveniently, some products can be pasteurized before refrigerated storage,which can lead to multiple log reductions of pathogenic members like E. coli and inactivation of the enzymes responsible for spoilage. However, the heat treatment in this process is not proper for all foods and can damage goods by modifying nutritional and sensory properties.Such losses render the products unacceptable as compared to otheravailable fresh foods. Furthermore, pasteurization is suited only for liquid foods – an exception which bars most household food items from protection. And while in theory, the application of preservatives and chemical treatment renders fresh food contaminant-free, in practice there is a great deal of public scrutiny due to the dangerous health effects of chemical preservatives. In response to the need for alternative methods for the treatment of heat-sensitive food products,new technologies have arisen that minimize the effect of preservation on the final good and assure safety and reliability. Ideas range from irradiation to the formation of synthetic skins on the surfaces of food. With approximately two out of every thousand ground beefpatties infected with E. coli O157:H7 (Sommers & Xuetong,2011), one certainty is clear: there is a serious need for the removal of contamination prior to packaging. This paper will examine the different criteria that must be met to qualify a technique as advantageous to sanitization against E. coli on solid food surfaces,followed by an evaluation of alternative technologies.
  6. 6. 5 BACKGROUND Food product quality considers a number of factors. Sensorial quality defines what the consumer sees, feels, smells and tastes.It is well established that the average consumer, when evaluating fresh produce, looks for the item with the least blemishes. Firmness, aroma and color are all inspected with reasonable attention paid to detail. Blotching, discoloration, soft spots in fruits and vegetables and odors are all related to senescence and are negative qualities. Senescence is the natural process by which a food product ages and decays.The sensorial quality of a product is therefore directly related to the rate of moisture loss, oxygenation and enzymatic activation, as they each change the composition of the produce. Bacteria, fungi and various other microorganisms accelerate this process as they use their digestive enzymes to consume the food. E. coli, for example, forms patches or colonies on the surface of the food which may not be seen by the naked eye, but are marked by discoloration as a result of the decomposition taking place. Decomposition also leads to the depletion of nutritional matter. Minerals, vitamins and aromatic compounds are healthy to the consumer but very sensitive to changes in chemistry. The physical effects of nutritional decay are recognizable by the average consumer. The health and wellness effects are also noticeable as a lack of certain vitamins, for instance, often manifests itself through deficiencies associated with those vitamins. Microbes present on a product are frequently associated with toxins and other infectious agents which they release to keep competing organisms out. As a colony of E. coli in a ground beef patty grows, so too does the toxic waste which it creates. While many strains of E. coli are harmless, strains like O157:H7 cause serious illness, and even death in individuals with weakened immune systems. If consumed in large enough concentrations,E. coli O157:H7 will render a human being dangerously ill with a wide range of severe symptoms from vomiting to bloody diarrhea. Immunization against E. coli O157:H7 is impossible due to its ability to adapt to living systems.Hence, culling the incidence of dangerous illness by E. coli infection must be performed in the processing stage.The current industry standard calls for a 5 log10 (99.999%) reduction in microbial content in post-processing produce (Gutsol & Niemira, 2011). It is believed that inactivation of this degree minimizes the probability of infection by E. coli O157:H7.
  7. 7. 6 It is microbial diversity and the ability to adapt that pose the greatest obstacle for food processing technologies.The bacteria of interest are classified into two categories: vegetative cells, which have an active metabolism, and spores, which exhibit no metabolic activity and present elevated resistance to all forms of treatment (Cebrian, Condon, & Manas,2011). Amongst the vegetative cells, there are two sub-categories:gram-negative and gram-positive cells. Gram-positive bacteria possess a thick peptidoglycan cell wall which acts as a strong barrier to disinfecting agents.Gram-negative bacteria do not have a dense cell wall but instead have a thin wall surrounded by an outer membrane, which allows for increased intra- and extracellular regulation. The majority of the inactivation technologies that inhibit bacteria do so through structuralor physiological changes in the microbial cells that may have crippling effects or lead to increased sensitivity. The most common target is the cellular membrane, which controls the influx and efflux of extracellular contents and manages pH levels. Loss of function in the lipid bilayer membrane undermines a cell’s ability to control its own equilibrium, which very often results in cellular destruction. E. coli O157:H7 is a gram-negative bacterium. It is also a facultative anaerobe, meaning that it can survive in an environment regardless of the presence of oxygen. Processing of food begins at the source, which may be at a farm or a slaughterhouse.At this early stage,it is required that a conscientious effort is made to provide food products with preliminary cleaning. For example, all cuts made from a beef carcass must undergo washing with clean water and all tools used to cut meat must be sterilized before and after each use. It is at this stage of processing where the largest reduction in pathogenic contamination occurs (Rodriguez-Romo, Vurma, & Yousef, 2011). At the processing stage,some techniques involve the use of heat treatment. High temperatures target critical enzymes vital to microbial metabolic pathways. The heat energy required for such inactivation, however, is high enough to alter the sensorial and nutritional qualities of produce. For example, the heat may fry an egg, cook beef or brown an apple. Chemical alternatives also represent a frequently used cleaning option, such as in the use of aqueous chlorine to wash fresh produce. These chemical agents are poisonous forthe microbes and pose no threat to the consumer. Like heat treatment, however, many chemical disinfectants currently in use cause sensorialand nutritional deficits in the food. Newer approaches focus on the use of various forms of energy to attack microbial cells while leaving the product unaffected. This is done by taking advantage of a range of optimum dosage levels.
