Abstract Thermal transitions in frozen foods may occur due to temperature fluctuations during sto... more Abstract Thermal transitions in frozen foods may occur due to temperature fluctuations during storage and distribution, inducing ice recrystallization and loss of food quality. This study evaluated the effects of state/phase transitions on ice recrystallization and on mechanical properties of unblanched and blanched potatoes. Potato samples were frozen at −32 °C for 5 days to achieve a glassy state and then subjected to temperature fluctuations of varying amplitudes to achieve different physical states: glassy state with temperature fluctuation, rubbery and thawed states. Ice crystal size of potatoes was evaluated using scanning electron microscopy (SEM) through pore analysis of freeze-dried potatoes. Hardness of potatoes was determined using texture analyzer. Temperature fluctuation increased the ice crystal size and reduced the hardness of potatoes-the changes depended on the severity of temperature fluctuations and the treatment medium. Findings may inform improved packaging design, storage and transportation strategies to minimize quality changes in frozen potatoes.
International Journal of Food Science and Technology, Mar 7, 2021
SummaryIn this study, the oxygen barrier and physical properties of two maltodextrin/gum Arabic (... more SummaryIn this study, the oxygen barrier and physical properties of two maltodextrin/gum Arabic (MD/GA) (3:1 w/w) microcapsules with dextrose equivalence (DE) 26 and 6 were assessed with or without the incorporation of cellulose nanofibres (CNF). The oxygen diffusion coefficient (Deff) was between 10.6 × 10−15 m2 s−1 and 17.3 × 10−15 m2 s−1 for all microcapsules. The addition of CNF improved the oxygen barrier of MD/GA microcapsules. The incorporation of CNF did not significantly impact Tg due to the low quantity of CNF present in the microcapsules. Wettability was higher in CNF incorporated microcapsules, and dispersibility was lower only for microcapsules with maltodextrin of DE 26. Spray‐dried microcapsules exhibited poor flowability and high cohesiveness due to the moisture content (2.0–2.5%) of the powders. The results suggest that incorporation of CNF can increase the oxygen barrier of MD/GA microcapsules which may lead to better oxidative stability of micronutrients incorporated in the microcapsules.
Metal oxide coated multilayered polymeric pouches provide a suitable alternative to foil-based pa... more Metal oxide coated multilayered polymeric pouches provide a suitable alternative to foil-based packaging for shelf-stable products with extended shelf-life. The barrier performance of these films depends upon the integrity of the metal oxide coating which can develop defects as a result of thermal processing and improper handling. In this work, we developed a methodology to visually identify these defects using an oxygen-sensitive model gel system. Four pouches with different metal oxide coatings: MOA (Coated PET), MOB (SiO x-coated PET), MOC (Overlayer-AlO x-Organiccoated PET), MOD (Overlayer-SiO x-coated PET) were filled with water and retort-processed for 30 and 40 min at 121°C. After processing, the pouches were cut open, dried and subsequently filled with a gel containing methylene blue that changes color in the presence of oxygen. The pouches were then stored at 23 and 40°C for 180 and 90 days, respectively. Defects were identified by observing the localized color change from yellow to blue in the packaged gel. These observations were confirmed through measurement of oxygen and water vapor transmission rates, as well as SEM and CLSM analyses. The MOC pouches showed the least change in barrier properties after thermal processing. This was due to crosslinking in the organic coating and protection provided by the overlayer. The melting enthalpy of all films increased significantly (P < 0.05) after sterilization. This may increase the brittleness of the substrates after processing. Findings may be used to improve the barrier performance of metal oxide coated polymeric films intended for food packaging applications.
