Washington State University, Department of Food Science, Richland, WA 99354.
Washington State University, Viticulture and Enology Program, Richland, WA 99354.
J Chromatogr A. 2023 Apr 26;1695:463936. doi: 10.1016/j.chroma.2023.463936. Epub 2023 Mar 20.
A novel method for the determination of "true" free sulfur dioxide (SO) in wine and cider was developed using capillary electrophoresis with direct ultraviolet-visible spectrophotometric detection (CE-UV/vis). Free SO was measured in model solutions with different SO-binding agents present (α-ketoglutarate, pyruvate, acetaldehyde, glucose, fructose, and malvidin-3-glucoside) as well as a variety of white and red wines and ciders. The CE method was compared to three conventional methods for measuring free SO, the Ripper method, Aeration-Oxidation (AO), and pararosaniline by discrete analyzer (DA). While some statistically significant differences (p<0.05) were found between the four methods in unpigmented model solutions and samples, the values generally agreed. In the presence of anthocyanins in model solution and red wines, free SO values found by CE were significantly lower than the other three methods (p<0.05). The difference in values found by Ripper and CE correlated strongly with anthocyanin content (R = 0.8854) and even more strongly when accounting for polymeric pigments (R = 0.9251). The results in red ciders differed from those in red wines, while the CE measured significantly lower free SO2 values than the other three methods, the difference in free SO values measured by CE and Ripper correlated more closely with anthocyanin concentration (R = 0.8802) than absorbance due to bleachable pigment (R = 0.7770). The CE method was found to be rapid (4 min/injection), sensitive (LOD=0.5 mg/L, LOQ=1.6 mg/L free SO in wine, 0.8 and 2.8 mg/L, respectively, in cider), robust, and repeatable (average RSD = 4.9%) and did not suffer from the issue of over-reporting free SO in pigmented samples often observed with currently accepted methods.
建立了毛细管电泳-直接紫外-可见分光光度检测法（CE-UV/vis）测定葡萄酒和苹果酒中“真实”游离二氧化硫（SO）的新方法。在存在不同 SO 结合剂（α-酮戊二酸、丙酮酸、乙醛、葡萄糖、果糖和矢车菊素-3-葡萄糖苷）以及各种白葡萄酒和苹果酒的模型溶液中测量了游离 SO。将 CE 方法与三种传统的游离 SO 测量方法（Ripper 法、曝气氧化法（AO）和对茴香胺-分光光度计法（DA））进行了比较。虽然在无色素模型溶液和样品中，四种方法之间存在一些统计学上显著的差异（p<0.05），但数值基本一致。在模型溶液和红葡萄酒中存在花色苷的情况下，CE 法测得的游离 SO 值明显低于其他三种方法（p<0.05）。Ripper 和 CE 法测得的游离 SO 值之间的差异与花色苷含量呈强相关（R=0.8854），考虑到聚合色素后相关性更强（R=0.9251）。红苹果酒中的结果与红葡萄酒不同，而 CE 法测量的游离 SO 值明显低于其他三种方法，CE 法和 Ripper 法测量的游离 SO 值之间的差异与花色苷浓度的相关性更强（R=0.8802），而与可漂白色素的吸光度的相关性较弱（R=0.7770）。CE 法具有快速（4 分钟/进样）、灵敏（LOD=0.5mg/L，葡萄酒中的 LOQ=1.6mg/L 游离 SO，苹果酒中分别为 0.8 和 2.8mg/L）、稳健和重复性好（平均 RSD=4.9%）的特点，并且不会像目前公认的方法那样，出现对有色样品中游离 SO 过度报告的问题。
