Preparation,characterisation and antioxidant activities of litchi (Litchi chinensis Sonn.) polysaccharides extracted by ultra‐high pressure

Litchi (Litchi chinensis Sonn.) is a fruit containing many nutrients. Based on a three level, three‐variable Box‐Behnken design, response surface methodology, was used to optimise the process of ultra‐high pressure (UHP) assisted extraction of litchi polysaccharides (LCP). The optimal extraction conditions were as follows: pressure 460 MPa, treatment time 17 min and liquid–solid ratio 15. The experimental yield for extracting LCP was 12.01% under the optimal conditions. The LCP had a high polysaccharide and low protein content. GC results showed that LCP was composed of rhamnose, fucose, mannose and galactose with the corresponding molar percentages of 7.89, 46.45, 9.71 and 19.63. Infrared analysis showed that LCP had a typical spectrum of an α‐configuration pyranose ring. Antioxidant activity analysis revealed that LCP possessed a strong reducing power and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity and could protect against the damage of hydroxyl radicals. The investigations demonstrated that UHP could be a valuable way to separate polysaccharides from litchi pulp, and LCP may be potentially developed to an antioxidant for food industries.