The development of brownies with substituted avocado for fat, to increase fiber and healthy fat intake for optimal nutrition Kelly Schreuder and Kelcie Walters Daniel NUTR 453
Abstract: Avocado is a good source of fiber as well as healthy unsaturated fat. Fiber is good for colon health while the unsaturated fat can be good for promoting heart health. By replacing the oil in brownies with avocado puree, brownies can be a lot healthier for consumption. Three variables of brownie recipes were prepared. There was a control, which followed the normal recipe on the box, with all oil used. Half of the amount of oil was substituted with avocado puree for the first variable. Finally, all of the oil was substituted with avocado puree for the second variable. The Texture Analyzer was used to measure compression, the Water Activity System Meter was used to measure water activity and the Hunter Colorimeter was used to measure color of the brownies to determine if there was a difference between the different variables. A sensory panel was also used to evaluate flavor, texture and appearance on a hedonic scale. Overall, the results show that avocado cannot be used as a fat replacer in brownies and the consumer will still accept the product. The control and both the 50% and 100% replacement showed significant difference for all four measurements (color, texture, water activity and hedonic scale). This means that avocado puree cannot be substituted for oil in brownie recipes, because it can affect the objective and subjective measurements. Introduction: The reason for performing this experiment is to help Americans consume more fiber in their diet, while also allowing for an increase in good fat intake. Avocado is an ingredient that can accomplish these things. If avocado can be added to a food that consumers already enjoy, while keeping a likable flavor, color, water activity and texture, then consumers are more likely to consume this product with the added benefits. In an article posted on the Nutrition Journal page, it was reported that, Avocado consumers had significantly higher intakes of vegetables (p < 0.05); fruit, diet quality, total fat, monounsaturated and polyunsaturated fats, dietary fiber, vitamins E, K, magnesium, and potassium (p < 0.0001); vitamin K (p = 0.0013); and lower intakes of added sugars (p < 0.0001) (Fulgoni, 2013). By being more likely to eat avocados, a person can improve their overall health with these added benefits. In a study found on PubMed, researchers substituted saturated fat for unsaturated fat, in order to raise HDL (good fat) and lower LDL (bad fat). The added benefits of this include, The reduction of saturated fat in the diet is associated with a lipoprotein profile that would be expected to reduce cardiovascular risk. The reduction of dietary saturated fat with partial replacement of unsaturated fat brings about
changes in total cholesterol, HDL- and LDL-cholesterol that are associated with a lower cardiovascular risk (Mendis, 2001). By changing which type of fat one ingests, it can have many positive health benefits. In order to help Americans consume more avocados, it will be used as a substitute for oil in brownies. For this experiment to be successful, it would need to be able to give the consumer an appropriate amount of dietary fiber based on daily needs and also still taste, look and feel like a regular brownie. Brownies are a common dessert in America and can be made healthier with the substitution of avocado for fat. A study posted on the Journal of Food Quality, had positive results when changing the fat in cookies, Because overall acceptability was unchanged and the substitutions improved the nutritional content, the results are positive and showed that both avocado and Oatrim at 50% fat substitution are capable of producing acceptable cookies. With the 50% level of fat replacement, the total fat content for the avocado and Oatrim cookies decreased by 35 and 39%, respectively (Navder, 2008). This shows that even with changing a main ingredient in a food, the consumer can prefer it more, while also getting added nutritional benefits. The substitution of avocado for fat in brownies will cause changes in flavor, appearance and water activity and texture. While researching, there was information on texture and flavor characteristics of using avocado as a substitute. However, there was no information found on the effect of color on the brownies. Also, some of the information found was only found on cookies or other products and not on brownies. This information will need to be answered by the experiment in order to make a conclusion regarding these. In order to measure if the consumer likes the brownie, a Hedonic scale will be used. Flavor would change due to the substitution of one ingredient for another. Oil and avocados both have fat, but they taste completely different on their own. This could cause a flavor change in the brownies. Color was also hypothesized to change because of the different colors between the oil and avocados. When mixing the brownie mix and the avocado, it is likely to take on a green color. This will need to be measured by the experiment. The water activity of the brownie is likely to change based on the moisture content in avocados. Avocado is a fruit and fruits tend to have higher water content than other foods. Finally, the texture analyzer will be used to measure compression and overall texture. The product s texture is likely to change due to the added water. Water activity and texture results are shown here when avocado was
