Effects of carbon dioxide on the mortality of four life stages of Tribolium castaneum (Herbst) and on some physicochemical characteristics of two types of rice
1987
Ho, S.H. | Choo, K.W. | Lee, J.Y.Y. (Singapore National Univ., Lower Kent Ridge Road (Singapore). Zoology Dept.)
Insects representing four life stages of Tribolium castaneum were placed in fragrant and non-fragrant milled rice and exposed to atmosphere of 65% and 80% carbon dioxide (CO2) at 25 deg C and 63.5% relative humidity (rh). All stages died within five days, the order of susceptibility being larvae adults eggs pupae. No significant difference in the effect on mortality was observed between the two CO2 concentrations and between the two types of rice. Samples of the types of rice sealed in atmospheres of 35%, 65% and 80% CO2 were compared with those stored in air. The moisture content of both types was relatively constant throughout the storage period in air and in CO2. A change in odor was detected in the non-fragrant rice stored in air after 16 weeks with a corresponding drop in fatty acid content. There were no significant decrease in fatty acid content and no unnatural odor detected in all CO2-treated non-fragrant rice. For the fragrant rice stored in CO2 to 12 weeks, there was no significant difference in fatty acid content between the CO2 treatments and the controls in air. The influence of sunlight and moisture on fragrant rice exposed to atmospheric air and 35%, 50% and 90% CO2 was also investigated. The amount of CO2 present did not affect the physical characteristics of the rice. However, sunlight produced a rancid odor and slight chalkiness even at a moisture content of 10.5%. A high moisture content of 15.8% produced a fermenting smell, a greenish color and crack lines in the grains.
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