Optimisation of pressurised water extraction of polysaccharides from blackcurrant and its antioxidant activity

Pressurised water extraction (PWE) of polysaccharides from blackcurrant fruits was investigated using a response surface methodology (RSM). The optimal conditions for PWE were: time 51 min, pressure 1.6 MPa, and temperature 52 °C. Under these conditions, the experimental yield of Ribes nigrum L. polysaccharides (RNLP) was 11.68 ± 0.12%, which closely agreed with the predicted value (11.77%). After preliminary purification with D4006 macroporous resin, RNLP I was obtained and its chemical characterisation was undertaken by GC, HPLC, and IR spectroscopy. RNLP I was composed of rhamnose, arabinose, xylose, mannose, galactose, and glucose with a molar ratio of 2.89:14.82:1.02:1.00:2.53:6.39 and its molecular weight was 1.49 × 104 kDa. The antioxidant activity of RNLP I was evaluated by free radical scavenging assays and a reducing power assay in vitro. RNLP I showed strong DPPH and superoxide radical scavenging activities and reducing power.