This section is from the book "A Treatise On Flour, Yeast, Fermentation And Baking Together With RecipesFor Bread And Cakes", by Julius Emil Wihlfahrt. Also available from Amazon: A treatise on flour, yeast, fermentation and baking, together with recipes for bread and cakes.
The natural amount of moisture varies from 9% to 13.5%; for freshly milled flour 12.5% may be given as a good average. More than 13.5% should be considered an over percentage of moisture, and would have detrimental effect on the storage properties of such a flour.
The moisture of a flour is determined by weighing carefully a small amount; dry same from 3 to 4 hours in a drying oven at 212° F., desiccate and weigh. Repeat the heating, cooling and weighing until the weight becomes constant. By the loss, calculate the amount of moisture contained in the sample under examination.
The strength of flour is dependent upon the quality, condition and quantity of gluten present, and can only be determined by making a careful test for absorption, followed up by a thorough baking test. Considering all points, the baking test gives the most satisfactory results.