猕猴桃中糖苷键合态C6醇/醛类香气物质的气调游离化机制研究

Kiwifruit aroma is a fundamental quality parameter responsible for its characteristic flavour, in which C6 alcohols and aldehydes are the aroma compounds with remarkable contents and excellent fragrance. Since the glycosidically bound C6 alcohols and aldehydes are non-volatile and their contents are much higher than that of the volatile free ones, which have been considered as a great potential source for kiwifruit aroma. Therefore, how to convert the glycosidically bound C6 alcohols and aldehydes into their free forms (called “freeing”) is a key issue for fully releasing the aroma potential of kiwifruit. For excellent kiwifruit cultivars, the post-harvest physiological regulation of kiwifruit is an important segment for further improve its aroma quality. Due to the lack of knowledge on the effect of postharvest controlled atmosphere (CA) on the freeing of kiwifruit aroma to date, this research will focus on: a) the development of an in-situ dynamic analysis system for CA involved process analysis that integrates processing section, automatic CA, and headspace detection; b) the investigation of the freeing law of glycosidically bound C6 alcohols and aldehydes in vitro and in vivo, based on the controlled atmospheric mixture; c) the interpretation of the freeing mechanism of glycosidically bound C6 alcohols and aldehydes and the postharvest regulation strategy aiming at enhancing the freeing process; d) the evaluation of the effect of freeing-aimed postharvest regulation strategy on the comprehensive quality of kiwifruit. The success of this project will provide great guidance for the fully releasing of C6 alcohols and aldehydes as well as the improvement of its aroma in kiwifruit.

香气是猕猴桃特征风味的重要品质指标，C6醇/醛类物质是猕猴桃中含量显著、香型优异的香气物质。猕猴桃中不挥发的糖苷键合态C6醇/醛类香气物质因其含量远高于其可挥发的游离态，是猕猴桃香气发生和演变的潜在根源。因此，如何使糖苷键合态C6醇/醛类香气物质游离化是充分发挥其香气潜力的关键。对于基因品种优良的猕猴桃，采后生理调控是进一步提升其香气品质的重要环节。鉴于目前对采后气调作用对猕猴桃香气品质的影响机制的认识甚微，本研究的焦点是：创建一套集过程发生、自动混合气调、气相检测为一体的专门用于气调过程的原位动态分析体系；从体外、体内分别考察糖苷键合态C6醇/醛类香气物质的气调游离化规律；阐明糖苷键合态C6醇/醛类香气物质的气调游离化的机制以及促进游离化的采后气调策略；评价促进游离化的气调策略对猕猴桃综合品质的影响。本研究的成功，将为猕猴桃中C6醇/醛类香气物质的充分演绎和提升香气品质提供科学依据。

猕猴桃是野生果树人工驯化栽培的成功典范，因其风味独特，富含维生素C、膳食纤维、多种矿质营养元素及氨基酸，而备受消费者的喜爱。香气是果实特征风味的重要品质指标，直接关系到食用者的嗅觉体验。揭示猕猴桃香气品质的物质基础及其关联因素，对于加强猕猴桃产业的品质控制和优质品种选育均具有重要意义。C6醇/醛类香气物质是猕猴桃主要的优异香型物质。本项目的研究内容主要有猕猴桃香气物质（包括C6醇/醛类）定性定量方法的建立，猕猴桃品种的标记性香气物质的鉴定，以及猕猴桃香气物质（尤其是C6醇/醛类）与果实理化性质的定量关联分析。重要成果有：（1）建立了猕猴桃香气物质的全组分（半定量）分析方法和C6醇/醛类物质的快速定量方法，并据此进行了不同成熟度的三种典型猕猴桃品类（翠玉、金桃和秃果毛花）香气物质的半定量分析和C6醇/醛类香气物质的定量分析。其中，己烯醛在翠玉、金桃和秃果毛花猕猴桃中的平均含量分别为145，51和50 μg/g，反式-2-己烯醇在翠玉、金桃和秃果毛花猕猴桃中的平均含量分别为729，470和351 μg/g，反式-3-己烯醇在翠玉和金桃猕猴桃中的平均含量分别为87和35 μg/g。（2）鉴定了三种典型猕猴桃品种的香气标记物，有四种香气物质仅存在于金桃猕猴桃中，有两种香气物质仅存在于翠玉猕猴桃中，这些物质可视为品种标记性香气物质。（3）鉴定了与猕猴桃采后果实硬度、固形物含量和酸度相关联的一系列香气物质。其中，18中物质与果实硬度关联，4中物质与果实固形物含量关联，19种物质与果实酸度相关。且主要香气物质己烯醛、反式-2-己烯醇和反式-3-己烯醇均与果实固形物含量呈显著的正相关。这些结果将为猕猴桃产业中香气品质检测，以标记物导向的优质品种选育，以及采后贮藏香气品质调控均具有重要的理论和实践意义。另外，本项目建立了用于检测生物培养过程中呼吸作用检测的系列方法，为后期猕猴桃香气物质采后生理相关的继承性研究奠定了较好的基础。