  8. 8. 7 Some definitions in this paper include terms that are related to various alternative processes in food preservation. The D-value refers to the amount of ionizing radiation required to kill 90% of microbial cells in a sample and is expressed in kiloGrays (kGy). The afore-mentioned radiation is provided by a radiation source. Spores are defined as dormant bacterial cells with a very resistant outer cell wall which renders nearly all disinfecting agents ineffective. Throughput refers to the amount of product treated with a specific dose within a defined period of time. Units for throughput vary according to each method but are typically taken as pound per hour or kilograms per hour. Throughput for batch processes is limited by the time it takes to remove a load and begin a new cycle. Throughput for continuous processes is limited by mechanical constraints such as the speed of the conveyorbelt carrying the product in and out of the unit operator. Process duration, for the food product,is the time it takes to reach a desired log10 reduction in a given process.And finally, compliance with food regulations refers to the design of the processing method, in that it agrees with good manufacturing practices and with government food processing regulations. CRITERIA A total of eight selection criteria will be considered for the analysis of alternative food processing technologies.These eight are categorized into two sections:essentialcriteria, which set the threshold values and desirable criteria, which refer to optimum quantities or what is preferable. From the combined analysis of all criteria and alternatives, it is possible to make an educated recommendation on which processing method should be preferred by the large-scale processing plant in question.The superior method would be one which satisfies all essentialcriteria and is the best fit for the desirable criteria. ESSENTIAL 1. The need for alternative food processing methods stems from the current method’s inadequacy with certain types of food, namely solids. Pasteurization is frequently used to eliminate foodborne pathogens in liquids, but cannot process solid products due to incompatibility in its design. Therefore,
  9. 9. 8 it is necessary that an alternative has the ability to process solid food, as this is where the need for treatment is greatest.While no numerical quantity can be put upon this, an alternative method’s capacity to handle solid foods is given as a percentage representing the fraction of solid food types than can be processed compared to all solid food options.The current heat treatment method can process only about 40% of solid foods.All others are too sensitive to large temperature increases (on the order of 150°C) for heat treatment to be an effective method. 2. The main focus of food treatment is the elimination of viable levels of E. coli O157:H7 present on or within the food product. Industrial standards hold that tolerable reduction levels for pathogenic material is on the order of 5 log10 for natural or artificial inoculations. Therefore, it is absolutely necessary that alternative methods of treatment inhibit the growth of E. coli O157:H7 by 99.999% for various food products.The reduction percentage is determined from sampling and analysis via either a plate count, viable cell count or through the turbidity method. Current heat treating methods are able to achieve a 5 log10 reduction of E. coli O157:H7. Simple washing, i.e. without processing,leads to only about a 2 – 3 log10 reduction for most solid food types. 3. As part of measuring a method’s effect on food quality, the temperature changes induced by the method are taken into consideration. Temperature largely influences the structure and composition of solid food products.While heat is effective for inactivating E. coli O157:H7, the treated produce may not be of adequate quality for sale to consumers if the treatment has changed its desired chemical or physical nature. The most noticeable side effect of heat treatment is discoloration and cooking of flesh. For heat treatment methods, the typical increase in temperature for a product occurs in a flash instance (1 – 2 seconds)and is between 125°C and 150°C. Alternatives therefore must not produce heat that raises the temperature of the product above this level. 4. Part of the purpose of replacing heat treatment as the current method is that food products treated with heat often have different texture, gloss,odor, taste and nutritional quality. An adequate replacement
  10. 10. 9 should therefore confer little to no physical or chemical change upon the processed product.Retention of sensorial and nutritive quality is measured in terms of shelf-life. A fresh product that has not undergone processing treatment has a base shelf-life, usually between two days and a week for most food types,though this is further specified by food type in the tables to follow. Decreases in sensorial qualities such as discoloration, spotting or losses in moisture content after treatment are unacceptable in a final product as they indicate a shorter shelf-life. Loss of nutritional value including the leaching of minerals or the volatilization of aromatics results in peculiar odors and is also deemed unappealing to consumers and has no shelf-life. For a processing method to qualify as a satisfactory replacement for heat treatment, the food product must retain the base shelf-life. DESIRABLE 1. Of the criteria that must be met in order to validate the appropriateness of each process,there are also parameters that are based on preferred product quality and economic sensibility. One of these desired criteria is taken from a manufacturing efficiency standpoint,which is that high throughput and ease of production are favorable to slower and more cumbersome operations.Therefore, throughput should be on the order of 500 pounds perday or 226 kg per day for all solid food types to meet the scale desired by a large food producer. Equipment that is simple to clean, easy to replace in the event of wear and which avoids frequent interruption is also preferable. This criterion has the highest relative importance compared to otherdesirable criteria. This is because the selection for an alternative must rely on the cost effectiveness of the alternative. A process which produces the most treated product at lowest cost is favored over other alternatives. 2. Certain techniques in sanitation,in addition to reducing E. coli O157:H7 counts,also confer improved product quality. This can be defined as better sensorial value or nutritional content,such as increased gloss,as well as slowed transpiration and oxygenation. Improvements in quality are measured in terms of shelf-life; any enhancement to a product’s preservation leads to a longer shelf-life than the standard, untreated product. Increased shelf-life is a desirable outcome of a processing method.
