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.
