‘玉露香’梨果实发育过程中糖、酸积累特性研究

Study on sugar and organic acid accumulation during fruit development in ’Yuluxiang’ pear

【目的】了解‘玉露香’梨果实发育中糖、酸含量变化。【方法】采用高效液相色谱法,对其糖、酸组分含量进行测定。【结果】在‘玉露香’梨果实生长发育过程中,总糖含量呈“慢—快—慢—快”的上升趋势;总酸含量呈先上升后下降的趋势;幼果期果实中的糖以山梨醇为主,酸以苹果酸为主;成熟果实中的糖以果糖为主,酸仍以苹果酸为主,成熟时果糖含量占总糖含量的43.07%,柠檬酸和苹果酸含量占总酸含量的71.9%。蔗糖含量从坐果到花后60 d内一直保持较低水平,从花后60 d开始迅速上升,直到成熟期其含量上升了3.81倍。山梨醇含量从坐果到花后75 d,含量逐渐上升并达到最大值,之后开始下降。【结论】‘玉露香’梨为高果糖型果实;按照苹果酸型、柠檬酸型和酒石酸型三大果实类型分类,属苹果酸型。

【Objective】Sugar and organic acid contents in the fruit are not only the dominant factor affecting fruit quality,but also the basic raw material for synthesis of carotenoids,vitamins,pigments and aromatic substances,which determines the quality of fruit flavor.Sugar and organic acid accumulated differently in different kinds of fruits.The aim of this research is to understand the changes about the sugar and organic acid contents during fruit development of‘Yuluxiang’pear.【Methods】The contents of sugar and organic acid were determined by the High Performance Liquid Chromatography(HPLC).Earlier researches showed that the major components of soluble sugars were sucrose,glucose,fructose and sorbitol.The fructose content showed the highest value,and the glucose content was the second,the proportion of these two sugars to total soluble sugars was 72.17%,and sucrose content was the lowest,and glucose and fructose showed a very significant positive correlation with total soluble sugars.The major components of organic acids were malic acid,citric acid,quinic acid,shikimic acid,and oxalic acid.The contents of malic acid and citric acid were significantly higher than others,and the proportion of the two organic acids to total organic acids was 89.79%,and this showed a very significant positive correlation with total organic acids.In terms to different species,the contents of total soluble sugars and total organic acids in Pyrus bretschnrideri Rehd.and P.pyrifolia(Burm.f.)Nakai were relatively lower,the contents in P.ussuriensis Msxim.were relatively higher,the content of total soluble sugars in P.sinkiangensis Yu was relatively higher,and total organic acids was intermediate,the content of total soluble sugars in P.communis Linn.was relatively higher,and total organic acid was the highest.The ratio of total sugars to total acids varied considerably and ranged from 6.95 to 33.87,and the ratio of total sugars to total acids was higher in P.bretschnrideri Rehd.and P.pyrifolia(Burm.f.)Nakai,P.ussuriensis Msxim.and P.sinkiangensis Yu were intermediate,and P.communis Linn.was relatively lower.【Results】The results showed that,during‘Yuluxiang’pear fruit development,the total sugar content showed the“slow-fast-slow-fast”ascending trend.It can be roughly divided into four stages:the first stage was from early May to late Jun,which was from fruit setting to 60 days after anthesis,when the soluble sugar content in fruit increased slowly;the second stage was from late June to late July(from 60 days after anthesis to 90 days after anthesis),when the total sugar content increased rapidly,which was the first peak of sugar accumulation;the third stage was from late July to early August(from 90 days after anthesis to 105 days after anthesis),when the total sugar content changed insignificantly;and the fourth stage was from early August to fruit maturity,which was the second peak of sugar accumulation,when the total sugar content began to increase rapidly,and reached the highest value at harvest.The total acid content was the“up-down”trend during‘Yuluxiang’pear fruit development.It can be roughly divided into three stages:the first stage was from early May to late June(from fruit setting to 60 days after anthesis),when the organic acid content increased slowly;the second stage was from late June to early August(from 60 days after anthesis to 105 days after anthesis),when the organic acid content accumulated rapidly and reached its peak;and the third stage was from early August to fruit maturity(after 105 days after anthesis),when the organic acid content began to decline rapidly.In the youngfruit period,the main type of sugar and acid was sorbitol and malic acid,respectively.In the mature period,fructose was the main fruit sugar,and malic acid was the main acid.In the mature period,the fructose took up 43.07%of the total sugar and the malic acid took up 71.9%of the total acid.The sucrose content remained low from fruit setting to 60 days after anthesis.From 60 days after anthesis to pre-maturity,sucrose content began to rise rapidly,and its content increased by 3.81 times.Sorbitol content increased gradually and reached its maximum from fruit setting to 75 days after anthesis,and then began to decrease.【Conclusion】‘Yuluxiang’pear is a fruit with high fructosecontent,and it should be classified as the malic acid type according to three conventional fruit classification:malic acid type,citric acid type and tartaric acid type.