Abstract

Effect of pHand temperature on selected functional properties of flour samples and protein isolate of cowpea (Vigna unguiculata) seeds

Author(s): Ijeoma Olawuni, Charles C.Osobie, Daniel Ebiringa, Chinyere Amandikwa, Chidi J.Ibeabuchi, Anthonia E.Uzoukwu

Cowpea seeds were processed into flours by defatting and by protein isolation. Full fat cowpea flour was also obtained from cowpea seeds and this served as control. Functional properties of full fat, defatted and protein isolate cowpea flours were determined. Effects of temperature and pH on bulk density (BD), water absorption capacity (WAC), gelatinization temperature (GT), foaming capacity (FC), swelling index (SI) and emulsion capacity (EC) were studied. Functional properties show that bulk density (BD) ranged from 0.06 – 1.88g/ml, WAC (2.13 – 3.03ml/g), oil absorption capacityOAC(2.32 – 5.49ml/g), FC (3.01 – 33.23%), emulsion capacity EC (46.57 – 88.07%), SI (1.62 – 3.14) and gelatinization temperature, GT (0 – 81.97oC). There were significant differences (p<0.05) in the functional properties of full fat, defatted and protein isolate cowpea flours. Effect of temperature showed that lower temperature gave higher values of WAC, FC and SI and vice versa for higher temperature. Temperature at 40oCgave high values ofWAC, FC and SIwhile temperature at 70oC gave lowvalues. Effect of pH on WAC, FC and SI of full fat, defatted and protein isolate cowpea flours showed no consistency in the values obtained. Generally the study revealed that full fat, defatted and protein isolate cowpea flours gave good functional properties. However, processing of cowpea seed into flour by defatting and protein isolation displayed good functionalities and could have promising food application in Nigeria.