This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
The texture or structure of the finished product depends partly upon the structure obtained in the batter or dough when it is mixed. The role the flour plays in batter and dough products is the same as in bread, but since the batter or dough may contain different proportions of liquid and other ingredients the structure of the baked product is often unlike that of bread.
The factors that affect the texture of the finished product may be grouped as follows: (1) the ingredients used, (2) the proportion of the ingredients used, (3) the kind and amount of baking powder used, (4) the extent of mixing, (5) the temperature of the ingredients when mixed, and (6) the method of mixing or combining ingredients.
Doughs and batters may also be considered in relation to their physical properties. One of the physical properties of batters and doughs which is intimately connected with their structure, and which can be measured, is viscosity. Viscosity of batters and doughs is important enough to repeat the ten factors listed by Ostwald, causing variation in viscosity, which have been previously mentioned in Chapter I (The Relation Of Cookery To Colloid Chemistry). They are: (1) concentration, (2) temperature, (3) degree of dispersion, (4) solvation, (5) electrical charge, (6) previous thermal treatment, (7) previous mechanical treatment, (8) the presence or absence of other lyophilic colloids, (9) the age of the lyophilic sol, and (10) the presence of both electrolytes and non-electrolytes.
The ingredients and their proportion. When factors (1) concentration, (8) the presence or absence of other lyophilic colloids, and (10) the presence of both electrolytes and non-electrolytes, are combined, we have a formula or a recipe, in other words the ingredients and their proportion or concentration. Batters and doughs consist of flour and a liquid. Usually some fat and egg are added, though one or the other may be omitted: fat is seldom used in popovers, and baking powder biscuits contain no egg. The proteins and starch of the flour are lyophilic systems. When eggs or milk are added their proteins add other lyophilic colloids.
As the concentration or the quantity of the different ingredients in the batter is varied, its properties and characteristics vary, which in turn influences the texture of the finished product. A batter with a high concentration of liquid has a greater fluidity; one with a smaller proportion has a greater viscosity. As the proportion of each ingredient is varied, the finished product is altered accordingly, the kind and extent of the alteration depending upon the particular quality imparted to the batter by the ingredient and upon the proportion of it used.
The proportion of liquid used also influences the degree of solvation or hydration of certain constituents of the batter, i.e., the protein and starch.
The presence of both electrolytes and non-electrolytes. Baking powder, salt, soda, and cream of tartar belong to the group of electrolytes. Salts affect the imbibition of water by gluten and coagulation by heat. Since baking powders contain different acid salts, it is possible that they may affect, in different degrees, the rate of hydration of the gluten and the total amount of water absorbed.
Sugar belongs to the group of non-electrolytes. Its presence in large quantity in a batter affects the structure and also the extent of mechanical treatment needed to obtain a certain type of grain.
Mechanical treatment. The extent of mixing a definite batter or dough may alter its viscosity or fluidity, and the texture of the finished product varies with this variation in viscosity.
In the laboratory outline an effort is made to control the amount of mixing in most of the batter and dough series by counting the number of strokes used to stir the batter, particularly after the flour is added. It has been found that this gives more uniform results when mixing is done with a spoon or similar utensil, than to mix for a definite time. Some girls will use more than twice as many strokes in a stated time as others. To have the strokes more uniform they should all be made across the bowl or all used in a stirring motion. If a very large spoon or one with slots is used, it may be necessary to mix with a smaller number of strokes than the ones suggested.
When it is possible a mechanical mixer with a definite speed is preferable to use for school work. Here, too, the amount of mixing required depends somewhat upon the size of the mixer and the quantity of material used. With large classes it is not always possible to have enough mixers not to delay the class work. Mixing with a spoon has the advantage of being the method used under most home conditions.
There is an amount of mixing, which partially or completely dissolves the sugar, develops the gluten network sufficiently, and distributes the fat throughout the batter, that gives the best flavor and texture to the finished product. The product is tender and the volume is good. This amount of mixing, which may be called the optimum amount, will vary with each recipe, i.e., with the ingredients and their proportion. One illustration is the kind of flour used, for the optimum amount of mixing is not always the same for bread and pastry flours. It will also vary with the temperature of the ingredients when they are mixed.
The temperature of the ingredients when mixed. The temperature of the ingredients when mixed influences the structure obtained, particularly in cakes and doughnuts. The protein particles of flour imbibe water more rapidly at higher temperatures. Sugar is more soluble with increasing temperature. But perhaps the consistency of the fat and its distribution throughout the batter are most affected by temperature. If the temperature is low a fat is firmer, and less plastic. It spreads less readily throughout the other ingredients. The temperature of the other ingredients may be such that fat is rendered more or less plastic, i.e., they may be warmer or colder than the fat. In cake batters, if an oil is used the oil may be partially or wholly emulsified as an oil-in-water emulsion, the flour and egg proteins acting as the emulsifiers and surrounding the spheres of oil. If a fat is melted and added to a cake batter and the temperature of the ingredients is such that they do not harden the fat, a portion or all of the fat may be emulsified as an oil-in-water emulsion and the structure is similar to that produced by oil. This distribution of the oil in a batter as well as adsorption of fat and proteins at interfaces is probably influenced by the electrical charge.