Flour and Flour Manufacture

FLOUR AND FLOUR MANUFACTURE. Flour is defined as the fine, clean, sound product made by bolting wheat meal. The word is used in a less definite sense of other cereals and even non-cereals or other substances in a finely powdered state, though in these cases it is usual to use such terms as bean, rice, potato or other flour. The term so defined is generic and covers a wide range of products differing by reason of the variety or form of wheat used in their manufacture, or by reason of certain distinctive qualities required for several purposes.

The modern miller usually provides many types and grades of flour, each in the highest degree suitable for certain purposes. This specialization has led to the modification of older milling processes and the adoption of new ones, to meet the demands for cleaner, whiter and better bread-stuffs, as well as owing to the necessity for producing these better flours from wheats differing fundamentally from those available 5o years ago.

Bread Flours.

As compared with wheat-flour, all other mate rials used for making bread are of secondary importance. Rye bread is consumed in some of the northern parts of Europe and is popular in many parts of the United States, and breads commonly called corn-pone, hoe-cake, Johnny cake, made from corn-meal are largely eaten in the Southern States and less generally throughout the corn belt. In southern Europe the meal of various spe cies of millet is used and in India and China durra and other cereal grains are baked for food. Buckwheat is employed in Russia, Holland and the United States, and in South America the meal of the tapioca plant ; the flour of peas, beans and other leguminous seeds is also baked in cakes.

But, excepting rye, none of these sub stances is used for making vesiculated or fermented bread, for only wheat and rye yield flours which, mixed with water, form Boughs capable of satisfactory aeration or leavening.

Aside from its high nutritive value, due to its starch and gluten or protein content, and to a less degree to the mineral substances present, the most important characteristic of wheat flour is its capacity, when made into a dough, to enmesh gas, thus forming an open-textured, spongy, light bread. The gas formed either by the use of yeast as a leavening agent, or by the chemical reaction between an acid ingredient and bicarbonate of soda, is carbon dioxide Gas required for inflating the dough is produced by the growth of yeast. Yeast is a plant requiring food, and it must have sugar, nitrogenous matter and mineral salts in forms which it can assimilate; all flours contain some of these necessary yeast foods. They also contain certain enzymes, which may be called generically diastase. When dough is made these enzymes begin to operate on the starch of the flour, converting some of it, by stages, into sugar. The limiting factor in the quantity of gas evolved during panary fermentation is frequently a shortage of yeast-food; for example, the quantity of pre-existing sugar is insufficient, particularly if the proportion of yeast used is sub stantial and a prolonged fermentation is required. Therefore the yeast depends largely, and in the later stages of fermentation ex clusively, for its 'saccharine food on the sugar produced in the dough by diastatic action. Modern bakery practice, in which all the operations between the mixing of the dough and the removal of the bread from the oven are performed to a definite time schedule, will not wait on the development of sugar in sufficient quantity to feed the growing yeast. Under certain conditions the addition of sugar or of special sugars made from corn starch is good practice, but it is preferable to use a highly diastic malt ex tract which produces sugar as the yeast uses it ; in any case the yeast requires a sufficiently mixed food which includes some form of assimilable nitrogenous matter. (See BREAD and BREAD