The Effects of Replacing Butter with Pureed Eggplant on the Quality of Chocolate Chip Cookies

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1 Lauren Doolittle F&N 453 November 19, 2007 The Effects of Replacing Butter with Pureed Eggplant on the Quality of Chocolate Chip Cookies Abstract: Obesity is a huge epidemic in America today. Its high prevalence and association with other major diseases make it a problem worth solving. By consuming more nutrient-dense and less energy-dense foods, Americans may be able to combat this illness. A possible method of reducing caloric intake involves replacing butter in cookies with eggplant. This creates a product that has a significant reduction in calories, as well as the added nutrients found in eggplant. For this experiment, successive amounts of butter were replaced with pureed eggplant in chocolate chip cookies. The flavor, color, and texture were measured subjectively by a taste panel. Color and texture were also measured objectively by a Hunter Colorimeter and Texture Analyzer, respectively. Color was found to remain fairly constant between the variables. Flavor was rated as lower in cookies with more eggplant and less butter. Also, these cookies had a softer texture. Overall, it was found that a healthier chocolate chip cookie can be made with eggplant instead of butter, though a decrease in flavor and rigidity should be expected. Introduction: The American population as a whole struggles with general nutrition and weight management. According to the American Obesity Association, 64.5% of adults in the U.S were overweight or obese in These individuals have an increased risk for chronic diseases such as type II diabetes. They also face social discrimination in areas such as employment. (AOA, 2007) The US Dept. of Agriculture and the U.S Dept. of Health and Human Services, in efforts to increase the overall health of the nation, recommend consuming nutrient-dense foods. These food choices contain high amounts of nutrients in relation to a low amount of energy (calories). The idea is to consume an adequate amount of nutrients to decrease the risk for chronic disease, yet still stay within

2 the range for daily calories. In addition, the Dietary Guidelines recommend consuming no more than 35% of daily calories from fat. (USDHHS and USDA, 2005) This experiment involves developing a chocolate chip cookie product that will help contribute to the health of consumers. Ideally, the new cookie will be more nutritionally dense than previous products. It will contain more nutrients than the control cookie due to the added eggplant, and fewer calories due to a decrease in the amount of butter. The independent variable will be the amounts of butter versus pureed eggplant. The dependent variables are the flavor (as measured by taste panel), color (as measured by taste panel and Hunter Colorimeter), and texture (as measured by taste panel and Texture Analyzer). Eggplant was chosen as the fat replacement because of its health benefits. A 2006 study published in the American Journal of Clinical Nutrition looked at the impact that certain vegetables, including eggplant, have on the risk for metabolic syndrome. The researchers used an observational design. They found that there is a significant inverse association between amount of vegetables consumed and the prevalence of metabolic syndrome. (Esmaillzadeh et al, 2006) Another related study looked at how eggplant affects the cholesterol metabolism of rats. The results showed that when rats are given eggplant with their meals, their cholesterol absorption decreases. This may be due to eggplant s ability to bind bile salts which are used to absorb cholesterol. (Kritchevsky et al, 1975) By replacing butter with eggplant, the total caloric value of the cookie will change. Eggplant has 35 kilocalories per cup, while butter has 1628 kilocalories per cup. (About, Inc., 2007) This large difference in energy will significantly alter the total calories of the cookie when eggplant is used in place of butter. Past studies show conflicting results relating to the acceptability of baked goods made with fat replacers. A study performed in 1996 tested the affects of three different commercially available fat replacers on chocolate chip cookies. The researchers found that consumers rated the flavor of the test cookies lower than the control, which was made with traditional fat. (Charlton et al, 1996) However, another study tested tofu as a

3 fat replacer in shortened cakes. It was determined that up to 50% of the fat in the cakes could be replaced without affecting sensory acceptability. (Power et al, 2007) Texture is of great concern in this experiment, because fat may play a role in creating the texture of baked products. The effect of eggplant on texture is not known. However, the tofu experiment contributes to the confidence of this experiment, considering that tofu and eggplant are both vegetable products. Another concern is the flavor of the cookie, a characteristic important to consumers. Chocolate chip was chosen with the expectation that the strong chocolate flavor will mask any change in flavor by the eggplant. In addition, there is concern about the color of the product. It is not known if cream-colored eggplant will take away from the browning of the product. Methods: The overall design of this experiment involves using a traditional chocolate chip cookie recipe and substituting various amounts of butter with pureed eggplant. The recipe used for this experiment is from Allrecipes ( and is entitled Best Chocolate Chip Cookies. The control recipe is listed below: 115 g butter, softened* 100 g white sugar 110 g packed brown sugar 1 egg 5 ml vanilla extract 190 g all-purpose flour 2 g baking soda 5 ml hot water 2 g salt 170 g semisweet chocolate chips 60 g chopped walnuts * For Test Variable #1, 57.5 grams eggplant and 57.5 grams butter were used instead of 115 grams butter. For Test Variable #2, 115 grams eggplant were used instead of 115 grams butter. The eggplant for the test variables was peeled and diced. Then the seeds were scooped out. The eggplant was placed in a bowl and microwaved for 1 minute. The vegetable was then put into a food processor for 45 seconds in order to puree it. To make the cookies, the oven was preheated to 350 F (175 C). Then, the butter (and/or eggplant in the case of the test variables), white sugar, and brown sugar were creamed together until smooth. Next, the egg was beaten in. The baking soda was

