Impact of pulsed electric field treatment on juice yield and recovery of bioactive compounds from raspberries and their by-products

Pulsed electric field (PEF) is a non thermal treatment, which could be employed for plant tissue disintegration which leads to increased juice yield and enhanced extraction of bioactive compounds. Since 97% of red raspberries (Rubus idaeus L.) are sold processed into juices or other products, it is important to increase juice yield and bioactive compounds extraction. This study investigated the effect of PEF pretreatment on red raspberries processing. After PEF pretreatment and mechanical pressing (1.32 bar for 6 min) the juice recovery from raspberries increased in the range of 9-25%. Compared to the untreated sample, press cake extracts contained significantly higher amounts of total phenolics (up to 22%), total anthocyanins (up to 26%) and higher ferric reducing antioxidant power (FRAP) (up to 24%). Mild PEF pretreatment (1 kV cm(-1) electric field strength and 6 kJ kg(-1) total specific energy) was sufficient to achieve higher raspberry juice recovery and to enhance extraction of bioactive compounds from raspberry press cake left after the juice pressing. PEF pretreatment of red raspberries is a promising technique to improve the efficiency of industrial processing of raspberries.