| ‘Starkrimson’pear is an early-maturing full-red European pear cultivar(Pyrus communis L.),which has few stone cells,plenty of juice and delicious flavor.As the most European pear varieties,‘Starkrimson’pear are not edible when harvested,it needs to be ripened and softened after low temperature storage to show its unique flavor.In this study,the optimum harvest time of‘Starkrimson’pear was discussed.Further,the trends of key indexes relating to fruit quality of‘Starkrimson’pear were analyzed.Finally,a postharvest storage model of‘Starkrimson’pear which was directly ripened at 15℃instead of refrigeration was proposed.In this study,the harvesting and softening system of‘Starkrimson’pear were optimized.It provides a theoretical basis for maintaining the commercial characteristics of‘Starkrimson’pear and postharvest preservation of European pears.The main research results as follows:1.Effects of different harvest time on the fruit quality of‘Starkrimson’pear.From 80 to 105 days after flower blooming of‘Starkrimson’pear,the fruit fresh weight was increased by 78.23%and its dry weight was increased by 67.61%.And the fruit size became bigger,its edible rate was increased from 67.18%to 72.15%.At the same time,the firmness and the density were decreased,the firmness declined from 16.04 kg/cm~2 to 6.98kg/cm~2,and the density reduced to less than 1 g/ML.About the soluble solids content,which was increased from 10.87%to 12.97%.And 100 days later,the peel color of‘Starkrimson’pear was faded.Pears which were harvested before 90 days after flower blooming,which had lower fruit rotted rate(about 2%),but its fruit size was small and the weight was light so that the yield of pear was low.Meanwhile the edible rate is also lower than that of pears which was harvested in other periods.So,the time before 90 days was not suitable for commercial harvesting.After 100 days after flower blooming,although both the weight of fruit and the content of soluble solids were higher,but the rotted rate of fruit was reached about 18%-25%at refrigerator as well as the rotted rate was higher than other picking time when the fruit was softing.Thus,the fruit which was harvested at this time is also not suitable for commercial harvesting.Generally speaking,the suitable harvest time of‘Starkrimson’pear is between 90 and 95 days.Pears which was harvested at 95 days was a better choice according to the principle of optimium output in production.2.Changes of peel color in‘Starkrimson’pear after harvest.Different refrigeration time had little effect on fruit firmness,color change,anthocyanin and chlorophyll contents of‘Starkrimson’pear during its softing time.The content of total chlorophyll,chlorophyll a and chlorophyll b decreased gradually during the soften process of‘Starkrimson’pear,while the contents of anthocyanin and carotenoid changed slightly.Therefore,the change of peel color is mainly caused by the degradation of chlorophyll.The expression level of chlorophyll degradation genes NYC,NOL,PPH,HCAR and RCCR were positively correlated with total chlorophyll content,so these genes were not the key gene to regulate chlorophyll degradation in‘Starkrimson’pear.The PAO and SGR gene were negatively correlated with total chlorophyll content,but the difference was not significant.Based on the results of previous studies,PAO may play a role in chlorophyll degradation of‘Starkrimson’pear.3.Effect of different temperature on the fruit quality of‘Starkrimson’pear.About the‘Starkrimson’pear which was stored at room temperature without refrigerated,it was not have climacteric peak of respiration,as well as its peel color had no difference in softing time,and the rotted rate of fruit also reached about 24%,so,it could not achieve the unique quality of‘Starkrimson’pear,therefore,we think it could not softing normally.Respiratory climacteric also did not occur in‘Starkrimson’pear which was stored at 20℃without refrigerated,but the color of its peel changed.By comparison,most of the indexes were better than those of the pear which were ripening at room temperature without refrigerated.However,the fruit which was placed at 15℃without refrigerated was able to soft normally.Its firmness decreased slowly,its soluble solids content was higher than others,also the fruit rotted rate was only 10.9%,as well as the fruit shelf life was longer(some pears could last up to more than 15 days),and there was a climacteric peak of respiration.At the same time,the peel color of‘Starkrimson’pear after riping was the same as that of pear which were refrigerated for a period of time.Therefore,it was considered that the pear could softing normally.However,the‘Starkrimson’pear,which was refrigerated for 30 days and then softing at room temperature,its firmness was decreased faster than that of pears ripening directly at 28℃,and the rotted rate of which was reached about 20%,but its soluble solids content was higher,as well as the peak of respiratory climacteric of which also appeared.So,it also could be considered that the pear could softing normally.To sum up,‘Starkrimson’pear softing normally had two ways,the one was that which directly placed at a temperature which was lower than a certain ambient temperature,and the other way was that which the fruit was placed at refrigerator for a period of time.However,above a certain ambient temperature,‘Starkrimson’pear needs a period of low temperature treatment to softing normally. |