  11. 11. 10 3. Reputation plays a significant role in the marketing of any product. In the United States and most westernized markets, it is required that producers include labels of the processing method used on the product.Thus, a product that is processed using a method that is generally regarded as safe by the uninformed public will fare much better on the shelf than a product that is processed using a controversial method. This will be taken into account in the decision making process,as the ability to market the final product has a major effect in choosing the appropriate processing technology. 4. There are numerous agencies across the world that regulate safety standards for consumer products, especially within the food industry.In the United States,the FDA and USDA set the bar for which processing techniques are acceptable. It is generally preferred in making a selection to choose an alternative that requires the least amount of regulatory hurdles. Technology not approved by the government that is used to process food cannot be sold to consumers. The FDA, for example, has a long list of requirements that a processing method must meet before it can be applied to production, and anotherlist of all the experimental parameters that a supplier must provide in order to claim that a product has certain attributes. These experiments and approval requirements take time and delay production substantially.The patents for the technology must also be checked, as certain manufacturers of food processing equipment may forbid alterations to equipment specific to a certain process.It is a desirable quality that a food processing technology is government-approved and reliable.
  12. 12. 11 THE SUBSTITUTES Ozone Sanitization Ozone is a triatomic molecule (O3) and is extremely reactive and unstable.It is produced through molecular oxygen (O2) interactions with chemicals, electrical discharges or ultraviolet radiation. It possesses a limited solubility in water which makes it usefulfor food applications as a surface sanitizer. Treatment processes that utilize chlorine dissolved in water are gradually being converted to ozone in the water-treatment industry only (Zorlugenc & Zorlugenc, 2012). The relationship between temperature and ozone solubility is given in Table 1. Table 1: Ozone Solubility in Water Temperature (°C) Solubility (L ozone/L water) 0 0.641 15 0.456 27 0.270 40 0.112 60 0.000 First introduced as a disinfectant in the treatment of drinking water, ozone inactivates microbial cells through a mechanism involving the oxidation of cellular constituents. Typicalreactions between ozone and microbial cells occur on unsaturated lipids in the cellular membrane, intracellular enzymes and genetic material (Rodriguez-Romo, Vurma, & Yousef, 2011). Enzymes are inactivated through the oxidation of sulfhydryl groups. Ozone can be generated with high-purity oxygen or dry air coming into contact with an energy source like a corona discharge generator. Due to its instability, ozone cannot be packaged and must be generated at the processing facility (Rodriguez-Romo, Vurma, & Yousef, 2011). Ozone detectors are therefore required for worker safety, as ozone can be lethal at doses above 25.0 ppm (Zorlugenc & Zorlugenc, 2012). Ozone is known to strongly inhibit the growth of all microbial life, including E. coli O157:H7. It acts at the cell surface, degrading the bacterial cell wall and membrane until the E. coli cell lyses.Ozone, through its antimicrobial action, also extends the shelf-life of food products and has application over a wider range of solid products than heat treatment. Due to its oxidative nature, however, ozone is not recommended for meat products as
  13. 13. 12 it very quickly changes the composition of fresh produce like beef and poultry. Ozone dissolved in water has no effect on heat generation, and thus can be trusted with heat-sensitive foods. Because it is dissolved in water and produced on-site, scaling up issues can be avoided. The treatment time required for different products is relatively small, allowing for high throughput in continuous processes assisted by a conveyorbelt. Ozone use in the treatment of food is also an approved process by all regulatory agencies. While it is not well-known amongst consumers, food processed by ozone treatment is generally preferred above standard untreated food items. Table 2: Ozone Effectiveness for Selected Food Products Product: Treatment Conditions Shelf-life (refrigerated): Inhibition of E. coli O157:H7: Temperature change due to exposure: Apple 21 - 25 mg O3 / L for 3 minutes 4 - 6 months 3.7 log10 reductions negligible Tomato 21 - 25 mg O3 / L for 3 minutes 3 - 4 weeks 4.2 log10 reductions negligible Lettuce 21 - 25 mg O3 / L for 3 minutes 2 - 3 weeks 3.6 log10 reductions negligible Potatoes 21 - 25 mg O3 / L for 3 minutes 3 - 4 months 4.7 log10 reductions negligible
  14. 14. 13 Irradiation (IR) Ionizing radiation causes genetic damage in microorganisms, primarily in the form of single- and double- stranded DNA strand-breaks.This results in various sorts of mutations that either kill the pathogenic bacteria or make them incapable of propagation. There are two mechanisms by which ionizing radiation effects DNA: one is photon-induced breakage of the phosphodiesterbackbone of DNA and the other is the creation of hydroxyl radicals which strip DNA of its molecules. Formation of radicals accounts formore than 70% of the genetic damage caused by exposure to a radioactive source (Sommers & Xuetong,2011). Survival of ionizing radiation is dependent on the organism’s sensitivity to a radiation source. Some cells have zero tolerance to radiation and are eliminated quickly at small doses,while others have resistive qualities due to chemical and physical structure as well as genetic repair attributes.The effectiveness of irradiation also depends on the composition of the medium, the moisture content,temperature, oxygen levels and fresh or frozen food state. A microbe’s resistance to ionizing radiation is determined by its inherent D-value. Larger D-values infer that a microorganism can withstand photon bombardment to a greater extent. Therefore larger doses ofradiation are required to induce inactivation. Irradiation