Real-Time Model for Carbonyl Value as a Function of Total Polar Compounds in Oil during Frying

Changes in total polar compounds (TPC) in 10 edible oils and their relationship with changes in carbonyl value (CV) were determined during intermittent frying at 180 degrees C. The study aimed to establish a model for the real-time determination of the carbonyl value based on changes in total polar compounds in frying oil. The results showed that the total polar compounds in the 10 oils increased linearly with heating time and that linoleic acid-rich oils increased faster compared with oleic acid-rich and linolenic acid-rich oils. The effect of unsaturated fatty acids (primarily linoleic acid) on the increase in total polar compounds was more significant than for tocopherols (primarily gamma-tocopherol) as determined by multiple linear regression analysis. Increases in the total polar compounds and carbonyl value during frying also showed a linear relationship (Delta TPCt = A Delta CVt),), where A is the proportionality coefficient related to the initial composition ratio of oil (the ratio of the sum of linoleic acid and gamma-tocopherol to the sum of oleic acid and linolenic acid-that is, (C18:2 + gamma)/(C18:1 + C18:3)). A prediction model (CVt = TPCt -TPC0/[0.057 (C18:2+gamma/C18:1+C18: 3) + 0.413] + CV0 was established based on the above conclusion. In accordance with the initial composition ratio of unsaturated fatty acid and tocopherol and the real-time total polar compounds, the carbonyl value of frying oil was rapidly determined by the model.