163. Capacity of Flour to absorb Water.—The capacity of a flour to absorb water is determined by adding water from a burette to a weighed amount of flour until a dough of standard consistency is obtained. Low absorption is due to low gluten content. A good flour should absorb from 60 to 65 per cent of its weight of water. In making the test, it is advisable to determine the absorption of a flour of known baking value at the same time that an unknown flour is being tested. Flours of low absorption do not make breads of the best quality; also there are a smaller number of loaves per barrel, and the bread dries out more readily.
164. Physical Properties of Gluten.—The percentages of wet and dry gluten in a flour are determined as outlined in Experiment No. 27. Flours of good character should show at least 30 per cent moist gluten and from 10 to 12 per cent dry gluten. The quality of a flour is not necessarily proportional to its gluten content, although a flour with less than 10½ per cent of dry gluten will not make the best quality of bread, and flours with excessive amounts are sometimes poor bread makers. The color of the gluten is also important; it should be white or creamy. The statements made in regard to color of flour apply also to color of the gluten. A dark, stringy, or putty-like gluten is of little value for bread-making purposes.[[64]] In making the gluten test, it is advisable to compare the gluten with that from a flour of known bread-making value. Soft wheat flours have a gluten of different character from hard wheat flours.
165. Gluten as a Factor in Bread Making.—The bread-making value of a flour is dependent upon the character of the wheat and the method of milling. It is not necessarily dependent upon the amount of gluten, as the largest volume and best quality of bread are often made from flour of average rather than maximum gluten content. But flours with low gluten do not produce high-grade breads. When a flour contains more than 12 or 13 per cent of proteids, any increase does not necessarily mean added bread-making value. The quality of the gluten, equally with the amount, determines the value for bread-making purposes.
Fig. 43.—Fungous Growth
in Unsound Flour.
166. Unsoundness.—A flour with more than 14 per cent of moisture is liable to become unsound. High acidity also is an indication of unsoundness or of poor keeping qualities. The odor of a sample of flour should always be carefully noted, for any suggestion of fermentation sufficient to affect the odor renders the flour unsuited for making the best bread. Any abnormal odor in flour is objectionable, as it is due to contamination of some sort, and most frequently to fermentation changes. A musty odor is always an indication of unsoundness. Some flours which have but a slight suggestion of mustiness will, when baked into bread, have it more pronounced; on the other hand, some odors are removed during bread making. Flours may absorb odors because of being stored in contaminated places or being shipped in cars in which oil or other ill-smelling products with strong odors have previously been shipped. Unsoundness is often due to faulty methods in handling, as well as to poor wheat, or to lack of proper cleaning of the wheat or flour.
167. Comparative Baking Tests.—To determine the bread-making value of a flour, comparative baking tests, as outlined in Experiment No. 29, are made; the flour in question is thus compared as to bread-making value with a flour of known baking quality. In making the baking tests, the absorption of the flour, the way in which it responds in the doughing process, and the general properties of the dough, are noted. The details should be carried out with care, the comparison always being made with a similar flour of known baking value, and the bread should be baked at the same time and under the same conditions as the standard. The color of the bread, the size and weight of the loaf, and its texture and odor, are the principal characteristics to be noted.
Fig. 44.—Comparative Baking Tests.
The quality of flour for bread-making purposes is not strictly dependent upon any one factor, but appears to be the aggregate of a number of desirable characteristics. The commercial grade of a flour can be accurately determined from the color, granulation, absorption, gluten and ash content, and the quality of the bread. Technical flour testing requires much experience and a high degree of skill.