Influence of carbon monoxide in package atmospheres containing oxygen on colour, reducing activity, and oxygen consumption of five bovine muscles

Steaks from five bovine muscles [psoas major (PM), longissimus lumborum (LL), deep semimembranosus (DSM), superficial semimembranosus (SSM), and semitendinosus (ST)] were packaged in atmospheres containing 20% or 80% oxygen, with and without 0.4% carbon monoxide. Steaks were evaluated on d 0, 4, and 7 of retail display for instrumental (CIE L∗, a∗, and b∗) and visual colour, total- and metmyoglobin-reducing activity, and oxygen consumption rate. Combining carbon monoxide with either oxygen level had no effect (P > 0.05) on any measured attribute. Using higher oxygen levels increased colour stability and reduced variability (P < 0.05) among muscles for all measured attributes. In general, colour stability and reducing activity for the muscles were LL > ST > SSM > PM > DSM. Including 0.4% carbon monoxide with 20% or 80% oxygen may not have impacted colour, due to preferential formation of oxymyoglobin, rather than carboxymyoglobin, at these oxygen levels.