Refining of High Free Fatty Acid Rice Bran Oil and its Quality Characteristics

Commercial rice bran contains 15–20% of oil and also an endogenous
lipase which degrades the oil and produces free fatty acids (FFAs). This study
was undertaken to examine the quality of refined oil prepared from crude oil
after the action of endogenous lipase in bran. The oil which was degraded by
lipase to low, medium and high FFAs, upon extraction in the rice bran oil
industry were obtained and were refined in the laboratory, and quality of the
oils was studied. The crude oils had FFA of 6.5, 36.0 and 87.0%; oryzanol
content of 1.52, 1.55 and 1.65%; color of 32.0, 65.0 and 65.0, lovibond units;
unsaponifiable matter of 3.2, 4.2 and 4.9%; phytosterol content of 4,600, 4,000
and 1,900 ppm; and sum of tocopherols and tocotrienols of 962, 56 and
96 ppm, respectively. After refining these three crude oils (6.5, 36.0 and 87.0%
FFA) were refined; the resultant oils had an FFA content of 0.4, 2.4 and 4.8%;
oryzanol content of 1.13, 2.5 and 6.35%; color of 20.0, 55.0 and 50.0 lovibond
units; unsaponifiable matter of 3.5, 6.5 and 33.4%, phytosterol content of
4,900, 6,100 and 13,800 ppm, and the sum of tocopherols and tocotrienols of
1,050, 880 and 740 ppm, respectively. The refined oils produced from high FFA
crude oil had high amounts of unsaponifiable matter, oryzanol, phytosterols
and sum of tocopherols and tocotrienols than the permitted level for refined
rice bran oil. The refined rice bran oil obtained from fresh rice bran (without
lipase action) contained about 90% of triacylglycerols whereas, the refined oil
from that of high FFA bran oil showed about 10% triacylglycerols. Hence the
latter cannot be used as an edible oil, but instead can be used at low levels as
a nutraceutical in foods.