Methods for measuring water activity (a_w) of foods and its applications to moisture sorption isotherm studies

ABSTRACT

Moisture sorption isotherm is commonly determined by saturated salt slurry method, which has defects of long time cost, cumbersome labor, and microbial deterioration of samples. Thus, a novel method, a_w measurement (AWM) method, has been developed to overcome these drawbacks. Fundamentals and applications of this fast method have been introduced with respects to its typical operational steps, a variety of equipment set-ups and applied samples. The resultant rapidness and reliability have been evaluated by comparing with conventional methods. This review also discussed factors impairing measurement precision and accuracy, including inappropriate choice of predryingwetting techniques and unachieved moisture uniformity in samples due to inadequate time. This analysis and corresponding suggestions can facilitate improved AWM method with more satisfying accuracy and time cost.

Keywords:

• Isotherm
• a_w measurement (AWM) method
• moisture adjustment
• water homogeneity
• water activity

Acknowledgment

Lida Zhang wishes to thank for valuable comments and language revision by Weiwei Liu.

Funding

The authors thank financial support from UCD-CSC scholarship.