Evaluation of Microbial Community Dynamics Impacting the Shelf-Life of Processed Meats

The objective of this study in its entirety was to utilize high next-generation genetic sequencing to evaluate the microbial communities involved with processed meat spoilage. High throughput 16S rRNA gene sequencing on the Illumina MiSeq© platform was used alongside traditional plating methods to characterize the growth and composition of bacterial communities in processed meats. Previous results from this lab indicated a relatively high prevalence of Pseudomonas in cooked, sliced, and vacuum packaged deli meats, which was contrary to conventional wisdom. Therefore, four studies were designed to further evaluate the factors that may influence microbial communities in processed meats. Study 1 aimed to identify differences between the processing environment in which sliced deli-ham is produced, handled, and packaged. Products within the same category description from three separate processors had significantly different bacterial community profiles, however, all had prevalence of Pseudomonas, to varying degrees. Study 2 was designed to determine differences in the bacterial communities of various phases throughout processing, from raw ground beef to cooking, slicing, and applying an antimicrobial or post-lethality treatment. Raw ground beef and sliced bologna had similar bacterial community profiles, having the least microbial diversity with a high prevalence of Pseudomonas, while both cured and uncured links, and bologna with high pressure processing (HPP) or with organic acid salts had a higher proportion of various Firmicutes and Proteobacteria. Study 3 aimed to determine the differences in microbial community composition of sliced bologna caused by different clean-label and traditional antimicrobials. Increased growth and a higher prevalence of Pseudomonas were observed in the control treatment with no antimicrobial, while all antimicrobial treatments had greater microbial diversity, with increased amounts of various organisms compared to the Control. Study 4 aimed to identify differences in the microbial community composition between franks smoked with natural hardwood smoke, dipped in liquid smoke, or unsmoked. Minimal bacterial growth was observed in all three treatments throughout 14 weeks of refrigerated storage, and there were minuscule differences in their bacterial community composition. Differences in the microbial community composition of processed meats are vital to extending the shelf-life of products and further understanding their relationship with meat spoilage. Advisor: Gary A. Sulliva

Influence of sodium chloride reduction and replacement with potassium chloride based salts on the sensory and physico-chemical characteristics of pork sausage patties

This study evaluated the effects of sodium chloride reduction and replacement with potassium chloride or modified potassium chloride based salts using a weight or molar equivalent basis on the sensory and physicochemical properties of pork sausage patties. Three independent replications of pork sausage patties were manufactured to compare five treatments: full sodium, reduced sodium, modified potassium chloride weight based replacement, modified potassium chloride molar based replacement, and standard potassium chloride weight based replacement. Salt replacement did not affect (P \u3e 0.05) moisture, protein, fat, textural properties, lipid oxidation, or redness. Sausage patties with modified potassium chloride were more acceptable than those with standard potassium chloride (P \u3c 0.001). Using modified potassium chloride replaced on a molar equivalent basis resulted in samples with more similar sensory characteristics to the full sodium control than replacement on a weight equivalent basis. The use of modified potassium chloride reduced sodium and improved sodium:potassium ratios while other changes in composition or physico-chemical characteristics were minimal

Shelf Life of Ground Beef from Cattle Fed Distillers Grains Containing Different Amounts of Oil

Beef shoulder clods were collected from steers fed one of four finishing diets: no distillers grains and three with distillers grains containing different amounts of oil. Raw ground beef patties were evaluated for changes in objective color, discoloration, and lipid oxidation during simulated retail display (7 days). Cooked beef links in refrigerated (18 days) and frozen storage (198 days) were analyzed for lipid oxidation throughout shelf life. Fatty acid profiles were evaluated in lean, subcutaneous fat, and ground composite samples. All distillers grain diets increased C18:2 and polyunsaturated fatty acids in beef. There were no dietary differences in lipid oxidation throughout shelf life of raw ground beef and cooked beef links and no differences in color characteristics of raw ground beef. Finishing cattle on distillers grains altered fatty acid composition but did not impact shelf life characteristics of raw or cooked ground beef. The amount of oil in the distillers grains did not result in any significant differences in fatty acid profile and shelf life measures

Effect of Ingredients and Packaging on Color of High Pressure Processed Ground Beef

High pressure processing is a non-thermal pasteurization technique to control pathogens, like E. coli. However, color changes in raw beef induced by processing restrict high pressure processing’s use within the beef industry. The objectives of this study were to investigate the effects of adding curing agents (nitrite) and packaging with or without reducing compounds (ascorbic acid/erythorbate) on color retention in high pressure processed ground beef. High pressure processing resulted in a detrimental effect on the color of the beef patties for all treatments. Lightness and yellowness increased and redness decreased after high pressure processing. The effect remained the same throughout the course of the study (up to 21 days). However, there was less color change in samples treated with reducing compounds. Both inorganic and natural sources of nitrite and ascorbic acid/erythorbate performed similarly in terms of their ability to maintain redness. Treatments leading to formation of nitrosylmetmyoglobin (Fe3+) had less color change as compared to the treatments leading to the generation of nitrosylmyoglobin (Fe2+)

