The Effect of Egg Substitutes on the Texture and Palatability of Brownies

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1 F&N 453 Food Chemistry Individual Project November 20, 2006 The Effect of Egg Substitutes on the Texture and Palatability of Brownies Rebecca E. Nelson Purdue University, West Lafayette, IN Abstract Vegetarianism is a growing trend in the United States in which many people are choosing not to consume eggs. Eggs are also listed as one of the eight most common food allergens. Therefore, appropriate egg substitutions are necessary for these populations to consume foods traditionally prepared with eggs. Pureed Tofu and ground flaxseed were investigated for their potential to replace eggs in a brownie box mix while providing nutritional benefits from soy protein and omega-3 fatty acids. A texture analyzer, water activity machine, and consumer taste panel evaluated the texture and palatability of brownies made with and without egg substitutes. Objective measures showed no significant different when egg was substituted in brownies, but the consumer panel detected a difference at a significant level. More work is needed to investigate the effectiveness of egg substitutes in varying amounts with different baked goods. Introduction Modifying convenience foods to accommodate the needs of people with restricted diets as well as to improve their nutritional quality was the overall goal for this experiment. A brownie box mix recipe calls for the addition of eggs which poses problems for vegetarians as well as people allergic to eggs. Therefore, substituting eggs with tofu or flaxseed not only eliminates the concern for vegetarians and people with egg allergies, but it also improves the nutritional profile of the brownie with soy protein or omega-3 fatty acids. According to the position paper from the American Dietetic Association, vegetarians constituted 2.5% of the adult population and 2% of adolescents in the United States in Vegans comprised approximately 1% and 0.5%, respectively (JADA 1003). While vegetarian and vegan convenience foods are on the rise in the marketplace, another route to accommodate these growing populations is via altering existing foods. According to Congress, about 2% of adults and 5% of children suffer from food allergies. Eggs are among the eight most common food allergens which account for approximately 90% of all food allergies (FDA 2004). While egg whites are often recommended to substitute for whole eggs in recipes, this method is inadequate for people with egg allergies. The nutritional benefits from incorporating soy protein from tofu and omega-3 fatty acids from flaxseed also account for the justification in substituting these ingredients for eggs. Research substantiates the health claim regarding soy protein consumption and a reduction in heart disease risk. Additional research investigates an association between soy protein and soy isoflavones

2 with bone mass maintenance in women and reducing menopausal hot flashes (IFIC 2005, Soy). Flaxseeds are rich sources of alpha-linolenic acid which falls into the category of omega-3 fatty acids. Diets rich in omega-3 fatty acids are linked to a lower incidence of cardiovascular disease and a positive effect on mental and visual function (IFIC 2005, Omega-3). Egg substitutes that adequately replace eggs in terms of functional and sensory characteristics are necessary for vegetarians and people with egg allergies to enjoy recipes with eggs as an ingredient. Eggs have two main functions in baked goods: binding and leavening. Therefore, egg substitutes in brownies must perform these two roles, with major emphasis on binding and less on leavening. Moisture is another attribute that egg adds to baked goods (Messina and Mangels 2004). Puréed tofu and ground flaxseed are two egg alternatives that can potentially replace eggs in a Duncan Hines Chewy Fudge Brownie Mix, Family-Style. Commercial egg replacers such as Ener-G are available in the market, and these products have proven to be quite effective in baked goods. A particular experiment studied the effects of egg substitutes on the palatability of two types of cookies, and the commercial egg replacer was an acceptable alternative (Totheroh and Ries 2004). While tofu and flaxseed are commonly mentioned on various vegetarian baking websites as well as cookbooks, there is a lack of scientific research investigating the effectiveness of these ingredients as egg substitutes. Due to the functional as well as sensory qualities of eggs, the dependent variables of texture, flavor, and preference are adequate measures in evaluating the outcome of this experiment. The question remains whether puréed tofu and ground flaxseed serve as effective egg substitutes in a box mix for brownies by evaluating the texture and palatability of the control against experimental variables. The objectives of this experiment were three-fold: (1) to produce a brownie with egg substitutes suitable for people with egg allergies and vegetarians who specifically do not consume eggs, (2) to incorporate the health benefits of soy protein from tofu and omega-3 fatty acids from flaxseed into a brownie box mix recipe, and (3) to successfully modify a brownie box mix recipe with egg substitutes which results in palatable brownies with acceptable texture, flavor, and appearance. Methods The brownies were produced from one (21-ounce) package of Duncan Hines Chewy Fudge Brownie Mix, Family-Style. The fudgy brownie recipe on the back of the box was followed. In addition to the entire dry ingredient contents provided in the package, the recipe called for eggs, water, and vegetable oil. The eggs were replaced with tofu and ground flaxseed in the experimental brownies. The egg substitute equivalents for one egg were found on a website adapted from the book Vegetarian Cooking for Dummies by Suzanne Havala (Discovering ). Ingredients: Below are the quantities of ingredients for each variable converted into metric units.

