Department of Food Science and Nutrition, College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, Zhejiang Province, China.
J Agric Food Chem. 2012 Jul 25;60(29):7177-84. doi: 10.1021/jf301599a. Epub 2012 Jul 12.
A steam explosion pretreatment process followed by methanol extraction has been applied for releasing and extracting phenolic compounds, as well as other effective components, from barley bran. The steam explosion treatment was performed at different temperatures ranging from 210 to 250 °C, with a residence time of 30 s. The effect of residence time was also studied in the range 10 s to 120 s at 220 °C. The extracts were evaluated for their total soluble phenolic content (TSPC) including total free phenolic acids (TFPC) and total soluble conjugates (TSC), identified phenolic acids, total antioxidant capacity (TAC), water-soluble carbohydrates (WSC) and total methanol extracts (TME). High-performance liquid chromatography (HPLC) coupled with a photodiode array detector (PDA) was used in this study for the analysis of p-coumaric acid and ferulic acid in barley bran before and after steam explosion. Our results indicate that TSPC and TAC increased with residence time. They also increased dramatically with temperature up to 220 °C. After steam explosion at 220 °C for 120 s, the TSPC reached 1686.4 gallic acid equivalents mg/100 g dry weight, which was about 9-fold higher than that of the untreated sample. The TSPC and TAC obtained were highly positively correlated (r = 0.918-0.993), which meant that the increase of TAC for the steam explosion pretreated barley bran extracts was due, at least in part, to the increase of TSPC in the methanol soluble fraction. Also, under optimum conditions, the WSC in aqueous solution was 5 times as much as that of the untreated sample, which demonstrated that steam explosion also hydrolyzes carbohydrates into water-soluble sugars. It can be concluded that a proper and reasonable steam explosion pretreatment could be applied to release the bound phenolic compounds and enhance the antioxidant capacity of barley bran extracts.
蒸汽爆破预处理工艺结合甲醇提取法已经被应用于释放和提取大麦皮中的酚类化合物和其他有效成分。蒸汽爆破处理在 210 至 250°C 的不同温度下进行，停留时间为 30 秒。在 220°C 下，还研究了停留时间在 10 至 120 秒范围内的效果。评估了提取物的总可溶性酚含量（TSPC），包括总游离酚酸（TFPC）和总可溶性缩合物（TSC）、鉴定的酚酸、总抗氧化能力（TAC）、水溶性碳水化合物（WSC）和总甲醇提取物（TME）。本研究采用高效液相色谱（HPLC）与光电二极管阵列检测器（PDA）联用，分析了蒸汽爆破前后大麦皮中对香豆酸和阿魏酸的含量。我们的结果表明，TSPC 和 TAC 随停留时间的增加而增加。它们随温度的升高也急剧增加，在 220°C 时达到最大值。在 220°C 下进行 120 秒的蒸汽爆破后，TSPC 达到 1686.4 没食子酸当量 mg/100g 干重，约为未处理样品的 9 倍。TSPC 和 TAC 之间高度正相关（r = 0.918-0.993），这意味着蒸汽爆破预处理大麦皮提取物的 TAC 增加至少部分归因于甲醇可溶部分 TSPC 的增加。同样，在最佳条件下，水溶液中的 WSC 是未处理样品的 5 倍，这表明蒸汽爆破也将碳水化合物水解成水溶性糖。可以得出结论，适当和合理的蒸汽爆破预处理可以用于释放结合的酚类化合物并提高大麦皮提取物的抗氧化能力。
