Triacylglycerols Containing Acetyl Group in Edible Oils and Fats

Most triacylglycerols (TAGs) in edible oils and fats are composed of long-chain fatty acids with 16 to 18 carbon atoms. In this study, we report the first identification of dioleoylacetylglycerol (OOAc), a TAG containing an acetyl group (AcTAG) in canola oil. AcTAG has been reported to exist in plants of the Akebia genus. In the process of analyzing minor components in canola oil using liquid chromatography / mass spectrometry (LC/MS), we found that OOAc was present in canola oil. Furthermore, when considering other edible oils (soybean oil, rice bran oil, olive oil, corn oil, palm oil, and lard), they contained OOAc at levels ranging from 9 to 210 mg/kg. Canola oil was found to contain a relatively high amount of OOAc. Although OOAc was initially detected in refined canola oil, a similar amount of OOAc was confirmed in unrefined oil extracted from canola seeds, suggesting that OOAc is naturally present in canola seeds and is not generated by refining processes such as neutralization, bleaching, and deodorization. The OOAc content varied depending on the origin of edible oils and fats. Subsequent LC/MS analysis of the edible oils and fats suggested the presence of other AcTAGs in addition to OOAc. This suggests that acetic acid could be generated from AcTAGs by hydrolyzing the oils and fats above. Therefore, measurement of acetic acid in edible oils was performed using high-performance liquid chromatography (HPLC) equipped with an electrical conductivity detector, revealing the presence of acetic acid in commonly used edible oils. The results showed that acetic acid was present in the abovementioned edible oils and fats at levels ranging from approximately 40 to 110 mg/kg. In particular, canola oil and soybean oil were found to contain higher amounts of acetic acid compared to other oils.