Effects of low-pressure storage of food commodities on the mortality of adult stored product insects

The food industry faces serious problems regarding pest infestation leading to high storage loss of food commodities. Due to adverse impacts of chemical preservation methods, a promising physical method of food protection could be considered as an urgent need. This study investigated the effect of low-pressure (vacuum) on the mortality of adults of three stored product pests of drug store beetle (Stegobium paniceum L.), southern cowpea weevil (Callosobruchus chinensis L.) and red flour beetle (Tribolium castaneum Herbst). The pests were exposed to 20 kPa and 10 kPa vacuum at 37 ºC and 75% relative humidity. Mortality of the insects was recorded at 8 h and 32 h after vacuum treatments. There were significant differences (p<0.05) in the susceptibility to the vacuum treatment among the tested pests. Adults of C. chinensis showed comparatively less susceptibility to the vacuum treatment compared to S. paniceum and T. castaneum. Mortality of insects exposed to two low-pressure treatments did not show 100% mortality at the two exposure periods, irrespective of the type of food materials and species. The mean percentage mortality increased by about 66.0±5.7% when vacuum pressure increases from 20 kPa to 10 kP irrespective of the species, exposure time and the products. The oxygen concentration decreased to >70% inside the vacuum chamber during treatments.