4 dissolved in hot water and added to the batter along with the salt. The flour, chocolate chips, and nuts were stirred in. The cookies were dropped by rounded tablespoon onto a baking sheet greased with PAM, and baked for 11 minutes. After they had cooled for 20 minutes, they were labeled, placed on white paper plates, and subjected to an evaluation by a taste panel of 7 people. The sensory scorecard appeared as follows: Please rank flavor, color, and texture of each cookie based on the following 9 point hedonic scale: For flavor, 0 = extremely unpleasant, 9 = extremely pleasant; for color, 0 = extremely light brown, 9 = extremely dark brown; for texture, 0 = extremely soft, 9 = extremely hard. Variable Flavor Color Texture To ensure randomization, the cookies were labeled as: 986 = Variable #1, 603 = Control, 297 = Variable #2. This was unknown to the taste panel. Also, the plates were placed in a triangle rather than a line. After the cookies had cooled for an hour, their texture was measured objectively by a Texture Analyzer. The machine settings were set to cookie and the knife probe was used. Also, the color of the cookies was measured on a Hunter Colorimeter. To ensure replication, all three cookie variables were baked three times. Each replication was subjectively and objectively evaluated as stated above. Also, to attempt to guard against sampling error, the cookies that were evaluated were taken from the center of the cookie sheet. Discussion: The data suggests that color stayed fairly constant between each of the variables. This is true of both the subjective (See attached: Table 1 and Figure 1) as well as the

5 objective (See Table 2 and Figure 2) data. Subjectively, Variable 2 (all eggplant) had the lightest color, with an average score of 5.90 on a 0 to 9 hedonic scale with 0 being the lightest and 9 being the darkest. The Control (all butter) was only very slightly darker, at Variable1 (½ butter, ½ eggplant) was the darkest at This is consistent with the objective data. The A and B values from the Hunter Colorimeter are fairly constant for each of the three variables. (See Figure 2) The most range between variables is found in the L value which measures degree of lightness. (BYU, 2007) Variable 2 and the Control have similar L values, while the value for Variable 1 is lower. This suggests that Variable 1 has the darkest hue. Color change was a concern in the experiment. It was hypothesized that the light color of the interior eggplant might make the overall color of the cookie lighter. However, the lack of change in color may be due to enzymatic browning of the eggplant. The color may have added to the normal brown color of the cookie. Eggplant contains polyphenols which can undergo enzymatic browning upon slicing and exposure to air to create brown quinones. (Almeida et al, 1995) The reaction is as follows: OH OH polyphenoloxidase ½ O2 + H20 Phenolic Quinone [Figure: (Daniel, 2007)] Flavor varied somewhat between each variable (See Figure 1) Overall, the tastepanel ranked the Control as having the best flavor (at 7.90 on a 0-9 hedonic scale), followed by Variable 1 (at 7.24), and Variable 2 (at 6.28). While the panelists did tend to prefer the Control cookie, Variable 1 was not far behind. This may be due to the strong flavor of chocolate in the cookies, as hypothesized. Also, Variable 1 still contained some butter (half as much as the Control). This may have been enough butter to maintain the flavor.

6 Butter is very important in the flavor of baked products. It enhances the mouthfeel on the palate, contributes its own unique flavor, and also carries other flavors. For example, it can help enhance a cheese flavor in bread. (Hodge, 1986) For chocolate chip cookies, fat may boost the chocolate flavor. This might explain why the Control cookies were ranked as having a better flavor than the cookies with progressively less butter. Texture was also affected by removal of butter and addition of eggplant. (See Figure 1) The taste panel ranked the Control as hardest (at 5.19), followed by Variable 1 (at 4.71). Variable 2 was the softest at This trend is consistent with findings made by the Texture Analyzer. (See Figure 3) These results are somewhat surprising. Typically butter lends softness to a product by interrupting the gluten chains. Without it, baked products tend to be tough and less tender. (Hodge, 1986) Variable 2, which had the least amount of butter, would theoretically be the hardest. However, the eggplant must have contributed more softness to the product than butter does. This may be due to the breakdown of middle lamellar substances in the eggplant upon heating, thus leading to a mushy product. As in any experiment, this one had room for error. For example, the first trial of cookies was baked on an ungreased baking sheet to a lack of supplies. The other two trials used greased baking sheets. This difference in experimental setup may have altered the results. The grease may have had an affect on the texture and flavor of the cookies. Also, Trial 3 cookies had mini chocolate chips whereas the first two trials had regular chips. This was also due to a lack of supplies. The size of chips could have affected the flavor as well as texture of the final products.

