Polymeric Trays Research Articles

In-package Antimicrobial Treatment of Chicken Breast Meat with High Voltage Dielectric Barrier Discharge–Electric Voltage Effect 1

Microbiological safety and quality of fresh chicken meat are important concerns to industry. The objective of this study was to investigate the effects of in-package, non-thermal high voltage dielectric barrier discharge (HVDBD) treatment on microbial quality, safety, and color of fresh chicken breast meat ( pectoralis major ). Boneless skinless chicken breast meat was collected from a local commercial plant. Non-inoculated meat samples and meat samples inoculated with Campylobacter jejuni and Salmonella Typhimurium were packed in polymeric trays under ambient air conditions. The packaged samples were HVDBD-treated at different voltages (0, 55, 70, or 85 kV) for 180 s, and stored at 4°C for 5 d. Microbial counts (psychrophiles, C. jejuni, S. Typhimurium) and meat color (L* a* b*) were measured before HVDBD treatment and after 5 d of post-treatment storage. Psychrophile growth was inhibited ( P < 0.05) and both foodborne pathogens were reduced ( P < 0.05) by HVDBD treatments regardless of treatment voltage. No differences in psychrophilic and S. Typhimurium counts were observed between the three treatment voltages; however, increasing treatment voltage beyond 55 kV resulted in additional inactivation of C. jejuni . In terms of meat color, there were no differences ( P > 0.05) in a* and b* values between pre-treatment and post-treatment measurements; however, all HVDBD treatments resulted in increased L* value ( P < 0.05). Results indicate that in-package HVDBD treatment can be used to reduce both microbial spoilage and foodborne pathogen risks; however, in-package HVDBD treatment may increase pale color in raw chicken breast meat.

In-Package Air Cold Plasma Treatment of Chicken Breast Meat: Treatment Time Effect

The objective of this study was to investigate the effects of in-package dielectric barrier discharge (DBD) atmospheric cold plasma (CP) on meat color, microbiological quality and safety of chicken breast meat (pectoralis major). Raw broiler breast meat was collected from a local commercial plant. Noninoculated meat samples and meat samples inoculated with Campylobacter and Salmonella were packed in polymeric trays with air. The packaged samples were CP-treated at 70 kV for different times (0, 60, 180, or 300 sec) and stored at 4°C for 5 days. Microbial counts (psychrophiles, Campylobacter, Salmonella) and meat color (International Commission on Illumination (CIE) L∗a∗b∗) were measured before CP treatments and after 5 days of posttreatment storage. Psychrophile growth was inhibited (P&lt;0.05), and both food-borne pathogens were reduced (P&lt;0.05) by more than 90% with CP treatments regardless of treatment time. No differences in pathogenic bacterial counts were observed between the three treatment times; however, increasing treatment time beyond 60 sec resulted in additional inhibition of psychrophilic growth. There were no differences (P&gt;0.05) in a∗ and b∗ values between pretreatment and posttreatment plus storage; however, all CP treatments resulted in increased L∗ value (P&lt;0.05). Results indicate that in-package CP treatments can be used to reduce both microbial spoilage and food-borne pathogen risks, which could increase microbial food safety, although it may result in an overall paler breast meat, and the reduction (about 1 log) in pathogenic and spoilage microbes are limited.

Biodegradable PLA (polylactic acid) hinged trays keep quality of fresh-cut and cooked spinach.

This work examines the effects of packaging using two different polymeric trays with hinged lids, polyethylene terephthalate (PET) and polylactic acid (PLA), on fresh-cut and cooked spinach (Spinacia oleracea). Samples were stored in a cold room for 16days at 4°C. Chemical (total pigments, total polyphenols, ascorbic acid, antioxidant activity), physical (water activity), technological (colour evaluation), sensorial (aroma, visual appearance and water accumulation) and microbial (total aerobic mesophilic and psychrotrophic counts) parameters were tested. Both polymeric trays maintained the overall quality of fresh spinach for 6days but spinach stored in PLA trays maintained its flavour longer. A significant increase in total polyphenols, antiradical activity, total carotenoids as well as a decrease in ascorbic acid in fresh spinach was observed in the first 3days of storage in both samples. Unfortunately, the PLA package accumulated condensed water. The total microbial load of fresh-cut spinach reached about 6.3-7.3logCFUg(-1) within 8days. Cooked spinach packed in PLA and PET polymeric hinged trays showed the same behaviour as fresh spinach in terms of quality and shelf life. In conclusion, PLA plastic hinged trays can be used for packaging fresh-cut and cooked cut spinach, but the problem of condensed water must be solved.

