FUNCTIONAL PROPERTIES OF PROTEIN ISOLATE EXTRACTED FROM BEEF BONES

Abstract

Bone protein isolate (BPI) extracted from beef bones with 2% added salt (i) and without salt (ii) has been analysed for functional properties as these properties are of importance when the protein isolate is used in different industries. Water absorption by the bone protein isolate (i) and (ii) was 0.35 and 0.46 H2O/g protein, respectively. The minimum solubility of protein isolate (i) was 65.85% at pH 3 while isolated protein (ii) had a minimum solubility of 52.30% at pH 5. An increase in solubility was observed below and above pH 3 for the protein isolate (i) (83.66% at pH 1 and 87.12% at pH 11) and below and above pH 5 for protein isolate (ii) (83.20% at pH 1 and 89.78% at pH 11). The emulsifying capacity of the BPI is great, being much better than that of many classical proteins (sodium caseinate, soy protein isolate). The emulsifying capacity (ml oil/g protein) progressively decreased with increasing protein concentration. On the other hand, alkaline pH improved the mentioned property more than acidic pH. The maximum emulsifying capacity was 1152.60 and 986.78 ml oil/g protein at pH 9 for protein isolate (i) and (ii) respectively. The best foaming capacity was observed at pH 4 for both protein isolates (i) and (ii) (96% and 89% volume increase, respectively). Foams had also high stability at pH 4, having 145 ml and 138 ml final volume for isolates (i) and (ii), respectively. The stability of foams decreased with increase in pH. Both protein isolates obtained had high solubility (NSI) and dispersibility (PDI); being 97.98%, 86.78% for NSI and 99.94%, 89.06% for PDI in case of isolates (i) and (ii). respectively. Such isolates had a satisfactory protein solubility in the pH range existing in many food products.