Improving the Extraction of Juice and Anthocyanin Compounds from Blueberry Fruits and Their by-Products by Pulsed Electric Fields
The aim of the study was to investigate the influence of PEF pre-treatment (1, 3, 5 kV/cm and 10 kJ/kg) of blueberry fruits on the extraction yield, anthocyanins content and antioxidant activity of the juice obtained by pressing (1.32 bar for 8 min). Additionally, the extraction with solvent of anthocyanins from the berry by-products (pressed cakes) was also evaluated. Blueberry juice obtained from PEF treated berries at 1 and 3 kV/cm showed the highest increase in juice yield (+32%), total anthocyanins content (+55%) and DPPH-RSC (+ 40%), compared with the untreated sample. The extracts from press cakes obtained after PEF assisted-pressing of berry fruits showed a significant higher content of total anthocyanins (+95%) and DPPH-RSC (+138%) when compared with the control sample. The higher the field strength applied the greater the recovery of antioxidant compound in the extracts. Significant differences in the contents of anthocyanin glycosides were detected between blueberry juice and press cake extracts. The results obtained from this study demonstrate that PEF-assisted pressing is promising for production of higher quality juices and for the valorization of berry by-products.