The Effects of Different Oils during Deep Fat Frying of Doughnut Holes on Sensory and. Quantitative Evaluations. By: Julie Sankbeil

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1 The Effects of Different Oils during Deep Fat Frying of Doughnut Holes on Sensory and Quantitative Evaluations By: Julie Sankbeil Abstract The purpose of this experiment was to observe sensory qualities of general impression, fat flavor, mouth feel and fat absorption of doughnut holes deep fried in different types of frying oils. This was performed by testing a variety of different types of oils. Characteristics evaluated were general impression, fat flavor, mouth feel and fat absorption percentage. The variation that was most preferred in the sensory evaluation was prepared in Crisco. It can be concluded that some oils are more ideal than others for deep frying to maintain sensory qualities. Introduction Doughnuts are sweet, deep-fried flour dough which is available in two types. They are the ring doughnut or the spherical piece of dough called a doughnut hole. Different variations of doughnuts are made all over the world; India is known for its unsweetened version while in the United States, some are baked instead of deep fried, or made into a variety of shapes. Doughnuts typically consist of an all-purpose flour, sugar, salt, baking powder, eggs, oil, milk and oil for deep frying after cooking, sprinkled with powdered sugar or a cinnamon-sugar mixture. When prepared at the optimum temperature, deep-fried products, like doughnuts, are a crispy, golden brown color with the optimal amount of oil absorption (Choe 2007). The purpose of this experiment was to observe fat absorption percentage and sensory qualities of doughnuts deepfried in different types of oils.

2 The process of deep-fat frying produces either a desirable or undesirable flavor. The combination of heat and mass transfer of oil, the food and air produce the desirable qualities of fried foods. Linolenic acid, commonly found in vegetable oils, is responsible for the desirable fat flavor. The chemical reactions most common in the frying of oil are hydrolysis, oxidation and polymerization (Choe 2007). Hydrolysis happens when water breaks a chemical bond, forming into two or more new substances; oxidation acts in the presence of oxygen producing a browncolored product and polymerization is the process in which free fatty acids link together (Brown 2007). Different oils produce different flavor during deep-fat frying because of different qualities and quantities of fatty acids within the specific frying oil being used (Choe 2007). Fat absorption is dependent on four different aspects, the time of cooking, the temperature of the cooking fat, surface area and the composition of the food. The longer amount of time a food is cooked in cooking fat, more fat absorption will occur. The exception to this is foods that are cooked at a higher temperature coagulate material and the hardened crust prevents fat absorption. This means there is less fat absorption at higher temperatures. A larger surface area gives more area for the fat to be absorbed. In the aspect of composition of foods, some foods absorb more than fat others, the first items put into the deep- fat frying oil typically yield the most fat absorption (Lowe 1937). Methods To create a doughnut hole for deep frying, take a package of commercially prepared biscuits, separate them into separate biscuits, then cut them into approximately 30 even-sized pieces and roll into holes. In a 1 quart pot, place enough oil so that the oil is at least 1 inch deep or use approximately 500 g of the solid fat, Crisco and lard. Oils used include, vegetable oil, peanut oil, and olive oil. Gently heat the fat to 190 o C or as directed by a specific variation. Make sure to

3 take temperature readings often to maintain the assigned temperature throughout cooking. When the fat reaches the temperature desired, transfer a uniformly-sized biscuit hole into the hot oil via a metal spatula. Start timing immediately. Continuously turn the hole so that each side is cooked to a golden brown color. When it is finished cooking, remove the biscuit hole from the hot oil via the metal spatula and cut in half to confirm that it is cooked thoroughly. Make note of the frying time and place the biscuit hole on a paper towel to drain excess fat. With the use of an accurate scale, weigh one biscuit hole before cooking and record the weight. Cook and drain the biscuit hole as done with the previous directions. Weigh the biscuit hole after cooking, record the weight, and set this biscuit hole aside for evaluation later. Repeat the cooking steps for the remaining biscuit holes, without having to weigh them. Place a minimum of holes into the hot oil, but note the more holes you add to the oil, the cooler the oil will get. In a plastic zip-lock bag, mix ¼ cup sugar and 1 T cinnamon, or powdered sugar, depending on the variation. Put the cooked biscuit holes in the bag and shake until coated with the mixture. For sensory evaluation, place the original biscuit hole without cinnamon and sugar and the sugared biscuit holes a plate labeled with the type of oil, weight before, weight after, and frying time (Adapted from HNF 348 Lab Manual). To measure fat absorption, use the formula: % Fat Absorption = Weight After Frying Weight Before Frying X 100 Weight Before Frying For sensory evaluation, the panel will evaluate each sample on its general impression, fat flavor and mouth feel using a scale from 1 to 5. Sensory Score Evaluation Basis General Impression: 1= dislike extremely, 2= dislike moderately, 3= neither like nor dislike, 4= like moderately, 5= like extremely

