Deliquescence Lowering in Food Ingredient Mixtures

Many common food ingredients (crystalline sugars, inorganic salts, and organic acids) exhibit deliquescence, a moisture‐induced solid to solution phase transition that occurs at a characteristic relative humidity, RH 0 . An automated gravimetric water vapor sorption balance was used to measure RH 0 , and a water activity (a W ) meter was used to measure a W of saturated solutions to characterize deliquescence of individual food ingredients and their mixtures. Measured RH 0 and a W values were similar ( P > 0.01), except for ingredients that form hydrates (confirmed by FT‐Raman spectroscopy) and for mixtures containing more than 2 ingredients. A significantly lower ( P < 0.01) RH 0 was obtained for all mixtures compared with individual ingredients, and optical microscopy images demonstrated the impact of ingredient contact on RH 0 lowering. Increasing temperature significantly decreased RH 0 ( P < 0.01). Results demonstrate that deliquescence lowering in ingredient mixtures has the potential to impact both chemical (for example, sucrose and citric acid mixtures) and physical stability (caking) of powdered ingredient mixtures.