Shelf life establishment of a sliced, cooked, cured meat product based on quality and safety determinants

In the present study, the distribution of the shelf life of cooked, cured meat products based on lactic acid bacteria growth and the distribution of the time to cause health risks based on Listeria monocytogenes growth were studied. Growth models, developed and validated on cooked meat products, were used to predict the growth of microorganisms. Temperature data were obtained from retail and home refrigerators. Distribution predictions were conducted by two approaches (time-temperature profiles and Monte Carlo simulation). Time-temperature profiles were more appropriate to be used, because Monte Carlo simulation overestimated the growth of L. monocytogenes. Shelf life was greatly influenced by storage temperature, but initial microbial load had a smaller effect. The expiration date of cooked meat products might be based on only the growth of the spoilage microorganisms, and only when product contamination with L. monocytogenes cell concentrations is high does a product fraction pose health risks for consumers. Sensitivity analysis confirmed that storage temperature and temperature variability were the most important factors for the duration of shelf life. Distributions of shelf life and time to cause health risks give valuable information on the quality and safety of cooked meat products and may be used as practical tools by meat processors.     

Shelf life of modified atmosphere packed cooked meat products: addition of Na-lactate as a fourth shelf life determinative factor in a model and product validation

Cooked meat products are often post-contaminated because of a packaging and/or slicing step after the pasteurisation process. The shelf life is therefore limited and can be extended by adding Na-lactate. A previously developed model for the spoilage of gas packed cooked meat products, including temperature, water activity and dissolved CO2 as independent variables, was extended with a fourth factor: the Na-lactate concentration in the aqueous phase of the meat product. Models were developed for the maximum specific growth rate mu(max) and the lag phase lambda of the specific spoilage organism Lactobacillus sake subsp. carnosum. Quadratic response surface equations were compared with extended Ratkowsky models. In general, response surface equations fitted the experimental data best but in the case of mu(max) the response surface model predicted illogical growth behaviour at low water activities and high Na-lactate concentrations. A extensive product validation of the mathematical models was performed by means of inoculated as well as naturally contaminated industrially prepared cooked meat products. The deviations of the experimentally determined versus predicted growth parameters in inoculated cooked meat products were in general small. Both types of models were also able to predict the shelf life of naturally contaminated cooked meat products, except for paté where an under-estimation of the shelf life was predicted by the response surface equations. The validation studies revealed higher accuracy of the extended Ratkowsky models in comparison to the response surface equations. A significant shelf life extending effect of Na-lactate was predicted, which was more pronounced at low refrigerated temperatures. A synergistic effect has also been noticed between Na-lactate and carbon dioxide which, at least partly, could be explained by the pH-decreasing effect of CO2.     

Shelf life of modified atmosphere packed cooked meat products: a predictive model

The effect of temperature, concentration of dissolved CO2 and water activity on the growth of Lactobacillus sake was investigated by developing predictive models for the lag phase and the maximum specific growth rate of this specific spoilage organism for gas-packed cooked meat products. Two types of predictive model were compared: an extended Ratkowsky model and a response surface model. In general, response surface models showed a slightly better correlation, but the response surface model for the maximum specific growth rate showed illogical predictions at low water activities. The concentration of dissolved CO2 proved to be a significant independent variable for the maximum specific growth rate as well as for the lag phase of L. sake. Synergistic actions on the shelf life-extending effect were noticed between temperature and dissolved CO2, as well as between water activity and dissolved CO2. The developed models were validated by comparison with the existing model of Kant-Muermans et al. (1997) and by means of experiments in gas-packed cooked meat products. Both developed models proved to be useful in the prediction of the microbial shelf life of gas-packed cooked meat products.     

Determination of the growth limits and kinetic behavior of Listeria monocytogenes in a sliced cooked cured meat product: validation of the predictive growth model under constant and dynamic temperature storage conditions

