1 F&N 453 Project Written Report Katharine Howe TITLE: Effect of wheat substituted for 10%, 20%, and 30% of all purpose flour by volume in a basic yellow cake. ABSTRACT Wheat is a component of wheat whole grains that are removed from allpurpose flour. Food products made from all-purpose flour then lacks the nutrients contained in the wheat. One way to increase the nutrient density of foods traditionally made with all-purpose flour is to substitute a portion of the all-purpose flour with wheat. In this study, the effects of substituting 10%, 20%, and 30% of the volume of all-purpose flour with wheat in a basic yellow cake was tested and evaluated. Specifically, water activity, texture in terms of force needed to compress each sample, and sensory qualities were evaluated. Water activity decreased as wheat concentration increased. There was no clear trend found relating texture to the concentration of wheat but each sample was different. Overall, the control cake received the greatest sensory ratings and the 20% and 30% cakes received the lowest sensory ratings. Although each variation had different sensory test results, overall each variation was acceptable. It can be concluded that altering the all-purpose content of a basic yellow cake to include 10%, 20% and 30% of wheat by volume does alter the physical and sensory characteristics of the different variation but does leave an acceptable product.
2 INTRODUCTION Improving the nutrition of everyday food products is one way to help improve the overall nutrient intake of those who consume it. One way of doing this is by taking a familiar food and altering it to make it more nutritious by changing its components. This is the basic principal of this study. A basic yellow cake recipe was altered to include wheat in substitution of different portions of the all-purpose flour. Specifically, 10%, 20%, and 30% of the all-purpose flour was removed and replaced with 10%, 20%, and 30% of wheat. Wheat is a component of the wheat whole grain that is removed during processing to produce all-purpose flour, a refined flour. Wheat contains important nutrients that become removed from the flour when the is removed from the whole wheat (Lauterbach 1995). All food products made with the refined flour will also be void of the nutrients lost with the unless the nutrients are added back. One way to add the nutrients back is to add back to the flour. It is important that when is added back to flour in a recipe that it replace it and not simply add onto the total volume of flour. This will ensure that the total volume of the dry ingredients will remain stable and not increase significantly because of the wheat addition. For this study, a basic yellow cake recipe was modified to include 10%, 20%, and 30% of the flour portion as wheat. A controlled protocol was designed to ensure that only the variables would be different amongst the different trials. Each cake was prepared according to the protocol. After the samples were prepared, each cake was evaluated for texture using the texture analyzer, water activity using the water activity machine, and for overall quality using a hedonic sensory evaluation.
3 The purpose of this study is to determine if substituting wheat for allpurpose flour for a basic yellow cake will produce a similar and desirable product compared to a regular basic yellow cake. If a wheat -substituted product is found comparable then it could serve as a way to improve nutrient content in an everyday food and help to improve the nutrient intake of those who consume it. METHODS A basic yellow cake recipe was found and served as the basis for the experiment. Once the recipe was found, the total volume of all-purpose flour was determined. 10%, 20%, and 30% of the flour was calculated and then 10%, 20%, and 30% of wheat was also calculated as the replacement to the removed flour. This was the only variation that needed to be made amongst the four different cakes. The ingredients for the cakes varied slightly based on specific cake. All four cakes; control, 10% wheat, 20% wheat, and 30% wheat, had the same amount of granulated sugar, baking powder, salt, whole milk, vegetable shortening, vanilla extract and eggs. Specifically, each cake included g granulated sugar, 8.05 g baking powder, 3.04 g salt, g whole milk, g vegetable shortening, 2.10 g vanilla extract, and g eggs. Each cake contained different amounts of flour and wheat. The control cake had all-purpose flour and 0.00 g wheat, the 10% wheat cake had g all-purpose flour and g wheat, the 20% wheat cake had g all-purpose flour and g wheat, and the 30% wheat cake had g all-purpose flour and g wheat.
