It demonstrated that the NaCl distribution on the outermost surface of the spray dried soy sauce powders was very limited, which is supported by other studies on spray drying in the literature. This was probably the reason for that the NaCl distribution on the powder surface decreased as the addition of WPI increased. It is interesting to note a higher percentage of chlorine than sodium for all the soy sauce powders analysed, which might be due to the existence of other chloride salts (e.g. KCl) and the residual chlorine in water.