International Journal of Food Microbiology, Jul 1, 2017
This study investigated the use of headspace oxygen in a model food system to prevent the growth ... more This study investigated the use of headspace oxygen in a model food system to prevent the growth of anaerobic pathogenic bacteria in in-pack pasteurized food at various storage temperatures. Three model food formulations prepared with tryptic soy broth and three agar concentrations (0.1, 0.4 and 1.0%) were sealed without removing the air from the package in high oxygen barrier pouches (OTR = 0.3 cm 3 /m 2 •day•atm). Important properties influencing bacterial growth, including pH and water activity (a w) were determined. The oxygen sorption kinetics of each model food were obtained at three different storage temperatures (8, 12, and 20°C) using an OxySense Gen III 300 system. An analytical solution of Fick's second law was used to determine the O 2 diffusion coefficient. Growth challenge studies at 12 and 20°C were conducted at three selected locations (top, center and bottom layers) in model foods containing 1% agar. Model foods were inoculated with Clostridium sporogenes PA 3679 (300 spores/mL), and were classified as low-acid (pH > 4.5, a w > 0.85). When the storage temperature decreased from 20 to 8°C, the oxygen diffusion decreased from 0.82 × 10 − 9 m 2 /s to 0.68 × 10 − 9 m 2 /s. As the agar concentration was increased from 0.1 to 1.0%, the effective oxygen permeability decreased significantly (p = 0.007) from 0.88 × 10 − 9 m 2 /s to 0.65 × 10 − 9 m 2 /s. When the inoculated model foods were stored at 12°C for 14 days, C. sporogenes PA 3679 was unable to grow. As the storage temperature was increased to 20°C, significant bacterial growth was observed with storage time (p < 0.0001), and the C. sporogenes PA 3679 population increased by around 6 log CFU/g. However, the location of the food did not influence the growth distribution of C. sporogenes PA 3679. These results demonstrate that oxygen diffusion from the pouch headspace was primarily limited to the food surface. Findings suggest that the air/oxygen present in the package headspace may not be considered as a food safety hurdle in the production of pasteurized packaged food.
Rice is an important component of many ready-to-eat frozen and refrigerated products. Changes in ... more Rice is an important component of many ready-to-eat frozen and refrigerated products. Changes in temperature during storage or handling of frozen cooked rice may lead to thermal transitions, ice recrystallization, and subsequent adverse changes in physicochemical properties. In this study, we explored the kinetics of starch retrogradation over a 12-week storage in frozen cooked rice of two varieties: 8% amylose and 0% amylose. Cooked rice was frozen at − 32 ± 1°C for 5 days to achieve a glassy state and then subjected to temperature fluctuations of varying amplitudes to achieve different physical states (e.g., glassy, rubbery, and thawed states). The temperature fluctuation refers to regular/cyclic change from storage temperature to preset temperature. Starch retrogradation enthalpy was measured using differential scanning calorimetry. There was significant (p < 0.05) increase in retrogradation enthalpy with the 12-week storage time, in both varieties of rice. Among the treated samples, with increased degree of temperature fluctuation, there was significant (p < 0.05) increase in retrogradation enthalpy: rice with temperature that fluctuated to the thawed state showed the highest increase in retrogradation enthalpy. A lower degree of starch retrogradation was observed in 8% amylose rice, indicating a lower susceptibility to changes in physicochemical properties as a result of retrogradation during frozen storage.
Ready-to-eat macaroni and cheese filled in novel oxygen scavenger and metal oxide-coated high-bar... more Ready-to-eat macaroni and cheese filled in novel oxygen scavenger and metal oxide-coated high-barrier polymer packages were processed in pilot scale 915-MHz microwave-assisted thermal sterilization system (MATS). Also, aluminum foil packages were processed in Allpax retort system to compare packaging performance. Physicochemical and sensory attributes of macaroni and cheese packaged in different oxygen and water vapor transmission rates were evaluated and stored for 6 months at 37.8°C. Findings showed oxygen transmission rate (OTR) increase by 2-7 times and water vapor transmission rate (WVTR) increase by 2.5-24 times after MATS processing. OTR of polymeric packaging had no significant effect on vitamin A and vitamin E, shear force, and food color. Comparable results between polymeric and aluminum foil packaging were observed throughout the shelf life. This indicates that oxygen scavenger and high-barrier packaging with OTRs~0.03-0.34 cc/m 2 day and WVTRs~0.62-7.19 g/m 2 day can be used for ready-to-eat meals with extended shelf life for soldiers and astronauts.
Innovative Food Science and Emerging Technologies, Mar 1, 2021
The purpose of this study was to develop a convenient method to assist the food industry in devel... more The purpose of this study was to develop a convenient method to assist the food industry in developing process schedules for production of ready-to-eat meals using microwave assisted pasteurization system (MAPS). An analytical model was applied to estimate the temperature increase in the cold zone in packaged foods during heating in a 915 MHz single-mode microwave system. This model was validated in a pilot-scale four-cavity MAPS using mashed potato-gellan gum model food with different thicknesses (22 to 36 mm) and salt contents (0.0 to 1.0%). Mobile sensors were placed in the packages to measure temperature at the predetermined cold spots. For 2.48 min of microwave heating with 5, 5, and 8.7 kW 915 MHz microwave powers, the highest temperature increase at the cold spot during microwave heating was 33.2 • C in the 22 mm thick model food with 0.6% salt content, whereas the lowest temperature increase was 10.3 • C in the 36 mm thick model food with 1.0% salt content. There was a deviation of 1.9 ± 1.2 • C between experimental and predicted data with an R 2 of 0.89. A simplified chart was developed based on the validated analytical results to allow rapid prediction of temperature increases in MAPS as influenced by food dielectric properties and package thickness. Examples were used to illustrate how the chart could assist in process scheduling. The chart can help assess the heating rates of various prepackaged food products in a specific industrial MAPS or guide product development for desired heating uniformity.
