USING THERMAL TREATMENT TO ELIMINATE COWPEA BEETLE CALLOSOBRUCHUS MACULATUS (F.) INFESTING FABA BEAN DURING STORAGE AND ITS EFFECT ON THE PHYSIOCHEMICAL AND TECHNOLOGICAL PROPERTIES

Abstract

Thermal disinfestations consider one of the methods of physical insect control. Eggs, larvae, pupae, and adults of callosobruchus maculates were introduced at 50,60,70 and-5, -10oC for varying durations 5,10,15,30,45,60,75 and 90 min. Results indicated that, adults survival decreased with exposure times increase, complete mortality was achieved at 50,60 and 70oC for 50,40 and 30 min. of exposure times respectively. On the other hand, highly sensitive due to low temperature was recorded at -10oC followed by -5oC within 25 and 30 min. respectively, which resulted in complete mortality. So, the degree of -10oC resulted in preventing any hatch and development of eggs, any emergence for all immature stages after 45 min. then, the reduction of progeny was 100%. Due to the above mentioned results, treatments of 60oC and -10oC for 75 and 45 min. respectively, were selected to evaluate the physiochemical and technological properties. Results indicated that the color of control and treated faba bean at low and high temperature indicated that both high and control samples L value significantly decreased (p > 0.05), a value increased after treated with high temperature while, b value increased in low temperature treated seeds. Protein content showed no significant differences of both low and high temperature and control. Cookability of seeds and protein digestibility were higher in high temperature samples than low temperature treated seeds and control. On other hand, bioactive compounds (phytic acid, tannins and total phenols) reduced in high temperature compared with low temperature treated seeds and control sample. Sensory evaluation of cooked faba bean showed non significant differences in all sensory parameters compared with control. Finally, it could be said that the thermal treatments of legumes is one of the best physical methods used to kill the insects of legumes and their stages and thus keep the seeds also maintaining its physicochemical properties and did not cause loss of protein.