Effect of Temperature and pH on the Soluble Proteins of Ham

SUMMARY A sensitive heat gelling test based upon the least protein concentration as the endpoint (LCE) was developed for salt‐soluble protein evaluation in extracted muscle. Although this is not readily applicable to quality‐control procedures, it appears to be an excellent research tool to study subtle protein changes occurring in muscle proteins during the post‐mortem transformation of muscle into meat. Using the LCE to study the effect of simulated physiological temperature and pH on muscle protein extracts it was found that pH has a profound and partially, but not complete, reversible effect on these proteins. A definite relation was found between post‐rigor muscle pH and the LCE of the extracted salt‐soluble proteins, which suggests that the rigor mortis transformation of muscle to meat determines the subsequent characteristics of these proteins. The most desirable post‐rigor muscle pH was 5.8‐6.1. No mechanism is proposed to explain the effect of pH on the salt‐soluble protein LCE. The effect of decreasing pH was linear on the solubility of both water‐ and salt‐soluble proteins, and on the increase of free heme with concomitant decrease in oxymyoglobin visual color. Mixing salt‐soluble proteins from extreme‐pH post‐rigor muscle resulted in an improved LCE while averaging the solution pH and ATP(ase) activity. This mixing effect may account for the lack of relation between sausage batter variation and product quality.