The aim of the study was to determine correlations between the concentration of thiamine in systems and indicators of the antioxidative activity of ethanol tea extracts in the presence of soybean oil. Variability of the thiamine form was assumed by comparison of the influence of thiamine hydrochloride or thiamine pyrophosphate and fermentation of ethanol tea extracts. The study provides practical knowledge about the antioxidative activity of ethanol tea extracts in products containing fat and thiamine. The study showed that all tea extracts exhibited higher antioxidative activity in the presence of thiamine amounts of 0.1 and 0.8 mg/100 g. The antioxidative activity of ethanol tea extracts was significantly reduced when the concentrations were higher than the natural level for foods (over 1.0 mg/100 g). The systems containing white tea extract were the most vulnerable, whereas those with black tea were the least vulnerable. The presence of thiamine pyrophosphate in the system was more strongly correlated with reduced activity of the extracts than the presence of thiamine hydrochloride.
Keywords: antioxidants; ethanol tea extracts; oils; oxidative stability; thiamine.