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During retail display tenderloin steaks packaged in PVC overwrap discolor quicker than strip loin steaks. This research determines the basis for muscle-specific differences in color stability. The results indicate that mitochondria present in tenderloin lose its functionality faster than strip loin mitochondria. Developing strategies to minimize muscle-specific differences in mitochondrial changes can increase color stability and value of fresh beef.

Escherichia coli O157: H7 (EHEC) is a major foodborne pathogen largely transmitted to humans through the consumption of undercooked ground beef. This study investigated the efficacy of two food-grade, plant-derived antimicrobials, namely rutin (RT), and resveratrol (RV) with or without chitosan (CH) in enhancing EHEC inactivation in undercooked hamburger patties. Further, the effect of aforementioned treatments on beef color and lipid oxidation was analyzed. Additionally, the deleterious effects of these antimicrobial treatments on EHEC was determined using scanning electron microscopy (SEM). Ground beef was inoculated with a five-strain mixture of EHEC (7.0 log CFU/g), followed by the addition of RT (0.05%, 0.1% w/w) or RV (0.1, 0.2% w/w) with or without CH (0.01% w/w). The meat was formed into patties (25 g) and stored at 4°C for 5 days. On days 1, 3, and 5, the patties were cooked (65°C, medium rare) and surviving EHEC was enumerated. The effect of these treatments on meat color and lipid oxidation during storage was also determined as per American Meat Science Association guidelines. The study was repeated three times with duplicate samples of each treatment. Both RT and RV enhanced the thermal destruction of EHEC, and reduced the pathogen load by at least 3 log CFU/g compared to control (P < 0.05). The combination of RT or RV with CH was found to be more effective, and reduced EHEC by 5 log CFU/g (P < 0.05). EHEC counts in uncooked patties did not decline during storage for 5 days (P > 0.05). Moreover, patties treated with RV plus CH were more color stable with higher a∗ values (P < 0.05). SEM results revealed that heat treatment with antimicrobials (CH + RV 0.2%) resulted in complete destruction of EHEC cells and extrusion of intracellular contents. Results suggest that the aforementioned antimicrobials could be used for enhancing the thermal inactivation of EHEC in undercooked patties; however, detailed sensory studies are warranted.

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Mitochondrial functionality affects muscle-specific beef color stability. Nonetheless, the relationship between mitochondrial proteome and muscle-specific beef color stability is yet to be examined. Therefore, the objective of the present study was to differentiate the proteomes of mitochondria from beef longissimus lumborum (LL; color-stable muscle) and psoas major (PM; color-labile muscle) steaks during retail display. LL and PM muscles from 7 beef carcasses (USDA Choice; 48 h postmortem) were fabricated into 1.92-cm-thick steaks and were aerobically packaged and retail displayed for 6 d. Mitochondria were isolated on day 3 and 6, whereas instrumental color and biochemical attributes were evaluated on day 0, 3, and 6. Mitochondrial proteome was analyzed employing two-dimensional electrophoresis. The protein spots exhibiting 1.5-fold or more intensity differences (P &lt; 0.05) between the muscles and display days were subjected to tryptic digestion and identified by tandem mass spectrometry. Whereas color stability decreased in both muscles during retail display, LL steaks demonstrated greater (P &lt; 0.05) color stability during display than their PM counterparts. Mitochondria could not be isolated from PM steaks on day 6 because of extensive degradation. Seven proteins were differentially abundant ( P &lt; 0.05) in LL and PM on day 3 of display. In LL steaks, 7 proteins were more abundant (P &lt; 0.05) on day 3 than on day 6 of retail display. The differentially abundant proteins were enzymes, binding proteins, and proteins involved in biosynthesis. These results indicated that differential abundance of mitochondrial proteome could also contribute to the variations in color stability of beef LL and PM muscles during retail display.