4 Once the ingredients were determined, the cakes were ready for preparation. The flour, wheat (for the non-control cakes), sugar, baking powder and salt were all weighed out in grams and then added to mixer. The dry ingredients were mixed together for 30 seconds on speed 1. After that, the milk, shortening and vanilla were weighed out in grams and mixed for 120 seconds on speed 3. After 60 seconds of mixing the mixer was stopped to allow the bowl to be scraped down followed by 60 additional seconds of mixing. Next, the eggs were weighed out and added to the mixture. This was mixed for 90 seconds at speed 3. After 60 seconds the mixer was stopped and the bowl was scraped down and then mixing was resumed for a following 30 seconds. Once the batter was prepared it was poured into an ungreased 8 inch square cake pan. Each cake was then baked at 177 C for 30 minutes. After 30 minutes of baking, each cake was cooled for 20 minutes. To test each sample, a square slice from the center of each cake was cut and removed. The center of the cake was used in each variable for testing to keep the tests as similar as possible. It is possible that the texture or water activity could vary from the center to the edge of the cake so consistently testing from the center helped to reduce other variations in the sample beyond the wheat substitution. For each slice, the crust on the top of the cake was removed before it was tested for texture and water activity. The cone probe was used on the texture analyzer machine and the reference food for the texture analyzer was set to cake. A test run was completed four times for each sample. Each time the cake was repositioned to allow a different portion of the cake to be tested. The average of the four readings was determined and used as the texture reading for each cake.
5 The sample cake slice was used in the water activity machine. The test cups were filled half-way full with crumbs from each cake sample. The cup was then placed in the machine and the water activity was determined. This procedure was repeated two times for each cake sample. For each repetition, a different cup and with different crumbs from the same cake sample was used. The average of the two readings was calculated and used as the water activity for that specific cake. Each cake was set out and portioned into slices for people to evaluate based on a hedonic scale. The scorecard included four hedonic scales for the evaluation. The hedonic scales were for appearance, moistness, mouthfeel/texture, and flavor. The scorecard also included a place to rank the four cakes from most prefer to least prefer. However, several evaluators did not complete this portion so it was omitted from the final analysis. For the hedonic scales, there were seven different descriptions for the evaluator to choose from. For appearance the scale ranged from very desirable to very undesirable, for moistness the scale ranged from very moist to very dry, for mouthfeel/texture the scale ranged from very desirable to very undesirable, and for flavor the scale ranged from strongly like to strongly dislike. For quantitative purposes, each ranking was assigned to a numerical value. The most desired characteristic received the number 7 and the least desired characteristics received the number 1. The average of each cake was determined based on the numerical averages. This entire procedure was duplicated three times. The average between the three trials was determined for the final analysis. DISCUSSION
6 Water Activity Water activity decreased as the percentage of wheat substituted for allpurpose flour increased. The control cake, with no wheat, had the greatest water activity and the 30% wheat cake variation had the lowest water activity. As the amount of wheat substitution increased, the amount of free water decreased. This change could be due to the variation in nutrient content of the wheat. Wheat contains greater amounts of fat, protein, sugar, minerals, and fiber than all-purpose flour that is made from refined flour (Al-Hooti 2002). As the amount of wheat in the products increases, the concentration of these nutrients also increases in the food products. The greater amounts of these nutrients can bind the available water, thus lower the water activity. Texture Analyzer Texture changed as the percentage of wheat changed in each cake variable. There was not a linear relationship between wheat concentration and texture measured in force by the texture analyzer. The 20% wheat cake required the least amount of force to compress it, followed by the 30% wheat cake, then by the control, and the 10% wheat cake required the most force. The of the wheat grain can be made up of as much as 27% of protein (Hlynka 1964). As the amount of wheat in the same sample increases, the amount of protein also increases in the sample. Gluten is a protein complex that is in flour products when water and protein from the flour are mixed (Lauterbach 1995). Gluten makes flour products less tender and would increases the amount of force needed to compress the cake sample. Based on this concept, it would be expected that as the percentage of wheat increases in a