4 Fat Flavor: 1= dislike extremely, 2= dislike moderately, 3= neither like nor dislike, 4= like moderately, 5= like extremely Mouthfeel: 1= dislike extremely, 2= dislike moderately, 3= neither like nor dislike, 4= like moderately, 5= like extremely Results and Discussion Table 1: Differences in Weight (g) Before and After Frying and Fat % Absorption Treatment Weight (g) Before Weight (g) After % Absorption Vegetable Oil 160ºC Vegetable Oil 175ºC Vegetable Oil 190ºC Vegetable Oil 205ºC Peanut Oil Olive Oil Lard Crisco Table 2: Frying Time for Doughnut Holes Treatment Vegetable Oil 160ºC Vegetable Oil 175ºC Vegetable Oil 190ºC Vegetable Oil 205ºC Peanut Oil Olive Oil Lard Crisco Frying Time (min) 1 minute 42 seconds 1 minute 5 seconds 2 minutes 1 minute 40 seconds 2 minutes 10 seconds 1 minute 15 seconds 1 minute 50 seconds 1 minute 30 seconds

5 Figure 1: Average Ratings of Sensory Evaluation Based on General Impression General Impression Figure 2: Average Ratings of Sensory Evaluation Based on Fat Flavor Fat Flavor

6 Figure 3: Average Ratings of Sensory Evaluation Based on Mouthfeel Mouth feel The purpose of this experiment was to observe sensory qualities of general impression, fat flavor, mouth feel and fat absorption of doughnut holes made with different types of frying oils. Sensory tests were performed to rate the variations on general impression, fat flavor and mouth feel. The variation most well-liked in the general impression category was Criso, receiving a rating of 4.095, which most closely corresponds to the rating like moderately (Figure 1). For rating the characteristics of fat flavor, both Criso and vegetable oil cooked at 160ºC received a rating of 3.81 which would fall between neither like nor dislike and like moderately (Figure 2). Crisco received the rating of 4.286, which would correspond with like moderately for mouth feel (Figure 3). The variation that received the lowest ratings in all categories was lard. Lard has a low smoking point, causing it burn easily, giving it a burnt taste; making it not appetizing for those performing the sensory evaluation (Brown 2007). Vegetable oil cooked at 205ºC having a fat absorption percentage of 0 is due to less fat absorption occurring at higher temperatures (Lowe 1937).

7 Typically, the longer a product is cooked there is an increase of fat absorption (Lowe 1937). In the case of this experiment, the variation cooked for 2 minutes and 10 seconds in peanut oil yielded 25% fat absorption (Table 1; Table 2). The variation with the most fat absorption, 50%, was olive oil (Table 1). Olive oil is resistant to high heat, causing it to be able to withstand oxidation, therefore resulting in higher quality products (Matthäus 2007). Conclusion Different types of frying oils produce a variety of flavors, affecting general impression, fat flavor and mouth feel. There is a wide difference in the amount of fat absorbed within doughnut holes, even when time of cooking is relatively standard and a standardized surface area is set. Results from the sensory evaluation yielded that the doughnut holes fried in Crisco were liked the most and those fried in lard were liked the least. It can be concluded that some frying oils are better for deep-frying than others for maintaining sensory attributes and optimum fat absorption. References Brown, Amy. Understanding Food: PRINCIPLES AND PREPARATION. [S.l.]: Wadsworth, Print. Choe, E., and D.B. Min. "Chemistry of Deep-Fat Frying Oils." Journal of Food Science 72.5 (2007): R Print. Lowe, Belle. "Experimental Cookery: From the Chemical and Physical Standpoint. By B. Lowe. 2nd Ed. Pp. Xi Coo. New York: J. Wiley & Sons, Inc.; London: Chapman & Hall, Ltd., s. Gd." Journal of the Society of Chemical Industry (1937): Print. Matak, K. E. HNF 348: Science of Food Preparation Lab Manual Print. Matthäus, Bertrand. "Use of Palm Oil for Frying in Comparison with Other High-stability Oils." European Journal of Lipid Science and Technology (2007): Print.