Microwave sterilization of sliced beef in gravy in 7-oz trays

This research was to investigate the feasibility for developing a short-time sterilization protocol for a highly inhomogeneous food prepackaged in polymeric trays using 915 MHz microwave (MW) energy. A 915-MHz, single-mode, 10-kW pilot-scale MW system developed at Washing State University was used for this study. The inhomogeneous food consisted of sliced beef and gravy packaged in 7-oz polymeric trays. Specially formulated whey protein gel, matching the beef product in their dielectric properties, was chosen as a model food to emulate the real food for determination of heating patterns and cold spots inside food trays. The heating patterns and cold spots were detected using a chemical-marker-assisted computer vision method. Processing schedules to achieve desired levels of F 0 for 7-oz trays of beef in gravy were established based on temperature histories measured at the identified cold spot location. The developed processing schedules were validated by inoculated pack studies using Clostridium sporogenes PA 3679 spores. The results of this study indicate that the 915-MHz single-mode MW sterilization technology is effective for processing of the inhomogeneous food. The procedure established could be used for developing MW sterilization processes for other packaged inhomogeneous foods, such as chicken meat in gravy in trays and salmon in sauce in pouches. The processing data collected could be helpful for industrial scale-up of the MW system.

Evaluation of Magnetic Resonance for Detection of Bacterial Contamination in Low-Acid, Shelf-Stable Packaged Soymilk

This study evaluated magnetic resonance (MR) as a nondestructive method for detection of bacterial contamination in shelf-stable soymilk and cheese sauce. To accomplish this, individual 355-ml polymeric trays filled with soymilk and inoculated with Bacillus stearothermophilus and Bacillus subtilis (103 CFU) were incubated for up to 28 h at 55°C and 62 h at 37°C, respectively. MR relaxation times (T2) of these samples were then correlated with the bacterial growth as well as viscosity and pH changes caused by the bacteria in the packaged soymilk. In addition, this study investigated the ability of MR to differentiate between regularly processed cheese sauce and cheese sauce that was modified with α-amylase as a spoilage simulation. Results showed increased MR T2 relaxation times after the bacterial populations reached 108 CFU/ml (after 18 h) and 107 CFU/ml (after 44 h) for B. stearothermophilus and B. subtilis, respectively. B. subtilis had an undetectable influence on viscosity but a profound influence on pH. B. stearothermophilus, in comparison, significantly lowered the pH and increased the viscosity of the soymilk. MR was able to distinguish between regularly processed 85-g pouches of cheese sauce and other pouches with sauce that were modified with 0.5 ml of 1% α-amylase solution. These results showed that MR has the potential to be used for nondestructive detection of physical changes in soymilk and cheese sauce induced by bacterial growth and enzymatic activities, respectively.

Sterilization of Scrambled Eggs in Military Polymeric Trays by Radio Frequency Energy

ABSTRACT: There is a current need for fresh-cooked-like yet shelf-stable egg products for U.S. military combat rations. Novel thermal processes based on radio frequency (RF) energy can shorten the heating time and reduce overheating. This technology was explored to produce shelf-stable egg products for combat ration development. Clostridium sporogenes (PA 3679) spores were used as a surrogate to validate the RF sterilization process to control Clostridium botulinum. Decimal reduction time (D value) of PA3679 in scrambled eggs was determined using aluminum thermal-death-time (TDT) tubes. The thermal inactivation kinetic information was then used in inoculated pack studies to validate a novel thermal process based on 27.12 MHz radio frequency (RF) pilot scale unit. Trays of scrambled eggs inoculated with PA 3679 were subjected to 3 processing levels: target process (F0 about 5.3 min), under-target process (F0 about 3.0 min), and over-target process (F0 about 9.1 min). The results of the microbial challenge study showed that microbial destruction from the RF process agreed with sterilization values calculated from time-temperature data measured at the cold spot in the treated trays. A comparison of RF- and retort-treated scrambled eggs showed significant differences in the degree of lightness (L*) and redness (a*). RF-processed egg was less brown compared with conventional retorted eggs. Retort treatment of fully cooked scrambled eggs had higher hardness, springiness, and smaller cohesiveness than RF -treated samples. This study suggests that RF thermal processes can produce safe, shelf-stable sterilized scrambled eggs for both military and civilian uses.

