The Case for Water Activity as a Specification for Wheat Tempering and Flour Production

Abstract

Moisture plays an important role in processing wheat grain into flour, from proper grain tempering to flour stability. The 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 whether water activity could be utilized as a more effective specification for wheat flour production, the water activity and moisture sorption properties of dry grain, tempered grain, farina, and flour were determined. Results showed the water activity of dry grain was sufficiently low for long-term stability. Dynamic isotherms of dry grain indicated critical water activity in which the seed coat lost its resistance to water penetration, which corresponded to the water activity of tempered wheat. Finally, the water activity of finished flour and farina typically was below the critical level for mold growth. Based on...