FUNCTIONAL PROPERTIES OF PROTEIN CONCENTRATE FROM BLACK COWPEA AND ITS APPLICATION

Black cowpea (Vigna unguiculata L. Walp.) is high in protein, which makes it suitable for use as a protein supplement in food products. However, direct application of cowpea flour in food products is limited as it may affect some quality aspects of foods. Protein concentrate and isolate are a form of the protein that is gaining interest in industry. Therefore, this study was carried out to compare functional properties of Cowpea Protein Concentrate (CPC) prepared using three different methods: (1) Isoelectric point (pI) Precipitation (CPC-pI), (2) ammonium sulfate precipitation and (3) pI-ammonium sulfate precipitation. The results showed that the protein concentrate prepared using pH adjustment provided the maximum yield of 17.92%, followed by the precipitation of proteins with ammonium sulfate with hydrochloric acid (15.05%), whereas the precipitation with ammonium sulfate yielded lowest amount (9.82%). The protein concentrate prepared by CPC-pI had the highest protein content of 85.89%, followed by CPC precipitated with ammonium sulfate with the hydrochloric acid (79.35%) and protein concentrate precipitated with ammonium sulfate (68.28%), respectively. CPC-pI had functional properties, including solubility, viscosity, water and oil holding capacity, foam ability, emulsion stability and gelation ability superior to CPC prepared by other methods. For the study on the application of CPC-pI to prepare sugar cookies, it was found that CPC could be used to replace wheat flour as much as 60% with comparable panelist acceptance to wheat flour cookie.