This study was the first to evaluate the influence of the combination strategies of flavor additi... more This study was the first to evaluate the influence of the combination strategies of flavor addition and microwave‐assisted thermal sterilization (MATS) processing for salt reduction implications. In freshly prepared mashed potatoes, a 30% and 50% salt reduction (w/w) in comparison to a 100% salt sample with three flavor variations (no additional flavor, garlic, and pepper) were investigated. Also, using the ideal profile method (IPM), the influence of MATS versus retort processing, in comparison to a freshly prepared sample, and flavor addition on mashed potato sensory properties and acceptance was investigated. Chemical characterization using the electronic tongue for nonvolatile compounds and headspace solid‐phase microextraction (HS‐SPME)/gas chromatography‐mass spectrometry (GC‐MS) for volatile analysis was completed. IPM revealed the ideal data were consistent at both the panel and consumer levels from a sensory and hedonic perspective. Results demonstrated the ideal mashed potato product would remain low in bitterness but have more intense pepper and potato aromas and flavors than the current samples evaluated. The salt level could be reduced by 50% while still maintaining flavor and overall acceptance in freshly prepared samples, but this was accompanied by a loss in saltiness intensity perception. The saltiness intensity was not different from the freshly prepared samples when processed via MATS but was different when processed by the retort. For chemical characterization, the electronic tongue showed a high discrimination index (&gt;89%) and correlated highly (&gt;0.8) with many sensory attributes. As salt concentration in the mashed potatoes decreased, the recovery of volatile compounds decreased. The present work contributes to the understanding of product reformulation for the purpose of salt reduction.Practical ApplicationProduct developers need strategies to bring salt down to target levels while maintaining consumer acceptance. The combination strategies of flavor addition and MATS processing may allow for a new strategy to assist product developers in reaching salt reduction targets. Furthermore, developers should bear in mind that noticeable intensity differences may not alter the preference for the product. Thus, intensity differences that result in changes in acceptance should be the focus of quality insurance rather than utilizing just noticeable differences.
Microwave (MW) sterilization alters the morphology of multilayer polymeric structures, containing... more Microwave (MW) sterilization alters the morphology of multilayer polymeric structures, containing, ethylene-vinyl alcohol (EVOH), polyethylene terephthalate and nylon leading to a decrease in oxygen barrier properties, and hence compromising quality and shelf life of the packaged food. Nano-particles coated multilayer structures with improved thermal stability and
Abstract This accelerated shelf life study of a ready-to-eat meal processed with a microwave-assi... more Abstract This accelerated shelf life study of a ready-to-eat meal processed with a microwave-assisted thermal sterilization (MATS) system aimed to evaluate the performance of double metal oxide coated polyethylene terephthalate (PET) layers-based ultra-high barrier packaging along with ethylene vinyl alcohol (EVOH)-based pouches, and aluminum (AL) foil-based pouches (served as control). First, we evaluated barrier changes in the two types of pouches (double-layered PET and EVOH) caused by MATS processing. Next, we determined the influence of barrier properties on the physical, chemical and sensory quality of MATS-processed chicken pasta meals at accelerated storage conditions at 49 °C. Sensory evaluation was also done at lower storage temperature of 38 °C. Results demonstrated that MATS processing did not affect the barrier properties of double metal oxide coated PET pouches, however, it significantly influenced the barrier properties of EVOH-based pouches. After storage at 49 °C for 60 days, there was a small total color change (ΔE = 3.5) in chicken pasta meals in the double coated film pouches. This result was similar to that obtained for aluminum foil pouches (p > 0.05), but significantly lower than that for the EVOH pouches (ΔE = 5.5). The double metal oxide coated PET packaging provided an excellent barrier against lipid oxidation similar to that of aluminum (AL) foil-based pouches. A trained sensory panel scored the recipe between 6.0 and 6.45 immediately after MATS processing on a labelled effective magnitude (LAM) scale from 1 to 9 (worst to best quality). Results indicate that the newly developed double-layered PET pouches offer an excellent alternative to higher density metal foil-based packaging.
