Determination of Antioxidant Capacity of Unprocessed and Processed Food Products by Spectrophotometric Methods

Two electron transfer (ET) reaction-based methods, ferric reducing antioxidant power (FRAP) and Folin–Ciocalteu (FC) reducing capacity, were used for the determination of total antioxidant capacity of vegetable oils (rapeseed, palm and extra virgin olive oils), meat samples (poultry and pork) and potatoes before and after the frying process under domestic frying conditions. Before frying, potatoes had the highest FRAP value (276.7 μmol Trolox/100 g), whereas extra virgin olive oil revealed the highest Folin–Ciocalteu Index (FCI = 443.2 μmol Trolox/100 g). Antioxidant capacity of methanolic extracts of raw meat (9.0–9.4 μmol Trolox/100 g and 135.7–160.1 μmol Trolox/100 g for FRAP and FC methods, respectively) was lower than FRAP (133.4–149.6 μmol Trolox/100 g) and FCI (156.2–443.2 μmol Trolox/100 g) of unheated rapeseed and extra virgin olive oils. However, antioxidant capacity of the studied food samples changed after frying process. Positive correlations (correlation coefficients ranged between 0.5742 and 0.9942) were found between the two analytical methods used to determine the antioxidant capacity of unprocessed and processed food products. The results of principal component analysis (PCA) indicate that there are differences between total amounts of antioxidants in raw and fried food products.