To describe the growth limits of Listeria monocytogenes NCTC10527 in a sliced vacuum-packaged cooked cured meat product, the binary logistic regression model was used to develop an equation to determine the probability of growth or no growth of L. monocytogenes as a function of temperature (from 0 to 10 degrees C) and water activity (from 0.88 to 0.98). Two inoculum concentrations were used (10 and 10(4) CFU g(-1)), and the growth limits for the two inocula were different. The kinetic behavior of L. monocytogenes as a function of temperature (4, 8, 12, and 16 degrees C) on the same meat product at the lower concentration (10 CFU g(-1)) was also studied. The Baranyi model appeared to fit the overall experimental data better than did the modified Gompertz and the modified logistic models. Maximum specific growth rate (micromax), lag phase duration (LPD), and maximum cell concentration (Nmax) derived from the primary model were modeled using the square root function (micromax and LPD) and a second order polynomial (Nmax) (secondary models). The selection of the best model (primary or secondary) was based on some statistical indices (the root mean square error of residuals of the model, the regression coefficient, the F test, the goodness of fit, and the bias and accuracy factor). The developed kinetic behavior model was validated under constant and dynamic temperature storage conditions. This prediction of L. monocytogenes growth provides useful information for improving meat safety and can be used for in-depth inspection of quality assurance systems in the meat industry.     

Microbial inactivation after high-pressure processing at 600 MPa in commercial meat products over its shelf life

The behaviour of spoilage and pathogenic microorganisms was evaluated after high-pressure treatment (600 MPa 6 min, 31 °C) and during chilled storage at 4 °C for up to 120 days of commercial meat products. The objective was to determine if this pressure treatment is a valid process to reduce the safety risks associated with Salmonella and Listeria monocytogenes, and if it effectively avoids or delays the growth of spoilage microorganisms during the chilled storage time evaluated. The meat products covered by this study were cooked meat products (sliced cooked ham, pH 6.25, a_w 0.978), dry cured meat products (sliced dry cured ham, pH 5.81, a_w 0.890), and raw marinated meats (sliced marinated beef loin, pH 5.88, a_w 0.985). HPP at 600 MPa for 6 min was an efficient method for avoiding the growth of yeasts and Enterobacteriaceae with a potential to produce off-flavours and for delaying the growth of lactic acid bacteria as spoilage microorganisms. HPP reduced the safety risks associated with Salmonella and L. monocytogenes in sliced marinated beef loin.     

IDENTIFICATION OF HURDLES FOR IMPROVING STORAGE STABILITY OF BRAISED KIDNEY BEANS, A KOREAN SEASONED SIDE DISH

The aim of this study was to identify factors affecting the preservation of braised kidney beans, a traditional Korean side dish, to extend its shelf life. The effects of ingredient formulation, refrigerated storage and modified atmosphere packaging on storage stability and/or sensory quality were examined. Count of yeast/mold was selected as a primary quality index from the storage test at 10C. A formulation was found in cooked kidney beans, sugar, soy sauce and corn syrup to provide the retarded microbial growth and affordable sensory quality. The temperature dependence value (Q₁₀) for the shelf life of the stretch-wrapped product was 2.0 for temperatures of 5 to 20C. Modified atmosphere packaging (60% CO₂/40% N₂ or 100% CO₂) extended the shelf life at 10C by 500% (to 36 days) compared to air packaging (6 days) based on criteria of yeast/mold growth. Equations for estimating microbial spoilage and shelf life were derived as function of temperature.

PRACTICAL APPLICATIONS

Microbial growth retardation by ingredient formulation change, chilled storage and high CO₂ modified atmosphere packaging is useful to design the processing, packaging and distribution of the Korean side dish product. Quality change kinetics of yeast/mold growth established can be used for determining shelf life of the product under different storage temperature conditions. Through the scale-up procedure, the knowledge found in this study will be useful for the industrial processing and storage of the seasoned side dishes.     

Modeling and predicting spoilage of cooked, cured meat products by multivariate analysis

A cooked, cured meat product is a perishable product spoiled mainly by lactic acid bacteria (LAB). LAB cause discoloration, slime formation, off-odors and off-flavors as the result of their metabolic activity producing various products. These microbial products in conjunction with the microbial population could be used to assess the degree of spoilage of this type of product. The spoilage evaluation was achieved by following a multivariate approach. Cluster analysis, principal component analysis and partial least square regression were employed to associate spoilage with microbiological and physicochemical parameters. The developed model was capable of giving accurate predictions of spoilage describing the spoilage associations. The study might contribute to the improvement of quality assurance systems of meat enterprises.     