In this study, the efficacy of UV-C treatment was determined on the reduction of foodborne pathog... more In this study, the efficacy of UV-C treatment was determined on the reduction of foodborne pathogens on artificially contaminated frozen food surfaces. At first, the UV-C inactivation rates on 100 ll of the respective cocktails of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes covered underneath 0.5-cm-thick ice were examined. Simultaneously, the energy percentage of UV-C transmitted through the ice was determined. The experiments showed that more than 65% of the UV-C light energy passed through the ice and that UV-C susceptibility was in the descending order of E. coli O157:H7, Salmonella, and L. monocytogenes. L. monocytogenes, the most UV-C-resistant strain, was then selected to test on frozen raspberries. The UV-C inactivation kinetic data of L. monocytogenes were well described using the Weibull equation. During 720 s of UV-C exposure, with a total dose of 7.8 3 10 2 mJ/cm 2 , a 1.5-log CFU/g reduction of L. monocytogenes population on the surface of frozen red raspberries was noted. No significant differences in total anthocyanins, total phenolics, and total antioxidant activity were observed between UV-C-treated and untreated frozen berries immediately after treatment. At the end of 9 months of storage at À358C, UV-C-treated berries had statistically lower total phenolics, higher total anthocyanins, and similar total antioxidant activity compared with untreated berries. This study shows that UV-C light can be used to reduce the L. monocytogenes population on frozen raspberries.
A mathematical model for predicting electromagnetic power dissipation within a rectangular dielec... more A mathematical model for predicting electromagnetic power dissipation within a rectangular dielectric slab heated by equal intensity 915 MHz plane waves from top and bottom was developed. A dimensionless parameter (J-T number) which is a combination of the loss factor (ε r ″), dielectric constant (ε r ′) and food thickness (L) was proposed. This unique number provided direct insight into the relationship between food dielectric properties, thickness, product temperature, and thermal lethality. For the validation tests, mashed potatoes, peas and rice samples with 0-2% salt content were processed in a pilot scale microwave assisted thermal sterilization (MATS) system. In each food, the combination of dielectric properties and thickness which gave J-T number of 1.8-2.2 at 100-121°C, provided the highest lethalities. MATS is a novel commercial technology being adapted in the food industry. A qualitative assessment of the combined effect of food properties on lethalities using this model will be helpful in process development for MATS systems.
Abstract Recent research has shown exponentially increased thermal resistance of pathogenic bacte... more Abstract Recent research has shown exponentially increased thermal resistance of pathogenic bacteria at a reduced water activity (aw) in thermal treatments. However, information on aw change as affected by food components at high temperatures is limited. The objective of this project was to quantify the influence of major food components on aw changes in low-moisture foods at elevated temperatures. Corn starch, soy protein, coconut, and cheddar cheese powders were selected as high-carbohydrate, high-protein, high-fat, and intermediate products. Vacuum dried powders were equilibrated in the jars containing saturated salt solutions to different aw from 0.11 to 0.84 at 25 °C. The aw of food powders were measured from 25 to 80 °C in hermetically sealed test cells using hight-temperature humidity sensors. For a given initial aw, high-carbohydrate product had more considerable aw increase than high-protein, intermediate, and high-fat foods with increasing temperature. The net isosteric heat of sorption increased from high-fat, intermediate, high-protein, to high-carbohydrate food at same moisture content. These relationships support findings in the literature that bacterial cells are more easily inactivated in high-carbohydrate and high-protein products than in high-fat foods. Understanding the correlation between food components and aw change at elevated temperatures helps predict the thermal resistance of bacteria in low-moisture foods.
The crewed suborbital and space flights launched by private companies over the past three years h... more The crewed suborbital and space flights launched by private companies over the past three years have rejuvenated public interest in space travel, including space tourism. Ready-to-eat meals (MREs) are the main source of nutrients and energy for space travelers. It is critical that those meals are free of bacterial and viral pathogens and have adequate shelf life. The participation of private companies in space programs will create new opportunities and demand for high-quality and microbiologically safe MREs for future space travels. In this article, we provide a brief review of nutrition and energy requirements for human activities in space. We discuss the general thermal processing requirements for control of bacterial and viral pathogens in MREs and introduce advanced thermal preservation technologies based on microwaves for production of MREs with different shelf-lives under various storage conditions. We also present the latest advancements in the development of polymer packagin...
