Long-Term Storage of Milled and Brown Rice

Abstract

The deterioration of milled (white) and brown rice through changes in rancidity when stored in different storage containers over 12 months, was measured by estimates of changes in the Refractive Index ND25 (RI) of rice oil. The storage containers used were cement storage jars, jute sacks, polythene bags and vacuum sealed polythene gage. The slowest increase in the RI occurred for grain stored in the vacuum sealed plastic bags; the index was highest for storage in concrete jars, for both types of rice. At the end of the 12 month period the RI for milled rice was lower than for brown rice in all four storage conditions.

The highest level of fat acidity for both types of rice was recorded in the storage jars and least in the vacuum sealed plastic bags.  The level of fat acidity generally increased rapidly in the second and third months of storage. For the milled rice stored in polythene baigs, both vacuum sealed and non-vacuum sealed, the level of fat acidity reached a peak at about six months, and then slowly declined.  The fat acidity level of brown rice stored in all four storage situations showed a steady increase throughout the 12 month period reaching levels considerably higher than for milled rice in all four storage situations.  The best storage for both milled and brown rice was provided by the vacuum sealed plastic bags, as shown by both levels of rancidity and fat acidity.