冯建文 韩秀梅 宋莎 王红林 解璞 杨华 李顺雨 吴亚维

摘要：【目的】研究糖心蘋果的品质特征，旨在明确贵州高海拔区苹果糖心现象形成特点和机制，为糖心苹果生产提供理论依据。【方法】以黔选3号苹果为试材，比较贵州高海拔区4个发育时期（果实膨大前期S1、可采成熟期S2、食用成熟期S3和生理成熟期S4）果实品质指标，以及果实糖心组织与非糖心组织的糖组分含量、矿质元素和山梨醇代谢相关酶活性差异，并对果肉组织石蜡切片进行分析。【结果】苹果果实纵径和横径在S1～S3时期显著增加（P<0.05，下同），S3时期较S1时期分别增加22.37%和22.67%;S1时期无糖心形成，S2时期后56%以上的果实均有糖心，S3和S4时期的糖心果率差异不显著（P>0.05，下同），但糖心指数差异显著;果实糖心果率和糖心指数与采摘时期、单果质量、果实含水率、可溶性固形物（SSC）含量及果皮a*值呈极显著正相关（P<0.01，下同），与去皮硬度呈显著负相关，与L*值和b*值呈极显著负相关。S2～S4时期糖心组织中果糖、葡萄糖和蔗糖含量均低于非糖心组织，而山梨醇含量显著高于非糖心组织，其含量是非糖心组织的1.10～1.92倍;S2～S4时期糖心组织中SDH活性呈波动降低的趋势，仅S3时期糖心组织与非糖心组织差异达显著水平，非糖心组织中SDH活性也逐渐降低;SOX活性在非糖心组织呈降低趋势，S2～S4时期糖心组织与非糖心组织间均差异显著;成熟果实糖心组织中Ca含量显著高于非糖心组织，是非糖心组织的1.80～2.79倍，K含量除S4时期外，也表现为糖心组织含量高于非糖心组织;Fe和Zn含量除S4时期外，糖心组织含量均低于非糖心组织;Mg含量除S2时期外，糖心组织含量均高于非糖心组织;Cu含量在糖心组织和非糖心组织中均呈下降趋势，但糖心组织Cu含量低于非糖心组织;生理成熟期果实糖心组织和非糖心组织细胞完整，未出现细胞组织破碎现象;2016—2018年9—11月昼夜温差18.43～23.34 ℃。【结论】贵州高海拔区域苹果成熟期昼夜温差大，叶片输送的山梨醇不能及时转化，从而在果心部位大量积聚，是导致糖心现象的主要原因。

关键词： 贵州高海拔区;苹果;糖心;品质特征;成因

中图分类号： S661.1                               文献标志码： A 文章编号：2095-1191（2021）05-1273-09

Abstract：【Objective】To study the quality characteristics of the watercore apples，to clarify the characteristics and mechanisms of the watercore phenomenon of apples in the high altitude region and provide a theoretical basis for watercore apple production. 【Method】Qianxuan 3 apple from Guizhou high altitude area was used as experimental material. The fruit quality indexes at four growth periods（early stage of fruit enlargement S1， harvesting mature stage S2， edible mature stage S3 and  physiology mature stage S4） were compared， difference in glucose component content， mineral elements， and sorbitol metabolism related enzyme activity between watercore and non-watercore tissues were analyzed and the paraffin sections of pulp tissue were studied. 【Result】The results showed that the longitudinal diameter and transverse diameter of the fruit increased significantly from S1 to S3（P<0.05， the same below），and the growth rates of S3 were 22.37% and 22.67% respectively compared to S1. There was no watercore in the S1 period，and more than 56% of the fruits after the S2 period had watercore，there was no significant difference in watercore rate between S3 and S4 periods（P>0.05， the same below），but the difference in watercore index was significant. The watercore fruit rate and watercore fruit index were extremely positively correlated with picking period，single fruit weight，fruit moisture content，soluble solid content（SSC） and peal a* value（P<0.01， the same below），whereas，were extremely negatively correlated with L* value and b* value of peel. During S2-S4，the contents of fructose，glucose and sucrose in watercore tissue were lower than those in non-watercore tissue，while the content of sorbitol in watercore tissue was significantly higher than that in non-watercore tissue，reached 1.10-1.92 times of that in non-watercore tissue. SDH activity in watercore tissue at S2-S4 period had decreasing trend in fluctuation，only S3 period had significant difference between watercore tissue and non-watercore tissue，and SDH activity in non-watercore tissues was gradually reduced. SOX activity in non-watercore tissue was reduced，difference between watercore tissue and non-watercore tissue at S2 and S4 periods was significant. Ca content in mature fruit in watercore tissue was significantly higher than that of non-watercore tissue，and was 1.80 to 2.79 times of non-watercore tissue. Except S4 period， K content manifested as a watercore tissue content higher than the non-watercore tissue. Except for S4， Fe and Zn content in watercore tissue was lower than the non-watercore tissue. Except for S2， Mg content in watercore tissue content was higher than the non-watercore tissue. Cu content decreased in watercore tissue and non-watercore tissue，but the watercore tissue Cu content was lower than the watercore tissue. In the physiological maturity stage，the cells were intact and no fragmentation occurred in both of the two tissues. In addition，from the year of 2016 to 2018， the diurnal temperature from September to November were ranged from 18.43 to 23.34 ℃. 【Conclusion】The apparent diurnal temperature at mature stage results in the inhibition of transformation process of sorbitol in time，hence，sorbitol from leaves accumulation in the core of the flesh，which may be responsible for the formation of the watercore in Guizhou high altitude area.

Key words： Guizhou high altitude areas; apple; watercore; quality characters; causes

Foundation item：Guizhou High-level Innovative Talent Cultivation Project（QKHPTRC〔2016〕4024）; Youth Fund Project of Guizhou Academy of Agricultural Sciences（〔2018〕41）

0 引言

【研究意义】苹果成熟时，果肉细胞间隙充满半透明的水渍状物质，且随着果实成熟水渍状物质会沿苹果心室射线由内向外扩展（刘小勇等，2008），这种现象被称为水心，也称为糖心、蜜果和糖蜜，而这种水渍状的物质主要由山梨醇高度积累所形成的表象，这一现象在苹果（Yamada et al.，2004）和梨（Drazeta et al.，2004）上均有发生。糖心现象多发生在成熟度较高的果实中，果实因品质好、口感佳而深受消费者喜爱，品牌效益及市场价值显著。在我国及日本等国家，消费者常把糖心作为成熟苹果的选购标准（Zupan et al.，2016）。糖心苹果在我国西南高海拔苹果产区和新疆阿克苏苹果产区较为普遍，目前，这2个区域已将糖心苹果作为区域特色进行宣传（鲁兴凯等，2017;周小魏，2019）。……