Novel technique for measuring salt concentrations in food using silver dichromate

Curing with salt reduces water content in food and extends its shelf life; therefore, understanding salt permeability in food is critical to food quality and safety. Although there are many new techniques to measure salt concentrations in food, they cannot be applied in practice owing to drawbacks such as the need for expensive equipment or the inability to image quickly; therefore, development of a fast and simple measurement method is crucial. Silver dichromate is converted to silver chloride when it encounters chloride ions. Based on this principle, we soaked radishes in NaCl solutions of different concentrations and added a layer of silver dichromate to it. Salt concentrations was observed in 5 min, as areas with NaCl concentration of ≥1 % appeared white, whereas the other regions appeared red. A strong correlation (r = 0.94/0.96) was observed between the area of salt concentrations measured using this method and that measured using the conventional salt measurement method, demonstrating the reliability of the method. This method will help advance research related to salt concentrations in food and its application in industrial scenarios.