Impact of slicing hygiene upon shelf life and distribution of spoilage bacteria in vacuum packaged cured meats

A model for studying spoilage in sliced cooked delicatessen meats using conventional plating procedures was characterized by following the transfer of adventitious lactic acid bacteria (LAB), thermotolerant LAB and pediococci from a dry fermented sausage to cooked ham and bologna during a simultaneous slicing procedure. The major group of organisms present in these products was LAB. Each of the three groups of organisms was transferred to the cooked meats, but during storage under vacuum at 7°C, only the adventitious lactobacilli from the sausage appeared to contribute to cooked meat spoilage. Pediococci declined within 28 days of co-slicing, thermotolerant LAB grew slowly and never reached levels of >5 log₁₀cfu cm⁻², but transferred adventitious LAB from the sausage grew and reached peak populations 4 weeks earlier in the co-sliced cooked meats than in controls. During storage at 7°C co-sliced cooked meats spoiled, as assessed by purge (liquid) and ropy slime formation, 2–4 weeks faster than the separately-sliced and vacuum-packaged products. The distribution of organisms on package slices differed. In control cooked products numbers of bacteria present on center package slices were lower than on outside slices. Bacterial numbers were greatest at the meat surface–packaging film interface. In co-sliced cooked products organisms were evenly distributed throughout slices in the packages. Based on findings from use of the co-slice model, in vacuum packages of sliced cured meats where >10⁵cfu bacteria cm₋₂are equally distributed throughout package slices, poor slicing hygiene is the cause. Commercially-sliced bologna was repackaged with allyl isothiocyanate (AIT) to test its ability to delay bacterial growth at the meat surface. The preservative effects of AIT were tested under vacuum or when backflushed with CO₂. CO₂alone was more effective than AIT in delaying LAB growth but neither treatment was particularly effective.     

Effect of L-glucose and D-tagatose on bacterial growth in media and a cooked cured ham product

Cured meats such as ham can undergo premature spoilage on account of the proliferation of lactic acid bacteria. This spoilage is generally evident from a milkiness in the purge of vacuum-packaged sliced ham. Although cured, most hams are at more risk of spoilage than other types of processed meat products because they contain considerably higher concentrations of carbohydrates, approximately 2 to 7%, usually in the form of dextrose and corn syrup solids. Unfortunately, the meat industry is restricted with respect to the choice of preservatives and bactericidal agents. An alternative approach from these chemical compounds would be to use novel carbohydrate sources that are unrecognizable to spoilage bacteria. L-Glucose and D-tagatose are two such potential sugars, and in a series of tests in vitro, the ability of bacteria to utilize each as an energy source was compared to that of D-glucose. Results showed that both L-glucose and D-tagatose are not easily catabolized by a variety of lactic bacteria and not at all by pathogenic bacteria such as Escherichia coli O157:H7, Salmonella Typhimurium, Staphylococcus aureus, Bacillus cereus, and Yersinia enterocolitica. In a separate study, D-glucose, L-glucose, and D-tagatose were added to a chopped and formed ham formulation and the rate of bacterial growth was monitored. Analysis of data by a general linear model revealed that the growth rates of total aerobic and lactic acid bacteria were significantly (P < 0.05) slower for the formulation containing D-tagatose than those containing L- or D-glucose. Levels of Enterobacteriaceae were initially low and these bacteria did not significantly (P < 0.20) change in the presence of any of the sugars used in the meat formulations. Compared to the control sample containing D-glucose, the shelf life of the chopped and formed ham containing D-tagatose at 10 degrees C was extended by 7 to 10 days. These results indicate that D-tagatose could deter the growth of microorganisms and inhibit the rate of spoilage in a meat product containing carbohydrates.     

Occurrence and growth of yeasts in processed meat products - Implications for potential spoilage

