CHANGES IN PARBOILED ROUGH RICE CAUSED BY IMPROPER DRYING AND MICROBIAL INFECTION

Molds and bacteria contaminate parboiled rough rice when it is improperly dried or while awaiting drying due to humid rainy weather. When IR 20 parboiled rough rice was not dried for 7 days due to humid weather molds increased to 2.45 × 10⁷ per gram from 6 × 10⁴ per gram and bacteria increased to 75.9 × 10⁶ per gram from 5.1 × 10⁶ per gram observed initially. The milled rice yield decreased to 60.1% from 72.2% and the head rice yield decreased to 55.0% from 98.8% due to infection. The resultant bran contained only 12.1% oil compared to 31.9% in normally dried and milted paddy with about 40.0% free fatty acids in oil. The infection induced breakdown changes increased the levels of sugars, amino acids and polyphenols in grains which might cause kernel discolouration in the associated heat development during infection.