Study On The Ralationship Between 1-methycylopropene And Ripening, Softening Of Postharvested Papaya Fruit

In this paper, the effects of different concentrations of 1-MCP treatment,the effects of 1-MCP, ethephon treatment and their combinations on fruit quality and enzymes related with softening of papaya fruit during storage were studied, moreover, the responses of'Risheng' and'Tainong'with different harvest maturities to 1-MCP were investigated.The results are shown as follows:1. Compared with the control, concentrations of 0.5μL/L,0.8μL/L,1.0μL/L and 2.0μL/L of 1-MCP maintained the high firmness of papaya fruit, protected the cell membrane, inhibited the changes in peel colour, the increasing in disease index, and significantly inhibited the activities of PG and CX. Besides this, I-MCP treatment delayed the decreasing in VC content, restrained the conversion from original pectin to water soluble pectin, and inhibited the softening of papaya fruit. For the four concentrations of 1-MCP,0.5μL and 2.0μL/L of 1-MCP were worse for overall quality, but 0.8μL/L and 1.0μL/L of 1-MCP were better. There were no obvious effects of 1-MCP on contents of TSS and TA.Correlation analysis showed that, there were closely relationship between PG,CX and firmness of papaya fruit, it suggested that PG and CX were key enzymes for ripening and softening of papaya fruit.2. Applications of ehephon separately, ehephon immediately followed by 1-MCP and ehephon for 24 hours then 1-MCP treatment all significantly increased the activities of CX, PG and PME, accelerated the increasing in soluble pectin content, membrane permeability and fruit softenig, enhanced the disease incidence and reduced the storage time of papaya fruit.However, treatments with 1-MCP alone,1-MCP treatment for Id then ehephon treatment all remarkablely inhibited the activities of CX, PG and PME, the decline in the original pectin content, the fruit softening of papaya fruit, and maintained the contents of TA and Vc, greatly reduced the disease index and extended the storage time of papaya fruit obviously.It indicated that there were closely relationship between the time when 1-MCP presented the effect of inhibiting softening and the time when exogenous ethylene was applied.3. For both'Risheng'and'Tainong',1-MCP treatment could significantly inhibit the PG, PME and CX activities, delay the change in peel colour, inhibit the breakdown of original pectin, and maintain the fruit firmness obviously, but the storage time of'Tainong'was longer than that of'Risheng', it suggested that the response of'Tainong'to 1-MCP was much positive than that of'Risheng'. For the same cultivar, whether'Risheng'or'Tainong', the changes in all physiological characteristics, including activities and quality components of fruit with higher maturity (90%) were faster than that with lower maturity (70%), it indicated that the storability of higher maturity fruit were worse than that of low maturity fruit, while, the flavor of higher maturity fruit was better than that of low maturity fruit when fruit ripened fully.