Tannin extraction and changes in content during the maturation of Mopan persimmon fruits
2021
An, Xiaowen | Feng, Runfang | Yang, Jie | Meng, Fenghua | Ao, Changwei
In this study, aqueous methanol is a way to extract free tannins from Mopan which is the main variety of persimmons in the north of China. A considerable number of persimmon tannins bound to cell walls may remain insoluble in the residues after methanol extraction. The extraction conditions of bound tannins in residues were optimised and the quantity of bound tannins was up to 221.8 mg/g under the circumstances (pH 1, 120 °C for 30 min). Gallic acid, gallocatechin, and catechin were the main constituents of hydrolysates. The changes in free and bound tannins were investigated during fruit maturation. Free tannin content reached the highest at the end of August to mid-September in northern China and then constantly decreased. The bound tannin content was relatively stable from June to August and significantly increased after September. It then became the main ingredient at the end of October. As a result, the composition of the free and bound tannins in Mopan persimmon was determined qualitatively and quantitatively, and the change in the tannin content during maturation of Mopan persimmon was analysed.
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