Effect of Direct Acidification and Heat on the Solubility of Protein Extracts from a Fermented Sausage Mix

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Abstract
A summer sausage (fermented semi-dry variety) mix was prepared using a commercial formula, and myofibrillar and sarcoplasmic proteins were fractionated directly from it prior to any processing. The protein fractions were subjected to various combinations of acidity, salt and temperature. The sarcoplasmic proteins showed a 10% decrease in solubility during acidification alone, and an insolubilization of up to 60% when acidification was conducted in the presence of added NaCl. In contrast, the myofibrillar proteins decreased drastically in solubility at pH 5.7 to 40%, and then a further reduction occurred to 10% solubility at pH 4.4. Low salt concentrations (.33M) caused loss of solubility of myofibrillar proteins at a higher pH than if the protein were in .67 or 1.4M salt. Application of heat to low pH (4.8 to 5.3) solutions reduced the solubility of both protein fractions further than that caused by acidification without heat. The effects of pH were more reversible with the sarcoplasmic proteins than with the myofibrillar proteins. Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.