3 Table 1. Quantities of Ingredients for Control Brownies Ingredient Amount One package of Duncan Hines Chewy Fudge Brownie Mix, Family-Style 595 grams Whole eggs 2 large Water 62.5 ml Vegetable oil 125 ml Table 2. Quantities of Ingredients for Tofu Variable Brownies Ingredient Amount One package of Duncan Hines Chewy Fudge Brownie Mix, Family-Style 595 grams Silken tofu, blended 125 ml Water 62.5 ml Vegetable oil 125 ml Table 3. Quantities of Ingredients for Flaxseed Variable Brownies Ingredient Amount One package of Duncan Hines Chewy Fudge Brownie Mix, Family-Style 595 grams Ground flaxseed 11 g Water 125 ml ml Vegetable oil 125 ml Preparation: Standard baking instructions from the box mix were followed for each variable, with slight modifications for the tofu and flaxseed brownies. (1) Preheat oven to 180 C. (2) Grease the bottom of the (33 cm x 23 cm x 5 cm) metal pan with shortening. (2a) (2b) Tofu brownies: Purée tofu in blender until completely smooth. Flaxseed brownies: Whisk together ground flaxseed and 125 ml water in small bowl until gel is formed. (3) Mix all ingredients in a large, room temperature bowl and stir until well-combined, specifically fifty strokes with the spatula. (4) Pour brownie batter into greased baking pan and spread. (5) Bake for 27 to 30 minutes, or until an inserted toothpick comes out clean. Analysis: Three replicates were performed from three trial weeks in which each variable was produced for each trial. The same oven and baking times were also used. The brownies were cooled for thirty minutes before objective and subjective analyses. Each pan of brownies was cut into servings yielding twenty brownies per pan, thus twenty servings per variable. The crust was eliminated from all brownies. A middle serving was analyzed via the texture analyzer with cone probe and

