| Satsuma mandarin(Citrus unshiu Marc.cv.)is native in China,famous for its thin skin,juicy,sugar and acid flavor.In this research,satsuma mandarin fruits were harvested at different full-ripend time from 2019 to 2020 and from 2020 to 2021.The changes of fruit quality were studied during storage at four different temperatures of 0℃,5℃,10℃,20℃,and simulating shelf life at 20℃.The effects of the harvest time and storage temperatures on the quality of full-ripend satsuma mandarin fruit were explored,and the proper time to harvest and storage temperature has been proposed.1.The effect of different harvest time on the quality of full-ripend satsuma mandarin fruits was analyzed.The results showed that at normal harvest time(harvest time 0),the citrus color index(CCI)and soluble solids(TSS)content of fruit were at low level.Delaying the harvest time of 10 d,the peel color of the fruit is fully developed,and the content of TSS,sugar and acid has increased significantly.Delaying harvest for 30-60 days is beneficial to the improvement of fruit sugar and acid quality.The TSS of the fruit harvested delayed 60 d is 15.64 °Brix,which is22.86% higher than the normal harvest(12.73 °Brix),and the total sugar content also increased from 110.57 mg/g to 136.97 mg/g,with an increase of 23.88%.However,delayed harvesting is also accompanied by an increase in fruit decay rate and odorous substances of ethanol and acetaldehyde.The decay rate,content of ethanol and acetaldehyde of fruits were 34.99%,735.78μg/g and 29.06 μg/g after 30 days storage at 20℃.However,fruit harvested 40 d and 50 d after normal harvest showed low decay rate,that is 19.87 and 23.26% respectively,and the ethanol and acetaldehyde content is 243.70 μg/g and 21.95 μg/g.Combined with the PCA(Principal components analysis),it is proposed that the harvest time11/21-12/21 days(harvested 20 d to 50 d after normal harvest)is better.2.The effect of different storage temperatures on the fruit quality of full-ripend satsuma mandarin fruit harvested at different time was analyzed.The results showed that the low temperature 5℃ could maintain the fruit quality with lower the decay rate,higher TSS content,and the level of organic acid was maintained.At the same time,it could effectively delay the accumulation of ethanol and acetaldehyde peculiar smell.It is considered to be the proper storage temperature for full-ripend satsuma mandarin.However,the high temperature 20℃ is not suitable for the storage of full-ripend fruit.The dacay rate and weight loss were high,and the sugar and acid flavor quality declined rapidly.The TSS content of the fruit harvested 60 days after normal harvest,decreased from 15.64 °Brix to 14.36 °Brix,a reduction up to 8.24% during storage.For fruit stored at 0℃ and 10℃,the accumulation of ethanol and acetaldehyde were higher.At the end of the shelf time of fruit harvested 60 days after normal harvest,the ethanol content at 10℃ and 0℃ reached 1162.95 and 823.31 μg/g respectively,while what at 5℃ was661.71 μg/g.3.Expression of genes related to sugar and acid metabolism during storage and shelf-period of satsuma mandarin fruit were analyzed.The results showed that the expression of CitNI5 was opposite to the change of sugar content,which may be related to sucrose degradation.the expression of CitAclα1 and CitAco3 genes were opposite to the change of citric acid content,which maybe play a role in citric acid degradation. |
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