Abstract
The objective of this research was to compare metabolite profiles between beef longissimus and psoas muscles during display. Beef short loins were collected 3 d postmortem (n = 10). Steaks were cut from each longissimus lumborum (LL) and psoas major (PM) muscle and displayed under retail conditions for 7 d. Surface color, biochemical properties, and metabolites were analyzed during storage. PM decreased in redness (P < 0.05) by d 3 of display compared with LL. There were differences in metabolite concentrations (P < 0.05) between each muscle type at each time point. Sugars, amino acids, tricarboxylic acid cycle intermediates, and glycolytic substrates were detected in both muscles. Glycolytic metabolites such as pyruvic acid, glucose–6–phosphate, and fructose were greater (P < 0.05) in LL than PM at all display times. On d 0, the intensity of pyruvic acid in LL and PM were 142 and 42, respectively. Citric acid and succinic acid were lower on d 0, but were greater (P < 0.05) in LL compared with PM by d 7 of display. Carnitine was lower (P < 0.05) in LL than PM at all display times. On d 7, carnitine level in LL was 4.1 while in PM was 13,500. The results suggest that in addition to muscle-specific differences in mitochondrial and enzyme activities, inherent metabolite differences also may contribute to muscle color stability.
Highlights
Myoglobin is a sarcoplasmic protein that is primarily responsible for meat color
The steak half assigned to metmyoglobin reducing activity (MRA) and Oxygen consumption (OC) was bisected parallel to the oxygenated surface to expose the interior of steak
The enzymes involved in glycolysis and tricarboxylic acid cycle (TCA) cycle remain active in postmortem muscles
Summary
Myoglobin is a sarcoplasmic protein that is primarily responsible for meat color. In fresh meat, myoglobin can exist in 3 different redox forms, namely deoxymyoglobin, oxymyoglobin, and metmyoglobin (AMSA, 2012). Deoxymyoglobin imparts purple color while predominant oxymyoglobin gives consumers the preferred bright-red color to beef. Oxidation of both oxy- and deoxymyoglobin result in the formation of metmyoglobin and discoloration of meat (Faustman and Cassens, 1990). The concentration of reduced nicotinamide adenine dinucleotide (NADH), myoglobin chemistry, and mitochondrial activity play a significant role in metmyoglobin reduction (Tang et al, 2005; Ramanathan and Mancini, 2010; Nerimetla et al, 2017). Various studies have shown that the addition of metabolites such as lactate, pyruvate, and succinate to meat or isolated mitochondria can regenerate NADH and can influence beef color (Tang et al, 2005; Kim et al, 2006; Ramanathan et al, 2011). Characterizing TCA and glycolytic substrate changes in postmortem muscle is critical to understand the fundamental basis for meat discoloration
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