4 cake setting as well as the water activity meter. Ten consumers, all students enrolled at Purdue University, comprised the taste panel and evaluated each brownie for its texture, flavor, and preference. Each brownie variable was assigned a random 3-digit number to reduce bias. An example of the sensory scorecard is included in the Appendix. Texture and flavor were rated on an unstructured category scale with extremes at each end. Preference was ranked (1, 2, 3) according to liking. Averages and standard deviations were obtained using Microsoft Excel, and Paired Samples t-tests were run using SPSS with statistical significance established at p-value of Discussion Tables 4 and 5 and Figure 1 and 2 display the results obtained from the objective analyses for texture and water activity, respectively. The texture analyzer measured the force in grams to penetrate each brownie sample. The egg control corresponded with 31.3 grams of force while the tofu and flaxseed fluctuated from this value. The tofu brownies required more penetrating force at 46.3 grams whereas the flaxseed brownies were softer and only required 18.1 grams of force. It is important to note that the standard deviation for the tofu variable is exceptionally high in that the brownies from trial one were tougher than the subsequent trials. The water activity machine indicated a change in water activity depending on the variable. Once again, the egg brownies results at fell between the other experimental variables with tofu brownies having less water activity and flaxseed brownies having more water activity. These results correlate indirectly to the texture analyzer results as a softer brownie with lower penetrating force is more likely to have higher water activity. Additionally, a harder brownie is likely to be dried out indicating less water activity. Paired samples t-test results from Table 9 indicates no significant difference between the water activities of neither tofu (p-value 0.163) nor flaxseed (p-value 0.616) with the egg control. A significant difference exists between the texture of flaxseed brownies (p-value 0.044) and the control but not with tofu (p-value 0.336). Tables 6 and 7 comprise the data obtained from sensory analyses for texture and flavor, respectively. Figures 3 and 4 graphically display the results. The consumer panel identified the texture of the brownie samples in order of increasing hardness as flaxseed (18.29 mm), egg (43.68 mm), and then tofu (73.42 mm). Lower values corresponded to extremely soft, and higher values corresponded to extremely hard. These results match up to the objective texture analyzer analysis. The flavor of the tofu brownies was least liked at mm followed by the flaxseed brownies at mm. The egg control brownies had the best flavor at mm on the scale marked from extremely dislike to extremely like. Paired samples t-test results from Table 10 indicates significant differences for texture between both flaxseed (p-value 0.000) and tofu (p-value 0.001) brownies with the control. The flavor of the flaxseed brownies were not determined to be significantly different by the consumer panel at p-value 0.052, but the tofu brownies flavor (p-value 0.000) was significantly different than the control brownies flavor.

5 The results displayed in Table 8 indicate the overall preference by the consumers for each brownie sample. Figure 5 graphically depicts the outcome as well. The order of preference from most to least preferred brownies was the egg control, followed by flaxseed, and then tofu. According to AmeriFlax, the trade organization that represents North Dakota flax producers, substituting ground flaxseed for eggs in baked products results in a chewier product with less volume. Additionally, the recommended substitution for one egg is fifteen milligrams (approximately one tablespoon) with forty-five milliliters of water. This ratio differs from that obtained at the vegetarian baking site which was utilized in this experiment (one tablespoon with sixty-two and a half milliliters of water). Altering the substitution may result in a more desirable product which would have less water activity and be chewier like the egg control brownie (Ameriflax website). Silken tofu works best when incorporated into products after being puréed. Additionally, soy products make good substitutes because they provide limited flavor to the finished product. However, the results indicated a significant difference for flavor between the tofu and egg control brownies (SoyFoods.com). This experiment showed that substituting egg with puréed tofu and ground flaxseed with water in brownies did not significantly affect the texture and water activity as measured objectively. The exception to this statement is in regard to the texture of flaxseed brownies. However, the substitutions resulted in significant differences of texture and flavor as determined by a consumer taste panel. The exception to this statement is in regard to the flavor or flaxseed brownies. Discrepancies between the subjective and objective data may exist because the sample size was extremely small (n=3) for statistically analyzing the objective results. Multiple values should have been obtained on the texture analyzer and water activity meter for each variable within the same trial. Nonetheless, the texture and palatability of brownies made with egg substitutes are not as highly accepted by consumers. Future experiments could investigate how the amount of egg substitute affects brownies by varying the ratios of ground flaxseed with water and tofu. Since these products resulted in opposite effects on the brownies in terms of water activity and texture, a combination of the two may be preferred. Furthermore, since commercial egg replacers were acceptable alternatives in cookies, these treatments could be tested in them rather than brownies (Totheroh and Ries 2004). Results Table 4. Effect of Egg Substitute on Texture as Measured by Texture Analyzer (Force in grams) Sample Average Standard Deviation Range Egg Tofu Flaxseed

6 Table 5. Effect of Egg Substitute on Water Activity (Aw) as Measured by Water Activity Machine Sample Average Standard Deviation Range Egg Tofu Flaxseed Table 6. Effect of Egg Substitute on Texture as Determined by a Consumer Taste Panel on an Unstructured Scale from Extremely Soft - Extremely Hard (mm) Sample Average Standard Deviation Range Egg Tofu Flaxseed Table 7. Effect of Egg Substitute on Flavor as Determined by a Consumer Taste Panel on an Unstructured Scale from Extremely Dislike - Extremely Like (mm) Sample Average Standard Deviation Range Egg Tofu Flaxseed Table 8. Effect of Egg Substitutes on Preference as Determined by a Consumer Taste Panel (1-Most Preferred, 3-Least Preferred) Sample Average 1 Average 2 Average 3 Egg Tofu Flaxseed Force (g) Egg Tofu Flaxseed Variable Figure 1. Effect of Egg Substitute on Texture as Measured by Texture Analyzer

