Primary oxidation products accumulation in walnut oil during heat treatment

Abstract

During this study walnut oil was heated at different technological conditions - 120°C, 160°C and 180°C. Free fatty acid, conjugated dienes and trienes, peroxide value and refractive index were investigated immediately after heat treatment. The data obtained from the experiment indicate that heat treatment cause initiation of walnut oil oxidation. The conjugated dienes (CD) content of the walnut oil samples ranged from 6.23 to 12.75 µmol/g, while the conjugated trienes (CT) content ranged from 1.58 to 6.25 µmol/g. The peroxide value (PV) was in the range of 5.81-26.55 mmol/kg of walnut oil. These data should assist in selecting conditions that are suitable and better for walnut oil heat treatment. However it is necessary to note that these data are not enough to make a final conclusion about the behavior of walnut oil in thermal oxidation conditions. Currently we obtained preliminary data about accumulation of secondary oxidation products in walnut oil during heat treatment. These data should help us to describe oxidation mechanism of walnut oil and to recommend optimal conditions for walnut heat treatment.