Minimum Leak Size Determination, under Laboratory and Commercial Conditions, for Bacterial Entry into Polymeric Trays Used for Shelf-Stable Food Packaging

This study sought to determine the minimum leak size for entry of Enterobacter aerogenes under laboratory conditions, and normal flora under commercial conditions, into tryptic soy broth with yeast extract (TSBYE), homestyle chicken, and beef enchilada packaged in 355-ml polyethylene terephthalate/ethylene vinyl alcohol/polypropylene trays. Channel leaks (diameters of 50 to 200 μm) were made across the sealing area of the trays. Pinholes (diameters of 5 to 50 μm) were made by imbedding laser-drilled metal and plastic disks into the tray lids. For the laboratory simulation, all trays were submerged and agitated for 30 min at 25°C in phosphate-buffered saline that contained 107 CFU/ml of E. aerogenes. Under commercial conditions, trays with channel leaks were processed in retorts to achieve commercial sterility. All trays were subsequently incubated at 37°C for 2 weeks, and their contents plated onto eosin-methylene blue agar (for laboratory simulation) to enumerate E. aerogenes and brain heart infusion agar (for commercial conditions) to determine the presence of any bacteria. Under laboratory conditions, minimum pinhole sizes for E. aerogenes entry approximated 5μm (TSBYE, metal disks; homestyle chicken, plastic disks), 20μm (beef, plastic disks), and 30μm (beef, metal disks). The minimum channel leak sizes for entry of E. aerogenes approximated 10μm (TSBYE), 70μm (chicken), and 200μm (beef enchilada). Under commercial conditions, the minimum channel leak size for bacterial entry approximated 40μm (TSBYE), 50μm (homestyle chicken), and more than 200μm (beef). Results showed that E. aerogenes can enter pinholes as small as 5μm under a worst-case scenario. This information can be used to set pass and fail parameters for leak detection devices.

Sterilization of Foodstuffs Using Radio Frequency Heating

ABSTRACT: A study was conducted with a pilot‐scale sterilization system based on 27‐MHz radio frequency (RF) energy to investigate the effectiveness in shortening process time and in improving quality for foods sealed in 6‐pound military‐ration polymeric trays. Chemical marker M‐1 was used to evaluate heating uniformity in 20% whey protein gels as a model food, and macaroni and cheese was processed to assess the influence of RF process on product quality. With the RF system, a lethality (F0= 10 min) was achieved in both model food and macaroni and cheese within 30 min with relative uniform heating, compared to a 90 min conventional retort process that delivered a similar lethality.

Non‐destructive packaging seal strength analysis and leak detection using ultrasonic imaging

AbstractThis study investigated the effectiveness of ultrasonic imaging for non‐destructive assessment of seal strength in 335 ml polymeric trays. In the first part of this study, the experimental procedures involved filling sample trays with beef enchilada, then sealing at temperatures of 170–260°C for 5 s at 3 bar. Ultrasonic measurements were conducted using an immersion technique in pulse/echo mode. The captured signal amplitudes of the reflections from the samples were digitized and analysed to construct high‐resolution C‐scan ultrasonic images of the seals. The acquired data were statistically analysed for each sample and used as a basis for comparison with the seal (peel) strength, measured as the energy at break. The energy at break was obtained from destructive peel strength analysis, performed using a tensile testing frame. In the second part of this study, ultrasonic imaging was used to predict the performance of the heat sealer used to fabricate the test trays by comparing the seal quality of each of the four quadrants of the samples trays. This study also investigated the minimum channel leak size that could be detected using this ultrasound system. The results of the peel strength analyses showed that a direct correlation exists between seal strength and sealing temperature (170–227°C). Results of the ultrasonic imaging showed that the statistical scatter in the signal amplitude decreased as the sealing temperature increased. This reduction in the scatter of the signal amplitudes indicated a trend of increasing uniformity in the fusion of the two seal faces. Between 170°C and 193°C, sharp changes in the scatter were observed; however, little change was noted for sealing temperatures greater than 193°C, indicating that 204°C could be a minimum recommended sealing temperature. To confirm this result, a drop test analysis was performed on trays filled with beef enchilada and sealed at temperatures of 170–260°C for 5 s at 3 bar. Results of this drop test confirmed that 204°C was the minimum critical sealing temperature. Based on these results, ultrasonic imaging appeared to offer a promising non‐destructive method for the prediction of seal quality in polymeric trays, sealing equipment monitoring and identification of channel leaks ⩾20 µm in diameter, and is comparable with the more established destructive peel strength analytical method. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Evaluation of a laboratory‐scale pressure differential (force/decay) system for non‐destructive leak detection of flexible and semi‐rigid packaging