7 Aw Egg Tofu Flaxseed Variable Figure 2. Effect of Egg Substitute on Water Activity as Measured by Water Activity Machine 120 Texture Rating (mm) Egg Tofu Flaxseed Variable Figure 3. Effect of Egg Substitute on Texture as Determined by a Consumer Taste Panel on an Unstructured Scale from Extremely Soft - Extremely Hard Flavor Rating (mm) Egg Tofu Flaxseed Variable Figure 4. Effect of Egg Substitute on Flavor as Determined by a Consumer Taste Panel on an Unstructured Scale from Extremely Dislike - Extremely Like

8 7.0 Number of Responses Average "1" Average "2" Average "3" 0.0 Egg Tofu Flaxseed Variable Figure 5. Effect of Egg Substitute on Preference as Determined by a Consumer Taste Panel (1-Most Preferred, 3- Least Preferred)

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10 Statistical Analysis for Objective Data: Table 9. Paired Samples Test for Objective Evaluation of Texture and Water Activity Mean Paired Differences 95% Confidence Interval of the Difference Std. Error Std. Deviation Mean Lower Upper t df Sig. (2-tailed) Pair 1 EggWA - TofuWA Pair 2 EggWA - FlaxseedWA Pair 3 EggTA - TofuTA Pair 4 EggTA - FlaxseedTA Statistical Analysis for Subjective Data: Table 10. Paired Samples Test for Sensory Evaluation of Texture and Flavor Mean Paired Differences t df Sig. (2-tailed) Std. Error 95% Confidence Interval Std. Deviation Mean of the Difference Lower Upper Pair 1 EggText - FlaxText Pair 2 EggText - TofuText Pair 3 EggFlav - FlaxFlav Pair 4 EggFlav - TofuFlav

11 References AmeriFlax. Accessed November 19, American Dietetic Association Position of the American Dietetic Association and Dietitians of Canada: Vegetarian Diets. J Am Diet Assoc 103: Discovering Egg Substitutes For Vegetarian Cooking Accessed September 24, Adapted from Havala S Vegetarian Cooking For Dummies. 360 p. International Food Information Council Functional Foods Fact Sheet: Omega-3 Fatty Acids. Accessed September 24, International Food Information Council Functional Foods Fact Sheet: Soy. Accessed September 24, Messina V, and Mangels R The Dietitian s Guide to Vegetarian Diets: Issues and Applications. 2 nd ed. Sudbury: Jones and Bartlett Publishers, Inc. 587 p. SoyFoods.com. Accessed November 19, Totheroh B, and Ries CP Palatability of peanut butter and sugar cookies made with egg substitutes. J Am Diet Assoc 94(3): U.S. Food and Drug Administration Food Allergen Labeling and Consumer Protection Act of Accessed September 24, Appendix 1. Sensory Scorecard 2. Pooled Subjective Data 3. Raw Data Sheets

12 Sensory Scorecard: Directions: Please taste each brownie sample in front of you. Place a dash along the line that corresponds to the texture of the brownie sample. Sample 344 Extremely Soft Extremely Hard Sample 625 Extremely Soft Extremely Hard Sample 198 Extremely Soft Extremely Hard Directions: Please taste each brownie sample in front of you. Place a dash along the line that corresponds to how much you like the flavor of the brownie sample. Sample 344 Extremely Dislike Extremely Like Sample 625 Extremely Dislike Extremely Like Sample 198 Extremely Dislike Extremely Like Directions: Please taste each brownie sample in front of you. Rank your preference for the brownies on a scale from 1 to 3 with 1 being the most preferred and 3 being the least preferred.. Sample 344 Sample 625 Comments: Sample 198