Abstract
The objective of current research was to determine the effects of extended aging, modified atmospheric packaging (MAP), and display time on metmyoglobin reducing activity (MRA) and oxygen consumption (OC) of high-pH beef using pH sensitive methodology for MRA and OC. Ten normal-pH (mean pH = 5.6) and 10 high-pH loins (mean pH = 6.4) were vacuum packaged on d 3 postmortem and aged for 0, 21, 42, and 62 d at 2°C. Following aging, 2.0-cm-thick steaks were cut from each of the normal- and high-pH loin sections and packaged in either PVC film, high-oxygen (HiOx-MAP), or carbon monoxide modified atmospheric (CO-MAP) packaging. Surface color, OC, and MRA were measured on d 0 and 6 of the respective aging periods. Steaks in HiOx-MAP and CO-MAP had similar (P > 0.05) L* values, which were greater (P < 0.05) than high-pH steaks packaged in PVC film. On 21-d of aging, steaks with at both pHs in CO-MAP and HiOx-MAP had greater (P < 0.05) a* values than steaks packaged in PVC. As aging time increased, MRA decreased (P < 0.05) for steaks with normal- and high-pH when packaged in PVC and HiOx-MAP. Steaks with a high-pH in CO-MAP had greater (P < 0.05) MRA than steaks with a normal-pH in CO-MAP at all aging periods. Steaks with a high-pH had greater (P < 0.05) OC on d 0 and 6 than normal-pH steaks. Steaks with a normal-pH aged for 21 d and packaged in PVC and HiOx-MAP had greater (P < 0.05) lipid oxidation than high-pH steaks aged for 21 d and packaged in PVC and HiOx-MAP. After 62 d of aging and 6 d of display, the greatest color stability chemistry (based on MRA and OC for all package types) were: high-pH meat > normal-pH meat; thus the MRA and OC methodology was useful in relative comparison of packaged meat color stability differences due to pH.
Highlights
High-pH beef or dark-cutting beef is one of the most prominent beef quality defects worldwide (Moore et al, 2012; Mahmood et al, 2017; Zhang et al, 2018)
A split-split plot design was utilized to determine the effects of muscle-pH, aging period, modified atmospheric packaging (MAP), and display time on Metmyoglobin reducing activity (MRA) and oxygen consumption (OC)
Extended aging decreased color stability of normal- and high-pH steaks packaged in PVC and HiOxMAP
Summary
High-pH beef or dark-cutting beef is one of the most prominent beef quality defects worldwide (Moore et al, 2012; Mahmood et al, 2017; Zhang et al, 2018). Consumers often associate bright-red color with beef freshness and wholesomeness. Than normal-pH conditions are an example of a color deviation in which beef failed to have a bright-red color, leading to discounted carcasses and economic losses to the meat industry (Boykin et al, 2017). Metmyoglobin reducing activity (MRA) and oxygen consumption (OC) are inherent biochemical properties that influence beef color (Madhavi and Carpenter, 1993; Seyfert et al, 2007; Mancini and Ramanathan, 2014). Both processes can affect the proportion of myoglobin forms on the surface of beef steaks.
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