techniques have been proven to cause at least a 5 log10 reduction in E. coli O157:H7 numbers for all forms of solid foods.Consequently,there is no visible damage done to a product at the required dosage and nutrition values are not effected. Heat effects of irradiation are negligible, ranging no more than 0.1˚C per 1 kGy of radiation. This amounts to less than a single degree Celsius increase in temperature, which is inconsequentialto the quality of the food. The shelf-life of irradiated food products is on average one of the longest, particularly when combined with effective packaging or refrigeration. Irradiation of food is a scalable process and it is possible to reach very high throughput levels in a continuous process with the aid of a conveyorbelt. Maintenance requirements are low, as mandatory replacement of the radiation source is no more than once every six months. Irradiation techniques are also approved by food regulatory agencies and a wide variety of methods are available depending on the dosage requirements for certain foods.Irradiation does not impart any new qualities on to the processed food,but is capable of extending shelf-life by a factor of up to four or five. Consumer opinion is improving as well. In 1993, only 29% of consumers answered
  15. 15. 14 positively on a survey that they would consume ground beef treated with irradiation technology.By 2003, this number had risen to 67% (Sommers & Xuetong, 2011). Table 3: IR Effectiveness for Selected Food Products Product: Dosage (at 10°C, atmospheric pressure): Shelf-life (refrigerated): Inhibition of E. coli O157:H7: Temperature changes due to energy increase: Frozen ground beef 0.30 - 0.98 kGy 1 - 2 months 7 log10 reductions 0.1°C per kGy Non-frozen ground beef 0.24 - 0.43 kGy 36 - 48 days 6.5 log10 reductions 0.1°C per kGy Frozen poultry 0.3 - 0.98 kGy 1 - 2 months 7 log10 reductions 0.1°C per kGy Non-frozen poultry 0.24 - 0.43 kGy 24 - 36 days 7 log10 reductions 0.1°C per kGy Apple 1.0 - 2.0 kGy 1 year 8 log10 reductions ˂ 0.1°C per kGy Non-frozen pork 0.422 - 0.447 kGy 36 - 48 days 6.5 log10 reductions 0.1°C per kGy Tomato 0.80 - 2.0 kGy 4 - 6 weeks 8 log10 reductions ˂ 0.1°C per kGy Cauliflower 0.564 kGy 6 - 7 weeks 7 log10 reductions ˂ 0.1°C per kGy Roast beef 0.569 kGy 2 - 3 months 6 log10 reductions ˂ 0.1°C per kGy Skim milk 1.0 - 2.0 kGy 9 - 12 months 6 log10 reductions 0.1°C per kGy High hydrostatic pressure (HHP) HHP is a method used in the food processing industry that subjects food to elevated pressures (up to 6000 atmospheres)to inactivate microorganisms or to alter food attributes.This is achieved with a minimal side effect on the quality of freshness and without the addition of heat. Pressure distribution throughout the product is rapid and uniform, hence there is no change in the physical structure of foods.The isostatic compression generated by HHP has critical effects on the structure of microorganisms like E. coli O157:H7. Produce treated using HPP is generally
  16. 16. 15 packaged to maintain a separation between the pressurized fluid and the food contents.The pressurizing fluid is compressed and exerts a force on the package that is transferred to the food. A typical pressure-transmitting fluid is water, as the compression heating characteristic of water is analogous to that of most food materials. Pressure is held for a number of minutes in order to ensure the desired inactivation. Inactivation of E. coli O157:H7 is related to the compressive heat that is generated during compression and damage is generally directed at the cell membrane. In addition to reducing E. coli O157:H7 counts on the surfaces of food, HHP confers longer shelf-life. It is limited in the types of foods that it can process due to physical constraints ofthe vesseland the structure of certain foods,such as whole eggs, which may crack. HHP is a batch process and involves a small amount of down-time for transfers in between cycles. Throughput sizes are also limited as containment becomes increasing difficult in larger vessels due to the increase in pressure to surface area ratio. HHP is approved by all regulatory agencies and in general has a positive consumer outlook. Table 4: HHP Effectiveness for Selected Food Products Product: Required Pressure: Shelf-life (refrigerated): Inhibition of E. coli O157:H7: Temperature changes due to pressure increase: Skim Milk 500 MPa 6 - 9 months 6.5 log10 reductions 3°C per 100 Mpa Cheese 400 MPa 2 - 4 months 7 log10 reductions 3°C per 100 MPa Pork 300 MPa 3 - 6 weeks 6 log10 reductions 5°C per 100 MPa Poultry 375 MPa 2 - 4 weeks 2 log10 reductions 4.5°C per 100 MPa
  17. 17. 16 Cooked Ham 500 MPa 10 - 12 weeks 4 log10 reductions 4.5°C per 100 MPa Oyster 300 MPa 3 - 7 days 4 log10 reductions 3.2°C per 100 MPa Beef 350 MPa 1 - 3 weeks 5 log10 reductions 6.3°C per 100 MPa Apple 400 MPa 4 - 6 months 6.5 log10 reductions 3°C per 100 MPa Tomato 300 MPa 2 - 5 weeks 6 log10 reductions 3.1°C per 100 MPa Pulsed electric fields Pulsed electric fields (PEF) is a non-thermal method of treatment for microbial inactivation in food products; however, it is only relevant for solid foods.High-voltage pulses (between 20-80 kV) are applied for short periods of time (µs to ms) to a product located between two electrodes (Elez-Martinez, Martin-Belloso, & Pena, 2011). PEF facilitates microbial inactivation by causing damage to the cell membrane through electroporation. Differences in charge across the bacterial membrane cause the expansion of existing pores and the creation of new pores. The introduction of these pores renders the cell permeable to small molecules, which eventually causes swelling and rupture of the cell. PEF is effective in causing reductions in E. coli O157:H7 of up to 5 log10 in liquid food media. It subsequently increases shelf-life due to the inactivation of enzymes responsible for spoilage. There is also no noticeable increase in internal temperature of the product,as the electric pulses are typically not sustained beyond a few microseconds. And despite its ability to process large volumes in a continuous process,PEF cannot process solid foods. It has attained approval by government regulatory agencies and its products are favored to untreated products.