Abstract Thermal transitions in frozen foods may occur due to temperature fluctuations during sto... more Abstract Thermal transitions in frozen foods may occur due to temperature fluctuations during storage and distribution, inducing ice recrystallization and loss of food quality. This study evaluated the effects of state/phase transitions on ice recrystallization and on mechanical properties of unblanched and blanched potatoes. Potato samples were frozen at −32 °C for 5 days to achieve a glassy state and then subjected to temperature fluctuations of varying amplitudes to achieve different physical states: glassy state with temperature fluctuation, rubbery and thawed states. Ice crystal size of potatoes was evaluated using scanning electron microscopy (SEM) through pore analysis of freeze-dried potatoes. Hardness of potatoes was determined using texture analyzer. Temperature fluctuation increased the ice crystal size and reduced the hardness of potatoes-the changes depended on the severity of temperature fluctuations and the treatment medium. Findings may inform improved packaging design, storage and transportation strategies to minimize quality changes in frozen potatoes.
International Journal of Food Science and Technology, Mar 7, 2021
SummaryIn this study, the oxygen barrier and physical properties of two maltodextrin/gum Arabic (... more SummaryIn this study, the oxygen barrier and physical properties of two maltodextrin/gum Arabic (MD/GA) (3:1 w/w) microcapsules with dextrose equivalence (DE) 26 and 6 were assessed with or without the incorporation of cellulose nanofibres (CNF). The oxygen diffusion coefficient (Deff) was between 10.6 × 10−15 m2 s−1 and 17.3 × 10−15 m2 s−1 for all microcapsules. The addition of CNF improved the oxygen barrier of MD/GA microcapsules. The incorporation of CNF did not significantly impact Tg due to the low quantity of CNF present in the microcapsules. Wettability was higher in CNF incorporated microcapsules, and dispersibility was lower only for microcapsules with maltodextrin of DE 26. Spray‐dried microcapsules exhibited poor flowability and high cohesiveness due to the moisture content (2.0–2.5%) of the powders. The results suggest that incorporation of CNF can increase the oxygen barrier of MD/GA microcapsules which may lead to better oxidative stability of micronutrients incorporated in the microcapsules.
Metal oxide coated multilayered polymeric pouches provide a suitable alternative to foil-based pa... more Metal oxide coated multilayered polymeric pouches provide a suitable alternative to foil-based packaging for shelf-stable products with extended shelf-life. The barrier performance of these films depends upon the integrity of the metal oxide coating which can develop defects as a result of thermal processing and improper handling. In this work, we developed a methodology to visually identify these defects using an oxygen-sensitive model gel system. Four pouches with different metal oxide coatings: MOA (Coated PET), MOB (SiO x-coated PET), MOC (Overlayer-AlO x-Organiccoated PET), MOD (Overlayer-SiO x-coated PET) were filled with water and retort-processed for 30 and 40 min at 121°C. After processing, the pouches were cut open, dried and subsequently filled with a gel containing methylene blue that changes color in the presence of oxygen. The pouches were then stored at 23 and 40°C for 180 and 90 days, respectively. Defects were identified by observing the localized color change from yellow to blue in the packaged gel. These observations were confirmed through measurement of oxygen and water vapor transmission rates, as well as SEM and CLSM analyses. The MOC pouches showed the least change in barrier properties after thermal processing. This was due to crosslinking in the organic coating and protection provided by the overlayer. The melting enthalpy of all films increased significantly (P < 0.05) after sterilization. This may increase the brittleness of the substrates after processing. Findings may be used to improve the barrier performance of metal oxide coated polymeric films intended for food packaging applications.