7 More experiments should be performed to explore this topic. Some changes could be made in the experimental set-up in the future. For example, dark chocolate chips could be tested against semi-sweet chocolate chips in cookies. Dark chocolate has a stronger flavor and thus might be able to cover up the eggplant taste to create a flavor closer to the Control cookie. Also, other vegetables should be used in place of eggplant. For example, turnips tend not to get as mushy as other vegetables, so they might be able to better retain the texture of the cookie. In addition, variations in the amount of other ingredients could be investigated. For example, by adding more flour there is a potential for more gluten production which would make a harder texture. These ideas should be tested in the future in order to gain a better understanding of this topic. Overall, the experiment was very informative. By replacing butter with pureed eggplant, chocolate chip cookies with a higher nutrient density can be created. These cookies tend to remain the same color and become softer in texture. Also, the subjective rate of the flavor drops slightly in cookies with eggplant instead of butter. As in any experiment, future research and investigation should be performed to learn more on the subject.

8 Results: Table 1: Subjective Evaluation of Cookie Flavor, Color, and Texture, as Measured by 7-Member Taste Panel On a 9-Point Hedonic Scale Trial Average of 3 Trials Variable Flavor Color Texture Mean St. Dev Mean St. Dev Mean St. Dev V1 (986) Control (603) V2 (297) V1 (986) Control (603) V2 (297) V1 (986) Control (603) V2 (297) V1 (986) Control (603) V2 (297) Table 2: Objective Evaluations of Cookie Texture and Color as Measured by Texture Analyzer and Hunter Colorimeter Trial Variable Texture Analyzer (g) Hunter L Hunter A Hunter B V1 (986) Control (603) V2 (297) V1 (986) Control (603) V2 (297) V1 (986) Control (603) V2 (297) Average V1 (986) of 3 Control (603) Trials V2 (297)

9 Average Score on 0-9 Hedonic Scale Flavor Color Texture Category of Evaluation Control (all butter) V1 (1/2 butter, 1/2 eggplant) V2 (all eggplant) Figure 1: Average Subjective Evaluation of Cookies as Measured by 7- Member Taste Panel Using 0-9 Hedonic Scale Value Control (all butter) V1 (1/2 butter, 1/2 eggplant) V2 (all eggplant) 5 0 L A B Hunter Colorimeter Variable Figure 2: Average Objective Evaluation of Color of Cookies as Measured by Hunter Colorimeter

10 Texture Analysis (g) Average of 3 Trials Trial Control (all butter) V1 (1/2 butter, 1/2 eggplant) V2 (all eggplant) Figure 3: Average Texture/Force Resistance of Cookies as Measured by Texture Analyzer

11 References: About, Inc Calorie-Count. Retrieved September 22, 2007 from Almeida, ME and Nogueira, JN The control of polyphenol oxidase activity in fruits and vegetables. Plant Foods for Human Nutrition. Vol. 47. No. 3: pg American Obesity Association Obesity in the U.S. Retrieved September 22, 2007 from Brigham-Young University Food Colorimetry. BYU Food Quality Assurance Laboratory. Retrieved November 16, 2007 from Charlton, Olivia; Sawyer-Morse, Mary Kaye Effect of fat replacement on sensory attributes of chocolate chip cookies. Journal of the American Dietetic Association. Vol. 96. Iss. 12: pg Daniel, James R Enzymatic Browning. Food Chemistry, F&N 453 Lecture Notes. v.3.0. pg. 244 Esmaillzadeh, Ahmad; Kimiagar, Masoud; Mehrabi, Yadollah; Azadbakht, Leila; Hu, Frank B; Willett, Walter C Fruit and vegetable intakes, C-reactive protein, and the metabolic syndrome. American Journal of Clinical Nutrition. Vol. 84. No. 6: pg Hodge, DG Fat in Baked Products. Nutrition Bulletin. Vol. 11. Iss. 3: pg Kritchevsky, D; Tepper, SA; Story, JA Influence of an eggplant (Solanum melongena) preparation on cholesterol metabolism in rats. Experimental Pathology. Vol. 10. No. 3. pg Power, L; Williams, C; Fremont, J; Gupta, N; Samuel, L, Navder, KP Effect of Tofu as a Fat Replacer on Texture of Shortened Cakes. Journal of the American Dietetic Association. Vol Iss. 8: pg. A74. U.S. Dept. of Health and Human Services; U.S Dept. of Agriculture Dietary Guidelines for Americans.