Effects of chilled-then-frozen storage (up to 52Â weeks) on an indicator of protein oxidation and indices of protein degradation in lamb M. longissimus lumborum

This study investigated the protein oxidation properties of lamb following chilled-then-frozen storage. Experimental (n = 360) M. longissimus lumborum (LL) were randomly sampled from the boning room of a commercial Australian abattoir, at 24 h post mortem, and assigned to five chilled storage periods (0, 2, 4, 6 and 8 weeks) and six subsequent frozen storage periods (0, 4, 8, 12, 24 and 52 weeks). Upon completion of each storage treatment combination, corresponding LL were sub-sectioned and analysed for carbonyl content, protein solubility, nitrate/nitrite content, particle size analysis and estimated myoglobin fractions. The association between these protein measures and shear force was also explored. During chilled storage, particle size and sarcoplasmic protein solubility decreased which indicated protein degradation, while frozen storage only affected myoglobin oxidation. Tenderness was best explained by decreased particle size, decreased deoxymyoglobin and increased oxymyoglobin. No carbonyl effects were observed. It can be concluded that, according to these analyses, that in chilled-then-frozen lamb carbonyl formation was negligible.