Effect of Heat Treatment on Oxidation of Hazelnut Oil

Abstract

Thermal processing, a common processing method of vegetable oil in daily life, is accompanied by the formation of some harmful substances. This study determined the peroxide value, anisidine value, total peroxide value, polar compound content, fatty acid content, and core aldehyde content of hazelnut oil under different thermal processing conditions. The oxidation kinetics equation of fatty acid and temperature of hazelnut oil was established, and the correlation between the contents of fatty acid and core aldehyde and four oxidation indexes was analyzed. The results showed that the TPC of hazelnut oil exceeds 24% when heated for 10 min at 210ºC, indicating that hazelnut oil is not suitable for high temperature and long-time heating. The contents of linoleic acid and oleic acid in hazelnut oil varied significantly at different thermal processing temperatures (p ≤ 0.01). The change of linoleic acid was more consistent with the first-order oxidation kinetics model. Two core aldehydes were detected in hazelnut oil, aldehyde 9-oxo and aldehyde 10- oxo-8. The core aldehyde 9-oxo content changed most obviously with the heating temperature, and it was the main non-volatile aldehydes of hazelnut oil thermal oxidation. Correlation analysis showed that the heating temperature of hazelnut oil had a significant effect on the oxidation index (p ≤ 0.01), and linoleic acid had the strongest correlation with the oxidation index, which could reflect the overall oxidation of hazelnut oil. The total amount of core aldehyde and the content of core aldehyde 9-oxo strongly correlated with the oxidation index (p ≤ 0.01), which can be used as one of the indicators to evaluate the oxidation degree of hazelnut oil. This study is of great significance for promoting the application of hazelnut oil in daily cooking and processing.

graphical abstract