An accurate water activity model for glycerol solutions and its implementation on moisture sorption isotherm determination

Abstract

H₂SO₄ and glycerol solutions are two commonly used unsaturated solutions for humidity control in moisture sorption isotherm (MSI) experiments. In a previous study, we reported an accurate water activity (a_w) model for H₂SO₄ solutions for use in MSI measurements. The current study aimed to construct a reliable a_w model of glycerol solutions and apply it to MSI measurements. Our research showed that the Wilson model could accurately predict a_w of glycerol solutions, with a root mean square deviation of 0.0096 a_w, in the concentration range of 9.47–99.62% glycerol by mass and in the temperature range of 0–100 °C. This a_w model considerably simplified the conventional glycerol solution (GSL) method. Finally, the reliability of this simplified GSL method was tested by comparing with the standard saturated salt solution method for MSI measurements of microcrystalline cellulose and apple at 25 °C. This proposed GSL method, based on the Wilson model, might be a reliable, safe, and inexpensive alternative method for MSI measurements in food areas in the future.

Highlights

• The Wilson model can precisely predict a_w of glycerol solutions.

• The Wilson model can remarkably simplify the known glycerol solution (GSL) method.

• The simplified GSL method is reliable and applicable for use in microcrystalline cellulose and apples.

• A working table of a_w of glycerol solutions was generated for convenience of use.

Keywords:

• Moisture isotherm sorption
• glycerol solution
• relative humidity
• water activity
• microcrystalline cellulose
• apple

Additional information

Funding

We acknowledge the UCD–CSC funding from University College Dublin and the China Scholarship Council.