Recent work has evaluated the kinetics of free and total sulfur dioxide (SO2) loss in wine following aerial exposure, but little work exists on the relationship between free and total SO2 during the oxidation conditions expected during wine storage. We report changes in free and total SO2 in three wines (Chardonnay, Merlot, and Cabernet Sauvignon) stored for up to 400 days at 19 or 31°C in different bag-in-box packages. The rate of total SO2 loss varied up to seven-fold for a given wine across storage conditions, e.g., 0.13 to 0.94 mg/L SO2 loss per day for the Chardonnay. Total rates of SO2 loss were linear even after free SO2 was undetectable, and only strongly bound SO2 remained. This finding indicated that bound SO2 adduct hydrolysis was fast, as compared to the rate of SO2 consumption in these packaged wines, likely because the SO2 consumption rate depended on the oxygen ingress rate. Total versus free SO2 plots were linear for free SO2 concentrations greater than ~5 mg/L. The slope (Δtotal/Δfree) of this linear region was wine dependent (Chardonnay = 1.33 to 1.49; Merlot = 1.91 to 2.10; Cabernet Sauvignon = 1.83 to 2.00). In contrast to the rate of total SO2 loss, this ratio varied negligibly with storage conditions, suggesting that minimal formation of new SO2 binders occurred over the course of oxidation. The apparent adduct dissociation equilibrium constant (Kd) of each wine as a function of free SO2 concentration was determined from the first derivative of [Bound]/[Free] versus [Free] plots (“Burroughs plots”). As free SO2 decreased to <10 mg/L, the apparent Kd values decreased to values between 1 × 10-4 M and 10-5 M, which are comparable to those reported for malodorous aldehydes.

中文翻译：

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葡萄酒氧化过程中的游离、结合和总二氧化硫 (SO2)

最近的工作评估了空气暴露后葡萄酒中游离和总二氧化硫 (SO2) 损失的动力学，但在葡萄酒储存期间预期的氧化条件下游离二氧化硫和总二氧化硫之间的关系几乎没有工作。我们报告了三种葡萄酒（霞多丽、梅洛和赤霞珠）在不同的盒中袋包装中在 19 或 31°C 下储存长达 400 天的游离和总 SO2 的变化。对于不同储存条件的给定葡萄酒，总 SO2 损失率变化高达 7 倍，例如，霞多丽每天 SO2 损失为 0.13 至 0.94 毫克/升。即使在无法检测到游离 SO2 之后，SO2 的总损失率也是线性的，并且只剩下强结合的 SO2。这一发现表明，与这些包装葡萄酒中 SO2 的消耗速度相比，结合的 SO2 加合物水解速度更快，可能是因为 SO2 消耗率取决于氧气进入率。对于大于~5 mg/L 的游离 SO2 浓度，总与游离 SO2 曲线呈线性关系。该线性区域的斜率（Δtotal/Δfree）取决于葡萄酒（霞多丽 = 1.33 到 1.49；梅洛 = 1.91 到 2.10；赤霞珠 = 1.83 到 2.00）。与 SO2 总损失率相反，该比率随储存条件变化可忽略不计，这表明在氧化过程中形成的新 SO2 粘合剂最少。每种酒的表观加合物解离平衡常数 (Kd) 作为游离 SO2 浓度的函数由 [Bound]/[Free] 与 [Free] 图（“Burroughs 图”）的一阶导数确定。随着游离 SO2 降至 <10 mg/L，表观 Kd 值降至 1 × 10-4 M 和 10-5 M 之间的值，