  18. 18. 17 Table 5: PEF Effectiveness for Selected Food Products Product: Treatment Conditions: Shelf-life (refrigerated): Inhibition of E. coli O157:H7: Temperature changes due to energy increase: Skim milk Batch, 45 kV/cm, 150 pulses, 8 µs, 40°C 6 - 9 months 3 log10 Reductions Negligible Liquid egg yolk Continuous, 30 kV/cm, 105 pulses, 2 µs, 40°C 2 - 3 months 5 log10 Reductions Negligible Pea soup Continuous, 33 kV/cm, 30 pulses, 2 µs, 40°C 1 year 5.3 - 6.5 log10 Reductions Negligible Apple juice Continuous, 30 kV/cm, 43 pulses, 4 µs, 25°C 1 year 5 log10 Reductions Negligible Melon juice Continuous, 35 kV/cm, 400 pulses, 4 µs, 39°C 1 year 3.8 - 4.3 log10 Reductions Negligible Antimicrobial films and coatings (AF) Antimicrobial films and coatings are an environmentally-safe technology that creates a selectively- permeable barrier to water vapor, oxygen and carbon dioxide. Films are a stand-alone layer surrounding the produce with mechanical and tensile properties similar to that of the food product.Coating formation occurs directly on the surface of the product and provides protection and enhancement. A layer of film or coating effectively blocks all E. coli O157:H7 contaminants from growing on the surface of produce. The mechanism is simple: the skin is not penetrable by E. coli and contains antimicrobial agents derived from nature that prevent growth. Some of these
  19. 19. 18 antimicrobial agents may be fruit-based, protein-based or lipid-based. Given any solid surface, there exists an effective treatment by antimicrobial films and coatings. Products treated with films and coatings exhibit longer shelf-life than standard untreated items. There is also no heat generation associated with the binding of films to surfaces.The mechanical and structuralproperties of the product remain the same as before treatment; however, films and coatings create the possibility of conferring new properties onto the skin of the product such as novel flavors or preserving compounds.The coating process is semi-batch and therefore slightly slower than continuous production,but with more control over the input and output of the system. Because the vessels used for coating of products can be made quite large, and therefore able to process many items at once,throughput is not negatively affected by the discontinuous nature of the spray-coating process.Antimicrobial films and coatings are being sought afterby numerous producers across the world, though they still require government testing.Consumer opinion, on the other hand,is hopeful. Table 6: Antimicrobial Film Effectiveness for Selected Food Products Product: Treatment Conditions Shelf-life (refrigerated) Inhibition of E. coli O157:H7: Temperature changes due to exposure: Non-frozen beef Whey-protein isolated matrix with oregano and pimento oils 10 - 12 weeks 6 log10 reductions none Non-frozen turkey Gelatin matrix with 0.50% nisin 10 - 12 weeks 6 log10 reductions none Apple Chitosan matrix with 0.50% nisin 16 - 20 weeks 8.7 log10 reductions none Tomato Chitosan matrix with 0.50% nisin 10 - 12 weeks 7.5 log10 reductions none Orange Chitosan matrix only 12 - 14 weeks 8.2 log10 reductions none
  20. 20. 19 Melon Chitosan matrix only 12 - 14 weeks 8 log10 reductions none Grapes Chitosan matrix with 0.50% nisin 8 - 9 weeks 7.5 log10 reductions none Strawberry Chitosan matrix with 0.50% nisin 8 - 9 weeks 6 log10 reductions none Squash Chitosan matrix with 0.50% nisin 10 - 12 weeks 7 log10 reductions none AN ANALYSIS OF SUBSTITUTES Acceptable Alternatives Ozone induces a moderate-to-high log reduction of E. coli O157:H7 for fruits and vegetables at cool temperatures. This reduction leads to a subsequently longershelf-life for the product than if it had been only treated by washing with water. However, ozone treatment has proven to be difficult and overly complicated when dealing with meat products,which comprise a large portion of total processed foods.The ozone molecules oxidize the meat, causing discoloration, deterioration and drastic reductions in nutritional content.Therefore, ozone treatment is not a satisfactory alternative to heat treatment. Pulsed electric field technologies are entirely incapable of processing solid food and cannot be considered as an acceptable alternative – this criterion is the single most relevant in selecting a method to replace heat treatment. While this technology is efficient in creating an absence of E. coli in liquid foods, the main interest of this analysis is solid foods. Irradiation causes enormous reductions in E. coli O157:H7 levels for all types of solid foods,ranging from meats to fruits and vegetables. This inactivation does not come at the cost of increased heating,as irradiation does not cook produce at the low doses required for multiple log reductions of E. coli. The shelf-life extension of
  21. 21. 20 products treated by irradiation is also unparalleled by any other method besides antimicrobial films. Sensorial and nutritional quality do not differ noticeably from untreated fresh products.It is therefore an acceptable alternative according to the essential criteria. High hydrostatic pressure processing lacks the flexibility of irradiation in that more energy is required to cause meaningful reductions of E. coli. However, HHP is applicable for many different solid food types and eliminates E. coli O157:H7 by up to 5 log10 reductions in most of these types.HHP is also good for maintaining the sensorial and nutritional quality of processed foods,thus meeting shelf-life requirements. The heat generated by HHP processing may be problematic for a limited range of products,but for the most part, temperature rises are inconsequentialto the quality of the final product.Heat treatment typically induces heating in the range of 125 – 150°C. HHP causes temperature increases proportional to the amount of pressure,which for most cases is no more than 600 MPa, corresponding to an 18°C increase. HHP therefore meets the heating requirements. Antimicrobial films are a rival only to irradiation as far as log10 reductions of E. coli numbers. The majority of products treated with films and coatings experience a reduction of over 5 log10.Films and coatings are applicable for all solid food types,ranging from meat to fruits and vegetables and