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U.S. Department of Health and Human Services

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Anal Bioanal Chem 2013 Oct;405(26):8615-20

Use of water activity characteristics enables a simplified approach for defining the reference moisture condition for FDA cocoa powder in-house reference material.

Cunningham WC


The Food and Drug Administration uses water activity behavior characteristics when adjusting test portion mass to correct for the moisture condition of its cocoa powder in-house reference material. The cocoa powder's moisture condition, and therefore weight, equilibrates according to the relative humidity (RH) of its surroundings. This process is predictable and defined by an isotherm. The reference values in the certificate of analysis are relative to the material's condition at 30 % RH, which is assumed to be mid-range for typical laboratory settings. Since mass variations are relatively small within a 15-50 % RH range, the mass may be measured immediately after removing a test portion from a storage bottle and used without correction if a standard uncertainty of 0.7 % is acceptable for the mass. If greater accuracy is needed and the laboratory RH is known, a very simple and quick procedure can be used whereby the test portion is left open and exposed to the laboratory air overnight before weighing. After applying a correction, the standard uncertainty for mass measurement drops to 0.3 %.

Category: Journal Article
PubMed ID: #23942587 DOI: 10.1007/s00216-013-7175-8
Includes FDA Authors from Scientific Area(s): Food
Entry Created: 2013-08-15 Entry Last Modified: 2013-10-26