Chemical characterization and evaluation of antioxidant properties of Açaí fruits (Euterpe oleraceae Mart.) during ripening

► A decrease of phenolic compounds (besides anthocyanins which increased) was observed by HPLC–MS/MS in the course of ripening. ► A decrease of the antioxidant capacity (assessed by TEAC and TOSC) was observed during ripening. ► Contribution of identified polyphenols to overall antioxidant capacity was not significant (assessed by authentic standards). ► A decrease of determined nutrients during ripening was observed (besides lipids which increased). Consumption of açaí fruits has been linked to positive health effects due to its phenolic content and nutritive value. The objective of this study was to characterize açaí fruits chemically and to determine the antioxidant capacity at three different maturity stages. With the exception of fat, amounts of macronutrients, minerals and titratable acids decreased during the ripening process. The same trend was observed for most of the phenolic constituents identified by HPLC–ESI-MS/MS. A consistent decline was shown for flavones and hydroxycinnamic acids. The concentration of the anthocyanins increased in the course of ripening. In accordance with the total amount of the identified phenolic compounds, the antioxidant capacity, measured by TEAC and TOSC, also decreased. However, the contribution of the main phenolic compounds to the overall antioxidant capacity evaluated by TOSC was estimated to be low.