maintain the sensorialand nutritional quality of fresh, untreated produce.Temperature increases are also completely eliminated by this process,therefore making it a suitable alternative according to the essentialcriteria. Desirable Alternatives Irradiation of food is often associated with negative connotation,likely because its name implies the need for a radioactive source.It is commonplace to believe that some of the essence ofthis radioactive source is transferred to the food being treated, where in reality only the E. coli cells are affected by the radiation. Despite the mixed opinions from consumers, food irradiation technologies have undergone rigorous testing by various U.S. regulatory agencies and have been approved for use.It is acknowledged by the FDA and USDA that irradiation of food in fact vastly improves quality over untreated or heat treated products by extending shelf-life to four to five times the untreated product.Irradiation technologies also boast a very high throughput – about 500 pounds per hour (226.8 kg/hr) – making application on the desired scale possible and economically beneficial.
  22. 22. 21 High hydrostatic pressure processing is typically employed by producers within a local but not regional market. This is because the pressure vessels used to achieve reduction in E. coli O157:H7 are not built above a certain volume due to design limitations associated with the high pressures needed to attain significant reduction. As a result, throughput is lower than for othercompeting methods like irradiation and antimicrobial films, on the order of 100 – 150 pounds perhour, maximum. The shelf-life conferred to treated products is also substantially shorter than either irradiation or antimicrobial films, as log reductions are not as numerable. HHP technologies are government approved and draw a reasonable amount of good reputation from consumers (between a 43 – 80% approval rating for various foods). Antimicrobial films are a progressive alternative to older techniques like pressure, heat and radiation treatment that currently lacks extensive government and consumer testing.Designs for coating processes take into account large-scale operations such as that which is the focus of this paper, but they are not continuous.Their semi- batch mechanism allows for greater control over conditions for different types of food, and the same processing chamber can be used for multiple products in different cycles. The process is also fairly quick, with the products only requiring a minute or less inside the coating chamber, which permits multiple cycles per hour. The materials needed for the coatings and films are inexpensive, mostly comprising isolated salts and proteins that effectively block the growth of E. coli O157:H7. Antimicrobial films offer a property that other processing technologies do not, which is the enhancement of produce with additives contained in the surface. This not only extends shelf-life but can lead to dramatic improvements in overall sensorial and nutritional quality. Compared to irradiation and high hydrostatic pressure processing,antimicrobial films boast the best reputation from consumer testing,though the technology is not yet mature. Antimicrobial films virtually have the largest application for solid foods sold by grocers. Potential Problem Analysis Irradiation techniques,though they offer feasibly high throughput,exceptional protection from E. coli O157:H7 and extremely long shelf-life, face problems in the public sector.Consumers are not entirely convinced of the safety of irradiated food. For all food categories, consumer approval trails behind alternatives like antimicrobial films and HHP. For example, 75% and 72% of consumers preferred non-frozen beef treated by antimicrobial films
  23. 23. 22 and HHP, respectively, while only 59% approved the beef processed using irradiation. Outside of the scope of the criteria, as a side note, the presence of a radiation source in a food processing plant is of substantialconcern. While the design of the process does not involve any produce coming in contact with the radiation source,errors in the systemor in mishandling can create opportunities for exposure. This would have catastrophic consequences forthe plant if the contaminated food is consumed. The radiation source must also be disposed when it has been exhausted ; however, it is still radioactive even once its use period has been finished. HHP has the disadvantage ofscaling-up problems, as the pressure vessels cannot be built above a certain volume and are capable of a limited number of cycles per day. There is also the down-time associated with transfer between cycles. As HHP is dealing with very high pressures,there is a risk of explosion. The equipment is under constant compressive and decompressive strain and the metal comprising the pressure vesselexperiences wear each time a cycle is run. Safety measures have been built into pressure vessels to gage the amount of wear a unit has taken; there is a design which leaks instead of undergoing rapid failure all at once. Even with this feature, however, the HHP unit would be under heavy usage in the plant being considered and fracture would be an imminent threat for the process and for workers. Antimicrobial films, like irradiation, support a very high throughput; however,this efficiency comes at the cost of uniformity. The coatings are sprayed onto the product from sprayers within the chamber. Due to the large number of products being processed percycle, food items will be put into the chamber in layers. There is a high probability that not all surfaces of the products will be exposed to the spray due to impediments such as other products in the chamber and uneven spraying. This would result in a patchy or incomplete surface coating. Additionally, the chamber must be cleaned prior to the start of every new cycle, particularly in the case where the same chamber is used for different foods.This creates a down-time that must be considered in throughput calculations. Such a down-time adds to the time that it takes to remove a load of produce and replace it with a new untreated load. Lastly, if films and coatings of different compositions are to be used,there is anotherdown -time associated with replacing the feed storage tank.
