蒸汽爆破加工对荞麦麸皮多酚释放机制及其抗氧化能力的影响

Phenolic compounds of whole grain, important secondary metabolites in cereals, are widely existed in grain bran. Great number of researches indicated that various bioactive activities of whole grain are closely related to its phenolic compounds. Therefore, increasing researches on natural products and/or food nutrition have focused grain phenolic compounds. Tartary buckwheat (Fagopyrum.tartaricum L. Gaerth) bran might serve as a natural source contains phenolic compounds with potential antioxidant activity and rich contents in polyphenols. However, traditional food processing methods can’t give whole grain polyphenols full play to biological activity with no consideration of fully saving its activity. Steam explosion technology is a great pretreatment processing to extract the polyphenol from the whole grain. It can improve the palatability of tartary buckwheat bran and increase the release of polyphenols through its releasing mechanisms which destroy the interconnection between fiber bundles. In this study, our purpose is to determine the effects of steam blasting pretreatment on the content and structure of polyphenols in tartary buckwheat bran, investigate the changes of polyphenol compounds in buckwheat bran and evaluate the effects of steam explosion on the antioxidant activity of buckwheat bran polyphenols. These results would provide unique insights to select a proper technology for saving bran nutrition, and industrialize the grain ban processing, as well as explore the effects of whole grain polyphenols on human health.

全谷物多酚化合物是谷物中重要的次生代谢产物，广泛存在于谷物麸皮中。大量研究证实，谷物麸皮多种生理活性的发挥与其多酚化合物密切相关，谷物多酚化合物已成为天然产物和食品营养学的研究热点。荞麦麸皮中含有极为丰富的酚类化合物，可作为抗氧化剂的重要来源，但传统的食品加工方式未能充分考虑全谷物多酚在食品加工体系中的活性保留，导致全谷物多酚难以发挥其生物活性。蒸汽爆破通过蒸汽压的瞬间释放可以破坏纤维束之间的相互连接，使细胞壁破裂，对全谷物多酚提取是非常好的预处理加工方式，既可以改善苦荞麸皮的适口性，又能增加多酚的释放率。本项目以苦荞麸皮为原料，系统研究蒸汽爆破预处理对荞麦麸皮多酚含量和结构变化的影响；揭示麸皮中多酚化合物的变化规律和反应机理；评价蒸汽爆破加工方式对荞麦麸皮多酚化合物的抗氧化活性影响。为指导选择荞麦麸皮营养保留的加工方式、促进麸皮加工产业化发展、深化全谷物多酚与健康关系的认识提供理依据。

蒸汽爆破是通过蒸汽压的瞬间释放破坏纤维束之间的相互连接，使细胞壁破裂，是一种有效的处理植物纤维原料的方法。本项目苦荞麸皮为原料，蒸汽爆破技术为其预处理方法，综合考察不同汽爆强度对苦荞麸皮多酚组成、含量及抗氧化活性的影响；采用细胞模型评价了汽爆苦荞麸皮多酚游离酚提取物的细胞抗氧化和抗增殖活性；并以葡聚糖硫酸钠盐（Dextran sulfate sodium, DSS）诱导的C57BL/6J小鼠结肠炎为模型，研究蒸汽爆破处理的苦荞游离酚对C57BL/6J小鼠结肠炎的缓解作用机制。研究结果表明：蒸汽爆破处理使苦荞麸皮游离酚含量降低，结合酚含量升高，并增强了游离酚与结合酚抗氧化能力增强；组分鉴定发现，蒸汽爆破处理使游离槲皮素含量提高，游离芦丁含量显著降低。细胞实验结果表明，SE处理后, 游离酚提取物的细胞抗氧化活性体外提高，总酚提取物对Caco-2细胞和结合酚提取物对HepG2细胞的体外抗增殖活性增强；动物实验结果表明，蒸汽爆破处理的苦荞游离多酚通过抑制NF-κB和Nrf2信号通路蛋白表达， 提高结肠炎小鼠肠道菌群的多样性和丰度促进菌群的SCFAs产生能力，缓解DSS引起的结肠炎症状，恢复肠道健康。同时研究还发现，蒸汽爆破处理有利于苦荞麸皮中可溶性膳食纤维的释放。为揭示荞麦麸皮多酚在蒸汽爆破加工中的变化、有效控制多酚释放、指导选择荞麦麸皮营养保留的加工方式、保障人们的膳食健康等提供理论和科学数据，具有非常重要的意义。