玛咖中芥子油苷和玛咖酰胺对干燥条件的响应机理

Maca (Lepidium meyenii Walp.), a new resource food of China, is one of the most important characteristics-agricultural-products in Yunnan Province. It is effective to improve sexual ability, enhance physical strength, anti fatigue, prevent cancer and so on. Glucosinolates and macamide are considered to be the two important quality indexes of maca as typical characteristic components. Reducing the loss of their contents is the key to maintain or improve the quality of maca products. There are great loss of glucosinolates and macamide in drying process, and with both significant difference in different drying methods. But their attenuation and routes in the drying process of maca are still unknown, any related research reports are unavailable. The objective of this proposal is to study the response mechanism of glucosinolates and macamide in drying process of maca. We plan to control the conditions by the techniques of vacuum freezing, ultrasonic, microwave, hot air in the dry process of fresh tuber of maca. And to study the changes of glucosinolates and macamide, the content and activity of their derivatives and related enzyme, such as isothiocyanates and myrosinase with HPLC technology in the drying process. To monitor their changes in fresh tubers which are added known content of glucosinolates and macamide, explore their attenuation routes, clarify their attenuation rules. There will be to provide scientific basis for improving of the drying technology and products quality.

新资源食品玛咖是云南省重要的新兴特色农产品之一，具有改善性功能、增强体力、抗疲劳、预防癌症等功效。玛咖酰胺和芥子油苷作为玛咖的典型特征成分，被认为是影响玛咖品质和功效的重要品质指标，减少二者含量的损失是保持和提高产品品质的关键。针对玛咖酰胺和芥子油苷在干燥过程中损失极大，不同干燥方式下二者含量差异显著，但其在玛咖干燥中的衰减规律和途径不明，相关研究尚属空白的现状，拟以新鲜玛咖为研究对象，从干燥过程入手，采用真空冷冻、超声波、微波、热风等干燥技术控制干燥条件，与HPLC技术结合，研究在干燥过程中玛咖酰胺和芥子油苷的变化，异硫氰酸酯等衍生物、芥子酶等相关酶含量和活性，跟踪监测标准品及衍生物在样品干燥过程中的变化，探索二者在玛咖干燥过程中的衰减途径，对阐明玛咖酰胺和芥子油苷对干燥条件的响应机理，揭示其在干燥过程中的衰减规律具有重要意义。可为改进干燥工艺，提高玛咖品质提供科学依据。

玛咖是一种原产秘鲁的十字花科独行菜属古老作物，具有强体力、抗疲劳等多种功效。自2011年被我国列为新资源食品后，逐渐成为关注重点。本项目从干燥方法、长时间自然晾晒、酶促调控等方面研究玛咖酰胺、芥子油苷等活性成分对干燥条件的响应机理，阐明其变化规律与途径。通过多维度干燥实验研究，发现干燥方法对玛咖酰胺含量影响显著，自然晾晒＞烘箱加热＞微波加热＞真空冷冻，自然晾晒最适宜玛咖酰胺的合成，积累含量最高。采用烘箱加热时，40℃最有利于玛咖酰胺合成，30℃～50℃是适宜温度范围，更高温度下含量下降。破坏新鲜玛咖组织结构有利于玛咖酰胺合成和积累，对样品组织结构的破坏程度越大含量越高，打浆>切丝>切片。不同生长时间的新鲜玛咖的酰胺含量在205.45～354.04μg/g DW之间，在6个月的自然晾晒中可持续增加至9.8～12.4倍，达到2425.21～3470.41μg/gDW；芥子油苷的含量变化则与玛咖酰胺呈现出明显的反向趋势，持续下降。含量最高的3种酰胺占总量的81.4%，与占芥子油苷总量84.3%的苄基-芥子油苷有共同的苄基(Ph—CH2—)；第2大类的3种酰胺与占芥子油苷总量15.3%的间甲氧基-苄基-芥子油苷有共同的间甲氧基-苄基 (CH3—O—Ph—CH2—)；这2种芥子油苷含量在干燥中的变化趋势均分别与2类玛咖酰胺相反，持续的转化减少。显然，玛咖酰胺的生成与芥子油苷的降解紧密相关。酶促调控结果表明，pH和温度显著影响内源酶活性，在40℃、pH=8时，内源酶活性最高，玛咖酰胺积累最多，而芥子油苷则降至初始含量的47.7%。芥子油苷对米曲霉菌、植物乳杆菌的良好耐受性，抑制了玛咖酰胺的转化生成。研究表明，玛咖酰胺主要在干燥过程中合成和积累，并受温度、时间、样品形态、酶活性等因子影响；芥子油苷是玛咖酰胺最重要的前体物质，前者的降解、转化与后者的合成、积累紧密相关。研究结果可为干燥中调控玛咖酰胺合成与芥子油苷的转化，改善产品品质提供技术支撑。项目发表SCI论文1篇，核心期刊4篇；申请发明专利1项。