Study On Physiological Ripening Traits And Nutrient Changes Of Akebia Trifoliata (Thunb.) Koidz. At Different Harvesting Stages

Akebia trifoliata(Thunb.)Koidz is a woody wine belonging to Lardizabalaceae family.Its fruit is rich in nutrition,sweet and refreshing,and has high nutritional and healthy function.In recent years,A.trifoliata has been cultivated on a large scale as a new type of fruit with both medicinal and edible functions in some areas of China.The fruits of A.trifolata split along the ventral suture when ripening,and are susceptible to exogenous source contamination,breeding bacteria,and being consumed by birds and animals,which thereof frequently result in serious decline in fruit quality and yield amount.Timely harvesting the fruits before its cracking is of great significance for improving fruit quality,preservation and transportation.Therefore,it is of great guiding significance to explore the change rules on the physiological characteristics and nutrient composition of this plant at different ripening stages,and this research also has a significant meaning in guiding when to harvest and how to transport and preserve its fruits effectively and economically.Taking the excellent clone of A.trifoliata in Zhangjiajie city as experiment materials,this study aims to figure out its fittest harvesting time.Based on the growing characteristics of A.trifoliata‘s fruits,this study gets samples from at S1 stage(120 days after flowering),S2 stage(134 days after flowering),S3 stage(148 days after flowering)and S4 stage(155 days after flowering,with split fruits)respectively,recording the appearance characteristic indexes of the fruits(such as size,length,width,the skin color,etc.),fruit quality indexes(soluble solids,p H,moisture content,sweets,flavonoids,total phenol)and nutrients indexes(minerals,Vc,amino acids and proteins).The main research contents and results are as follows:(1)The growing span of A.trifoliata fruits is from the end of April to October,with a letter―S‖growing pattern,which can be divided into four stages,namely,fast growing period,slow growing period,fruit-filling period and pre-ripening period.The appearance characteristic indexes of the fruits are around 2.1 to 2.5,which represents the fruit shape is oblong.As fruits become ripen gradually,the indexes decline.The appearance characteristic indexes decline obviously from 2.44 to 2.11.The colour of fruits at first stage is green,while at stage 2 turquoise,at stage 3 light yellowish-green,at stage 4yellow-green.The content of chlorophyll in the skin becomes less slowly as the fruits becomes more and more ripen.The hardness of the fruits also declines in the ripening process,with the minimum of 8.99kg/cm~2in stage 4,next to 11.61 kg/cm~2at stage 3.(2)Among fruit quality indexes,the index of fruit soluble solids firstly decreases and then increases,and the maximum value of soluble solids was 22.24%in S4 stage,followed by 22.31%in S3 stage.The fruit p H changes little during the four stages and remains between p H6 to 7.The contents of total flavonoids and phenols in fruits showed a downward trend,and there was a great turning point from S2 stage to S3 stage.According to the amount of different sugar components,the up-order of the sugar composition is maltose>fructose>glucose.Glucose showed an overall upward trend,with the maximum value of 8.69%in S4 stage.Maltose takes a invert―U‖trend,increases firstly and then decrease,with the maximum value of 5.15%in S2 stage.Fructose showed an upward trend,with a maximum value of 0.28%in S4 stage.In a word,while maltose content decreased continuously with fruit ripening,the contents of fructose and glucose increases continuously as fruits become ripen.(3)The nutritional changes of A.trifoliata fruits are as following:among the 10mineral elements tested,the contents of P,K,Ca and Mg in fruits show a downward trend;The amounts of Na,Fe,Cu and B show a slow downward trend,and Mn and Zn showed a downward trend first and then an upward trend.Potassium is the most abundant,while boron is the least.The overall trend of the vitamin C content in the fruits decrease first and then increase,with the maximum value of 1.16mg/100g in S4 stage(1.16mg/100g),followed by 1.07 mg/100g at S3 stage.Aspartic acid,glutamic acid and alanine are the top three amino acids with higher concentrations among the total 17amino acids detected in the pulp tissue of A.saponicum.The overall concentration trend of the 17 amino acids is that:the amount of aspartic acid and glutamic acid shows an upward trend in the ripening process,while the amount of other amino acids shows a downward trend.The contents of starch,fat and protein decrease as fruits become more and more ripen,with an obvious decline from S2 stage to S3 stage.With the above analysis,it is easy to see that the appearance characteristic indexes of A.trifolata fruits are stable at S4 stage;the max value of fruit quality index is also at S4 stage;the Vc content also reaches the peak at S4 stage,even though the nutrient content is the richest at S1 stage.Taking the fruit quality,texture,hardness and the factors of split into consideration,it is advisable to harvest the fruits at S3 stage(148days after flowering).In this study,we analyzed the quality changes in four stages of fruit development and provided evidence for fruit production and processing.