荔枝果实成熟特性的研究

Maturity Characters of Litchi Fruit

为研究荔枝果实的成熟特性,以‘糯米糍’和‘桂味’2个花期和成熟期较一致的荔枝品种为试验材料,当‘桂味’果皮首先开始转黄时,定期测量2种果实的纵横径和果实各部分质量,测定果实固形物(TSS)、糖、酸和Vc等含量,从果实外观成熟度变化、果实的生长情况和果实品质等方面探讨荔枝的成熟特性。结果表明,‘糯米糍’果实的初始缓慢生长期较‘桂味’长,果皮推迟转黄约13天,但后期大部分时间内生长速度更快,两者果径和单果重的差异在缩小,成熟度趋于一致;后期果径的生长以横径为主;当果实的鲜食品质趋于最佳时,果径有暂时收缩的趋势;‘糯米糍’和‘桂味’的果肉分别以积累蔗糖和还原糖为主,过熟时还原糖含量增加;可滴定酸持续下降,当可滴定酸含量位于0.23%~0.69%、糖酸比位于20.93~61.75时,果实鲜食品质较佳;‘糯米糍’可食率较高,维持在约80%,过熟时‘桂味’可食率下降,单果重的增加以果皮和果核增重为主;2种果实过熟时继续生长,‘糯米糍’生长速度较快,但果实TSS下降,Vc含量较低,果实品质劣变更加严重。2个荔枝品种的果实具有独特的成熟特性。可滴定酸和糖酸比可作为判断果实成熟度的参考指标。‘糯米糍’成熟果实衰退快速,维持适宜含酸量和糖酸比的时间较短,宜鲜食的品质保持期和适宜采收期较短,‘桂味’果实衰退速度较慢,适宜保质采收期较‘糯米糍’长,这也是‘桂味’品种的成熟特征。

The paper aims to explore maturity characters of litchi fruit. Two litchi varieties,‘Nomici＇and‘Guiwei＇were chosen as materials, both flowered and matured nearly at the same time. When the color of‘Guiwei＇began to turn from green to yellow at first, the experiment was carried out. Longitudinal andtransverse diameters of fruit were measured. Every part of fruit was weighed. The contents of Vc, titratable acid（TA）, sugar and the total soluble solids（TSS） were determined. Fruit maturity characters were investigatedaccording to changes of fruit appearance, fruit growth and nutrients. The initial slow-growing stage of fruitdevelopment of‘Nomici＇was longer than that of‘Guiwei＇.‘Nomici＇turned yellow nearly 13 days later than‘Guiwei＇. But in most of late stage,‘Nomici＇grew much faster than‘Guiwei＇. Differences of fruit diameterand single fruit mass between‘Guiwei＇and‘Nomici＇were smaller and smaller. Both fruits were mature at nearly the same time. In the late stage, transverse diameter always increased faster than long diameter. Whentable quality was up to the best, diameters were apt to decrease temporarily. Saccharose was dominant in‘Nomici＇flesh while reducing sugar was in‘Guiwei＇. Reducing sugar increased when fruit was overripe. TAdecreased incessantly. Table qualities of both fruits were good when TA ranged in 0.23%-0.69% and sugaracid ratio ranged in 20.93-61.75 in coincidence.‘Nomici＇maintained a higher flesh recovery rate around80%. Flesh recovery rate of overripe‘Guiwei＇dropped down because single fruit mass increased due to thegrowth of rind and seed. Both fruits continued to grow in overripe stage.‘Nomici＇grew faster than‘Guiwei＇.Table quality of‘Nomici＇was worse because of lower TSS, lower Vc content and poorer flavor, etc. Differentintrinsic maturity characters were shown in litchi fruits of‘Nomici＇and‘Guiwei＇. Content of TA and sugaracid ratio could be the reference for assessment of fruit maturity and determination of harvest time.‘Nomici＇fruit in maturity turned senescence more rapidly than‘Guiwei＇. It was shorter for TA and sugar acid ratio of‘Nomici＇to be kept in the desirable range. So the time for‘Nomici＇to maintain the acceptable table qualityand be harvested was shorter. The quality retention and harvest period of‘Guiwei＇fruit was much longer,which was one of its main maturity characters.