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ARS Home » Pacific West Area » Pullman, Washington » WHGQ » Research » Publications at this Location » Publication #318028

Research Project: Wheat Quality, Functionality and Marketablility in the Western U.S.

Location: Wheat Health, Genetics, and Quality Research

Title: The case for water activity as a specification for wheat tempering and flour production

item CARTER, BRADY - DeCagon Devices, Inc
item GALLOWAY, MARY - DeCagon Devices, Inc
item Morris, Craig
item WEAVER, GLEN - Ardent Mills
item CARTER, ARRON - Washington State University

Submitted to: Cereal Foods World
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2015
Publication Date: 7/31/2015
Publication URL:
Citation: Carter, B.P., Galloway, M.T., Morris, C.F., Weaver, G.L., Carter, A.H. 2015. The case for water activity as a specification for wheat tempering and flour production. Cereal Foods World. 60:166-170.

Interpretive Summary: The purpose of this study was to provide an argument for making water activity level a commonly requested specification for flour. The study investigated the impact of particle size, tempering conditions, and storage conditions on the water activity, moisture content, and moisture sorption properties of grain, flour, and farina. The information generated in this study should help explain some confusion over recommended moisture levels for flour, hightligh the impact of storage conditions on flour moisture, and determine if water activity may be a preferable metric for tracking moisture in grain and grain-based products.

Technical Abstract: Moisture plays an important role in processing wheat grain into flour, from proper grain tempering to the stability of the flour. Moisture properties of dry grain, tempered grain, and finished flour are currently tracked using moisture content. However, stability factors such as microbial growth and chemical stability are better correlated to water activity rather than moisture content. To determine if water activity could be utilized as a more effective specification for flour production, the water activity and moisture sorption properties of dry grain, tempered grain, farina, and flour were determined. The water activity of dry grain was found to be sufficiently low enough for long term stability. Dynamic isotherms of dry grain indicated a critical water activity where the seed coat lost its resistance to water penetration, which corresponded with the water activity of tempered wheat. Finally, the water activity of finished flour and farina was found to typically be below the critical water activity for mold growth. Based on the results of the study, it appears that all current recommended moisture levels for grain were established unknowingly based on water activity. Consequently, it would be more effective to set specifications for grain handling and processing based on water activity rather than moisture content.