Monitoring the Aflatoxin Content of Brown and Milled Rice (Oryza Sativa Linn.) During Storage Period

Abstract

Rice (Oryza sativa Linn.) is one of the most essential grains produced in the Philippines since it is used as a staple food. Milling, often called "whitening", removes the outer bran layer of the rice grain and differentiates the brown rice from the milled rice even if it has the same variety. Climatic conditions in the tropics and storage practices of grains are favorable for the growth of toxigenic fungi such as Aspergillus flavus and A. parasiticus which produce aflatoxin, a carcinogenic substance, as its secondary metabolite. This study is designed to determine the increase in the aflatoxin content of brown rice and milled rice stored at room temperature after one-, two-, and three-month storage period and to evaluate the relationship between the increase in the aflatoxin content and the three-month experimental storage period. Knowledge of the amount of increase in the aflatoxin content of stored foods will improve their keeping quality for safe public consumption. Using the Bond-elute Method and HPTLC quantitation, the samples stored at room temperature were analyzed initially and after one, two and three months of storage. The moisture content of the grains was also determined using the oven method before, and after one, two, and three months of storage. The results showed a significant difference on the increase in the aflatoxin content of brown and milled rice throughout the storage period. The brown rice exhibited a higher increase in aflatoxin content compared to the milled rice only after the third month of storage. Also, there is a high positive correlation between the moisture content and aflatoxin content of milled and brown rice. The chi-square test of association showed that the increase in aflatoxin content of brown and milled rice is dependent of the three-month experimental storage period. If storage conditions are favorable for 4. flavus, aflatoxin concentration will increase in stored grain previously infected in the field. Aflatoxin contamination increases with time regardless of the initial moisture content of the grain. However, the rate of aflatoxin build up is faster in grains with higher moisture content.