The effects of varying gas concentrations and exposure times on colour stability and shelf-life of vacuum packaged beef steaks subjected to carbon monoxide pretreatment

The aim of this study was to assess the effects of a range of carbon monoxide (CO) concentrations and exposure times on the colour stability and shelf-life of vacuum packaged Longissimus thoracis et lumborum (LTL) beef steaks. Steaks were exposed to five pretreatments: 0 (Control), 0.4, 1, 3 and 5% CO combined with 60% CO₂ (balance N₂) for 5, 7 or 24 h. They were then vacuum packed and stored at 2 °C for 28 days. The optimum pretreatment was 1% CO for 5 h as this enhanced initial desirable colour yet allowed discolouration to reach unacceptable levels (a* = 12, C* = 16) by the use-by-date (28 days). K/S ratios verified that the optimum CO pretreatment does not mask spoilage. All CO pretreatments had no effect on pH or purge loss (P > 0.05). Reducing the CO concentration and decreasing the exposure time achieved a desirable colour, without masking spoilage, thereby minimizing the processing time and improving the safety of workers.