Department of Agricultural, Food and Nutritional Science, University of Alberta , Edmonton, Alberta T6G 2P5, Canada.
J Agric Food Chem. 2012 Aug 29;60(34):8444-9. doi: 10.1021/jf3000482. Epub 2012 Aug 20.
The presence of phenolic acids in cereal grain is thought to influence starch hydrolysis during liquefaction and saccharification of grain flours in the bioethanol industry. As a basis for remodeling starch hydrolysis systems and understanding inhibition mechanisms, the composition and concentration of phenolic acids in whole grain flours of triticale, wheat, barley, and corn were analyzed by high-performance liquid chromatography. The total phenolic acid contents (sum of nine phenolic acids) in the four grains were 1.14, 1.70, 0.90, and 1.25 mg/g, respectively, with more than 90% found in the bound form. Ferulic, coumaric, and protocatechuic acids were the major phenolic acids in triticale and wheat. Gallic acid was also rich in triticale. Ferulic, coumaric, hydroxybenzoic, and gallic acids were predominant in barley. In corn, ferulic, coumaric, gallic, and syringic acids were abundant. On the basis of these profiles, pure phenolic acids were added individually and collectively to isolated starches at amounts either equivalent to or 3 times those in the whole grains for hydrolysis. The degree of starch hydrolysis with α-amylase and amyloglucosidase decreased up to 8% when individual phenolic acids were present in cooked starch slurry. The decreases were more pronounced when phenolic acids were added collectively (4-5% with α-amylase and 9-13% with sequential α-amylase and amyloglucosidase). The study of a phenolic acid-starch-enzyme model system indicated that the interactions of phenolic acid-enzyme and phenolic acid-starch significantly contributed to the inhibitory effect of starch hydrolysis. Heating facilitated the interactions. Phenolic acids thus play a significant role in the resistance of starch to enzyme and/or the loss of enzyme activity during starch hydrolysis.
谷物中酚酸的存在被认为会影响谷物淀粉在生物乙醇工业中的液化和糖化过程中的水解。为了改造淀粉水解系统并理解抑制机制，本研究采用高效液相色谱法分析了黑小麦、小麦、大麦和玉米全谷物粉中酚酸的组成和浓度。四种谷物的总酚酸含量（9 种酚酸的总和）分别为 1.14、1.70、0.90 和 1.25mg/g，其中 90%以上以结合态存在。阿魏酸、香豆酸和原儿茶酸是黑小麦和小麦中的主要酚酸。黑小麦中还富含没食子酸。阿魏酸、香豆酸、羟基苯甲酸和没食子酸是大麦中的主要酚酸。在玉米中，阿魏酸、香豆酸、没食子酸和丁香酸含量丰富。根据这些图谱，将纯酚酸分别和一起以相当于或 3 倍于全谷物中酚酸的量添加到分离的淀粉中进行水解。当在煮过的淀粉糊中存在单个酚酸时，α-淀粉酶和淀粉葡萄糖苷酶对淀粉的水解程度分别下降了 8%。当酚酸一起添加时，下降更为明显（α-淀粉酶下降 4-5%，α-淀粉酶和顺序淀粉酶-葡萄糖苷酶下降 9-13%）。酚酸-淀粉-酶模型系统的研究表明，酚酸-酶和酚酸-淀粉的相互作用对淀粉水解的抑制作用有显著贡献。加热促进了相互作用。因此，酚酸在淀粉对酶的抗性以及淀粉水解过程中酶活性的丧失方面发挥了重要作用。