7 variable, the more gluten that would form, and the more tough it would become. However, the higher amount of sugar and fat in the wheat can also interact with the water and cause reduction in the amount of water available to interact with the protein and form gluten. The interaction of sugar and fat in the gluten formation can decreases the amount of gluten formed and reduce the amount of force needed to compress the cake variation. Based on the results of the three trials, no conclusive trend was found in terms of percentage of wheat and tenderness of the cake measured in the amount of force required to compress the samples. A study published in the 2002 Nahrung/Food Journal examined how adding wheat to pan bread affected the texture of the bread product. This study included a control, a 10% wheat bread, and a 20% wheat bread. The results of this study showed that as the amount of wheat increased in the cake, the amount of force needed to compress the bread also increased (Al-Hooti 2002). This trend did not occur in this current cake study. Possible problems contributing to this could have been if the amount of mixing for each batter was slightly different between the variations. The time of mixing was set in terms of seconds and was monitored using a wall clock. Each cake was supposed to be mixed for the same amount of time but it is possible that some batters were mixed slightly more or less than others due to error. The more mixing that the batter went through, the greater the chance of it forming gluten and this could have been a reason for the results to be incorrect. Sensory Evaluation
8 The sensory panel evaluated the four cake samples for appearance, moistness, mouth-feel/texture, and flavor. For appearance the control cake was evaluated as most desirable and the 20% wheat was evaluated as least desirable. For moistness, the 10% wheat cake was evaluated as the moistest and the 30% wheat cake was evaluated as the least moist. For mouth-feel/texture, the control cake was evaluated as the most desirable and the 30% wheat was evaluated as the least desirable. Finally, for flavor, the control cake was evaluated as the most liked flavor and the 20% wheat cake was evaluated as the least liked product. None of the variations were evaluated as the most desirable product for all four evaluation criteria and none of the variations were evaluated as the least desired product for all four evaluation criteria. The control cake did rate the highest for three of the four evaluations and the 20% and the 30% variations both rated as the least desired for two of the evaluations. None of the samples received very undesirable evaluations for any of the sensory tests. The results of the sensory panel show that there are variations in the sensory qualities of each of the sample, with the control cake having the greatest overall sensory quality rating and the 20% and 30% products matching for the lowest overall sensory quality rated products. However, since none of the evaluations were strongly negative, it can be concluded that all four variables, control, 10% wheat, 20% wheat, and 30% wheat, are all acceptable products in terms of sensory quality. A study published in the Nahrung/Food Journal examined how the inclusion of wheat into sponge cakes affected the sensory quality of the cake in terms of tenderness. Three cakes were made in the study; one was a control, and two were diabetic cakes. Of the two diabetic cakes, one had wheat added and the other did
9 not. Based on the sensory testing, the control had the greatest evaluation and the two diabetic cakes had lower ratings. However, of the two diabetic cakes, the one made with wheat great had a slightly higher rating than the one made without wheat (Baeva 2000). Possible error in the sensory test could be from several causes. It is possible that people may have mixed up the samples when they were testing them and may have recorded their evaluations wrong. Also, the overall acceptability of the products could have varied from tester to tester based on how hungry they were or how much they personally like or dislike basic yellow cake. The testers were not trained sensory evaluators and may have recorded their evolutions inaccurately. The different variations of the basic yellow cake did results in cakes with different water activity, tenderness, and overall sensory qualities. Changing the composition of the cake batter to include wheat in substitution of 10%, 20% and 30% of the allpurpose flour did change the physical and sensory qualities of the cake. However, despite the changes that did occur, the different variations remained acceptable products. Altering a cake batter to include wheat in substation of up to 30% of the all-purpose flour would be an acceptable way to increase the overall nutrition of common foods such as a basic yellow cake. There are several avenues of future research that can be done to expand on this concept. Further increasing the percentage of wheat beyond 30% would be interesting to test to see how great the percentage of wheat can be in a cake before the sensory qualities become undesirable. Also, substituting all-purpose flour for wheat bran and even wheat flour would be important to see if further nutrient changes can be
