Investigation On Shelf Quality And ADH Gene Expression Of Mopan Persimmon By Different Methods Of De-astringency

Astringent persimmon fruit is the main cultivar in the northern part of China.It is easily softened after deastringency and it is hard to store and transport.The commercial value of persimmon fruit is affected directly.Therefore,it is necessary to choose a suitable deastringency and preservation method.Three maturity stages(7,8,9)of Mopan persimmon from Beijing Fangshan were used as test materials.Under ambient temperature,Mopan persimmon fruits were treated by different methods,including vacuum and dry-ice treatment.The effects of soluble tannins on Mopan persimmon and the changes of nutrient quality,respiratory intensity,hardness,color and volatile components of fruits were studied during shelf life,in order to find the best suitable conditions for persimmon fruit deastringency and keeping crispness.The test results are as follows:1.Maturity stages 7,8 and 9 persimmon were completely de-astringent treated by vacuum treatment for 144,72 and 60 h,respectively,the soluble tannin content of persimmons were lower than the taste threshold,while these were completely de-astringent treated by dry-ice for 48,24 and 24 h,respectively.With the increase of maturity,the fruit firmness and deastringency time decreased gradually,but the soluble solid content gradually increased.The rate of change of volatile components of maturity stage 7 persimmon fruit changed faster than that of maturity stage 8 and9 persimmon fruit.In addition,the content of V_C before deastringency of three kinds of persimmon was higher than that after deastringency.The time of deastringency of dry-ice was faster than that of vacuum treatment,and that method effectively delayed the decline of fruit hardness after deastringency.The maturity stage 8persimmon fruit is bright,and the hardness and soluble solid content change little during the shelf life.The dry-ice treatment has the best effect on the quality of the maturity stage 8 Mopan persimmon.2.The effects of modified atmosphere(MA),modified atmosphere with 1-MCP(MA+1-MCP),modified atmosphere with dry-ice(MA+dry-ice),modified atmosphere with 1-MCP and dry-ice(MA+1-MCP+dry-ice)on the soluble tannins,quality indicators,physiological indicators,hardness and color of maturity stage 8Mopan persimmon fruit was used as test material.PCA,HCA,OPLS-DA were used to analyze the data and select the best storage and preservation treatment.The results showed that the soluble tannin content of persimmon fruit after dry-ice treatment was reduced,and the value was below the astringency threshold within 7 d.The fruit shelf quality score was the highest on the shelf at 21 d,and the MA+1-MCP treatmentgroup was clearly distinguishedfrom MA,MA+dry-ice,MA+1-MCP+dry-ice three treatments.The different indexs between these treatments were identified by OPLS-DA as V_C,respiratory intensity,and ethylene production rate.The results showed that at the shelf 21 d,from the perspective of fruit quality and physiology,the treatment of MA+1-MCP could ensure the Vc content of fruit,inhibit the increase of respiration rate and the decrease of fruit hardness for a long time.From the point of view of taste,the treatment of MA+1-MCP+dry ice can effectively remove the astringency from the fruit and delay the softening of the fruit.3.In order to further explore the effects of four treatments:air conditioning,air conditioning+1-MCP,air conditioning+dry ice,air conditioning+1-MCP+dry ice on the softening and aging of the persimmon and the mechanism of deastringency.Beijing Fangshan Mopan persimmons were used as test material,to observe the change of malondialdehyde,lipoxygenase,cellulase,polygalacturonase,alcohol dehydrogenase and pyruvate decarboxylation of persimmon,and the effects on the relative expression levels of the alcohol dehydrogenase gene and the pyruvate decarboxylase gene.The results showed that the content of malondialdehyde gradually increased under the four treatment methods in the whole shelf life,and the activities of lipoxygenase and polygalacturonase increased first and then decreased.The cellulase activity of persimmon fruit treated by 1-MCP did not change much.The cellulase activity of persimmon fruit without 1-MCP treatment had obvious peak.Moreover,the activities of the two enzymes related to astringency firstly increased and then decreased,and the corresponding gene expression also showed this trend.