International Journal of Food Microbiology, Jul 1, 2017
This study investigated the use of headspace oxygen in a model food system to prevent the growth ... more This study investigated the use of headspace oxygen in a model food system to prevent the growth of anaerobic pathogenic bacteria in in-pack pasteurized food at various storage temperatures. Three model food formulations prepared with tryptic soy broth and three agar concentrations (0.1, 0.4 and 1.0%) were sealed without removing the air from the package in high oxygen barrier pouches (OTR = 0.3 cm 3 /m 2 •day•atm). Important properties influencing bacterial growth, including pH and water activity (a w) were determined. The oxygen sorption kinetics of each model food were obtained at three different storage temperatures (8, 12, and 20°C) using an OxySense Gen III 300 system. An analytical solution of Fick's second law was used to determine the O 2 diffusion coefficient. Growth challenge studies at 12 and 20°C were conducted at three selected locations (top, center and bottom layers) in model foods containing 1% agar. Model foods were inoculated with Clostridium sporogenes PA 3679 (300 spores/mL), and were classified as low-acid (pH > 4.5, a w > 0.85). When the storage temperature decreased from 20 to 8°C, the oxygen diffusion decreased from 0.82 × 10 − 9 m 2 /s to 0.68 × 10 − 9 m 2 /s. As the agar concentration was increased from 0.1 to 1.0%, the effective oxygen permeability decreased significantly (p = 0.007) from 0.88 × 10 − 9 m 2 /s to 0.65 × 10 − 9 m 2 /s. When the inoculated model foods were stored at 12°C for 14 days, C. sporogenes PA 3679 was unable to grow. As the storage temperature was increased to 20°C, significant bacterial growth was observed with storage time (p < 0.0001), and the C. sporogenes PA 3679 population increased by around 6 log CFU/g. However, the location of the food did not influence the growth distribution of C. sporogenes PA 3679. These results demonstrate that oxygen diffusion from the pouch headspace was primarily limited to the food surface. Findings suggest that the air/oxygen present in the package headspace may not be considered as a food safety hurdle in the production of pasteurized packaged food.
Rice is an important component of many ready-to-eat frozen and refrigerated products. Changes in ... more Rice is an important component of many ready-to-eat frozen and refrigerated products. Changes in temperature during storage or handling of frozen cooked rice may lead to thermal transitions, ice recrystallization, and subsequent adverse changes in physicochemical properties. In this study, we explored the kinetics of starch retrogradation over a 12-week storage in frozen cooked rice of two varieties: 8% amylose and 0% amylose. Cooked rice was frozen at − 32 ± 1°C for 5 days to achieve a glassy state and then subjected to temperature fluctuations of varying amplitudes to achieve different physical states (e.g., glassy, rubbery, and thawed states). The temperature fluctuation refers to regular/cyclic change from storage temperature to preset temperature. Starch retrogradation enthalpy was measured using differential scanning calorimetry. There was significant (p < 0.05) increase in retrogradation enthalpy with the 12-week storage time, in both varieties of rice. Among the treated samples, with increased degree of temperature fluctuation, there was significant (p < 0.05) increase in retrogradation enthalpy: rice with temperature that fluctuated to the thawed state showed the highest increase in retrogradation enthalpy. A lower degree of starch retrogradation was observed in 8% amylose rice, indicating a lower susceptibility to changes in physicochemical properties as a result of retrogradation during frozen storage.
Ready-to-eat macaroni and cheese filled in novel oxygen scavenger and metal oxide-coated high-bar... more Ready-to-eat macaroni and cheese filled in novel oxygen scavenger and metal oxide-coated high-barrier polymer packages were processed in pilot scale 915-MHz microwave-assisted thermal sterilization system (MATS). Also, aluminum foil packages were processed in Allpax retort system to compare packaging performance. Physicochemical and sensory attributes of macaroni and cheese packaged in different oxygen and water vapor transmission rates were evaluated and stored for 6 months at 37.8°C. Findings showed oxygen transmission rate (OTR) increase by 2-7 times and water vapor transmission rate (WVTR) increase by 2.5-24 times after MATS processing. OTR of polymeric packaging had no significant effect on vitamin A and vitamin E, shear force, and food color. Comparable results between polymeric and aluminum foil packaging were observed throughout the shelf life. This indicates that oxygen scavenger and high-barrier packaging with OTRs~0.03-0.34 cc/m 2 day and WVTRs~0.62-7.19 g/m 2 day can be used for ready-to-eat meals with extended shelf life for soldiers and astronauts.
Innovative Food Science and Emerging Technologies, Mar 1, 2021
The purpose of this study was to develop a convenient method to assist the food industry in devel... more The purpose of this study was to develop a convenient method to assist the food industry in developing process schedules for production of ready-to-eat meals using microwave assisted pasteurization system (MAPS). An analytical model was applied to estimate the temperature increase in the cold zone in packaged foods during heating in a 915 MHz single-mode microwave system. This model was validated in a pilot-scale four-cavity MAPS using mashed potato-gellan gum model food with different thicknesses (22 to 36 mm) and salt contents (0.0 to 1.0%). Mobile sensors were placed in the packages to measure temperature at the predetermined cold spots. For 2.48 min of microwave heating with 5, 5, and 8.7 kW 915 MHz microwave powers, the highest temperature increase at the cold spot during microwave heating was 33.2 • C in the 22 mm thick model food with 0.6% salt content, whereas the lowest temperature increase was 10.3 • C in the 36 mm thick model food with 1.0% salt content. There was a deviation of 1.9 ± 1.2 • C between experimental and predicted data with an R 2 of 0.89. A simplified chart was developed based on the validated analytical results to allow rapid prediction of temperature increases in MAPS as influenced by food dielectric properties and package thickness. Examples were used to illustrate how the chart could assist in process scheduling. The chart can help assess the heating rates of various prepackaged food products in a specific industrial MAPS or guide product development for desired heating uniformity.
