发酵菜粕挥发性硫苷降解风味物质形成机理研究

Chinese feed industry has developed quickly over the last decade to meet Chinese people's demand for livestock products. Lack of valuable feed ingredients is the main problem of the industry, protein is what China needs most. In China, more than 70% feeding protein relay on import. China has abundant resources that contain protein. Seven million tonnes of rapeseed meal per year is one of the most important resource. While the toxicity and adverse flavor of glucosinolate degradation products limit the addition of rapeseed meal in feed and cause the problem of feed safty and low feeding value. In order to improve the feeding value of rapeseed meal, the project team researched on the technology of solid state fermentation of rapeseed meal and the effect of fermentation on glucosinolate degradation. It has been found that nitriles-the degradation of glucosinolates- are the main reason of the bad flavor of rapeseed meal. However, the relationship between the glucosinolates degradation and the formation of flavor substances during fermentation is not clear. It affected further enhance the product value. In order to solve this problem, this project use bacillus to ferment high, medium, low and zero glucosinolate content rapeseed meal, and analyse the typical volatile compounds in rapeseed meal. Combined with the change of extracted glucosinolates and monomer glucosinolates during liquid fermentation and enzymatic hydrolysis, the model system would be built and the formation mechanism of volatile glucosinolate degradation compounds in fermentated rapeseed would be explored. The results of this project would provide theoretical guidance for the improvement of solid state fermentation technology and feeding value of rapeseed meal.

我国饲用植物蛋白对外依存度达70%以上，供需矛盾十分突出。国内菜粕年产量700万吨左右，但由于硫苷降解产物的毒性及不良风味，影响了菜粕的饲用安全和动物采食，限制了菜粕饲用效价的提升。为提高菜粕饲用品质，项目申请团队研究开发了菜粕固态发酵技术，开展了发酵对硫苷降解效果的初步研究，发现硫苷降解产生的腈类化合物等是菜粕不良风味的主要来源。但发酵过程硫苷降解产生的挥发性风味物质的形成机理尚不明确，影响了产品品质的进一步提升。为解决这一问题，本项目拟选用硫苷降解效果好的芽孢杆菌,研究不同硫苷含量和组成菜粕及发酵菜粕的特征风味物质；结合提取的混合硫苷和单体硫苷在液态发酵和酶解过程中的降解途径，构建模拟体系，探讨菜粕发酵过程中挥发性硫苷降解风味物质形成机理，为高品质发酵菜粕的制备与安全饲用以及工程菌的构建提供理论指导，项目的开展对推动菜粕生物改良技术的发展具有重要意义。

我国植物蛋白严重依赖进口，供需矛盾十分突出。国内菜粕年产量700万吨左右，但由于硫苷降解产物的毒性及不良风味，影响了菜粕的使用。为提高菜粕品质，了解菜粕加工过程中硫苷的变化机理，项目组以现行研究热点菜粕发酵技术为基础，开展了发酵菜粕挥发性硫苷降解风味物质形成机理研究。. 通过本项目的实施，探讨了菜籽加工工艺对菜粕硫苷的影响及其原因，发现微波对菜籽中芥子酶酶活有显著影响。不同品种的菜籽，芥子酶酶活随时间变化的速率不同，微波处理4、5min可以使高硫苷和中硫苷的菜籽中芥子酶失活，而6min后低硫苷菜籽芥子酶仍有活性。微波对菜籽饼中硫苷含量的影响与菜籽中残留的酶活显著相关。推断出菜籽饼粕中硫苷含量的变化是芥子酶的降解和热降解的综合作用。通过不同品种菜粕发酵前后挥发性物质的对比分析发现发酵后菜粕中刺激性的腈类的含量显著降低，而吡嗪类、酚类、酸类和醇类物质显著增加；同时发酵后菜粕中大的蛋白体被降解，主要抗营养因子均得到一定程度降低。通过对液态、固态发酵过程中芥子酶产生情况和硫苷变化情况的研究，认为本试验中导致发酵菜粕硫苷降解及挥发性物质形成的主要原因是发酵过程中湿热、金属离子等。在以上基础上，对以菜粕作为氮源开发高附加值产品的优势进行了研究，发现菜粕作为氮源比蛋白胨和硝酸铵更有利于次级代谢产物（如伊枯草菌素A）的表达，从而为菜粕的高值化利用奠定了基础。. 项目实施以来，已发表SCI论文3篇，核心期刊论文4篇，会议论文2篇；参与编写著作1部，申请专利2项。通过本项目的实施，对油料饼粕发酵酶解过程中抗营养物质和营养物质的流变规律及其机理有了更加深入的认识，为油料饼粕的利用提供了有力的技术支撑。2015年“油料饼粕发酵酶解高效饲用关键技术研究与应用”获得湖北省科技进步二等奖，已公示。