  24. 24. 23 TABLES OF COMPARISON Table 7: Application of Methods Process: % of solid foods in which treatment is viable Heat Treatment 40.00 HHP 70.00 IR 90.00 PEF 2.00 Ozone 60.00 Films 95.00 Table 8: Comparison of Quality/Shelf-life Process Product: Pre-process cleaning only HPP IR PEF Ozone Films Beef (non-frozen) 2 - 3 days 1 - 3 weeks 6 - 7 weeks N/A N/A 10 - 12 weeks Poultry (non-frozen) 2 - 3 days 2 - 4 weeks 4 - 6 weeks N/A N/A 10 - 12 weeks Apple 14 - 20 days 4 - 6 months 1 year N/A 4 - 6 months 4 - 5 months Tomato 8 - 12 days 2 - 5 weeks 4 - 6 weeks N/A 3 - 4 weeks ~ 3 months
  25. 25. 24 Table 9: Comparison of Inhibition Abilities for E. coli O157:H7 Process Product: Pre-process cleaning only HPP IR PEF Ozone Films Beef (non-frozen) 2.9 log10 reductions 5 log10 reductions 6.5 log10 reductions N/A N/A 6 log10 reductions Poultry (non-frozen) 2.5 log10 reductions 2 log10 reductions 7 log10 reductions N/A N/A 6 log10 reductions Apple 2.4 log10 reductions 6.5 log10 reductions 8 log10 reductions N/A 3.7 log10 reductions 8.7 log10 reductions Tomato 2.6 log10 reductions 6 log10 reductions 8 log10 reductions N/A 4.2 log10 reductions 7.5 log10 reductions Table 10: Comparison of Heating Process Product: Heat treatment HPP IR PEF Ozone Films Beef (non-frozen) 150˚C 6.3°C per 100 Mpa 0.1°C per kGy negligible negligible none Poultry (non-frozen) 150˚C 4.5°C per 100 MPa 0.1°C per kGy negligible negligible none Apple 150˚C 3°C per 100 MPa ˂ 0.1°C per kGy negligible negligible none Tomato 150˚C 3.1°C per 100 MPa ˂ 0.1°C per kGy negligible negligible none Table 11: Evaluation of Throughput for HHP Product: Process type: Equivalent working days: Cycles per 12- hr day: Volume per cycle: Beef (non-frozen) Batch 256 12 250 L
  26. 26. 25 Poultry (non-frozen) Batch 316 12 250 L Apple Batch 328 16 1000 L Tomato Batch 322 15 1000 L Table 12: Evaluation of Throughput for IR Product: Process type: Equivalent working days: Process Duration: Throughput (per day): Beef (non-frozen) Continuous 324 0.5 min. 2700 kg Poultry (non-frozen) Continuous 330 0.5 min. 2700 kg Apple Continuous 344 2 min. 2700 kg Tomato Continuous 335 2 min. 2700 kg Table 13: Evaluation of Throughput for Ozone Product: Process type: Equivalent working days: Process Duration: Throughput (per day): Beef (non-frozen) N/A Poultry (non-frozen) N/A Apple Continuous 330 3 min. 2700 kg Tomato Continuous 320 3 min. 2700 kg
  27. 27. 26 Table 14: Evaluation of Throughput for Antimicrobial Films Product: Process type: Equivalent working days: Process Duration: Throughput (per cycle): Throughput (per day): Beef (non-frozen) Semi-batch 286 1 min. 18 kg 720 kg Poultry (non-frozen) Semi-batch 313 1 min. 18 kg 720 kg Apple Semi-batch 324 1 min. 20 kg 800 kg Tomato Semi-batch 316 1 min. 20 kg 800 kg Table 15: Percent of Untrained Consumers Who Favor Processed Food over Non-processed (2009) Process Product: HPP IR PEF Ozone Films Beef (frozen): 68% 48% N/A N/A 72% Beef (non-frozen): 72% 59% N/A N/A 75% Poultry (frozen): 69% 42% N/A N/A 69% Poultry (non-frozen): 64% 60% N/A N/A 71% Apple: 80% 52% N/A 52% 83% Tomato: 43% 61% N/A 47% 90%
  28. 28. 27 RECOMMENDATION Antimicrobial films and coatings are best suited for the non-thermal treatment of solid food products.This method is designed to support all types of solid foods and is fairly simple as far as operation and the mechanism of E. coli reduction. Films and coatings also provide extended protection,where techniques such as irradiation and HHP eliminate bacteria in only one instance,which is at the processing stage.The surfaces created by antimicrobial films are designed to last and provide a continuous barrier against exposures to E. coli O157:H7. E. coli can neither grow on the film nor penetrate it. Large-scale production on the order of hundreds of kilograms per hour is limited but not abated by the throughput capacity of the coating unit. In addition to increased shelf-life, antimicrobial films also create the possibility for new products that combine different salts, lipids, proteins and minerals for enhanced smell, flavor, appearance or nutritional value. It is suggested that the down-time can be diminished and the throughput increased by the operation of multiple spraying units. The units are simple and inexpensive, and the necessary materials are easy to attain and non-toxic to store.There is no heating associated with films and coatings and complete inhibition is guaranteed,especially when multiple coatings are applied. FUTURE WORK Antimicrobial films and coatings have not yet reached the full approval stage by the FDA or USDA. Their presence elsewhere in the world is limited and is not on a large commercial scale. Therefore, the technology must be made scalable so that the larger volumes of produce required by the concerned plant can be treated in an efficient and economically sensible manner. Most of the validation that remains for films and coatings lies in repeatability and reproducibility of their experiments. Once approval has been gained, however, throughput can be further enhanced by the design of a continuous process,which may be possible with the use of sprayers assisted by a conveyorbelt. Further along, once the technology has been established and found to be effective, there is a strong possibility of further development of films and coatings for the post-processing packaging stage.In lieu of plastic packaging, which is dangerous to the environment, thick films or coatings that can be eaten or peeled off and composted can be used to protect food during transportation and storage.Such technology is not far from reality considering the success already found by current antimicrobial films and coatings.
