Optimization of extraction process for Citrus reticulata 'Chachi'peel by multiple antioxidative indexes of response surface methodology

Hydroxyl radical scavenging ability, 1, 1-diphenyl-2-picrylhydrazyl (DPPH radical) scavenging ability and the reducing power to Fe3+ (ferric reducing/antioxidant power assay, FRAP value) as the evaluation indexes of extraction process, the effects of extraction time, extraction temperature, ethanol concentration and liquid to solid ratio on the in-vitro antioxidant ability of Citrus reticulata 'Chachi' peel extract were determined by single factor tests.Based on the single-factor tests, the Design-Expert 7.0 software was used with Box-Behnken method (4 factors and 3 levels 6 center response surface experiments) to study the response values and the best combination of variables.The optimum antioxidant extraction conditions were obtained as following:17:1 as liquid/solid ratio, 42% (V/V) ethanol concentration, 62℃ water-bath and refluxed 3.1h.The results of three repeated experiments indicated that the extraction yield as (37.32±1.21) g/100g, hydroxyl radical scavenging rate as 67.83%±7.87%, DPPH radical scavenging rate as 54.00%±3.42%, the reducing power to Fe3+ (FRAP value) as (44.62±2.67) μmol/L.The contents of extract were determined that total flavonoids of 18.84mg/100g, total polysaccharide of 4.024mg/100g.The extraction conditions of Citrus reticulata 'Chachi'peel antioxidant extracts were reliable.