An investigation into the effects of bioactive substances from vegetable oils on the antioxidant properties of bakery products
Peter the Great St Petersburg Polytechnic University, Institute of Industrial Management, Economics and Trade, Graduate School of Commodity and Service, Novorossiyskaya Street 50, 194021 St Petersburg, Russia
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This article discusses ways in which the antioxidant capacity of bakery products (otherwise referred to as ‘BPs’) can be increased by adding various types of vegetable oil to the dough: chosen as test oil was unrefined rice bran oil, unrefined pumpkin seed oil, and refined and deodorised sunflower oil. The authors conducted a study of fatty acid compositions and biologically active substances to be found in vegetable oils. The antioxidant properties of vegetable oils were analysed according to the following characteristics: the formation of the primary (peroxide value) and secondary (anisidine value) oxidation products; the oxidation coefficient (IR spectroscopy) which can be determined in the process of applying thermal treatment (with five hours of heating at 120 °C), which leads to the Vitamin E being destroyed. The biochemical composition of vegetable oils affected their resistance to the thermal oxidation process in the following sequence: unrefined rice bran oil > unrefined pumpkin seed oil > refined and deodorised sunflower oil. BPs were made from wheat flour dough with the addition of 4% of the corresponding vegetable oil and 5% of sugar, and were baked at two temperature regimes: at 200 °C and at 220 °C. The antioxidant activity of the BPs was determined by means of two methods: by chemiluminescence, and by DPPH radical assay. The antioxidant activity of the BPs varies depending on the vegetable oil being used, with the differences being revealed in the following way: BPs with unrefined pumpkin seed oil > BPs with unrefined rice bran oil > BPs with refined and deodorised sunflower oil. Any increase in the baking temperature reduced the antioxidant activity of the BPs; the antioxidant properties in the crust and the crumb were reduced at differing rates.