Variation in the fatty acid profile of two Listeria monocytogenes strains grown at varying temperatures was determined. The fatty acid profiles varied greatly at different temperatures. General decreases in relative percentages of branched and medium chain (up to C16:0) fatty acids and variable changes in long chain fatty acids were found with increasing growth temperature. Individual fatty acid percentages between strains were variable. The relative percentages of unknown long chain fatty acids, detected in both strains at various temperatures, were greatest in Scott A (7.07%) and ATCC 19114 (13.15%) at 35C. Results demonstrated that L. monocytogenes had altered fatty acid profile in response to changes in growth temperature.
Traditional thermal treatments are the cornerstone of the food processing industry, providing required safety requirements and extension of the shelf life. This chapter provides an overview of the published data regarding high hydrostatic pressure (HHP) processing as well as basic knowledge and its current applications. A high-pressure processing unit operation involves filling a sterile container with food that is then sealed and placed inside a pressure chamber filled with a pressure-transmitting hydraulic fluid for pressure transmission, with ethyl vinyl alcohol or polyvinyl alcohol suggested as the packing material. The chapter investigates the effects of HHP processing on a wide variety of fruit and vegetable products, especially fresh produce and minimally processed food. Efficacy of HHP treatment has been reported on meat and seafood products including bay scallops and oyster. High-pressure processing has been recognized as a viable alternative to thermal processing among emerging food preservation technologies.
Foods ............................................................................................... 5 1.2.3 Strategies for Controlling L. monocytogenes in RTE Foods ....... 91.3 Salmonella enterica .................................................................................... 13 1.3.1 Outbreaks Associated with Salmonella in RTE Foods ............ 14 1.3.2 Incidence and Prevalence of Salmonella in RTE Foods .......... 17 1.3.3 Strategies for Controlling Salmonella in RTE Foods ............... 181.4 Escherichia coli O157:H7 ........................................................................... 20 1.4.1 Outbreaks Associated with E. coli O157:H7 in RTE Foods ..... 21 1.4.2 Incidence and Prevalence of E. coli O157:H7 in RTE Foods ...... 23 1.4.3 Strategies for Controlling E. coli O157:H7 in RTE Foods ....... 241.5 Clostridium perfringens ............................................................................ 27 1.5.1 Outbreaks of C. perfringens in RTE Foods ............................... 29 1.5.2 Incidence and Prevalence of C. perfringens in RTE Foods ..... 31 1.5.3 Strategies for Controlling C. perfringens in RTE Foods ......... 321.6 Conclusion ............................................................................................... 39 1.7 Future Outlook ........................................................................................ 40 References .......................................................................................................... 41consumers. Surveys of consumer purchase behaviors show an increasing trend in the consumption of RTE foods (Anonymous, 2001, 2003). Hence, the demand for these products from the food industry is huge. Ready-to-eat sandwiches account for 32% of sales from vending machines and include a large share of a multibillion-dollar annual business in the United States (Anonymous, 2001). Supermarkets and convenience stores carry a large selection and variety of RTE food products.
The goal of this study was to determine the inactivation kinetics of Salmonella in commercial 10% salted liquid whole egg (LWE) to assist the U.S. Department of Agriculture in writing new liquid egg pasteurization guidelines. Current data are not sufficient for predicting thermal inactivation kinetics of Salmonella spp. for use in updating pasteurization guidelines for many types of liquid egg products, including salted LWE (SLWE). This is, in part, due to variations in Salmonella strains and changes in the processing of liquid egg products that have arisen in the past 40 years. Pasteurization guidelines are currently being reevaluated in light of recent risk assessments. Heat-resistant Salmonella serovars Enteritidis and Oranienburg were composited and mixed into 10% SLWE, resulting in final populations of approximately 5.7–7.8 log colony-forming units (CFU)/mL. Inoculated egg was injected into glass capillary tubes, flame-sealed, and heated in a water bath at 60, 62.2, 63.3, 64.3, or 66°C. Contents were surface-plated and incubated at 37°C for 24 h. Survival curves were not log-linear (log levels versus time), but decreased rapidly, and after initial periods became linear. Asymptotic decimal reduction values at each temperature were calculated from survivor curves with a minimum inactivation of 5.0 log CFU/mL. The asymptotic thermal D-values for SLWE were 3.47, 2.23, 1.79, 1.46, and 1.04 min at 60, 62.2, 63.3, 64.3, or 66°C, respectively. The calculated thermal z-value was 11.5°C. A model that predicts lethality for given times and temperatures that was developed predicted that the current pasteurization requirements for 10% SLWE (i.e., 63.3°C for 3.5 min, or 62.2°C for 6.2 min) are not sufficient to inactivate 7 log CFU/mL of Salmonella and only achieve approximately 4 log CFU/mL inactivation. This model will assist egg-products manufacturers and regulatory agencies in designing pasteurization processes to ensure product safety.
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