酚酸对甘薯贮藏期品质的影响及调控机理

Pursuiting longer storage life and better edible quality is a key issue of sweet potato production and processing. Current sweet potato storage technologies mainly concentrat in the storage methods and conditions, and have not adjusted quality with the endogenous composition. This project mainly study the influence and regulation mechanism of phenolic acids on quality of sweet potato during storage,and solve following two important scientific problems from a fundamental theory point of view. (1) How to determine the key indicator of quality of sweet potato during storage, so as to monitor the quality of sweet potato during storage more accurately? Endogenous phenolic acids have direct influence on the budding, decay and nutrional value of sweet potato, so we adopt endogenous phenolic acids as the key indicator of quality of sweet potato during storage,and analyze the correlation between taxonomy, quantity, existence form, distribution of endogenous phenolic acids and quality deterioration of sweet potato such as budding and decay, so as to accurately monitor the quality of sweet potato during storage. (2) How to induce the changes of endogenous factors in sweet potato by exogenous factors, and resist the degradation of sweet potato from within? We adjust the content and form of endogenous phenolic acids by means of exogenous phenolic acids, enhancing the defensive capabilities of sweet potato against budding and bacterial infection, to effectively ensure the quality of sweet potato during storage. The study of this project will provide deeper theory support for the further development of sweet potato storage technologies.

延长贮藏寿命和保持贮藏期品质是甘薯生产加工领域中的重要基础问题。现有甘薯贮藏保鲜技术主要集中在贮藏方式和贮藏条件方面，未利用甘薯内在成分调节其品质。本项目研究酚酸对甘薯贮藏期品质的影响及调控机理，从基本理论角度解决两个重要科学问题：（1）如何确定与甘薯贮藏期间品质有关的关键指标，以更准确监控甘薯贮藏期的品质变化？内源酚酸对甘薯的萌芽、腐烂、营养价值等方面均有直接影响，因此本项目采用内源酚酸作为描述甘薯贮藏期品质的关键指标，分析内源酚酸种类、数量、存在形式、分布状况等因素与甘薯萌芽、腐烂等品质劣变行为的联系，实现甘薯品质的准确监控；（2）如何通过外界因素诱导甘薯内在因素发生变化，进而由内而外地主动抑制甘薯品质劣变？本项目通过外界胁迫调节内源酚酸含量和存在形式，进而增强甘薯自身对萌芽和病菌的抑制能力，实现甘薯品质的有效维持。本项目的研究将为甘薯贮藏保鲜技术的进一步发展提供更深层次理论基础支持。

延长贮藏寿命和保持贮藏期间品质是甘薯生产加工领域中的重要基础问题。本研究包括三部分内容：1. 甘薯内源酚酸的组成与分布；2. 低温胁迫对甘薯采后酚类代谢的影响；3.外源酚酸处理对甘薯发芽和贮藏寿命的影响。采用HPLC测定了甘薯中八种酚酸的含量，即咖啡酸、香豆酸、阿魏酸、芥子酸、绿原酸、对羟基苯甲酸、没食子酸和香草酸。结果表明薯皮中酚酸含量大大高于薯肉；薯皮薯肉中都以苯甲酸型酚酸为主，肉桂酸型含量较少；甘薯中香草酸是所测八种酚酸中含量最高的。对甘薯中酚酸组成与分布的研究可望应用于鉴别甘薯的贮藏品质。低温胁迫对采后甘薯酚类代谢的影响，结果表明低温胁迫会促进甘薯块根内总酚含量，抑制苯丙氨酸解氨酶（PAL）和多酚氧化酶（PPO）活性，同时会导致过氧化酶（POD）活性先下降后上升。不同处理对低温下甘薯酚类代谢的影响，结果表明 UV-C、乙烯和 CAT 处理均能增加甘薯块根组织内总酚含量和增强 PPO 活性，乙烯和 CAT 处理还能够增加甘薯块根组织内 PAL 活性，但 UV-C 处理会抑制 PAL 活性，至于 POD 活性，UV-C和 CAT 处理均在贮藏前期显著提高 POD 酶活性；同时，UV-C、乙烯和 CAT 处理则会促进甘薯块根内超氧阴离子自由基的清除率，CAT 处理还能促进甘薯块根内还原能力。针对贮藏期间发芽对甘薯品质的变化情况，实验结果表明，甘薯发芽前后诸多成分都有明显变化；水分、淀粉、总糖、还原糖和总酚含量，以及抗氧化能力随发芽进行都呈下降趋势。可见，发芽会降低甘薯的食用和加工价值。为探讨酚酸对甘薯贮藏寿命的影响，以不同浓度的香草酸、绿原酸、对羟基苯甲酸及香豆酸处理心香品种甘薯，实验结果表明，酚酸处理有效推迟了甘薯的初始发芽时间10—20d，当酚酸浓度为800mg/L时，效果最好；可以降低发芽率33—43%，降低了贮藏期间的发芽率和腐烂率，而且提高了贮藏期间的总酚含量。可见，外源酚酸可对甘薯的发芽起到一定的调控作用，但发芽进程无法完全抑制。本研究的结论将为甘薯贮藏保鲜技术的进一步发展提供更深层次理论基础支持。