α-酸是啤酒花软树脂中的一个重要组分,在啤酒酿造过程中会生成苦味更强、水溶性更好的异α-酸,是啤酒苦味的主要来源,也是提供啤酒防腐能力的主要成分.以正交试验为基础,直接以啤酒花浸膏为原料,不分离浸膏中的啤酒花油和β-酸等软树脂类,考察了溶剂、反应温度、反应体系的pH值、催化剂镁盐的使用量、以及反应时间等多个因素对异构化反应的影响.试验结果表明,尽管啤酒花浸膏的黏度较高,但无需添加溶剂稀释即可完成反应;在保证浸膏中α-酸完全异构,而啤酒花风味和β-酸基本不发生变化的情况下,镁盐与α-酸的摩尔比为2.0∶ 1、反应温度为100℃、反应时间为60min、pH值为11.0作为异构化反应的最佳条件,并在此条件下进行了放大验证,浸膏中的异α-酸收率超过96%.%α-acids, one of the important components of hop soft resin, were isomerized into iso-α-acids in the brewing process.Iso-α-acids are not only a major bitterness source, but also provide a specific antibacterial effect in beer.Effects of solvents, reaction temperature, reaction times, pH and the content of magnesium salt on isomerization reaction were studied in this paper.The optimal reaction condition of synthesizing pre-isomerized hop extracts were obtained by orthogonal experiments as reaction temperature 100°C, reaction time 60min.Under these optimal conditions, the yield of iso-α-acids were above 96% in the scale-up experiment.
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