Improving the Extraction Yield of Juice and Bioactive Compounds from Sweet Cherries and their by-products by Pulsed Electric Fields

The influence of pulsed electric fields (PEF) pre-treatment of sweet cherry (Prunus Avium) fruits of “Duroni Nero” variety both on the extraction yield and antioxidant properties of juice obtained by pressing, and on the subsequent extraction with solvent of bioactive compounds from cherry by-products (press-cake) was investigated. PEF pre-treatments were performed at constant specific energy input (WT = 10 kJ/kg) and different electric field strength (E= 0.5-3 kV/cm) before applying a pressure of 1.64 bar for 5 min. PEF-assisted pressing (E = 1 kV/cm) led to a significant increase of juice yield (+40%), anthocyanins (+80%), and antioxidant power (+27%) with respect to untreated samples. However, PEF treatment intensity higher than 1 kV/cm did not significantly improved the quantitative and qualitative characteristics of juice. Compared to the untreated samples, the extracts from electroporated press-cakes achieved after PEF-assisted pressing of cherry fruits at 0.5 kV/cm showed the highest increases in anthocyanins (+38%) and antioxidant activity (+21%). No evidence of selective release or degradation of individual anthocyanins in juice and press cake extracts due to PEF application was observed. Overall, the results of this investigation demonstrated the potential of PEF as a mild technology to improve the efficiency of industrial processing of cherry fruits.