EFFECT OF IRRADIATION DOSE ON PHYSICAL, FUNCTIONAL AND PASTING PROPERTIES OF COWPEA (VIGNA UNGUICULATA [L.] WALP) CULTIVARS

Abstract

ABSTRACTCowpea grains, stored as dry seeds, form an enormous reserve of foodstuff in the semi‐arid tropics covering Asia, Africa, Central and South America. Effect of γ‐irradiation on seed color, functional and pasting properties of six selected cowpea cultivars was investigated. Color (L*a*b*) of non‐ and γ‐irradiated cowpea cultivars was measured, and the deltachroma (ΔC), color difference (ΔE) and hue angle were calculated. Functional and physicochemical (pasting) of the milled cowpeas were determined using standards methods and rapid visco‐analyzer, respectively. Generally, L*, a* and b* values of cowpea seeds were significantly (P ≤ 0.05) affected by irradiation dose. Calculated chroma, color intensity and hue angle varied with cultivar and γ‐irradiation dose. Oil absorption capacities of the nonirradiated and irradiated cowpea flours varied from 1.08 to 1.30 and 0.94–1.20 g oil/ g sample, while the water absorption capacities ranged from 1.59 to 2.00 and 1.58–2.01 g water/g sample, respectively. Nonirradiated cowpea flours showed higher pasting properties (peak, trough, breakdown, final and setback viscosities) than the irradiated cowpea. Aside from breakdown viscosity, the pasting properties decreased significantly (P < 0.05) with increased γ‐irradiation dose. The IT96D‐610 and IT97K‐568‐18 cultivars showed significantly higher peak, trough, final and setback viscosities compared with other cowpeas.PRACTICAL APPLICATIONSExposing foods to ionizing radiations such as gamma rays emitted from the radioisotopes 60Co and 137Cs, or high energy electrons and X‐rays produced by machine sources, helps to destroy microorganisms or insects present in the food. Depending on the absorbed radiation dose, various effects can be achieved resulting in reduced storage losses, extended shelf life and/or improved microbiological and parasitological safety of foods. Microorganisms and pests can no longer proliferate and continue their activities, and insect gametes do not survive or become incapable of proliferation. Large quantities of stored legumes are lost annually as a result of mould contamination and insect attack which continues after harvesting even to storage. Irradiation of cowpea is a viable alternative to the use of chemicals, which have adverse effects on both food and environment, associated with residues and ozone depletion, and are perceived to be carcinogenic.