used in cookies, Both fat replacers had significantly higher water activities compared with the control. Water activity was significantly higher in avocado cookies compared with both the control and the Oatrim cookies. Consequently, the avocado cookie had a softer texture compared with the Oatrim or the control (Navder, 2008). By adding the avocado to the brownies the water activity will increases as well as producing a softer texture. These dependent variables will be studied by the experiment using the independent variables discussed below. The experiment will be done by making a control with the same amount of oil that is on the box. This allows a comparison to be made between the variables, to see if it would be more or less preferred over the others. For the control the directions on the box will be followed. The first variable will be taking half the amount used for the control of oil and the other half from mashed and pureed avocado. This will give an in between value to see if some avocado is preferred over none or all avocado. For the first variable, the same directions will be followed except for the oil where it will be halved and combined with avocado. Finally, the second variable will use the entire amount of oil but as mashed and pureed avocado instead. This will determine if there are differences between the control and this variable as well as if it will be preferred more. For the second variable, the same directions will be followed except all of the oil will be substituted with avocado. The procedure for the control is standard and there are many recipes with avocados used in brownies. However, the recipe for half oil and half avocado is somewhat different, but will help see changes between the two. It was decided to use the half oil and half avocado variable due to not wanting to change texture too drastically and by looking at the other variables that would be affected from the change. Methods: Overall Design: This experiment used three trials with a control and two different variables. The control was made with the standard recipe on the Pillsbury brownie mix box with the addition of eggs, oil (120 ml) and water. The first variable included the Pillsbury brownie mix box and the necessary ingredients with the substitution of half of the oil with avocado puree. This variable contained 60 ml of oil and 60 ml of avocado puree. The second variable used the same recipe on the Pillsbury brownie mix box with the substitution of 120 ml of mashed avocado for the oil. Three trials were performed for each of the variables and the control. Each recipe was baked at the same temperature for the same amount of time to allow for consistency.
Preparation Technique: All variables and trials were baked at 176º C. While the oven is heating, grease three pans and set them aside. Next, combine ingredients according to Pillsbury brownie mix in a mixing bowl with a rubber spatula. Pour into pan. For the second variable, combine ingredients according to Pillsbury brownie mix in a mixing bowl with a rubber spatula with the exception of the oil. Replace half of the oil (60 ml) with 60 ml of mashed avocado and place into the second pan. Combine ingredients according to the Pillsbury brownie mix in a mixing bowl with a rubber spatula with the substitution of the avocado for oil (120 ml), place in the third pan for the third variable. Bake all pans for about 28-31 minutes or until done. Remove all pans from the oven and let cool 2-3 minutes. Cut into uniform squares and label properly for sensory panel. Clean-up workstations and wash dishes used. Randomization and Sampling: Variables will be controlled by closely monitoring the temperature of the oven. The time the brownies are baking will be consistent for all of the batches using oven timers. Mixing procedures will remain consistent across all three variables with the same technique used on each brownie and with the same instruments. For the sensory panel, the brownies will measure to about 1.5 x 1.5 squares to create enough samples for tests. All of the samples will have random 3-digit numbers to use instead of their ingredients. The samples should be presented in the same way with the same plates and utensils. The panel testing the samples will be the classmates present in lab during the procedure. The sensory scorecard is used to determine which one is preferred more by the sensory panel. Objective Measurements The Water Activity System Meter will be used to measure related moisture. The sample should be placed in the system drawer, closed, and the knob turned to READ. Record the reading displayed on the screen for data. The Hunter Colorimeter will be used to measure color and must be calibrated with a black and white tile before testing the sample. The sample should be placed on the dish and record the Master Color Data needed. To use the texture analyzer, the settings on the computer should be on the cake setting (shown below) and ensure that the cone probe is set about one centimeter above the brownie sample. Select T.A. and then quick run test. When the test has finished, record the force, in grams, for data. Each objective test should be replicated three times for each variable.
