Abstract
Soy sauce is a common condiment that has a unique flavor, one that is derived from its rich amino acids and salts. It is known that excessive intake of high-sodium food will affect human health, causing a series of diseases such as hypertension and kidney disease. Therefore, removing sodium from the soy sauce and retaining the amino acids is desirable. In this study, electrodialysis (ED) was employed for the desalination of soy sauce using commercial ion exchange membranes (IEMs). The influence of the current density and initial pH on the desalination degree of the soy sauce was explored. Results showed that the optimal desalination condition for ED was reached at a current density of 5 mA/cm2 and pH of 5, with the desalination degree of 64% and the amino acid loss rate of 29.8%. Moreover, it was found that the loss rate of amino acids was related to the initial concentration and molecular structure. In addition, the amino acid adsorption by IEMs was explored. Results implied that the molecular weight and structure affect amino acid adsorption. This study illustrated that the ED process can successfully reduce the salt content of the soy sauce and retain most of the amino acids without compromising the original flavor.
Highlights
Soy sauce is a traditional condiment that is used in many Asian countries
To our knowledge, there has not been a study focusing on the individual amino acid transport across the anion exchange membrane during soy sauce desalination with ED nor its relationship with the flavor of soy sauce
This final desalination degree ranged from 64% to 70% when the current density was between 5 and 15 mA/cm2
Summary
Soy sauce is a traditional condiment that is used in many Asian countries. It can bring an appetizing taste to a certain food [1]. 2.5–3.5 3.5–4.5 chloride content between 5 and 10% (w/v) in soy sauce can benefit human health without compromising taste [8] Several techniques such as electrodialysis (ED) [9,10], ion exchange resin [11,12], freeze concentration [13], and nanofiltration [14] have been claimed as effective approaches to remove sodium chloride from soy sauce. To our knowledge, there has not been a study focusing on the individual amino acid transport across the anion exchange membrane during soy sauce desalination with ED nor its relationship with the flavor of soy sauce. In this study, the effect of current density and pH on the desalination rate, current efficiency, and amino acid lost rate during the soy sauce desalination process was investigated. A set of operational strategies was proposed in order to achieve optimal salt removal and amino acid retention
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