This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
The using of the proportion of liquid required by the flour is one important factor in obtaining a desirable texture in biscuits. Since hydration capacity of different flours varies, it is necessary to determine this for the various brands and grades of flour. The same brand of flour in different sections of the United States is not always from the same kind of wheat. For example, Gold Medal flour in Iowa is an all-purpose flour, but in Alabama or Mississippi it is made from soft wheat, the type used extensively in the southern states.
Method of combining ingredients for biscuits. In biscuits, a different method of mixing is used from those heretofore considered in the batter and dough series. Oil may be used. Fats are not melted, and either oil or fat is added directly to the flour. If a colored fat is used it can be readily seen that the fat is distributed in layers or pools and absorbed on the surface of the starch granules. In this dough, with its small proportion of liquid and no egg, there seems to be little tendency for the fat to form an oil-in-water emulsion.
Fat is added to biscuits to give shortness. It is important in making good biscuits to mix the fat and flour sufficiently, but not too much. Using a fine, wired fat mixer, or rubbing lightly between the finger tips, is the easiest and quickest way of mixing the fat with the flour. Some cooks prefer to pick up a portion of the fat and flour, letting it fall gradually back into the bowl while mixing it. In this way the mixture may remain more light and fluffy, because more air is retained. In adding the liquid to the mixture of fat and flour, a two- or three-tined fork is preferable to a spoon, for the dough is packed less during the mixing. Usually about 25 to 35 strokes are needed to combine the liquid and flour. With longer stirring of the dough the biscuits stand up better and the texture is less coarse. The texture of rolled biscuits is improved by folding over and rolling out about 4 times, which gives a very flaky texture, or by kneading a short time in addition to the stirring. For kneaded biscuits the dough is removed to a bread board and kneaded very lightly 10 to 20 times. Kneading tends to develop sheets or layers with a fine texture, which is considered desirable. Excess kneading toughens the dough more rapidly than stirring with a fork. If the proportion of fat used is large, or if a pastry flour is used, the mixing and kneading can be continued for a slightly longer time. The crust of biscuits is less crisp with longer mixing or when they are kneaded. Those who prefer a very crisp crust may like dropped biscuits better than kneaded ones. See Experiment 83.
Beaten biscuit. The beaten biscuit of the South is made without the addition of baking powder or soda. While the dough is beaten, it is folded over and over so that it contains air. Since the beating is prolonged the gluten may be modified or softened and becomes more tender. This is similar to the long mixing used by Swanson in modifying the gluten of bread. The amount of beating to give the best texture is indicated by a Negro mammy when she says, "I use 300 strokes for every day, but when I'se spectin' company in, I use 500 sure."
Soft-wheat flour and biscuit. The addition of calcium acid phosphate to soft-wheat flours improves their quality for biscuit. Alexander states that, "It is almost impossible to sell flours in some districts in the South unless the sack is marked 'Phosphate added.' "The acid calcium phosphate is acid in reaction. It has a pH of about 4.0. Alexander states, "We know-that the gluten proteins tend to imbibe water, and disperse in a weakly alkaline medium, so that a slightly alkaline dough is sticky. Excess alkali in dough produces a yellow color and a soapy taste."
Alexander reports that dough quality, biscuit volume, crumb, texture, and color are improved by treating soft-wheat flour with 0.5 per cent calcium acid phosphate. Logue and Ranker have reported results similar to those of Alexander.
Smith and Bailey have reported "The Effect of Chemical Leavening Agents on the Properties of Bread." Their conclusions, in part, for the biscuits and their experimental work follow. "Gluten properties, including elasticity and hydration capacity, are affected by baking powder, and by the residual salts resulting from the chemical reaction of baking powder ingredients.
"Disodium phosphate, the residual salt resulting from the reaction of monosodium phosphate baking powder, affects gluten more than the residues from other types of baking powders."