DETERMINATION OF WATER ACTIVITY USING THE DECAGON AQUALAB CX-2 AND SERIES 3

Laboratory Procedure MFLP-66
June 2006

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1. APPLICATION

This method is applicable to the measurement of water activity in foods and food ingredients to determine compliance with the requirements of Sections 4 and 7 of the Food and Drugs Act, Section B.27.001 of the regulations of the Food and Drugs Act and any other federal regulation.

This revised method replaces MFLP-66, dated October 2001.

2. PRINCIPLE

Water activity plays an important role in the preservation of food and the control of microbial growth, especially pathogens. Decagon AquaLab models CX-2 and Series 3 use the chilled-mirror dewpoint technique to measure the water activity of a product.

3. DEFINITION OF TERMS

See Appendix A of Volume 3, items 1,2,3,4.

Water activity (a_w) : is the ratio of the water vapour pressure in any food system to the water vapour pressure of pure water at the same temperature.

Equilibration: When the aw values of any two readings are less than .001 apart, the instrument has reached equilibrium and the measurement process stops.

Humidity standard (slush) : is a saturated solution of a salt of a known % relative humidity at a designated temperature.

Commercial humidity standard: is an unsaturated salt solution of a specific molality representing a know Aw.

4. COLLECTION OF SAMPLES

See Appendix B of Volume 3.
Keep samples sealed to prevent loss or gain of moisture during transport.