Proteolysis of meat and bone meal to increase utilisation

Abstract

Meat and bone meal (MBM), an important by-product of the meat industry, is the ground, rendered remainder of farm animals after removal of the hide and meat. Most protein in MBM is insoluble, which limits its usefulness. Defatted, milled porcine MBM was subjected to saturating amounts of trypsin, a selective protease, and subtilisin, a protease with broad selectivity. Samples were withdrawn over a 48-h time course of hydrolysis and filtered to remove insoluble material. The rate at which the MBM protein was converted to a soluble form was equivalent for both proteases. Over the time course, trypsin generated fewer free amino groups than did subtilisin, and at a specified time, the molecular weight (MW) of the soluble trypsin hydrolysate was higher than that of the subtilisin hydrolysate. Assay of amino group formation showed that the proteases were still active even after soluble protein generation had ceased. The hydrolysates are useful for a variety of food and non-food uses. The hydrolysates were tested for flocculation activity in an ongoing effort to find sources for renewable flocculant. Kaolin flocculant activity was observed with the soluble fraction obtained before hydrolysis of MBM and also observed with the relatively high MW hydrolysates from short treatment with trypsin and subtilisin. Low MW fractions obtained from by subtilisin treatment at 30–48 h also showed kaolin-settling ability, probably through a coagulation or charge neutralisation process.