TIME - MORTALITY RELATIONSHIPS FOR THE LIFE STAGES OF RED FLOUR BEETLE, TRIBOLIUM CASTANEUM EXPOSED TO HIGH AND LOW TEMPERATURES, AND THEIR RELATION WITH FLOUR TECHNOLOGY

Abstract

Temperature treatments of stored grains and grain products are the best physical method which successfully kills several life stages of insects. Survival of adults, pupae, younger larvae and older larvae of Tribolium castaneum exposed to 40, 50, 60, -5 and -10 oC at different exposure periods (15, 20, 25, 30, 40, 45, 60, 90 and 120 min) were investigated. Probit analysis was used to determine the lethal time required for 50 and 95% kill (LT50 and LT95) of the population of tested insect, results indicated that: Younger and older larvae were the most heat susceptible stages with LT50 and LT95 as compared the pupae and adult stages at the higher temp. (60 oC). Pupae and adult stages were the most heat tolerant stage at 60 oC. Exposing the beetles to 60 oC and -10 oC resulted in higher mortality than for beetles that were maintained at two previous tested temperature. The cold tolerance of different stages from lower to highest at -5 and -10 oC were older larvae < younger larvae < adult < pupae. Grain Technology studied were carried out on samples of wheat flour exposed to 60 oC for 120 min. and to -10 oC for 90 min. to determining chemical composition, Rheological properties and organoleptic characteristics of balady bread. Results indicated that No significant differences were observed between treated samples and untreated control. Finally, it could be concluded that the influence of both heat or cold treatments on the mortality rate of the tested insect was positively correlated with the time of exposure, the increase of heat or cold temperature and the stage of an insect.