Effect of temperature on the deliquescence properties of food ingredients and blends

Deliquescence is a first-order phase transformation of a crystalline solid to a saturated solution that is triggered at a defined relative humidity (RH), RH₀. Previous studies demonstrated that the RH₀ of an inorganic substance with a positive heat of solution (ΔH) will decrease with increases in temperature. In this study, the relationships between ΔH, solubility, and deliquescence RH for single-ingredient and multicomponent systems were investigated. The deliquescence RHs of inorganic and organic crystalline solids and their mixtures were measured at temperatures ranging from 20 to 40 C using a water activity meter and various gravimetric moisture sorption analyzers. The deliquescence behavior as a function of temperature for organic food ingredients was thermodynamically modeled and followed similar trends to those of the previously investigated inorganic ingredients. Furthermore, the models can be used as a predictive approach to determine physical stability and deliquescence RHs of deliquescent ingredients and blends if the storage temperature and ingredient ΔH and solubility are known.