Abstract
Although the stability of rice bran oil (RBO) has been showed on several studies, the factors which make it capable on maintaining its stability under thermal oxidation has not been sure yet. We hypothesized that its fatty acid composition [high composition of oleic acid (OA), lower composition of linoleic acid (LA) and α-linolenic acid (LnA)] and/or its antioxidant agents [γ-oryzanol (OZ)] and vitamin E [tocopherol (Toc), tocotrienol (T3)] might be the biggest factor.To prove the hypothesis, we thermally oxidized RBO under 40 °C for 17 days to mimic the harsh daily storage condition, and compared it with soybean oil (SO) and rapeseed oil (RPO) then monitoring their primary oxidation products [triacylglycerol hydroperoxide (TGOOH)] from easily oxidized fatty acid contained in triacylglycerol (TG) and the amount loss of antioxidant agents. As a result, RBO showed the lowest TGOOH/TG ratio, followed by RPO and SO. The superior stability RPO compared SO might occur due to because of the influence of the fatty acid profile (higher OA and lower LA). For RBO’s case, besides its fatty acid profile, the existence of OZ and the synergistic effect of OZ and vitamin E might have a greater contribution in maintaining its stability under thermal oxidation.
Highlights
The stability of rice bran oil (RBO) has been showed on several studies, the factors which make it capable on maintaining its stability under thermal oxidation has not been sure yet
Its fatty acid profile and/or its antioxidant agents might be one of the biggest reasons; namely, contents of oxidized fatty acids [i.e. poly-unsaturated fatty acid such as linoleic acid (LA) and α-linolenic acid (LnA)], stable fatty acid [i.e. mono-unsaturated fatty acid such as oleic acid (OA)] and/ or antioxidants [tocopherol (Toc), tocotrienol (T3), and γ-oryzanol (OZ)] in RBO have been hypothesized as possible factors that made RBO showed a stability under thermal o xidation[8,9,10,11,12,13]
To evaluate the role of fatty acids during the thermal oxidation, we investigated the contribution of specific fatty acid (i.e., OA, LA, and LnA) contained in RBO towards its thermal oxidation stability
Summary
The stability of rice bran oil (RBO) has been showed on several studies, the factors which make it capable on maintaining its stability under thermal oxidation has not been sure yet. Its fatty acid profile and/or its antioxidant agents might be one of the biggest reasons; namely, contents of oxidized fatty acids [i.e. poly-unsaturated fatty acid such as linoleic acid (LA) and α-linolenic acid (LnA)], stable fatty acid [i.e. mono-unsaturated fatty acid such as oleic acid (OA)] and/ or antioxidants [tocopherol (Toc), tocotrienol (T3), and γ-oryzanol (OZ)] in RBO have been hypothesized as possible factors that made RBO showed a stability under thermal o xidation[8,9,10,11,12,13]. Verification of the above hypothesis has been severely hampered, because of the fact that the common methods used to determine the oils’ stability [e.g., peroxide value (POV), rancimat method, and spectrophotometry] cannot provide enough information, especially about which and how much fatty acids are oxidized[14] and whether the antioxidant agents can affect/improve RBO’s stability during the thermal o xidation[13] Overcoming this issue will lead to developing more quality and confident RBO and its related products. This might be the reason why RBO obtained its ability to be stable under
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