This investigation was carried out to study the possibility of extraction of some natural antioxidative phenolic compounds from rice milling by-products (defatted black rice bran, defatted white rice bran, black rice hull and white rice hull). The extracted phenolic compounds were tested as natural antioxidants using cotton seed oil after deep frying (170-180)°C of potato for 25 hours.
The results indicated that Ethanol gave the highest extract yield of all extracts. Ethanol exhibited the highest extraction ability for phenolic compound (5.31, 4.80, 2.90 and 2.10 mg/g), for Defatted black rice bran, Defatted white rice bran, white rice hull, and black rice hull extracts, respectively and also showed the strongest antioxidant activity of Defatted black rice bran extract activity owing to its high content of phenolic and flavonoids compounds.
Ferulic acid was the major phenolic compounds presented and identified in defatted black rice bran; defatted white rice bran and black rice hull while, Caffeic acid was the major phenolic compounds presented and identified in White rice hull. The highest inhibition ratio IC50 was (0.097) found in TBHQ extract following by Defatted black rice bran, Defatted white rice bran, Black rice hull and White rice hull.
Peroxide value, Thiobarbituric acid)TBA( value and polymer content of cotton seed oil increased by increase of frying time, furthermore, defatted black rice bran ethanolic extract (400 ppm) was more effective as antioxidant than those of the other studied by-products of the rice milling .