Abstract An inexpensive data acquisition method was developed to validate the exact number and sh... more Abstract An inexpensive data acquisition method was developed to validate the exact number and shape of the pulses applied during pulsed electric field (PEF) processing. The novel validation method was evaluated in conjunction with developing a PEF process for pasteurizing strawberry puree. Both buffered peptone water (BPW) and fresh strawberry puree (pH 2.4) were inoculated with Escherichia coli (ATCC 35218) and processed using a pilot plant PEF system at field strengths of 24.0–33.6 kV/cm, outlet temperatures of 45.0–57.5 °C and a flow rate of 100 l/hr. An accelerated aging storage study was performed on the quality of a strawberry beverage made from the strawberry puree. The populations of E. coli were reduced by 6.5 log in BPW at 30 kV/cm and 57.5 °C and 7.3 log in strawberry puree at 24 kV/cm and 52.5 °C. The taste and color of strawberry beverage initially made from PEF processed puree was fresh and bright red, respectively. The color remained good for the first 3 months-equivalent of storage and there was only a very slight drop in flavor. The data acquisition system captured the details of every pulse applied at a rate of 400 Hz for 1 h for a total of over 1.4 million pulses. Strawberry puree was pasteurized in a pilot-scale PEF unit. In addition, a data acquisition system was developed to validate the process which should aid in obtaining FDA approval of the PEF process.
Effects of pulsed electric fields (PEF) at 35 kV/cm for 59 micros on the quality of orange juice ... more Effects of pulsed electric fields (PEF) at 35 kV/cm for 59 micros on the quality of orange juice were investigated and compared with those of heat pasteurization at 94.6 degrees C for 30 s. The PEF treatment prevented the growth of microorganisms at 4, 22, and 37 degrees C for 112 days and inactivated 88% of pectin methyl esterase (PME) activity. The PEF-treated orange juice retained greater amounts of vitamin C and the five representative flavor compounds than the heat-pasteurized orange juice during storage at 4 degrees C (p < 0.05). The PEF-treated orange juice had lower browning index, higher whiteness (L), and higher hue angle (theta) values than the heat-pasteurized orange juice during storage at 4 degrees C (p < 0. 05). The PEF-treated orange juice had a smaller particle size than the heat-pasteurized orange juice (p < 0.05). degrees Brix and pH values were not significantly affected by processing methods (p > 0. 05).
Bovine immunoglobulin G (IgG) solutions were subjected to pulsed electric fields (PEF) or heat tr... more Bovine immunoglobulin G (IgG) solutions were subjected to pulsed electric fields (PEF) or heat treatment to investigate the effect of processing on secondary structure monitored using circular dichroism spectrometry. Under heat treatment, the critical temperature for bovine IgG to change secondary structure at neutral pH in borate buffer is 72 degrees C. A conversion of the secondary structure from beta-sheets into random coils along with the loss of immunoactivity of bovine IgG was observed when heated at 82 degrees C for 120 s. In contrast, PEF treatment at 41.1 kV/cm for 54 mus with bipolar pulses (outlet at 43.8 degrees C) caused no detectable changes in the secondary structure or the thermal stability of secondary structure. A shape factor, S (200nm) over (217nm), ratio of magnitude of the positive CD band at 200 nm to that of the negative CD band at 217 nm, was closely correlated to the immunoactivity of bovine IgG (r(2) = 0.99) and quantifies changes of secondary structure.
Effects of commercial scale pulsed electric field (PEF) processing on the quality of tomato juice... more Effects of commercial scale pulsed electric field (PEF) processing on the quality of tomato juice were studied and compared with those of thermal processing. Tomato juice was prepared by hot break at 88 degrees C for 2 min or by cold break at 68 degrees C for 2 min and then thermally processed at 92 degrees C for 90 s or PEF processed at 40 kV/cm for 57 micros. Thermally processed, PEF processed, and unprocessed control juices were packed into 50 mL sterilized polypropylene tubes in a sanitary glovebox and stored at 4 degrees C for 112 days. Both thermally and PEF processed juices showed microbial shelf life at 4 degrees C for 112 days. The lipoxygenase activities of thermally and PEF processed juices were 0 and 47%, respectively. PEF processed juice retained more ascorbic acid than thermally processed juice at 4 degrees C for 42 days (p < 0.05). No significant differences were observed in the concentration of lycopene, degrees Brix, pH, or viscosity between thermally and PEF processed juices during the storage (p > 0.05). Sensory evaluations indicated that flavor and overall acceptability of PEF processed juice were preferred to those of thermally processed juice (p < 0.05).
