Biochemical parameters and oxidative resistance to thermal treatment of refined and unrefined vegetable edible oils

Abstract

Vidrih R., Vidakovič S., Abramovič H. (2010): Biochemical parameters and oxidative resistance to thermal treatment of refined and unrefined vegetable edible oils. Czech J. Food Sci., 28: 376-384.In human nutrition fats are physiologically important food constituents but also the components most liable to oxidative degradation. The oils included in the study were refined (sunflower, extra-sunflower, soybean, and rapeseed) as well as unrefined (olive and pumpkin-seed) oils. The aim of our study was to determine the fatty acid composition, tocopherol content, and quality parameters such as the free fatty acid content, peroxide value, and induction time. Extra virgin olive oil had the highest average peroxide value, while unrefined pumpkin seed oil had the lowest one. The acid value of the unrefined oils was higher on average than that of the refined oils. Soybean oil had the highest total tocopherol content and extra virgin olive oil the lowest one. The refined oils with higher contents of saturated and monounsaturated fatty acids and lower polyunsaturated fatty acid contents had a high oxidative stability. A negative correlation has been found in the oils between the induction time and polyunsaturated fatty acid content. Among the oils investigated, unrefined pumpkin seed oil was the most oxidatively stable, the other oils following in the decreasing order: extra virgin olive > high oleic sunflower > rapeseed > soybean > sunflower oil. The oxidative stability of the unrefined oils was better than that of the refined oils.

Effects of the contents of impurities and seed hulls on the quality of cold-pressed sunflower oil

“…The obtained values of the correlation coefficients agree well with those reported by Vidrih et al (2010).…”

Degradation of selected nutrients in sunflower oils during long-term storage

“…The determined fatty acid profile of fresh sunflower oils is shown in Table 2. Some authors show a similar range of major fatty acids in regular sunflower oil (Vidrih et al 2010). Aladedunye and Przybylski (2013) mentioned that some researchers variously reported the influence of fatty acid composition of oils on stability.…”

“…Oxidative stability, known as the resistance to oxidation under defined conditions, is one of the most important indicators of maintaining the quality of edible oils (Vidrih et al 2010). Determination of the oxidative stability index by Rancimat is the (Velasco et al 2009).…”

“…Determination of the oxidative stability index by Rancimat is the (Velasco et al 2009). It has been shown that the oxidation of edible oils proceeds through a series of chemical reactions that essentially starts with an induction stage (Vidrih et al 2010). In Figure 1, it can be seen that oils stored for 10 months had shorter induction periods than initial oils.…”

“…The determination was based on the conductometric detection of volatile acids. The results were expressed as the induction period (IP) in hours (Vidrih et al 2010).…”