Effect of Ripening Condition on Some Chemical Contents of Persimmon Fruit Nhanhau Variety

Abstract

One of the successful deastringency methods for persimmon is exposing them to ethanol vapour at high temperature during ripening process. However, ethanol was reported as ripening inhibitor of some climacteric fruits and high temperature caused adverse effect on carotenoid biosynthesis. Therefore, this experiment was conducted to find out a ripening condition in which persimmon quality is improved.  Fruits were picked at maturity in August 2007. They were sorted, treated with ethrel solution then divided into 4 lots: one was kept at ripening temperature of 25⁰C, the second at room temperature (27 ± 3⁰C), the third at 40⁰C until fruit ripen and the last at 40⁰C for only 20h. Each of these 4 lots was separated  into 2 batches: one exposed to ethanol vapor (2ml/kg fruit), another was non treated. The main fruit chemical contents, which were analyzed before and during ripening, are dry matter, total soluble solids, soluble tannin, vitamin C and total carotenoid.  

At different ripening conditions, content of dry matter, total soluble solid, vitamin C, soluble tannin were markedly decreased while total carotenoid content was increased. High ripening temperature of 40⁰C showed adverse effect on carotenoid biosynthesis. In consequence, the rate of  total carotenoid content was minimal. This effect was overcome when persimmon fruits were hung at 40⁰C for only 20 hours. Optimum temperature for persimmon carotenoid biosynthesis was 25⁰C. During exposure to ethanol vapour, soluble tannin was polymerized by acetaldehyde to form insoluble compound that was not astringent. The incubation at 40⁰C for 20 hours and ethanol treatment (2ml/kg)  appeared to be optimum ripening conditions for Nhanhau persimmon.