Abstract
Norrish’s equation, \(a_{{\text{w}}} = X_{{\text{w}}} \exp {\left( { - KX^{2}_{{\text{s}}} } \right)}\), where a w is water activity, X w and X s are molar fractions of water and solute, respectively, and K is the correlating constant, has been widely used to predict a w of aqueous nonelectrolyte solutions in connection with development of intermediate moisture foods, i.e., food having a w ≥ 0.85. Present work evaluated the ability of Norrish’s equation to model the water activity of solutions of sugars, polyols, and some polyethylene glycols, in a wide range of concentration, i.e., from low to highly concentrated solutions. For sugar and polyols, a relatively small modification of the “most accepted” literature parameters K allowed the fitting of the data for the wide range of solute concentrations corresponding to a range of a w from 0.99 to about 0.3 for same solutes. However, a modified Norrish’s model needs to be used to model the behavior of polyethylene glycols 400 and 600 up to water activities as low as 0.5.
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The authors acknowledge the financial support of Agencia Nacional de Promoción Científica y Tecnológica, PICT (2005) no. 31951.
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Baeza, R., Pérez, A., Sánchez, V. et al. Evaluation of Norrish’s Equation for Correlating the Water Activity of Highly Concentrated Solutions of Sugars, Polyols, and Polyethylene Glycols. Food Bioprocess Technol 3, 87–92 (2010). https://doi.org/10.1007/s11947-007-0052-8
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DOI: https://doi.org/10.1007/s11947-007-0052-8