10 made in flour based foods such as cake to increase the nutrient content. Furthermore, since the amount of gluten formation is expected to increase as the protein content increases, it would be interesting to test if a batter made with a greater percentage of wheat but that was mixed for less time would compare in texture and tenderness to a control product that was mixed for a greater amount of time. RESULTS Table 1.0 Water activity of basic yellow cake decreases as the percent of wheat replacing all-purpose flour increases. Test Trial 1 Trial 2 Trial 3 Average Control % wheat % wheat % wheat Control 10% wheat 20% wheat Cake Variation 30% wheat Figure 1.0 Effect of wheat replacement for all-purpose flour in basic yellow cake on water activity of cake. Water activity decreases wheat concentration increases. Table 2.0 Texture of basic yellow cake measured in force (g). Force is the greatest when 10% of all-purpose flour is replaced with 10% wheat, followed by control cake, followed by 30% wheat cake, and finally with 20% wheat cake. The 20% wheat is the most tender product. Test Trial 1 Trial 2 Trial 3 Average Control % wheat
11 20% wheat % wheat Control 10% wheat 20% wheat Cake Variation 30% wheat Figure 2.0 Effect of wheat substitution for all-purpose flour in basic yellow cake on texture as measured by force. Table 3.0 Sensory evaluation of the appearance of basic yellow cake with 10%, 20%, and 30% of the allpurpose flour substituted with wheat as evaluated on a hedonic scale. Control cake was rated as the most desirable appearance, followed by 10% wheat cake, 30% wheat cake, and finally with 20% wheat cake receiving the lowest rating. Trial 1 Trial 2 Trial 3 Average Control % wheat % wheat % wheat Control 10% wheat Cake Variation 20% wheat 30% wheat Figure 3.0 Effect of wheat substitution for all-purpose flour in basic yellow cake on appearance as measured by sensory evaluation. Control cake was rated as most desirable appearance and 20% wheat cake had the lowest rating.
12 Table 4.0 Sensory evaluation of the moistness of basic yellow cake with 10%, 20%, and 30% of the all-purpose flour substituted with wheat as evaluated on a hedonic scale. 10% wheat cake was rated as the moistest product, followed by control cake, 20% wheat cake, and finally with 10% wheat cake receiving the lowest rating. Trial 1 Trial 2 Trial 3 Average Control % wheat % wheat % wheat Control 10% wheat 20% wheat Cake Variation 30% wheat Figure 4.0 Effect of wheat substitution for all-purpose flour in basic yellow cake on moistness as measured by sensory panel. 10% wheat cake was rated as the moistest and 30% wheat cake was rated as the least moist. Table 5.0 Sensory evaluation of the mouthfeel/texture of basic yellow cake with 10%, 20%, and 30% of the allpurpose flour substituted with wheat as evaluated on a hedonic scale. Control cake was rated as having the most desirable mouthfeel, followed by 10% wheat cake, 20% wheat cake, and finally with 30% wheat cake receiving the lowest rating. Trial 1 Trial 2 Trial 3 Average Control % wheat % wheat % wheat
13 Control 10% wheat Cake Variation 20% wheat 30% wheat Figure 5.0 Effect of wheat substitution for all-purpose flour in basic yellow cake on mouthfeel/texture as measured by sensory panel. Control cake was rated as the most desirable mouthfeel and the 30% wheat cake was rated as the least desirable. Table 6.0 Sensory evaluation of the flavor of basic yellow cake with 10%, 20%, and 30% of the all-purpose flour substituted with wheat as evaluated on a hedonic scale. Control cake was rated as having the most desirable flavor, followed by 10% wheat cake, 30% wheat cake, and finally with 20% wheat cake receiving the lowest rating. Trial 1 Trial 2 Trial 3 Average Control % wheat % wheat % wheat Control 10% wheat Cake Variation 20% wheat 30% wheat Figure 6.0 Effect of wheat substitution for all-purpose flour in basic yellow cake on flavor as measured by sensory panel. Control cake was rated as the most desirable flavor and the 20% wheat cake was rated as the least desirable.
14 REFERENCES Lauterbach S. and Albrecht JA Functions of baking ingredients. The University of Nebraska-Lincoln Cooperative Extension, Institute of Agriculture and Natural Resources. Al-Hooti SN, Sidhu JS, Al-Saqer JM, and Al-Othman A Effect of raw wheat addition on the physical texture and objective color of a designer food (pan bread). Nahrung/Food 46(2): Hlynka I Wheat chemistry and technology. American Association of Cereal Chemists. St. Paul, MN. Baeva MR, Panchev IN, and Terzieva VV Comparative study of normal and energy reduced sponge cakes. Nahrung/Food 44(4):