Division of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, Taiwan.
Faculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, Taiwan.
Front Endocrinol (Lausanne). 2023 Mar 9;14:1058695. doi: 10.3389/fendo.2023.1058695. eCollection 2023.
Soy sauce is widely used in a variety of Asian dishes to enhance flavor. Soybean and most soybean products, including soy sauces, are listed as prohibited foods in a low iodine diet. However, the iodine content in soy sauces is largely unknown. The aim of this study was to determine the iodine content in domestic soy sauces in Taiwan.
Twenty-five different kinds of soy sauces were diluted with distilled water and with a dilution factor of fifty or above. Iodine concentrations of the diluted samples were measured colourimetrically based on the Sandell-Kolthoff reaction by a modified microplate method. All the measurements were repeated twelve times on three different days for determination of mean and standard deviation (SD), and coefficients of variance (CV). Serial dilution and recovery tests were also performed for validation. The results were confirmed by an inductively coupled plasma mass spectrometry (ICP-MS) method.
Among the twenty-five surveyed soy sauces, most of them (n=22) were iodine-free (<16 ug/L, and thus un-detectable). The iodine concentrations (mean ± SD) of the three iodine-containing soy sauces were 2.7 ± 0.1, 5.1 ± 0.2, and 10.8 ± 0.6 mg/L, respectively. The inter-assay, intra-assay and total CVs were all <5.3% for the modified microplate method. The results obtained by ICP-MS were consistent with those of the modified microplate method. The recovery rates in the serial dilution test and recovery test ranged from 94.7% to 118.6%. Two of the three iodine-containing soy sauces were supplemented with kelp extract, while the other one without kelp extract had the highest amount of salt among the three iodine-containing soy sauces. Therefore, we postulate that iodized salt instead of kelp extract is the source of higher iodine content in that sauce.
The results suggest that most soy sauces are iodine-free and may be allowed during low iodine diets.
酱油在各种亚洲菜肴中被广泛使用，以增强风味。大豆和大多数大豆制品，包括酱油，在低碘饮食中被列为禁忌食品。然而，酱油中的碘含量在很大程度上是未知的。本研究的目的是确定台湾国产酱油中的碘含量。
将 25 种不同类型的酱油用蒸馏水稀释，稀释倍数为 50 倍或以上。根据 Sandell-Kolthoff 反应，用改良的微孔板法比色法测量稀释样品中的碘浓度。所有测量在三天内重复十二次，以确定平均值和标准差（SD）以及变异系数（CV）。还进行了系列稀释和回收测试以验证。结果通过电感耦合等离子体质谱（ICP-MS）法进行确认。
在所调查的 25 种酱油中，大多数（n=22）是无碘的（<16ug/L，因此无法检测到）。三种含碘酱油的碘浓度（平均值±SD）分别为 2.7±0.1、5.1±0.2 和 10.8±0.6mg/L。改良微孔板法的批内、批间和总 CV 均<5.3%。ICP-MS 法得到的结果与改良微孔板法一致。系列稀释试验和回收试验的回收率在 94.7%至 118.6%之间。三种含碘酱油中的两种添加了海带提取物，而另一种不含海带提取物的含碘酱油的盐含量在三种含碘酱油中最高。因此，我们推测碘盐而不是海带提取物是该酱油中碘含量较高的来源。
结果表明，大多数酱油是无碘的，在低碘饮食期间可能是允许的。
