Laboratory of Food Chemistry, Wageningen University, Wageningen, The Netherlands.
J Agric Food Chem. 2013 Feb 20;61(7):1563-72. doi: 10.1021/jf305093u. Epub 2013 Feb 8.
The quantitative fate of chlorogenic acid (ChA) during enzymatic browning of potato juice was investigated. Potato juice was prepared in water without the use of any antibrowning agent (OX treatment). As a control, a potato juice was prepared in the presence of NaHSO(3) (S control). To study the composition of phenolic compounds in potato in their native states, also a potato extract was made with 50% (v/v) methanol containing 0.5% (v/v) acetic acid (MeOH control). Water-soluble low molecular weight fractions (LMWFs) and high molecular weight fractions (HMWFs) from S and OX extracts were obtained by ultrafiltration and dialysis, respectively. Pellets obtained after the OX treatment and the S and MeOH controls were also analyzed for ChA content. Whereas in the S-LMWF all ChA was converted to sulfonic acid adducts, no free ChA was found in the OX-LMWF, indicating its high reactivity upon enzymatic browning. Analysis of protein in the HMWFs showed a higher content of "reacted" ChA in OX (49.8 ± 7.1 mg ChA/100 g potato DW) than in S (14.4 ± 1.5 mg ChA/100 g potato DW), as evidenced by quinic acid release upon alkaline hydrolysis. The presence of quinic acid in S-HMWF was unexpected, but a mass balance incorporating the ChA content of LMWF, HMWF, and pellet for the three extractions suggested that ChA might have been attached to polymeric material, soluble in the aqueous environment of S but not in that of MeOH. Size exclusion chromatography, combined with proteolysis, revealed that ChA reacted with patatin and protease inhibitors to produce brown soluble complexes.
研究了酶促褐变过程中绿原酸（ChA）的定量命运。在没有使用任何防褐变剂的水中制备马铃薯汁（OX 处理）。作为对照，在 NaHSO3 的存在下制备了马铃薯汁（S 对照）。为了研究马铃薯中原态酚类化合物的组成，还使用含有 0.5%（v/v）乙酸的 50%（v/v）甲醇（MeOH 对照）制备了马铃薯提取物。通过超滤和透析分别从 S 和 OX 提取物中获得水溶性低分子量分数（LMWF）和高分子量分数（HMWF）。还对 OX 处理、S 和 MeOH 对照后的沉淀物进行了 ChA 含量分析。虽然 S-LMWF 中的所有 ChA 都转化为磺酸加合物，但在 OX-LMWF 中未发现游离 ChA，表明其在酶促褐变中具有很高的反应性。对 HMWF 中的蛋白质分析表明，在 OX（49.8±7.1mg ChA/100g 马铃薯 DW）中“反应”ChA 的含量高于 S（14.4±1.5mg ChA/100g 马铃薯 DW），这是通过碱性水解释放奎尼酸证明的。S-HMWF 中存在奎尼酸是出乎意料的，但结合 LMWF、HMWF 和三种提取物的沉淀的 ChA 含量的质量平衡表明，ChA 可能附着在聚合物材料上，可溶于 S 的水相环境中，但不溶于 MeOH。尺寸排阻色谱法与蛋白水解结合揭示了 ChA 与马铃薯蛋白和蛋白酶抑制剂反应，产生棕色可溶性复合物。