AbstractThis study evaluated the capabilities of a bench‐top non‐destructive pressure differential leak tester using 355 ml polyethylene terephthalate/ethylene vinyl alcohol/polypropylene (PET/EVOH/PP) trays. This evaluation was done by monitoring the equipment's force/decay responses to leaks, changes in the package headspace volume and differences in the seal strength of 986 sample trays. Leak detection evaluation was done using artificially created channel leaks (10–200 µm) in the sealing areas and pinholes (5–50 µm) in the lids of the polymeric trays. Seal strength evaluation included the ability of the equipment to identify non‐leaking but weak seals and the extent to which the pressure differential unit affected good seals during a normal test run. The results showed that the equipment had a detection limit of 40 µm for channel leaks 6 mm in length and 15 µm for pinholes. The results also showed that the pressure differential unit caused a 9% reduction in the seal strength of the tested packages. However, peel strength analysis and distribution testing showed that this reduction in seal strength did not compromise the integrity of 99% of the packages tested. Results showed that the equipment could also detect weak but non‐leaking seals that had potential to lose integrity during transportation and retail handling. The results of this study could be used to determine the capabilities and limitations of a non‐destructive pressure differential bench‐top leak testing device intended for food packaging quality control. Copyright © 2002 John Wiley &amp; Sons, Ltd.

INSPECTION OF SEAL INTEGRITY OF FOOD PACKAGES USING ULTRASOUND AND PRESSURE DIFFERENTIAL TECHNIQUES

Food packages undergo incubation and inspection to ensure that packages are sealed tight and protect the foodfrom contamination and spoilage. Over the years many inspection techniques are used with varying degrees of success. Withthis study, two techniques, ultrasound and pressure differential technique, were assessed and the effectiveness of thesetechniques was quantified. Noncontact, immersion type ultrasonic testing in pulse/echo mode using high frequency soundwaves was evaluated for use in defect detection in the seal area of semirigid cups and polymeric trays. At disparities withinthe seal, sound waves generated by 20MHz ultrasonic transducer were reflected back to the receiver. Received ultrasonicsignals, or echoes, were used to develop Ascan and Cscan presentations. Discontinuities in the seal, short seal, nonbondedareas, imbedded foreign matter such as wire and Teflon in the seal, contaminated seal, and abrasion were detected usingultrasound based on reduced signal strengths.Integrity of mealsreadytoeat (MRE) pouches was inspected using a new pressure (vacuum) differential technique. Thistechnique is based on a threestep approach. To evaluate the system, air was linked into a test chamber through a calibratedneedle valve simulating a leak at different leak rates. A simulated leak that generated values higher than reference, anddependant upon the leak rate, was accepted or rejected by the leak tester. The technique proved to be effective, although,shortsealed nonvacuum packed pound cake pouches failed during subsequent leak testing.

Polymeric self‐sealing distillation and extractor trays

AbstractA suitable polymeric material offers several advantages over metals and alloys normally used for self‐sealing or friction‐fit trays in distillation and extraction columns, by reducing the capital cost and maintenance charges and by improving the efficiency of small diameter columns. The hydrophobic nature of polymeric materials also increases the plate efficiency of an extractor when the plate is wetted by a continuous organic phase which passes to a dispersed water phase.The plate efficiency and performance of a small column are often reduced by leakage or by passing of vapor and liquor at the periphery of the trays. This problem can be overcome by using self‐sealing polymeric trays arranged in cartridges which are assembled and inserted into the column shell as a unit. The flexible nature of polymers ensures a tight fit between the trays and the shell of the column, notwithstanding normal out‐of‐roundness of the shell.