Zhang/Nonthermal Processing Technologies for Food, 2011
Kim, M. and Zhang, HQ (2010) Improving Electrode Durability of PEF Chamber by Selecting Suitable ... more Kim, M. and Zhang, HQ (2010) Improving Electrode Durability of PEF Chamber by Selecting Suitable Material, in Nonthermal Processing Technologies for Food (eds HQ Zhang, GV Barbosa-Cánovas, V. Balasubramaniam, CP Dunne, DF Farkas and JT Yuan), Wiley-...
ABSTRACT Pulsed electric field (PEF) processing of juice has been intensively studied with bencht... more ABSTRACT Pulsed electric field (PEF) processing of juice has been intensively studied with benchtop scale experiments. However, there is still limited information regarding critical factors to be considered for PEF efficacy in microbial reduction with PEF processing during pilot or commercial scale production of juice. In the present study, continuous benchtop (3.6–7.2 L/h) PEF processing systems with co-field treatment chambers and bipolar square waveform pulses were used and simulated production conditions were tested for pomegranate juice. Microbial reductions of Escherichia coli, as affected by PEF process conditions (field strength, pulse width, pulse frequency, total treatment time, input energy), production conditions (flow rate, juice holding time and temperature), and juice properties (pH, conductivity, particulate), were investigated. Flow rate, PEF process parameters, production conditions, type of target microorganism, and properties of juice significantly affected microbial reductions by PEF treatments. E. coli ATCC 35218, a non pathogenic surrogate bacterium, exhibited higher resistance to PEF treatments than E. coli O157:H7 and E. coli K12 in pomegranate juice. Increase of a single PEF parameter (field strength, pulse width, pulse frequency, total treatment time, or energy input) is insufficient to achieve maximum microbial reduction. Optimal PEF treatment conditions for maximum microbial reduction depend on multiple factors including PEF processing parameters, production conditions and product properties. This study demonstrates that scale-up and validation studies in a specific PEF system for specific products are very important and necessary before successful commercial application of this novel technology is possible.
Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high... more Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high voltage electric field to kill spoilage microorganisms in foods. PEF treatment maintains flavor, color, taste and nutritional value of foods while destroying microorganisms. PEF is useful in processing liquid foods where the food can flow between two electrodes. The generation of PEF processing requires a pulsed power supply, a series of treatment chambers and a temperature regulating system. Therefore, a PEF system usually consists of a high voltage pulse generator, a treatment chamber and a fluid handling system. To process a product using PEF in a continuous system, the product flows through a series of PEF treatment chambers where it is exposed to the desired electric field strength for a desired amount of time. The pulse generator is capable of converting low voltage electricity into high voltage energy to be stored in capacitors until discharged. Three different shapes of high voltage waveforms can be generated and applied to foods. The three waveforms are square wave, exponential decay and under-damped RCL (resistive capacitive and inductive discharge circuit). High voltage electricity is transferred into the food product in the treatment chambers, which may be designed for either static (batch) or continuous processing.
Illnesses resulting from contaminated fruits and vegetables are a continuing concern for the fres... more Illnesses resulting from contaminated fruits and vegetables are a continuing concern for the fresh produce industry. Conventional tools to identify where contamination problems exist have not given the industry adequate information to quickly and economically respond to potential problems. The lack of a reliable, broad-based, economical kill step (e.g., a treatment capable of inactivating human pathogens) suitable for use on fresh produce is a limiting factor in responding to the increased demands for more stringent food safety targets in the fresh produce arena. This chapter summarizes recent data in two critical areas of research. First, is a review of new detection tools and technologies that are being developed to enhance our ability to rapidly locate and quantify contamination when and where it occurs. Second, information is presented on new interventions and antimicrobial processes than can reduce or eliminate populations of human pathogens on fresh and fresh-cut fruits and vegetables. Also, this chapter will briefly discuss the applicability of these new technologies to the production and processing of organic fruits and vegetables, and will consider the challenge of technology development for this growing market segment.
Abstract: The Combat Rations Network (CORANET) is a Defense Logistic Agency (DLA) sponsored manuf... more Abstract: The Combat Rations Network (CORANET) is a Defense Logistic Agency (DLA) sponsored manufacturing technology program to improve the quality, reduce the cost, and increase the productivity of operational rations while increasing DLA's surge capability in ...
Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high... more Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high voltage electric field to kill spoilage microorganisms in foods. PEF treatment maintains flavor, color, taste and nutritional value of foods while destroying microorganisms. PEF is useful in processing liquid foods where the food can flow between two electrodes. The generation of PEF processing requires a pulsed power supply, a series of treatment chambers and a temperature regulating system. Therefore, a PEF system usually consists of a high voltage pulse generator, a treatment chamber and a fluid handling system. To process a product using PEF in a continuous system, the product flows through a series of PEF treatment chambers where it is exposed to the desired electric field strength for a desired amount of time. The pulse generator is capable of converting low voltage electricity into high voltage energy to be stored in capacitors until discharged. Three different shapes of high voltage waveforms can be generated and applied to foods. The three waveforms are square wave, exponential decay and under-damped RCL (resistive capacitive and inductive discharge circuit). High voltage electricity is transferred into the food product in the treatment chambers, which may be designed for either static (batch) or continuous processing.
ABSTRACT Effects of process parameters such as forming temperature, forming air pressure and heat... more ABSTRACT Effects of process parameters such as forming temperature, forming air pressure and heating time on wall thickness distribution in plug-assist thermoformed food containers using multilayered material were investigated. Multilayered rollstockbase material formed into containers by thermoforming process using a Benco aseptic packaging machine. Forming temperatures in the range of 131–170°C, airforming pressures of 2, 3, 3. 5 and 4 bars, and heating times of 66, 74, 84, 97 and 114 seconds were used in the thermoforming process. Analysis of wall thickness data obtained for the thermoforming parameters used in this study showed that wall thickness was significantly affected by forming temperature, pressure and heating time at 0.05 significance level. Besides the processing parameters, wall location, container side, and their interactions significantly affected wall thickness. Forming temperature was found to be the principle parameter influencing wall thickness distribution in a plug-assist thermoforming operation. The optimum operating conditions of the packaging machine for the thermoforming process are: 146–156°C for forming temperature, 2–4 bars for air-forming pressure and 74–97 seconds for heating time.
Abstract An inexpensive data acquisition method was developed to validate the exact number and sh... more Abstract An inexpensive data acquisition method was developed to validate the exact number and shape of the pulses applied during pulsed electric field (PEF) processing. The novel validation method was evaluated in conjunction with developing a PEF process for pasteurizing strawberry puree. Both buffered peptone water (BPW) and fresh strawberry puree (pH 2.4) were inoculated with Escherichia coli (ATCC 35218) and processed using a pilot plant PEF system at field strengths of 24.0–33.6 kV/cm, outlet temperatures of 45.0–57.5 °C and a flow rate of 100 l/hr. An accelerated aging storage study was performed on the quality of a strawberry beverage made from the strawberry puree. The populations of E. coli were reduced by 6.5 log in BPW at 30 kV/cm and 57.5 °C and 7.3 log in strawberry puree at 24 kV/cm and 52.5 °C. The taste and color of strawberry beverage initially made from PEF processed puree was fresh and bright red, respectively. The color remained good for the first 3 months-equivalent of storage and there was only a very slight drop in flavor. The data acquisition system captured the details of every pulse applied at a rate of 400 Hz for 1 h for a total of over 1.4 million pulses. Strawberry puree was pasteurized in a pilot-scale PEF unit. In addition, a data acquisition system was developed to validate the process which should aid in obtaining FDA approval of the PEF process.
Effects of pulsed electric fields (PEF) at 35 kV/cm for 59 micros on the quality of orange juice ... more Effects of pulsed electric fields (PEF) at 35 kV/cm for 59 micros on the quality of orange juice were investigated and compared with those of heat pasteurization at 94.6 degrees C for 30 s. The PEF treatment prevented the growth of microorganisms at 4, 22, and 37 degrees C for 112 days and inactivated 88% of pectin methyl esterase (PME) activity. The PEF-treated orange juice retained greater amounts of vitamin C and the five representative flavor compounds than the heat-pasteurized orange juice during storage at 4 degrees C (p < 0.05). The PEF-treated orange juice had lower browning index, higher whiteness (L), and higher hue angle (theta) values than the heat-pasteurized orange juice during storage at 4 degrees C (p < 0. 05). The PEF-treated orange juice had a smaller particle size than the heat-pasteurized orange juice (p < 0.05). degrees Brix and pH values were not significantly affected by processing methods (p > 0. 05).
