Effect of microwave aided disinfestation of Callosobruchus maculatus on green gram quality

Abstract

Pulses constitute an important part of the daily diet of vegetarian population as a major source of protein. It is estimated that insects cause the most damage to the pulse grains during storage and pulse bruchids are the major storage pests. The stored pulses are usually fumigated to wade away the insect infestation. The residual effect of these chemicals on public health and growing resistance of these insects to chemicals have encouraged use of chemical free disinfestations measures. Microwave radiation provides safe and hygienic mode of disinfestation. Dielectric heating of the biomaterials (grain and insects), depends largely on the moisture content in the product. Therefore, differential heating during microwave exposure seems to be a better option for food grain disinfestation. The most heat tolerant stage of pulse bruchids, adult (Callosobruchus maculatus), adults were subjected to microwave heating in a domestic microwave (2450 MHz, 900W) oven for different grain bed thickness (single layer to 2.0 cm). It was observed that as the grain bed depth increased the death time for the adults increased. Hundred per cent mortality was achieved for adults in green gram (mc=8%, wb) at 50, 60, 90, 110, and 120 s for single layer,0.5, 1, 1.5, and 2cm with corresponding microwave power densities of 13, 5, 3, 1.75 and 1.5 W/g, respectively. Quality of the green gram in terms of germination ability, cooking quality, loss of moisture, colour values, were evaluated. The germination percentage and cooking time varied from 58 to 100 % and 27 to 31 minutes, respectively. The textural hardness decreased with progress in cooking time. Total moisture loss and Hunter Lab scale colour change (E) values varied from 0.054 to 0.622 % and 1.23 to 0.34, respectively for different treated samples with respect to control sample.