This study was the first to evaluate the influence of the combination strategies of flavor additi... more This study was the first to evaluate the influence of the combination strategies of flavor addition and microwave‐assisted thermal sterilization (MATS) processing for salt reduction implications. In freshly prepared mashed potatoes, a 30% and 50% salt reduction (w/w) in comparison to a 100% salt sample with three flavor variations (no additional flavor, garlic, and pepper) were investigated. Also, using the ideal profile method (IPM), the influence of MATS versus retort processing, in comparison to a freshly prepared sample, and flavor addition on mashed potato sensory properties and acceptance was investigated. Chemical characterization using the electronic tongue for nonvolatile compounds and headspace solid‐phase microextraction (HS‐SPME)/gas chromatography‐mass spectrometry (GC‐MS) for volatile analysis was completed. IPM revealed the ideal data were consistent at both the panel and consumer levels from a sensory and hedonic perspective. Results demonstrated the ideal mashed potato product would remain low in bitterness but have more intense pepper and potato aromas and flavors than the current samples evaluated. The salt level could be reduced by 50% while still maintaining flavor and overall acceptance in freshly prepared samples, but this was accompanied by a loss in saltiness intensity perception. The saltiness intensity was not different from the freshly prepared samples when processed via MATS but was different when processed by the retort. For chemical characterization, the electronic tongue showed a high discrimination index (&gt;89%) and correlated highly (&gt;0.8) with many sensory attributes. As salt concentration in the mashed potatoes decreased, the recovery of volatile compounds decreased. The present work contributes to the understanding of product reformulation for the purpose of salt reduction.Practical ApplicationProduct developers need strategies to bring salt down to target levels while maintaining consumer acceptance. The combination strategies of flavor addition and MATS processing may allow for a new strategy to assist product developers in reaching salt reduction targets. Furthermore, developers should bear in mind that noticeable intensity differences may not alter the preference for the product. Thus, intensity differences that result in changes in acceptance should be the focus of quality insurance rather than utilizing just noticeable differences.
Microwave (MW) sterilization alters the morphology of multilayer polymeric structures, containing... more Microwave (MW) sterilization alters the morphology of multilayer polymeric structures, containing, ethylene-vinyl alcohol (EVOH), polyethylene terephthalate and nylon leading to a decrease in oxygen barrier properties, and hence compromising quality and shelf life of the packaged food. Nano-particles coated multilayer structures with improved thermal stability and
Abstract This accelerated shelf life study of a ready-to-eat meal processed with a microwave-assi... more Abstract This accelerated shelf life study of a ready-to-eat meal processed with a microwave-assisted thermal sterilization (MATS) system aimed to evaluate the performance of double metal oxide coated polyethylene terephthalate (PET) layers-based ultra-high barrier packaging along with ethylene vinyl alcohol (EVOH)-based pouches, and aluminum (AL) foil-based pouches (served as control). First, we evaluated barrier changes in the two types of pouches (double-layered PET and EVOH) caused by MATS processing. Next, we determined the influence of barrier properties on the physical, chemical and sensory quality of MATS-processed chicken pasta meals at accelerated storage conditions at 49 °C. Sensory evaluation was also done at lower storage temperature of 38 °C. Results demonstrated that MATS processing did not affect the barrier properties of double metal oxide coated PET pouches, however, it significantly influenced the barrier properties of EVOH-based pouches. After storage at 49 °C for 60 days, there was a small total color change (ΔE = 3.5) in chicken pasta meals in the double coated film pouches. This result was similar to that obtained for aluminum foil pouches (p > 0.05), but significantly lower than that for the EVOH pouches (ΔE = 5.5). The double metal oxide coated PET packaging provided an excellent barrier against lipid oxidation similar to that of aluminum (AL) foil-based pouches. A trained sensory panel scored the recipe between 6.0 and 6.45 immediately after MATS processing on a labelled effective magnitude (LAM) scale from 1 to 9 (worst to best quality). Results indicate that the newly developed double-layered PET pouches offer an excellent alternative to higher density metal foil-based packaging.
