Comparative effects of three levels of insect infestation on selected properties of five Nigerian cowpea (Vigna unguiculasta (L.) walp) varieties

Abstract

Effect of three insect infestation levels (25%, 50% and 75%) on selected properties of five Nigerian cowpea varieties (Ife brown, Iron beans, Isiocha, Patasco, and Sokoto white) were compared and studied. Infestation levels of each variety were obtained by counting and combining infested and uninfested seeds. Samples were analyzed for protein, total dietary fiber (TDF), blue value index (BVI), swelling index (SI), foaming capacity (FC) and foam stability (FS). Infestation at all levels significantly (p?0.05) reduced mean TDF (12%-21%), SI (3%-13%) and FS (22%-37%) of the cowpeas. Infestation also significantly (p?0.05) reduced protein (21%-24%) and FC (21%-41%) of the cowpeas while it significantly (p?0.05) increased BVI (49-80%). No significant difference (p?0.05) was observed between mean values of control and 25% infested samples for BVI and FC. No significant difference (p?0.05) was observed among mean values of 25%, 50% and 75% infested cowpeas for FS and between mean values of 25% and 50% infested cowpeas for protein. Infestation
caused higher reduction in protein and FS of Iron beans and higher increase in BVI and decrease in FC of Isiocha and Sokoto white. Patasco was least affected by insect infestation in protein content, level of starch damage and foaming capacity; Iron was least affected in TDF and SI while Ife brown was the least affected in foaming stability. Un-infested samples were better in all properties evaluated and these varied among the varieties. Un-infested Sokoto possessed better foam properties, with 2.0g/g foam stability.

Key words: Cowpea varieties, infestation levels, blue value index, protein, Nigeria.