Total reducing capacity of fresh sweet peppers and five different Italian pepper recipes

Processing and preparation methods are generally believed to result in a depletion of naturally occurring antioxidants in food. To evaluate the antioxidant properties of fresh sweet peppers (Capsicum annuum) and five different Italian recipes based on sweet peppers (pickled; “peperonata”; grilled; in sour–sweet condiment; salted), water- and lipid-soluble extracts from fresh and processed peppers were analysed using high-performance liquid chromatography coupled with an electrochemical detector. Total reducing capacity (TRC) and contributions of hydrophilic reducing capacity (HRC) and lipophilic reducing capacity (LRC) to the TRC were determined in all the samples. Three important antioxidant compounds were measured: ascorbic acid, β-carotene and lycopene. The contribution of these individual compounds to TRC was estimated. pepper had the highest TRC, the highest HRC and the greatest content of ascorbic acid. HRC and ascorbic acid content decreased with processing, whilst LRC was generally increased. Ascorbic acid was the major component of HRC in all samples (ranging from 72% in peperonata to 88% in fresh pepper), confirming the high content of this vitamin in peppers. Lycopene was detected only in peperonata. Many liposoluble compounds present in the lipophilic extract were not identified (only 6–20% of LRC was β-carotene).