Bovine immunoglobulin G (IgG) solutions were subjected to pulsed electric fields (PEF) or heat tr... more Bovine immunoglobulin G (IgG) solutions were subjected to pulsed electric fields (PEF) or heat treatment to investigate the effect of processing on secondary structure monitored using circular dichroism spectrometry. Under heat treatment, the critical temperature for bovine IgG to change secondary structure at neutral pH in borate buffer is 72 degrees C. A conversion of the secondary structure from beta-sheets into random coils along with the loss of immunoactivity of bovine IgG was observed when heated at 82 degrees C for 120 s. In contrast, PEF treatment at 41.1 kV/cm for 54 mus with bipolar pulses (outlet at 43.8 degrees C) caused no detectable changes in the secondary structure or the thermal stability of secondary structure. A shape factor, S (200nm) over (217nm), ratio of magnitude of the positive CD band at 200 nm to that of the negative CD band at 217 nm, was closely correlated to the immunoactivity of bovine IgG (r(2) = 0.99) and quantifies changes of secondary structure.
Effects of commercial scale pulsed electric field (PEF) processing on the quality of tomato juice... more Effects of commercial scale pulsed electric field (PEF) processing on the quality of tomato juice were studied and compared with those of thermal processing. Tomato juice was prepared by hot break at 88 degrees C for 2 min or by cold break at 68 degrees C for 2 min and then thermally processed at 92 degrees C for 90 s or PEF processed at 40 kV/cm for 57 micros. Thermally processed, PEF processed, and unprocessed control juices were packed into 50 mL sterilized polypropylene tubes in a sanitary glovebox and stored at 4 degrees C for 112 days. Both thermally and PEF processed juices showed microbial shelf life at 4 degrees C for 112 days. The lipoxygenase activities of thermally and PEF processed juices were 0 and 47%, respectively. PEF processed juice retained more ascorbic acid than thermally processed juice at 4 degrees C for 42 days (p < 0.05). No significant differences were observed in the concentration of lycopene, degrees Brix, pH, or viscosity between thermally and PEF processed juices during the storage (p > 0.05). Sensory evaluations indicated that flavor and overall acceptability of PEF processed juice were preferred to those of thermally processed juice (p < 0.05).
Zhang/Nonthermal Processing Technologies for Food, 2011
Kim, M. and Zhang, HQ (2010) Improving Electrode Durability of PEF Chamber by Selecting Suitable ... more Kim, M. and Zhang, HQ (2010) Improving Electrode Durability of PEF Chamber by Selecting Suitable Material, in Nonthermal Processing Technologies for Food (eds HQ Zhang, GV Barbosa-Cánovas, V. Balasubramaniam, CP Dunne, DF Farkas and JT Yuan), Wiley-...
ABSTRACT Pulsed electric field (PEF) processing of juice has been intensively studied with bencht... more ABSTRACT Pulsed electric field (PEF) processing of juice has been intensively studied with benchtop scale experiments. However, there is still limited information regarding critical factors to be considered for PEF efficacy in microbial reduction with PEF processing during pilot or commercial scale production of juice. In the present study, continuous benchtop (3.6–7.2 L/h) PEF processing systems with co-field treatment chambers and bipolar square waveform pulses were used and simulated production conditions were tested for pomegranate juice. Microbial reductions of Escherichia coli, as affected by PEF process conditions (field strength, pulse width, pulse frequency, total treatment time, input energy), production conditions (flow rate, juice holding time and temperature), and juice properties (pH, conductivity, particulate), were investigated. Flow rate, PEF process parameters, production conditions, type of target microorganism, and properties of juice significantly affected microbial reductions by PEF treatments. E. coli ATCC 35218, a non pathogenic surrogate bacterium, exhibited higher resistance to PEF treatments than E. coli O157:H7 and E. coli K12 in pomegranate juice. Increase of a single PEF parameter (field strength, pulse width, pulse frequency, total treatment time, or energy input) is insufficient to achieve maximum microbial reduction. Optimal PEF treatment conditions for maximum microbial reduction depend on multiple factors including PEF processing parameters, production conditions and product properties. This study demonstrates that scale-up and validation studies in a specific PEF system for specific products are very important and necessary before successful commercial application of this novel technology is possible.
Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high... more Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high voltage electric field to kill spoilage microorganisms in foods. PEF treatment maintains flavor, color, taste and nutritional value of foods while destroying microorganisms. PEF is useful in processing liquid foods where the food can flow between two electrodes. The generation of PEF processing requires a pulsed power supply, a series of treatment chambers and a temperature regulating system. Therefore, a PEF system usually consists of a high voltage pulse generator, a treatment chamber and a fluid handling system. To process a product using PEF in a continuous system, the product flows through a series of PEF treatment chambers where it is exposed to the desired electric field strength for a desired amount of time. The pulse generator is capable of converting low voltage electricity into high voltage energy to be stored in capacitors until discharged. Three different shapes of high voltage waveforms can be generated and applied to foods. The three waveforms are square wave, exponential decay and under-damped RCL (resistive capacitive and inductive discharge circuit). High voltage electricity is transferred into the food product in the treatment chambers, which may be designed for either static (batch) or continuous processing.
Illnesses resulting from contaminated fruits and vegetables are a continuing concern for the fres... more Illnesses resulting from contaminated fruits and vegetables are a continuing concern for the fresh produce industry. Conventional tools to identify where contamination problems exist have not given the industry adequate information to quickly and economically respond to potential problems. The lack of a reliable, broad-based, economical kill step (e.g., a treatment capable of inactivating human pathogens) suitable for use on fresh produce is a limiting factor in responding to the increased demands for more stringent food safety targets in the fresh produce arena. This chapter summarizes recent data in two critical areas of research. First, is a review of new detection tools and technologies that are being developed to enhance our ability to rapidly locate and quantify contamination when and where it occurs. Second, information is presented on new interventions and antimicrobial processes than can reduce or eliminate populations of human pathogens on fresh and fresh-cut fruits and vegetables. Also, this chapter will briefly discuss the applicability of these new technologies to the production and processing of organic fruits and vegetables, and will consider the challenge of technology development for this growing market segment.
Abstract: The Combat Rations Network (CORANET) is a Defense Logistic Agency (DLA) sponsored manuf... more Abstract: The Combat Rations Network (CORANET) is a Defense Logistic Agency (DLA) sponsored manufacturing technology program to improve the quality, reduce the cost, and increase the productivity of operational rations while increasing DLA's surge capability in ...
Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high... more Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high voltage electric field to kill spoilage microorganisms in foods. PEF treatment maintains flavor, color, taste and nutritional value of foods while destroying microorganisms. PEF is useful in processing liquid foods where the food can flow between two electrodes. The generation of PEF processing requires a pulsed power supply, a series of treatment chambers and a temperature regulating system. Therefore, a PEF system usually consists of a high voltage pulse generator, a treatment chamber and a fluid handling system. To process a product using PEF in a continuous system, the product flows through a series of PEF treatment chambers where it is exposed to the desired electric field strength for a desired amount of time. The pulse generator is capable of converting low voltage electricity into high voltage energy to be stored in capacitors until discharged. Three different shapes of high voltage waveforms can be generated and applied to foods. The three waveforms are square wave, exponential decay and under-damped RCL (resistive capacitive and inductive discharge circuit). High voltage electricity is transferred into the food product in the treatment chambers, which may be designed for either static (batch) or continuous processing.
ABSTRACT Effects of process parameters such as forming temperature, forming air pressure and heat... more ABSTRACT Effects of process parameters such as forming temperature, forming air pressure and heating time on wall thickness distribution in plug-assist thermoformed food containers using multilayered material were investigated. Multilayered rollstockbase material formed into containers by thermoforming process using a Benco aseptic packaging machine. Forming temperatures in the range of 131–170°C, airforming pressures of 2, 3, 3. 5 and 4 bars, and heating times of 66, 74, 84, 97 and 114 seconds were used in the thermoforming process. Analysis of wall thickness data obtained for the thermoforming parameters used in this study showed that wall thickness was significantly affected by forming temperature, pressure and heating time at 0.05 significance level. Besides the processing parameters, wall location, container side, and their interactions significantly affected wall thickness. Forming temperature was found to be the principle parameter influencing wall thickness distribution in a plug-assist thermoforming operation. The optimum operating conditions of the packaging machine for the thermoforming process are: 146–156°C for forming temperature, 2–4 bars for air-forming pressure and 74–97 seconds for heating time.
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