2019 Volume 19 Issue 3 Pages 89-92
When frying oil is used for a long time, secondary products of lipid thermal oxidation, such as polar polymers, carbonyl compounds, etc., accumulate in the oil, accompanied by an increase in acid value. So far, the increase in acid value has been thought to be based on the hydrolysis of triglycerides by water transferred from frying materials. However, the acid value of oil heated while spraying water was not increased in the low oxygen atmosphere where thermal oxidation does not progress. The addition of long chain free fatty acids, short chain free fatty acids or hydroperoxides into heated oil did not potentiate the increase in acid value under the low oxygen atmosphere. These results suggest that the increase in acid value of frying oil is not simple hydrolysis of triglycerides but the result of ester decomposition mediated by initial oxidation intermediates or oxygen molecules themselves.
