Polyphenol content and antioxidant capacity in organic and conventional plant foods

Abstract

Fruit and vegetable intake is associated with lower risk of chronic diseases as a result of consumption of antioxidant substances. Organic foods are thought to have higher antioxidant capacity, because this form of agricultural management could induce synthesis of secondary compounds such as polyphenols. The objective of this work is to evaluate polyphenol content and antioxidant capacity in organically (OG) and conventionally (CV) grown fruits and vegetables, as well as in different parts of the plants. Soluble and hydrolysable polyphenols were quantified by Folin–Ciocalteu reagent, and the antioxidant capacity was measured by the DPPH radical method. The results showed that organic fruits tend to have higher hydrolysable polyphenol contents than conventional ones, with values being 11.5% in orange peels, to 72.6% in papaya peels, higher for hydrolysable polyphenols. Fruit peels also showed higher concentration of polyphenols than pulp, reaching, for bananas and tangerines, twice the amount found in pulps, which reflected in higher antioxidant capacity. Polyphenol content and antioxidant capacity varied among organic and conventional vegetables with no prevalence from either agricultural type. This study suggests that the effect of organic practices results in different effect patterns according to the plant species analysed, with fruits being more susceptible to the induction of polyphenol synthesis, and the greatest accumulation of polyphenols in external plant tissues. In general, organic agriculture results in food products with similar or slightly higher polyphenol content and antioxidant capacity.