Amylograph Pasting Properties And Swelling Power Of Six Varieties Of Cowpea (Vigna unguiculata) Starch

Abstract

The Amylograph pasting properties and swelling power of starch extracted from six varieties of cowpea were studied. Significant differences (P ≤ 0.05) were found in starch pasting properties and swelling power. Non-distinct peak viscosities characterized starches. The hot paste viscosity at 95oC ranged between 880 – 1320 BU and the cooked paste viscosity, after holding at 95oC for 15 minutes, ranged between 880 – 1200 BU. The set back viscosity on cooling to 50oC ranged between 1780 and 2500 BU indicating strong retrogradation tendency in the starches. All the starches presented restricted, single-stage swelling pattern. Swelling power increased progressively with increasing temperature for all varieties. The hot paste viscosity at 95oC (HTPV) explained 90% of variance in pasting properties and appears to be the most discriminating property among the varieties. The swelling power at 70oC and 95oC accounted for 89% of variance in swelling power and at 70oC, had strong positive correlation with the hot paste viscosity. The properties of hot and cold paste of cowpea starch indicate possible application as thickeners in soup and puddings.

Key words: Pasting properties, Swelling power, Cowpea Starch

Nigerian Food Journal Vol.22 2004: 33-39