FUNCTIONAL PROPERTIES OF FOOD‐GRADE BOVINE HIDE COLLAGEN IN COARSE BOLOGNA

Abstract

ABSTRACTThe effect of the addition of food‐grade bovine collagen at 10,20 and 30% levels on other protein fractions in raw and cooked bologna sausages was investigated. The proportion of sarcoplasmic and myofibril‐lar proteins and acid‐soluble fration of stroma proteins tended to decrease, while alkali‐soluble and alkali‐insoluble fractions of stroma protein increased with increasing levels of hide collagen in raw bologna formulations. The extent of swelling of stroma proteins in acid, however, did not vary between raw products.On heating bologna to an internal temperature of 68° C, 54 to 84% sarcoplasmic protein, 35 to 54% Guba‐Straub buffer‐soluble myofilbril‐lar protein, 75 to 82% 0.6 M Kl buffer‐soluble myofibrillar protein and 18 to 41% acid‐soluble protein became insoluble. The insolubility was possibly caused by forming acid‐stable cross‐linkages within and/or between different species of proteins. This was evident from a significant decrease in the swelling factor of the stromal residue of the cooked product on 0.1 M lactic acid. These cross‐linkages seem to be labile to the hydrolytic action of alkali as revealed by a two‐fold increase in alkali‐soluble protein. A decrease in the solubility of sarcoplasmic protein in cooked product was inversely related to the level of hide collagen in the bologna. Conversely, some of the collagen content on cooking was transformed into gelatin consisting mainly of high molecular weight aggregates.