This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
The factors that affect the amount of fat absorbed by doughnuts may be outlined as follows. Other factors than those listed may also affect the amount of fat absorbed: (1) surface area, (2) the temperature of the ingredients when mixed, (3) the extent of mixing, (4) the kind and brand of flour used, (5) the amount of flour, (6) the cooking temperature and the length of time of cooking, (7) letting the dough stand before frying, and (8) variation in the proportion of ingredients used in the recipe. All the above factors either directly or indirectly affect the texture and also the tenderness of the doughnuts.
Surface area. Other things being equal, the greater the surface area the greater the fat absorption. The total surface area of doughnuts may be increased by stretching the dough in handling and by cracks on the surface of the dough. The thicker the doughnut is rolled, the smaller the total surface area in proportion to the weight of the doughnut. The thickness of the dough in all the following experiments is 1/4 inch. This is controlled by rolling the dough between cleats tacked to a bread board.
Temperature of ingredients when mixed. The results in Table 61 show that the temperature of the ingredients when mixed has a decided effect upon the amount of fat absorbed during cooking. The tenderness of the doughnuts was as marked as the fat absorption, for all the doughnuts of series II were tougher than those of series I. The dough made from the materials that had been incubated at 40°C. developed very rapidly, becoming quite elastic and rubbery in a short time. The dough stretched yet was so tenacious that it was difficult to divide it. It had a tendency to draw up and shrink after rolling. With this temperature even 60 strokes was too long to mix the dough to secure tender doughnuts. The best temperature of the ingredients to secure doughnuts of desirable texture and tenderness is about 22° to 27°C. (72° to 80°F.).
Variation in Fat Absorption Due to Difference in Temperature of the Ingredients of the Dough When Mixed, Six Doughnuts in Each
Lot. Cooked 3 Minutes at 175° to 180°C.
Number strokes for mixing
Tempera-ture of in-gredients when first mixed
Weight of uncooked dough-nuts, grams
Weight of cooked dough-nuts, grams
A word of explanation is necessary regarding the percentage of fat absorbed. As given in the tables it is only approximate. Doughnuts both lose and gain weight during cooking. Moisture is lost and fat is absorbed. The only accurate way to obtain the percentage of fat absorbed in doughnuts is to run an analysis on the ingredients used, i.e., to determine the amount of fat in the dough and in the cooked doughnuts. This requires too long for regular class work. Denton has suggested that the percentage of fat be calculated on the weight of the cooked doughnuts, and this has been followed in determining the percentage of fat given in the tables. The uncooked weight of the doughnuts is also given.
Extent of mixing. Both the manner of mixing the ingredients and the length of time of mixing the dough influence the texture obtained in doughnuts. Doughnuts, like cakes, seem to have a finer, more even texture if the eggs are thoroughly creamed with the fat and sugar. Adding the flour and milk in different portions may also affect the texture. Too little mixing after the flour and liquid are added gives a coarse, harder, rather crystalline texture, for the ingredients are not thoroughly blended. With over-mixing the doughnuts are tougher and more compact. The temperature of the ingredients affects the amount of mixing required to obtain a tender doughnut. As the temperature increases less mixing is required; at too low a temperature, the fat does not blend with the other ingredients. The length of time of mixing the dough also affects the amount of fat absorbed by doughnuts. In general, the longer the dough is mixed the more the gluten is developed unless mixing is extremely long. The development of the gluten by mixing forms thin filaments of gluten throughout the dough that probably tend to prevent fat absorption. The longer mixing produces a more uniformly mixed dough, which has a smoother crust. The smoother crust has less surface for fat absorption than a dough with a rougher surface.
Kind and brand of flour used. The amount of fat absorbed by doughnuts varies with the kind or brand of flour used, if other conditions are standardized. In general, the strong flours show greater decrease in fat absorption with longer mixing. The soft-wheat flours tend to increase the fat absorption. The amount of flour, that is of bread or soft-wheat flour, to give a soft tender doughnut also varies. This is apart from varying the proportion of flour.
The amount of flour. As the amount of flour in the recipe is increased the amount of fat absorbed by the doughnuts is decreased. This is shown in Table 62.