Deliquescence describes the transition from a crystalline solid to a dissolved state when a critical, material-specific relative humidity is exceeded. Such behavior is typically observed for hygroscopic substances due to their high affinity for the adsorption of moisture – usually in the form of water vapor from the surrounding atmosphere. With such products, this already occurs at low relative humidities. As a result, caking and, at higher moisture, deliquescence of the solids occurs frequently. Due to the associated adverse effects on the technological and sensory properties as well as the shelf life, hygroscopic products generally require special attention to the product-moisture interaction. In this context, dynamic water vapor sorption measurements play a decisive role in assessing the stability of both individual raw materials and the end products.
By understanding the hygroscopic behavior of a product, e.g. the storage conditions or the composition of the formulation can be optimized.
Deliquescence and deliquescence lowering of food ingredients and blends
Deliquescence can be observed with many crystalline food ingredients such as sugar, salts, organic food acids and vitamins.
Furthermore, mixtures of such ingredients often show deliquence-lowering, i.e. dissolution at a lower critical relative humidity. This applies, for example, to dried food preparations as instant drink powder, food supplements or spice mixtures. Due to the adverse effects on the product quality and handling properties, deliquescence is an important topic in food research.
The application note investigates water vapor sorption and moisture-induced dissolution as well as the effect of deliquescence-lowering of some relevant hygroscopic food ingredients and mixtures.
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Literature references for investigating deliquescence with the ProUmid DVS instruments
A.M. Stoklosa, R.A. Lipasek, L.S. Taylor, L.J. Mauer, Effects of storage conditions, formulation, and particle size on moisture sorption and flowability of powders: A study of deliquescent ingredient blends, Food Res. Int. (2012). doi:10.1016/j.foodres.2012.09.034.
M. Allan, L.J. Mauer, Comparison of methods for determining the deliquescence points of single crystalline ingredients and blends, Food Chem. (2016). doi:10.1016/j.foodchem.2015.05.042.
R.A. Lipasek, N. Li, S.J. Schmidt, L.S. Taylor, L.J. Mauer, Effect of temperature on the deliquescence properties of food ingredients and blends, J. Agric. Food Chem. (2013). doi:10.1021/jf402585t.
L.J. Mauer, L.S. Taylor, Deliquescence of pharmaceutical systems, Pharm. Dev. Technol. (2010). doi:10.3109/10837450903397594.