Extraction of Phenolic Compounds from Black Mulberry Using Aqueous, Ethanol and Aqueous-Ethanol Solvents: Effects of Heat Treatments on Chemical Properties of the Extracts

Background and Objectives: Black mulberry is a juicy and dark purple to black fruit with a good balance of sweetness and tartness. This fruit is highly interested due to high quantities of anthocyanins. The bioactive compounds are often present in fruit tissues and should be released. The aim of this study was to extract bioactive compounds of black mulberries and assessment of heating process effects on the extracted compounds. Materials and Methods: Aqueous, ethanol and aqueous-ethanol solvents were used for the extraction processes. The physicochemical properties of extracts, including total phenol, total anthocyanin content, anthocyanin profile, antioxidant activity, acidity and total solids, were investigated. Then, the aqueous-ethanol extract was subjected to direct heating, microwave heating and non-thermal (gamma radiation) processes to assess their possible effects on the extract. Results: The aqueous-ethanol extract included higher total phenol (68.94 mg GAE/g) and anthocyanin contents (226.16 mg/ml), higher antioxidant activity (DPPH of 90.29% and FRAP of 1.42) as well as higher quantities of anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutinoside and cyanidin-3-xyloside of 277.36, 53.21, and 11.44 mg/ml, respectively). It was observed that less time and power of heating, microwave and gamma radiation conditions included less deteriorative effects on anthocyanin compounds and thus a higher antioxidant activity was seen. Conclusions: Aqueous-ethanol solvents include further extraction efficiencies on phenolic compounds and anthocyanins and are considered as appropriate chemicals for the extraction of bioactive compounds from black mulberries. Furthermore, moderate heating conditions can preserve higher quantities of anthocyanins.