Study of the impact of rapeseed oil quality indicators on shelf life

Abstract

Goal. To determine the influence of the content of oxidation and hydrolysis products on the period of induction of rapeseed oil oxidation. Methods. The peroxide and acid numbers of the refined rapeseed oil samples were determined according to GOST ISO 3960 and GOST ISO 660, respectively. The induction period of the refined rapeseed oil model samples was determined at 110°C using differential scanning calorimetry. Methods of mathematical statistics and software packages Microsoft Office Excel 2003 and Statistica 6.0 were used to process the data. Results. The dependence of the induction period of rapeseed oil oxidation on the level of primary oxidation and hydrolysis products was established. The obtained approximation model made it possible to predict the change in oil stability depending on peroxide and acid numbers, which was confirmed by a high coefficient of determination (more than 93%). It was found that increasing the peroxide number by 1 mmol of 1/2 O/kg reduced the induction period by 32.85 min, and increasing the acid number by 1 mg of KOH/g — by 19.84 min. The use of natural tocopherols (0.05%) as antioxidants changed the kinetics of the accumulation of oxidation products, which was reflected in the proposed mathematical models. Conclusions. A regression equation was compiled, which described the dependence of the induction period of accelerated oxidation of refined rapeseed oil on two factors — oxidation and hydrolysis products. Both of these factors adversely affected the stability of refined rapeseed oil. Increasing the peroxide number shortened the induction period of model oil samples by 32.8512 units for each additional mmol of 1/2 O/kg. An increase in the acid number of oil samples, in turn, reduced the induction period by 19.8424 units for each additional mg of KOH/g. The influence of a mixture of tocopherols on the dynamics of accelerated oxidation of refined rapeseed oil with different contents of oxidation and hydrolysis products was determined. It was concluded that different dynamics of oxidation of its model samples depended on the concentration of primary oxidation and hydrolysis products. The presence of natural tocopherols as antioxidants negatively affected the rate of accumulation of peroxides, but the kinetic model of accelerated oxidation would be different for different initial compositions of samples. The results obtained can be used to optimize storage conditions and predict the shelf life of rapeseed oil.