This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Fat absorption in doughnuts by McKee. McKee has determined the amount of fat absorbed in frying doughnuts. The doughnuts were made under standard conditions and fried for 5 minutes at 200°C. The standard recipe averaged 34.7 per cent fat absorbed. When the fat was doubled and quadrupled in the doughnut recipe the fat absorption was increased to 43.4 and 47.8 per cent, respectively; sugar doubled caused an increase to 44.3 per cent. But when the sugar was quadrupled the doughnut disintegrated during cooking, absorbing large quantities of fat.
Fat absorption in doughnuts. From various sources. Morgan and Cozens have determined the amount of fat absorbed in frying doughnuts. Their dough contained less egg and more flour than the dough used by McKee. Their doughnuts were larger than McKee's, which gave a relatively larger surface for a given weight of dough for the McKee doughnut. They cooked their doughnuts for 3 minutes at 205° to 210°C, which resulted in an average fat absorption of 17.4 per cent. The time of cooking, the temperature of the cooking fat, and the proportion of ingredients in the recipes used by McKee and Morgan-Cozens were not the same; hence the fat absorption differed.
The cooperators in lard investigations at Iowa State College Experiment Station determined the amount of fat absorbed by doughnuts and the changes in the fats caused by cooking doughnuts in each fat, the period of heating each fat being kept constant at 10 1/4 hours. These studies were continued over a period of 3 years, the same operator, Jensen, making and frying all the doughnuts, so that a highly specialized technic was developed. Standardized conditions of mixing, which included incubation of all materials at a definite temperature before mixing and mixing with a Kitchen-Aid, were maintained. Six mixes or batches of dough were required for the doughnuts fried in each fat. The term "firsts" was applied to doughnuts cut after the first rolling of the dough. The scraps were then collected and rerolled. The doughnuts from this lot were designated as "rerolls." Again the scraps were collected and rerolled, the doughnuts from this lot designated as "re-rerolls." The following results are from tests during the third year only.
A total of 12 fats were used, of which 2 were open-kettle rendered lards, 5 were prime-steam rendered lards, 1 hydrogenated lard, 1 hydro-genated cottonseed oil, and 1 corn oil.
Number of "firsts" cooked in each fat 12 dozen
Number of "rerolls" cooked in each fat 6 dozen
Number of "re-rerolls" cooked in each fat 2 1/2 dozen
Average fat absorption from all fats for "firsts" 28.6 per cent
Average fat absorption from all fats for "rerolls" 22.3 per cent
Average fat absorption from all fats for "re-rerolls" 18.5 per cent
The analysis of variance indicated exceedingly high uniformity among rollings, i.e., "firsts" always absorbed the most fat, etc., but great variation among different mixes or batches so that the variation from mix to mix was used as the experimental error. The variation of amount of fat absorbed by the different fats was also highly significant. Further analysis of the data showed a significant negative correlation between the smoking point of the fat and the amount of fat absorbed by the doughnuts, which indicated that the lower the smoking point the greater the amount of fat absorbed by the doughnuts. The iodine value, the percentage of free fatty acids, and the refractive index had no effect on the amount of fat absorbed. However, a highly significant negative correlation was found between the free fatty acids content and the smoking point of the fat which agrees with former findings of Blunt and Feeney and Morgan and Cozens.
Denton and co-workers have also published results for fat absorption in doughnuts and other foods. Their conclusions are similar to those of the investigators mentioned above and to the following class results, so will not be given in detail.