Texture Analyzer Cake Settings: Cake Pre-Test Speed 1 mm/sec Test Speed 1 mm/sec Post-test speed 1 mm/sec Distance of Penetration 3 mm Trigger Force 1 gram Variables: 1. The recipe on the Pillsbury brownie mix box for the control: 1 box of Pillsbury Brownie mix 2 eggs- whole 120 ml oil 60 ml water 2. To make the half oil and half avocado recipe, half the amount of oil on the box will be used and the other half will come from avocados: 1 box of Pillsbury Brownie mix 2 eggs- whole 60 ml oil 60 ml mashed avocado 60 ml water 3. To make the all avocado recipe, the amount of oil that the box calls for will be replaced by avocado in the same amount: 1 box of Pillsbury Brownie mix 2 eggs- whole 120 ml mashed avocado 60 ml water Sensory Scorecard: Instructions: Please taste all of the samples. Please mark which statement to agree with based on overall FLAVOR, TEXTURE and APPEARANCE for each of the samples.
548 652 287 _Like extremely _Like extremely _Like extremely _Like very much _Like very much _Like very much _Like moderately _Like moderately _Like moderately _Like slightly _Like slightly _Like slightly _Neither like nor dislike _Neither like nor dislike _Neither like nor dislike _Dislike slightly _Dislike slightly _Dislike slightly _Dislike moderately _Dislike moderately _Dislike moderately _Dislike very much _Dislike very much _Dislike very much _Dislike extremely _Dislike extremely _Dislike extremely Comments: Discussion: The null hypothesis for this experiment was that the substitution of avocado for fat in brownies will have no effect on flavor, appearance, color, water activity and texture. This experiment was replicated three times with a control and two variables, while keeping the procedures and techniques as similar as possible to prevent errors. Each trial went through subjective and objective testing. The objective testing was done in triplicate while the subjective testing was done multiple times to produce accurate data. If the null hypothesis were true, this would allow brownies to be prepared with avocados to increase fiber and healthy fat intake for consumers. The first objective test measured was the color of the brownie through the use of the Hunter Colorimeter. Table and Figure 1 show the different reflective values measured by the Hunter Colorimeter. The different values are explained here, L* is the luminance or lightness component, which ranges from 0 to 100, and parameters a* (from green to red) and b* (from blue to yellow) are the two chromatic components, which range from -120 to 120 (Leon, 2006). The greatest L value is seen in the variable with 100% replacement of oil, followed by 50% replacement and then the control variable with the lowest L value. From this, the brownie with all avocado puree was the lightest; while the brownie will all oil was the darkest. The variable with all avocado also had the highest a and b values indicating it contained the most red and
yellow. The 50% replacement brownie values for a and b were in-between the control and the all avocado. The control had the lowest a and b averages indicating the most green and blue color. As more avocado puree was added, the brownie became lighter and had more red and yellow colors to it. There was no significant difference between the 50% replacement and the 100% replacement (p > 0.05), but there was significant difference found between the control and the 50% replacement and the control and the 100% replacement (p > 0.05). There is a notable difference in color between the control and both the 50% and 100% replacement brownie, meaning that a certain threshold level was met to produce this change. Experimental error in this section could be due to the area of the brownie that was tested by the Hunter Colorimeter. Each sample was tested three times in different areas, so depending on the area chosen the color could be different. Also, it is important to ensure that the brownie covers the entire region, being read by the Hunter Colorimeter. The second objective test measured was the texture of the brownie by using the texture analyzer. Table and Figure 2 show that the control variable had the highest average force needed to compress the brownie. The 100% replacement brownie was in the middle and the 50% replacement had the lowest average force needed to compress the brownie. The values for the 100% and 50% were very close, leading to the conclusion that the addition of avocado caused a softer texture. By having a softer texture, less force is needed to compress the brownie. This was also seen in experiment where avocado was used as a fat replacer for cookies, Control cookies had significantly higher initial stiffness compared with both the avocado and the Oatrim cookies (as measured by the gradient in Fig. 1). This indicated that the control cookies had stiffer