Spoilage of meat products is in general attributed to bacteria but new processing and storage techniques inhibiting growth of bacteria may provide opportunities for yeasts to dominate the microflora and cause spoilage of the product. With the aim of obtaining a deeper understanding of the potential role of yeast in spoilage of five different processed meat products (bacon, ham, salami and two different liver patés), yeasts were isolated, enumerated and identified during processing, in the final product and in the final product at the end of shelf life. Yeasts were isolated along the bacon production line in numbers up to 4.2 log (CFU/g). Smoking of the bacon reduced the yeast counts to lower than 1.0 log (CFU/g) or non-detectable levels. In general, yeasts were only isolated in low numbers during the production of salami, cooked ham and liver paté. In the final products yeasts were detected in low numbers in a few samples (3 out of 30) samples, 1.0-1.3 log (CFU/g). By the end of storage, yeasts were only detected in 1 out of 25 investigated samples 1.8 log (CFU/g). A combination of phenotypic and genotypic methods was used to identify the yeast microflora present during production of the processed meat products. The yeast microflora was complex with 4-12 different species isolated from the different production sites. In general, Candida zeylanoides, Debaryomyces hansenii and the newly described Candida alimentaria were found to be the dominant yeast species. In addition, three putatively previously undescribed yeast species were isolated. Fourteen isolates, representing seven different species isolated during the production of the processed meat products and one species isolated from spoiled, modified atmosphere packed, sliced ham, were screened for their ability to grow in a meat model substrate under a low oxygen/high carbon-dioxide atmosphere (0.5% O(2), 20% CO(2), 79.5% N(2)) at two different temperatures (5 and 8°C). Eleven out of the tested 14 strains were able to grow in the meat model substrate with C. zeylanoides, D. hansenii, Pichia guilliermondii and Candida sake reaching levels of 10(5)-5×10(6) log (CFU/g), where sensoryical changes appear.     

Storage Changes of Fresh and Pasteurized Blue Crab Meat in Different Types of Packaging

We investigated pasteurization and storage of blue crabmeat in steel cans, aluminum cans, plastic cans, nonbarrier pouches, and barrier pouches. Fresh meat was packed in copolymer polyethylene/polypro-pylene cups, Saran® over-wrapped or vacuum skin packaged polystyrene trays, and nonbarrier pouches. Meat pasteurized in plastic and aluminum cans had better sensory and microbiological quality and longer shelf life than meat packed in steel cans. Oxygen-barrier pouches had the lowest quality and shortest shelf life. Nonbarrier pouches had product with quality similar to meat in steel cans, but with an extended shelf life. No packaging materials improved the microbiological shelf life of freshly cooked meat. Vacuum skin packaging resulted in improved sensory qualities of freshly cooked and picked meat.     

Modeling the growth of lactic acid bacteria in sliced ham processed by high hydrostatic pressure

The main responsible for the spoilage of cooked cured meat products stored under refrigerated and anaerobic conditions are lactic acid bacteria. The application of high hydrostatic pressure (HHP) reduces the lactic acid bacterial growth extending the product shelf-life and preserving natural taste, texture, color and vitamin content. This work studied the influence of pressure level and holding time on the lactic acid bacterial growth in vacuum-packaged sliced ham. Modified Gompertz and Logistic models were used to fit experimental data obtained from post-treatment microbial counts carried out along the product storage. Samples of sliced vacuum-packaged ham treated by HHP and control samples (non-treated) were stored at 8 °C until the microorganism population reached 10⁷ CFU/g. An experimental planning 2² with triplicate at the central point was designed to determine the influence of pressure level (200, 300, and 400 MPa) and holding time (5, 10, and 15 min) on the product shelf-life. The results have shown that the pressure intensity and the holding time significantly influenced microbial population over the product storage. Shelf-life of ham treated at 400 MPa for 15 min was extended from 19 (control samples) to 85 days.     

水产品特定腐败菌应用价值及分析技术研究进展

特定腐败菌（specific spoilage organism,SSO）是影响水产品腐败的主要因素之一。本文分析SSO在水产品货架期预测与延长中的实际应用价值,总结水产品SSO多种分析技术,如细菌基因组重复序列聚合酶链式反应、变性梯度凝胶电泳、限制性片段长度多态性和高通量测序等,为水产品SSO分析技术的研发提供理论参考,也为水产品SSO的深入研究提供理论依据。     

肉制品预测微生物模型的研究进展

肉制品贮藏过程的预测微生物模型是预测微生物学的重要分支。简述了肉制品货架期与特定腐败菌的相关性,综述了预测微生物模型的发展过程及其最新研究进展,分析预测微生物模型实际应用于肉制品质量监测的可行性,介绍几种有关食品微生物的数据库和预测软件,讨论了预测微生物模型存在的问题,展望了预测微生物模型的发展方向和应用前景。     

