The effect of juicing methods on the phytochemical and antioxidant characteristics of the purple prickly pear (Opuntia ficus Indica)—preliminary findings on juice and pomace

Abstract

Prickly Pear (PP) is often overlooked due to its’ short shelf-life. Juicing may improve marketability but often affects quality, thereby warranting investigation. Purple PP (whole (WF) and flesh (FF)) was juiced using blenders; stick (SB) and jug (JB); and juicers; commercial (CJ) and cold-pressed (CP). Juices and methanolic (70%) pomace extracts were analysed for; bioactives; Total Phenolic (TPC; µgGAE/mL), Flavonoid (TFC; µgCE/mL) and Betalain Content (TBC; mg/100 g; Betacyanin; BE; Betaxanthin; IE); and antioxidant characteristics; DPPH, FRAP (µMTE) and vitamin C (mgAAE/mL). Juicing techniques had effects on phytochemicals in; juice: TPC (WF/FF; p = 0.022–0.025), TFC (FF; p = 0.034), Betacyanin (WF/FF; p = 0.029–0.026), FRAP (WF/FF; p = 0.016–0.024) and Vitamin C (WF/FF; p = 0.015–0.016); and pomace: TPC (WF/FF; p = 0.015), TBC (FF; p = 0.034), Betacyanin (FF; p = 0.047), Betaxanthin (FF; p = 0.017), DPPH (WF/FF; p = 0.016–0.024), FRAP (WF/FF; p = 0.015–0.023) and Vitamin C (WF/FF; p = 0.016–0.022). Processing-style (blend/juice) affected; TPC, DPPH and FRAP in juice and pomace. Overall, fruit-preparation (WF/FF) had minimal effects. Additionally, correlations existed between; juice TFC and TBC (p = 0.001; τ = −0.044); TBC and vitamin C (p = 0.001; τ = −0.637); pomace TPC and DPPH (p = 0.003; τ = 0.440), TPC and vitamin C (p = 0.011; τ = 0.440); and TFC and FRAP (p = 0.001; τ = 0.519). The best methods overall for juice were SB (FRAP), JB (TPC, TBC), CJ (TFC) and CP (DPPH, VitC); and for pomace extracts; SB(FRAP), JB (TPC, VitC), CJ(TFC), and CP (TBC, DPPH).