Effect of Myoglobin State on Color Stability of High Pressure Processed Ground Beef

High pressure processing, a non-thermal pasteurization technique, can reduce E. coli in beef but the use is limited due to discoloration of raw beef after high pressure processing. Different states of myoglobin have inherently different color stability. The objective of this study was to determine the impact of myoglobin state on color stability of raw beef patties treated with high pressure processing. Modified atmosphere packaging (high oxygen-oxymyoglobin, carbon monoxide-carboxymyoglobin), vacuum packaging (deoxymyoglobin) or added potassium ferricyanide (metmyoglobin) treatments were used to prepare patties with desired myoglobin states. Color was measured (CIE L*, a*, b*) before and after high pressure processing over a storage period of 21 days. Regardless of pressure and duration, beef patties lost redness after high pressure processing. However, carboxymyoglobin showed better color retention as compared to deoxymyoglobin, oxymyoglobin and metmyoglobin

The Effects of Source and Amount of Nitrite on Quality Characteristics of All-Beef Frankfurters

In an effort to meet consumers’ demand for foods with more natural ingredients, processors have begun manufacturing meat products cured with natural nitrite sources. The objective of this study was to evaluate the quality characteristics of all-beef frankfurters cured with traditional or alternative sources of nitrite and using equivalent amounts of nitrite. Frankfurters cured with alternative sources of nitrite had a slightly darker, less red exterior and slightly more yellow interior than those containing sodium nitrite. No differences were observed for pH or water activity. Both curing methods can be used to manufacture all-beef frankfurters with similar characteristics when using equivalent amounts of nitrite

Effect of Ingredients and Packaging on Color of High Pressure Processed Ground Beef

High pressure processing is a non-thermal pasteurization technique to control pathogens, like E. coli. However, color changes in raw beef induced by processing restrict high pressure processing’s use within the beef industry. The objectives of this study were to investigate the effects of adding curing agents (nitrite) and packaging with or without reducing compounds (ascorbic acid/erythorbate) on color retention in high pressure processed ground beef. High pressure processing resulted in a detrimental effect on the color of the beef patties for all treatments. Lightness and yellowness increased and redness decreased after high pressure processing. The effect remained the same throughout the course of the study (up to 21 days). However, there was less color change in samples treated with reducing compounds. Both inorganic and natural sources of nitrite and ascorbic acid/erythorbate performed similarly in terms of their ability to maintain redness. Treatments leading to formation of nitrosylmetmyoglobin (Fe3+) had less color change as compared to the treatments leading to the generation of nitrosylmyoglobin (Fe2+)

The Effects of Source and Amount of Nitrite on Quality Characteristics of All-Beef Frankfurters

In an effort to meet consumers’ demand for foods with more natural ingredients, processors have begun manufacturing meat products cured with natural nitrite sources. The objective of this study was to evaluate the quality characteristics of all-beef frankfurters cured with traditional or alternative sources of nitrite and using equivalent amounts of nitrite. Frankfurters cured with alternative sources of nitrite had a slightly darker, less red exterior and slightly more yellow interior than those containing sodium nitrite. No differences were observed for pH or water activity. Both curing methods can be used to manufacture all-beef frankfurters with similar characteristics when using equivalent amounts of nitrite

Effect of Salt Reduction on the Quality and Shelf Life Characteristics of Deli-Style Roast Beef

Concerns with excessive sodium intake have led to increased pressure on meat processors to reduce added salt in meat products. Quality characteristics and microbial growth were evaluated on deli- style roast beef slices formulated to contain varying concentrations of added salt. Salt concentration had no effect on microbial community composition, however increasing salt slowed microbial growth over time. Increasing salt increased cooking yield and decreased water activity. Salt reduction negatively impacts the texture, yield, and shelf life of deli- style roast beef, however salt concentrations within this range do not significantly alter spoilage flora community composition

A Survey of the Microbial Communities of Commercial Presliced, Packaged Deli-Style Ham Throughout Storage

The goal of this study was to evaluate the variation in spoilage microbiota associated with sliced, prepackaged deli-style ham from varying processing environments available in the retail market in the United States. Three different brands of presliced ham, water added were purchased at local markets and evaluated every 2 wk beginning 4 wk prior to the sell-by date until 4 wk beyond the sell-by date. Analysis of 16S ribosomal RNA genes using operational taxonomic units showed that Brand A had a different bacterial community structure compared with Brands B and C, according to unweighted (P=0.006) and weighted (P<0.001) UniFrac distance matrices. Brand A had a greater proportion of sequence reads mapping to Carnobacterium, Bacillus, and Prevotella, whereas B and C had greater proportions of Pseudomonas, Photobacterium, and Lactococcus. Brand A also had a lower salt concentration (P<0.007), greater moisture percentage and less fat percentage (P<0.012), and increased aerobic plate count (P=0.017). Differences in spoilage microbiota can in part be attributed to the factors involved with different processing locations, as shown by 3 different brands of ham, as well as slight differences in formulation including salt concentration and organic acid use