Establishment of rational conditions for extracting antioxidants from oak bark for use in the oil and fat industry

Abstract

Goal. To establish rational conditions for extracting substances with antioxidant properties from oak bark, which will be used in the oil and fat industry in the future. Methods. The peroxide number of sunflower oil was determined according to the standard method, and its oxidative stability was determined according to the accelerated method of «reactive oxygen», which involved setting the induction period taking into account the change in the peroxide number during the oil’s exposure to a certain temperature. To establish rational conditions for the extraction of antioxidant substances, a full factorial experiment of the first order was used. Results. The induction periods of original and experimental sunflower oil samples, to which antioxidant substances extracted from oak bark under different extraction parameters were added, were studied. The dependence of the induction period of sunflower oil on such extraction parameters as the ratio of vegetable raw materials: solvent (hydromodule), volume fraction of ethyl alcohol in the extractant (%), and extraction temperature (°C) was established. The total concentration of antioxidant extracts in the oil was 0.02% on a dry matter basis. The study of the process of increasing the peroxide number of oil in the presence of extracts was carried out at a temperature of 110 °C. A mathematical model of the dependence of the oil induction period on the conditions of extraction of antioxidant substances was calculated and its adequacy was analyzed. Conclusions. Rational conditions for the extraction of antioxidant substances from oak bark were determined, under which the maximum induction period of sunflower oil was observed (304 min): the ratio of vegetable raw materials: solvent (hydromodule) — 1:5; the volume fraction of ethyl alcohol in the extractant was 30%; the extraction temperature was 75°C. Under these conditions, the oak bark extract made it possible to increase the induction period of sunflower oil by 1.9 times. The studied antioxidant substances were recommended to be used to increase the oxidative stability of oils, fats, and fat-containing products. This will make it possible to increase the quality, safety, and minimum shelf life of various types of food products, which include oils and fats.