不同贮藏温度西式火腿切片品质变化规律研究

为研究市场上低温火腿切片的质量和安全性,对不同贮藏温度的真空包装火腿切片的品质变化进行动态跟踪,分析产品在0～4、7～11℃条件下,其感官品质、菌落总数、大肠菌群、色泽、pH值、水分含量、保水性和质构特性的动态变化。结果表明：两种产品品质变化的规律大致相同。0～4℃贮藏比7～11℃产品的菌落总数增长相对缓慢,pH值、水分含量,保水性和质构特性的变化更加稳定。低温更有利于保持产品品质的稳定性和安全性,延长肉品的货架期。     

Development of a Monte Carlo simulation model to predict pasteurized fluid milk spoilage due to post-pasteurization contamination with gram-negative bacteria

Psychrotolerant gram-negative bacteria introduced as post-pasteurization contamination (PPC) are a major cause of spoilage and reduced shelf life of high-temperature, short-time pasteurized fluid milk. To provide improved tools to (1) predict pasteurized fluid milk shelf life as influenced by PPC and (2) assess the effectiveness of different potential interventions that could reduce spoilage due to PPC, we developed a Monte Carlo simulation model that predicts fluid milk spoilage due to psychrotolerant gram-negative bacteria introduced as PPC. As a first step, 17 gram-negative bacterial isolates frequently associated with fluid milk spoilage were selected and used to generate growth data in skim milk broth at 6°C. The resulting growth parameters, frequency of isolation for the 17 different isolates, and initial concentration of bacteria in milk with PPC, were used to develop a Monte Carlo model to predict bacterial number at different days of shelf life based on storage temperature of milk. This model was then validated with data from d 7 and 10 of shelf life, collected from commercial operations. The validated model predicted that the parameters (1) maximum growth rate and (2) storage temperature had the greatest influence on the percentage of containers exceeding 20,000 cfu/mL standard plate count on d 7 and 10 (i.e., spoiling due to PPC), which indicates that accurate data on maximum growth rate and storage temperature are important for accurate predictions. In addition to allowing for prediction of fluid milk shelf life, the model allows for simulation of “what-if” scenarios, which allowed us to predict the effectiveness of different interventions to reduce overall fluid milk spoilage due to PPC through a set of proof-of-concept scenario (e.g., frequency of PPC in containers reduced from 100% to 10%; limiting distribution temperature to a maximum of 6°C). Combined with other models, such as previous models on fluid milk spoilage due to psychrotolerant spore-forming bacteria, the data and tools developed here will allow for rational, digitally enabled, fluid milk shelf life prediction and quality enhancement.     

Psychrotolerant spore-former growth characterization for the development of a dairy spoilage predictive model

Psychrotolerant spore-forming bacteria represent a major challenge regarding microbial spoilage of fluid milk. These organisms can survive most conventional pasteurization regimens and subsequently germinate and grow to spoilage levels during refrigerated storage. To improve predictions of fluid milk shelf life and assess different approaches to control psychrotolerant spore-forming bacteria in the fluid milk production and processing continuum, we developed a predictive model of spoilage of fluid milk due to germination and growth of psychrotolerant spore-forming bacteria. We characterized 14 psychrotolerant spore-formers, representing the most common Bacillales subtypes isolated from raw and pasteurized milk, for ability to germinate from spores and grow in skim milk broth at 6°C. Complete growth curves were obtained by determining total bacterial count and spore count every 24 h for 30 d. Based on growth curves at 6°C, probability distributions of initial spore counts in bulk tank raw milk, and subtype frequency in bulk tank raw milk, a Monte Carlo simulation model was created to predict spoilage patterns in high temperature, short time-pasteurized fluid milk. Monte Carlo simulations predicted that 66% of half-gallons (1,900 mL) of high temperature, short time fluid milk would reach a cell density greater than 20,000 cfu/mL after 21 d of storage at 6°C, consistent with current spoilage patterns observed in commercial products. Our model also predicted that an intervention that reduces initial spore loads by 2.2 Log₁₀ most probable number/mL (e.g., microfiltration) can extend fluid milk shelf life by 4 d (end of shelf life was defined here as the first day when the mean total bacterial count exceeded 20,000 cfu/mL). This study not only provides a baseline understanding of the growth rates of psychrotolerant spore-formers in fluid milk, it also provides a stochastic model of spoilage by these organisms over the shelf life of fluid milk, which will ultimately allow for the assessment of different approaches to reduce fluid milk spoilage.     

