Effect of muscle type and CO-pretreatment combinations on the colour stability, protein oxidation and shelf-life of vacuum packaged beef steaks

This study investigated the effects of CO-pretreatments on three bovine muscles: Psoas major (PM), Gluteus medius (GM) and Semitendinosus (ST) on colour stability and quality attributes under anaerobic conditions. Steaks were exposed to one of four pretreatments: 1% CO for 5 h, 5% CO for 5 h, 1% CO for 24 h, with 60% CO₂ (balance N₂) or untreated (control) and then vacuum packaged and displayed (28 days at 2 °C). CO pretreatments improved redness for colour labile muscles (PM and GM). The optimum CO pretreatment was 1% for 5 h as this induced surface redness while discolouring (a* = 12, C* = 16) by the use-by-date (28 days). CO pretreatments decreased protein oxidation (P < 0.01), and had no negative effect on pH and spoilage bacteria (P > 0.05). Applying a 1% CO pretreatment for 5 h effectively enhanced the colour of various muscles while not masking spoilage thus addressing consumer concerns.