Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method
BackgroundSoy 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 io...
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Frontiers Media S.A.
2023-03-01
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| Series: | Frontiers in Endocrinology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fendo.2023.1058695/full |
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| author | Chun-Jui Huang Chun-Jui Huang Chun-Jui Huang Lin-Hsuan Lee Lin-Hsuan Lee Cheng-Pin Cheng Shan-Fan Yao Harn-Shen Chen Harn-Shen Chen Chii-Min Hwu Chii-Min Hwu Kam-Tsun Tang Kam-Tsun Tang Fan-Fen Wang Fan-Fen Wang Chiao-Wei Shih Chen-Chang Yang Chen-Chang Yang Chen-Chang Yang Chen-Chang Yang Wen-Sheng Huang Wen-Sheng Huang |
| author_facet | Chun-Jui Huang Chun-Jui Huang Chun-Jui Huang Lin-Hsuan Lee Lin-Hsuan Lee Cheng-Pin Cheng Shan-Fan Yao Harn-Shen Chen Harn-Shen Chen Chii-Min Hwu Chii-Min Hwu Kam-Tsun Tang Kam-Tsun Tang Fan-Fen Wang Fan-Fen Wang Chiao-Wei Shih Chen-Chang Yang Chen-Chang Yang Chen-Chang Yang Chen-Chang Yang Wen-Sheng Huang Wen-Sheng Huang |
| author_sort | Chun-Jui Huang |
| collection | DOAJ |
| description | BackgroundSoy 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.MethodsTwenty-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.ResultsAmong 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.ConclusionThe results suggest that most soy sauces are iodine-free and may be allowed during low iodine diets. |
| first_indexed | 2024-04-09T18:19:22Z |
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| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-04-09T18:19:22Z |
| publishDate | 2023-03-01 |
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| series | Frontiers in Endocrinology |
| spelling | doaj.art-e069af90b9664692b2d3402ca0d837592023-04-12T16:50:09ZengFrontiers Media S.A.Frontiers in Endocrinology1664-23922023-03-011410.3389/fendo.2023.10586951058695Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate methodChun-Jui Huang0Chun-Jui Huang1Chun-Jui Huang2Lin-Hsuan Lee3Lin-Hsuan Lee4Cheng-Pin Cheng5Shan-Fan Yao6Harn-Shen Chen7Harn-Shen Chen8Chii-Min Hwu9Chii-Min Hwu10Kam-Tsun Tang11Kam-Tsun Tang12Fan-Fen Wang13Fan-Fen Wang14Chiao-Wei Shih15Chen-Chang Yang16Chen-Chang Yang17Chen-Chang Yang18Chen-Chang Yang19Wen-Sheng Huang20Wen-Sheng Huang21Division of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanFaculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanInstitute of Public Health, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanInstitute of Food Safety and Health Risk Assessment, School of Pharmaceutical Science, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanDepartment of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanFaculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanFaculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanFaculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanDepartment of Medicine, Yangming Branch, Taipei City Hospital, Taipei, TaiwanDivision of Endocrinology and Metabolism, Department of Medicine, Taipei Veterans General Hospital (TVGH), Taipei, TaiwanFaculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanInstitute of Public Health, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanInstitute of Environmental & Occupational Health Sciences, School of Medicine, National Yang Ming Chiao Tung University (NYCU), Taipei, TaiwanDepartment of Occupational Medicine and Clinical Toxicology, Taipei Veterans General Hospital, Taipei, TaiwanDepartment of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, TaiwanDepartment of Nuclear Medicine, Cheng-Hsin General Hospital, Taipei, TaiwanBackgroundSoy 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.MethodsTwenty-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.ResultsAmong 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.ConclusionThe results suggest that most soy sauces are iodine-free and may be allowed during low iodine diets.https://www.frontiersin.org/articles/10.3389/fendo.2023.1058695/fulliodinelow iodine dietsoybeansoy sauceTaiwan |
| spellingShingle | Chun-Jui Huang Chun-Jui Huang Chun-Jui Huang Lin-Hsuan Lee Lin-Hsuan Lee Cheng-Pin Cheng Shan-Fan Yao Harn-Shen Chen Harn-Shen Chen Chii-Min Hwu Chii-Min Hwu Kam-Tsun Tang Kam-Tsun Tang Fan-Fen Wang Fan-Fen Wang Chiao-Wei Shih Chen-Chang Yang Chen-Chang Yang Chen-Chang Yang Chen-Chang Yang Wen-Sheng Huang Wen-Sheng Huang Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method Frontiers in Endocrinology iodine low iodine diet soybean soy sauce Taiwan |
| title | Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method |
| title_full | Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method |
| title_fullStr | Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method |
| title_full_unstemmed | Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method |
| title_short | Measurements of elemental iodine in soy sauces in Taiwan using a modified microplate method |
| title_sort | measurements of elemental iodine in soy sauces in taiwan using a modified microplate method |
| topic | iodine low iodine diet soybean soy sauce Taiwan |
| url | https://www.frontiersin.org/articles/10.3389/fendo.2023.1058695/full |
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