Detection of controlled atmosphere changes in CO2-flushed sealed enclosures for pest and quality management of bagged milled rice
1996
Hodges, R.J. | Surendro.
Long-term pest and quality control for milled rice, by sealing bag stacks into large plastic enclosures flushed with carbon dioxide (CO2), is a relatively new technique used by the Indonesian National Logistics Agency (BULOG). To improve understanding of this technique, which has potential for more widespread use, an evaluation of gas content was undertaken in a survey of 165 sealed stacks for over 400 days and a limited study made of associated rice quality change (yellowing). The CO2 content declined with time in all sealed stacks. In the majority of stacks, oxygen (O2) content also declined so that they became anoxic (< 2% O2) by 160 days after gassing. In a few cases, this condition was not reached until about 300 days after gassing. Even when stacks failed to conform to current minimum standards of air tightness so that the CO2 content 10 days after gassing fell below the prescribed 50% to as low as 35%, these stacks later became anoxic and no insect-related problems arose. The quality of well or poorly milled rice, judged by the extent of yellowing, was slightly different in samples stored for 9 months, under high CO2, or for the same period, under low O2 conditions, and both were superior to rice stored in a normal atmosphere. It is concluded that in enclosures where the CO2 content has dropped below the BULOG official minimum for long-term storage of 10%, if oxygen levels have fallen to less than 3%, then good quality preservation can still be expected and there is no need for regassing with CO2. A tentative stack classification system is proposed, which can be used to prioritise the discharge of sealed stacks and decide upon the requirement for regassing with CO2.
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