Protein Fractionation and Functional Properties Characterization of Okara Flour.

Abstract

Okara is the solid by product of soymilk and tofu processing with less utilization. The high water content of okara makes it deteriorated easily and therefore needs strategies to utilize it. Conversion to okara flour is one of best strategies. The utilization of okara must be based on its functional properties and characteristics of protein as the major composing components. Protein fractionation and functional properties are used to characterize the okara flour. Osborne method has been applied in fractionation using 4 solvents, namely water, 0.5N NaCl, ethanol 70%, and 2% NaOH. Protein content of each fraction was quantified using Bradford method. The molecular weight was identified by SDS- PAGE electrophoresis. Functional properties determined were solubility, water absorption capacity, oil absorption capacity, emulsion capacity and stability, foaming capacity an stability, and gel formation. Coefficient of variant value δ 10% was used to obtain homogenized data. First attempt to fractionationate of protein from okara flour gave result that the recovery was only 8,59%. It was presumed that protein of okara flour in this research dominantly insoluble protein due to thermal processing during tofu making. Based on that fact, efforts to increase its protein recovery was developed using variables of appropriate extraction time, suspension pH and extraction temperature. Three step extraction for 3 hours combined with pH 9 and extraction temperature of 80 °C increased protein recovery to 46,23%. However, fractionation and its conditions did not affect the molecular weight of protein in fractions. Potential functional properties were the emulsion capasity and stability and also the water absorption capacity. Emulsion capacity of okara flour was 4,7867 ml oil/g sample or 18,0562 ml oil/g protein with its stability after 24 hours storage was 1,90 ml water/gram sample and the water absorption capacity was 5,9349 ml water/g sample or 22,3874 ml water/g protein.