  29. 29. 28 REFERENCES Badii, F., & Maftoonazad, N. (2009). Use of Edible Films and Coatings to Extend the Shelf Life of Food Products. Recent Patentson Food,Nutrition & Agriculture, 1, pp. 162-170. Badler, N. I., Jr., J. T., & Raja, S. (2011). Fruit Senescence and Decay Simulation. The Eurographics,30(2). Balasubramaniam, V., & Nguyen, L. T. (2011). Fundamentals of Food Processing Using High Pressure. In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 3-18). Blackwell Publishing Ltd. Balasubramaniam, V., Kaletunc, G., & Ramaswamy, R. (2011). High Pressure Processing: Fact Sheet for Food Processors.In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 596- 598). Blackwell Publishing Ltd. Black, E. P., Hoover, D. G., & Stewart, C. M. (2011). Microbiological Aspects ofHigh-Pressure Food Processing. In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 51-71). Blackwell Publishing Ltd. Bruhn, C. M. (2011). Frequently Asked Questions About Food Irradiation. In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 612-613). Blackwell Publishing Ltd. Caillet, S., Lacroix, M., Salmieri, S., Saucier, L., & Oussalah, M. (2004). Antimicrobial and Antioxidant Effects of Milk Protein-Based Film Containing Essential Oils for the Preservation of Whole Beef Muscle. Journal of Agricultural and Food Chemistry, 52, pp. 5598-5605. Cebrian, G., Condon,S., & Manas,P. (2011). Novel Technologies in Combined Processes.In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 379-404). Blackwell Publishing Ltd. Chauvin, M. A., & Swanson, B. G. (2011). Biochemical Aspects ofHigh-Pressure Food Processing . In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 72-88). Blackwell Publishing Ltd. Dawson, P., Han, I., & Min, B. (2010). Antimicrobial gelatin films reduce Listeria monocytogenes on turkey bologna. Poultry Science,89, pp. 1307-1314. Elez-Martinez, P., Martin-Belloso, O., & Pena, M. M.-d. (2011, March 23). Food Preservation by Pulsed Electric Fields: An Engineering Perspective. Food Engineering Review, 3, pp. 94-107. Farkas, J. (1998). Irradiation as a method for decontaminating food: A review. International Journal ofFood Microbiology,44,pp. 189-204. Farkas, J. (2006). Irradiation for better foods. Trends in Food Science & Technology,17, pp. 148-152. Gutsol, A., & Niemira, B. A. (2011). Nonthermal Plasma as a Novel Food Processing Technology.In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 271-287). Institute of Food Technologists. Han, J. H., & Lee, D. S. (2011). Antimicrobial Packaging. In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologiesfor Food (pp. 462-471). Blackwell Publishing Ltd. . Palou, L., Perez-Gago, M. B., Rio, M. A., & Valencia-Chamorro, S. A. (2011). Antimicrobial Edible Films and Coatings for Fresh and Minimally Processed Fruits and Vegetables: A Review. In Critical Reviews in Food Science and Nutrition (pp. 872-900). Taylor & Francis.
  30. 30. 29 Rodriguez-Romo, L. A., Vurma, M., & Yousef, A. E. (2011). Basics of Ozone Sanitization and Food Applications. In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 291-313). Blackwell Publishing Ltd. Sommers, C., & Xuetong,F. (2011). Irradiation of Ground Beef and Fresh Produce. In C. Dunne, D. Farkas, & a. J. Yuan, Nonthermal Processing Technologies for Food (pp. 236-248). Institute of Food Technologists. Ting, E. (2011). High-Pressure Processing Equipment Fundamentals. In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 20-34). Blackwell Publishing Ltd. Tonello, C. (2011). Case Studies on High-Pressure Processing of Foods.In C. Dunne, D. Farkas, & J. Yuan, Nonthermal Processing Technologies for Food (pp. 36-50). Blackwell Publishing Ltd. Zorlugenc, B., & Zorlugenc, F. K. (2012). Ozone in Food Preservation. In A. K. Alias, R. Bhat, & G. Paliyath (Eds.), Progress in Food Preservation (1 ed., pp. 231-245). John Wiley & Sons,Ltd.

×