Effect of muscle condition before freezing and simulated chemical changes during frozen storage on protein functionality in beef.

The effect of rigor temperature (RT, 35 versus 10°C), increased ionic concentration (MS: 0 versus 0·2% mixed salts), oxidized lipids (OL, 0 versus 1% added oxidized fat), increased free amino acids (FAA, 0 versus 0·3% added mixture of amino acids), fat content (FC, 0 versus 15% added fat) and excluding atmospheric gases (V, 0 versus 99·9% vacuum) on protein functionality in mince stored 1 month at -20°C was studied using a complete 2(6) factorial design. All factors studied affected the functional properties of beef. Fresh 24hr samples that entered rigor at 35°C had lower total (TPS), myofibrillar (MPS) and sarcoplasmic (SPS) protein solubilities than samples entering rigor at 10°C (p<0·01). During frozen storage, RT, MS and OL alone did not affect protein solubilities, FAA increased TPS but did not affect MPS and SPS, increasing the meat's fat content raised TPS and SPS but did not affect MPS, applying a vacuum increased TPS and MPS but lowered SPS (p<0·05). Cook yield of frozen stored mince increased with higher FAA but decreased with higher fat content, and the peak force of patties made from frozen stored mince was lowered by increased MS and low FC during storage. Various significant interactions are tabulated and discussed.