Optimization of the extraction process of persimmon tannin from persimmon residue by response surface methodology

【Objective】 The response surface methodology(RSM) was used to optimize the extraction process of persimmon tannin in persimmon residue, providing technical support for the extraction and separation of persimmon tannin and the comprehensive development and utilization of persimmon tannin.【Method】 Solvent extraction of persimmon tannin from persimmon residue was carried out. The persimmon tannin was determined by Folin-Ciocalteu method. The pH (water extraction), volume fraction of ethanol(ethanol extraction), the material-liquid ratio, extract time, and extract temperature were selected as different experimental factors, persimmon tannin extraction rate(Y) as response value. Based on the experiment of single factor, the combined experimental design of Box-Behnken center was carried out. Establishing regression equation to optimize the extraction process of persimmon tannin from persimmon residue.【Result】 The results showed that the extraction rate of persimmon tannin:alkaline water extraction>acid water extraction>ethanol extraction.Established regression equation of alkaline water extraction was:Y=1.75-0.0424A+0.0164B+0.0118C+0.01AB+0.0015AC- 0.0005BC-0.2528A²-0.0003B²-0.0179C²(A was the pH, B was the extraction time and C was the extraction temperature). The influence order of the three factors on yield of extraction rate of persimmon tannin by alkaline water extraction was pH>extraction time>extraction temperature. The interaction between the two factors on extraction rate of persimmon tannin was not significant(P>0.05).The optimal process conditions were:pH 11, solid-liquid ratio 1:3, extraction time 129 min, extraction temperature 96.5℃, and the extraction yield was 1.75%, which was close to the theoretical prediction (1.76%).【Conclusion】 The response surface method is used to optimize the extraction process of persimmon tannin in persimmon residue, which is stable and feasible. It has practical value and can be popularized in p