EFFECT OF METAL IONS FROM GINKGO BILOBA EXTRACTS ON THE OXIDATIVE STABILITY OF RAPESEED OIL AND ITS TRIACYLGLYCEROLS

Total antixodative effect is difficult to predict because the total antiradical capacity depends not only on properties of individual compounds, but also on their mutual interactions. The study examined the effect of the addition of Ginkgo biloba antioxidants to refined rapeseed oil on the stabilization of the oil and its triacylglycerols, measured by an Oxidograph accelerated oxidative stability test and the Rancimat test. The mineral composition of oil was also determined. The tested samples were observed to respond differently in terms of the induction period, which was the longest periods for ethanolic extracts, and the shortest for aqueoeus ones. The highest values of the protective factor were observed in the samples with added ethanolic extract of green leaves, while the lowest ones were noted in all aqueous extracts. In all the tested samples, values of the protection factor increased along with the growing extract concentration in a sample. Among the tested additives, butylated hydroxytoluene added to a sample of oil resulted in the longest induction period. Among the analysed microelements, iron was the prevalent one, with its concentration being significantly higher in water extracts. The least abundant was selenium. The antioxidative capacity of Ginkgo biloba extract resulted from the presence of transitional metals and polyphenols, as the presence of zinc, copper and iron affects the bioavailability of flavonoids. Negative relationships were noted between microelements in the extracts and its oxidative stability, which indicated the oxidative activity of the former. G. biloba extracts may be a new source of stabilising additives for high-fat foods. However, further reasearch I needed to confirm this assumption, particularly because food is a complex matrix, in which ingredients might interact with one another, causing higher or lower antioxidative capacity.