In this study, the efficacy of UV-C treatment was determined on the reduction of foodborne pathog... more In this study, the efficacy of UV-C treatment was determined on the reduction of foodborne pathogens on artificially contaminated frozen food surfaces. At first, the UV-C inactivation rates on 100 ll of the respective cocktails of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes covered underneath 0.5-cm-thick ice were examined. Simultaneously, the energy percentage of UV-C transmitted through the ice was determined. The experiments showed that more than 65% of the UV-C light energy passed through the ice and that UV-C susceptibility was in the descending order of E. coli O157:H7, Salmonella, and L. monocytogenes. L. monocytogenes, the most UV-C-resistant strain, was then selected to test on frozen raspberries. The UV-C inactivation kinetic data of L. monocytogenes were well described using the Weibull equation. During 720 s of UV-C exposure, with a total dose of 7.8 3 10 2 mJ/cm 2 , a 1.5-log CFU/g reduction of L. monocytogenes population on the surface of frozen red raspberries was noted. No significant differences in total anthocyanins, total phenolics, and total antioxidant activity were observed between UV-C-treated and untreated frozen berries immediately after treatment. At the end of 9 months of storage at À358C, UV-C-treated berries had statistically lower total phenolics, higher total anthocyanins, and similar total antioxidant activity compared with untreated berries. This study shows that UV-C light can be used to reduce the L. monocytogenes population on frozen raspberries.
A mathematical model for predicting electromagnetic power dissipation within a rectangular dielec... more A mathematical model for predicting electromagnetic power dissipation within a rectangular dielectric slab heated by equal intensity 915 MHz plane waves from top and bottom was developed. A dimensionless parameter (J-T number) which is a combination of the loss factor (ε r ″), dielectric constant (ε r ′) and food thickness (L) was proposed. This unique number provided direct insight into the relationship between food dielectric properties, thickness, product temperature, and thermal lethality. For the validation tests, mashed potatoes, peas and rice samples with 0-2% salt content were processed in a pilot scale microwave assisted thermal sterilization (MATS) system. In each food, the combination of dielectric properties and thickness which gave J-T number of 1.8-2.2 at 100-121°C, provided the highest lethalities. MATS is a novel commercial technology being adapted in the food industry. A qualitative assessment of the combined effect of food properties on lethalities using this model will be helpful in process development for MATS systems.
Abstract Recent research has shown exponentially increased thermal resistance of pathogenic bacte... more Abstract Recent research has shown exponentially increased thermal resistance of pathogenic bacteria at a reduced water activity (aw) in thermal treatments. However, information on aw change as affected by food components at high temperatures is limited. The objective of this project was to quantify the influence of major food components on aw changes in low-moisture foods at elevated temperatures. Corn starch, soy protein, coconut, and cheddar cheese powders were selected as high-carbohydrate, high-protein, high-fat, and intermediate products. Vacuum dried powders were equilibrated in the jars containing saturated salt solutions to different aw from 0.11 to 0.84 at 25 °C. The aw of food powders were measured from 25 to 80 °C in hermetically sealed test cells using hight-temperature humidity sensors. For a given initial aw, high-carbohydrate product had more considerable aw increase than high-protein, intermediate, and high-fat foods with increasing temperature. The net isosteric heat of sorption increased from high-fat, intermediate, high-protein, to high-carbohydrate food at same moisture content. These relationships support findings in the literature that bacterial cells are more easily inactivated in high-carbohydrate and high-protein products than in high-fat foods. Understanding the correlation between food components and aw change at elevated temperatures helps predict the thermal resistance of bacteria in low-moisture foods.
The crewed suborbital and space flights launched by private companies over the past three years h... more The crewed suborbital and space flights launched by private companies over the past three years have rejuvenated public interest in space travel, including space tourism. Ready-to-eat meals (MREs) are the main source of nutrients and energy for space travelers. It is critical that those meals are free of bacterial and viral pathogens and have adequate shelf life. The participation of private companies in space programs will create new opportunities and demand for high-quality and microbiologically safe MREs for future space travels. In this article, we provide a brief review of nutrition and energy requirements for human activities in space. We discuss the general thermal processing requirements for control of bacterial and viral pathogens in MREs and introduce advanced thermal preservation technologies based on microwaves for production of MREs with different shelf-lives under various storage conditions. We also present the latest advancements in the development of polymer packagin...
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Papers by Shyam Sablani