IMPACT OF ULTIMATE PH ON MYOGLOBIN REDOX FORMS AND CIE COLOR ON LONGISSIMUS LUMBORUM AGED STEAKS OF NELORE BULLS (BOS INDICUS) DURING LONG-TERM FROZEN STORAGE

Frozen storage is important in the meat industry to ensure shelf life, but the formation of ice crystals during freezing and a high ultimate pH (pHu) can degrade quality, resulting in a dark red color. Thus, the objective of this work was to evaluate the influence of pHu ranges (normal (≤5.79), intermediate (5.80 to 6.19), and high (≥6.20)) and freezing storage on the redox forms of myoglobin and CIE color of Longissimus dorsi muscles of non-castrated Nellore cattle bulls. A total of 115 animals were slaughtered in a commercial slaughterhouse, and 4 muscles were selected (72h post-mortem) for each pHu range. Muscles were processed into steaks, randomly distributed among treatments, vacuum packed, aged 14 days at 2 °C, and stored at -20 °C for 3, 6, 9, and 12 months. A significant effect of pHu and frozen storage time was observed. Steaks showed a significant decrease in metmyoglobin (10%) and deoxymyoglobin (5%) values, and an increase in oxymyoglobin (84%) after 12 months of freezing. Steaks frozen for 9 and 12 months showed decreased brightness (L*, 30), and increased red (a*: 25), yellow (b*: 18), saturation (C*: 31), and hue (h*: 35). Conversely, all color parameters of intermediate and high pHu steaks were lower (P<0.05) in all freezing periods compared to normal pHu steaks. These changes are related to the inactivation of enzymes involved in mitochondrial respiration, which reduces the oxygen consumption rate, consequently favoring oxygen penetration and the formation of oxymyoglobin, resulting in a bright red color in the meat. These findings may assist the meat industry in establishing freezing times to preserve the quality of meat with different pHu ranges in the supply chain.