冷链条件下马鲛鱼优势腐败菌生长动力学研究及货架期预测

为快速预测冷链马鲛鱼在不同冷链物流温度下优势腐败菌生长动态及货架期,进行了马鲛鱼0,4,10℃下3种典型冷链温度的贮藏模拟试验,分析了马鲛鱼不同温度下的菌落总数、希瓦氏菌数和假单胞菌数以及各个温度下马鲛鱼货架期终点时的挥发性盐基氮含量和感官评定质量指数,采用修正的Gompertz和Belehradek方程建立了冷链马鲛鱼中优势腐败菌在0~10℃的一级、二级生长预测模型与货架期预测模型。结果表明,修正的Gompertz方程能准确表达马鲛鱼在3种贮藏温度下假单胞菌的生长规律,拟合度R^2高达0.99,采用Belehradek方程描述温度对最大比生长速率(μ_max)和延滞期(λ)的影响呈现良好的线性关系,相关性R^2>0.90。进一步用贮藏于2,8℃马鲛鱼中假单胞菌数来验证模型的可靠性,偏差度为1.010 4~1.024 5,准确度为1.026 8~1.038 7,货架期预测模型的相对误差绝对值为6.09%~8.95%。     

Quantitative assessment of the shelf life of ozonated apple juice

Sterile apple juice inoculated with S. cerevisiae ATCC 9763 (10³ CFU/mL) was processed in a bubble column with gaseous ozone of flow rate of 0.12 L/min and concentration of 33–40 μg/mL for 8 min. The growth kinetics of S. cerevisiae as an indicator of juice spoilage was monitored at 4, 8, 12 and 16 °C for up to 30 days. The kinetics was quantitatively described by the primary model of Baranyi and Roberts, and the maximum specific growth rate was further modeled as a function of temperature by the Ratkowsky type model. The developed model was successfully validated for the microbial growth of control and ozonated samples during dynamic storage temperature of periodic changes from 4 to 16 °C. Two more characteristic parameters were also evaluated, the time of spoilage of the product under static temperature conditions and the temperature quotient, Q ₁₀. At lower static storage temperature (4 °C), no spoilage occurred either for unprocessed or ozone-processed apple juice. In the case of ozone-processed apple juice, the shelf life was increased when compared with the controls, and the Q ₁₀ was found to be 7.17, which appear much higher than that of the controls, indicating the effectiveness of ozonation for the extension of shelf life of apple juice.     

Shelf life evaluation for ready-to-eat sliced uncured turkey breast and cured ham under probable storage conditions based on Listeria monocytogenes and psychrotroph growth

The growth variability of three Listeria monocytogenes ribotypes in ready-to-eat (RTE) sliced uncured turkey breast and cured ham was studied under storage conditions that RTE foods are likely to encounter. Three product treatments studied were: (1) a control; (2) a formulation subjected to high pressure processing to reduce initial microbial load (HPP); (3) a formulation containing 2.0% potassium lactate and 0.2% sodium diacetate (PL/SD). After separate inoculation with individual L. monocytogenes ribotypes and packaging each treatment under air and vacuum, the packages were stored at 4, 8, or 12 degrees C and the counts of L. monocytogenes and psychrotrophic bacteria (PPC) were determined for several weeks. The Baranyi model was used to estimate lag times and growth rates. Significant effect of strain difference was noted in both sliced products (P<0.05). In the absence of antimicrobials (HPP and control), the growth rate (GR) of L. monocytogenes strains increment from 4 to 8 degrees C and from 8 to 12 degrees C was approximately 10 and 2 fold, respectively. The addition of PL/SD was effective in restricting the growth of L. monocytogenes and PPC at 4 degrees C, but at 8 and 12 degrees C significant growth was observed (more than 100-fold increase) (P<0.05). In PL/SD samples, vacuum packaging slowed down the onset and the rate of growth of L. monocytogenes at 12 degrees C in sliced ham and at 8 and 12 degrees C in sliced turkey breast. Generally, the time to increase by 2-logs was greater in control samples than as observed in HPP-treated samples. When antimicrobials were present, the current results showed that L. monocytogenes was able to grow more than 100-fold within the typical quality-based shelf life of 60 to 90 days at 8 and 12 degrees C. The findings of this study should be useful in setting the duration of a safety-based shelf life for RTE sliced meat and poultry foods.