crusts compared with the fat-replaced cookies (Navder, 2008). The samples had inconsistent results when texture was measured. The significance levels could not be calculated based on these results. A source of error in this test could come from the calibration and the accuracy of the texture analyzer and the size of each sample. Each test was done at different parts of the brownie, which can cause inaccuracies with the data. This experiment should be replicated to be able to draw conclusions from the data based on texture. The third objective test measured the water activity of the different brownies. Water activity is important when studying texture and can also be helpful in determining spoilage. If there is a lower water activity then bacteria and mold cannot grow as well. This also means the sample can stay on the shelf longer. Table and Figure 3 show the water activity for each of the
three samples. The variable with 100% avocado had the highest average water activity at about 0.8. The variable with 50% avocado had the next highest average water activity and the control variable had the lowest water activity at about 0.6. There were significant differences between the control and the 50% and also the control and the 100%, but there no significant difference between the 50% and 100% replacement brownies (p > 0.05). A similar experiment had the same results, Both fat replacers had significantly higher water activities compared with the control. Water activity was significantly higher in avocado cookies compared with both the control and the Oatrim cookies. Consequently, the avocado cookie had a softer texture compared with the Oatrim or the control (Navder, 2008). The portion of the brownie that was used for the testing could cause errors. Middle pieces could react differently than the outer pieces would. There was an attempt to use the middle pieces as much as often for testing. The subjective tests are used to help determine texture, flavor and appearance acceptance amongst the different samples. Table and Figure 4 show the sensory evaluations for taste, texture, and appearance of the brownies. Participants were asked to sample each variable and pick the statement they agreed with the most for each sample on the sensory score card for each trial. The control variable had the highest rating at about 8 on the Hedonic scale. The variable with 50% replacement was the second highest at about 7. The lowest scoring variable was the 100% replacement brownie. As the amount of avocado increased in the samples, the rating of the brownie decreased. There was a significant difference (p > 0.05) between all of the variables. This means the consumer saw a difference between the variables overall and therefore preferred one over the other. This was not shown in a similar study, No significant differences were seen in overall acceptability. Mean scores were between 4 (like) and 3 (neither like nor dislike), indicating that all cookies were liked to some degree. Our preliminary study with avocado puree at 25, 50 and 75% replacement levels had shown no significant difference between the control, 25 and 50% replacements, but the 75% substitutions were rated significantly different (Navder 2008). Errors include subjects who knew something was substituted or could visually see avocado in the brownie. The purpose of this experiment was to see if substituted avocado for oil in brownies would cause a difference in the flavor, appearance, color, texture and water activity between the different variables. It was determined that the brownies with more avocado puree were lighter and had more red and yellow colors. Results show that when more avocado puree was added,
the brownie became softer. Also, there was a significant difference in water activity between the control and both the 50% and 100% replacement brownie. The final taste results show that there was a significant difference between all of the samples. Overall, the results show that avocado cannot be used as a fat replacer in brownies and the consumer will still accept the product. The control and both the 50% and 100% replacement showed significant difference for all four measurements (color, texture, water activity and hedonic scale). This means that avocado puree cannot be substituted for oil in brownie recipes, because it can affect the objective and subjective measurements. For these, the null hypothesis was proven incorrect based on significant difference between the samples. However, the null hypothesis was proven accurate between the 50% and 100% replacement since it is not significantly different for the color and water activity. This experiment should be repeated to see if it can open up the possibility for avocado to be substituted for oil in brownies and other products while keeping consumer acceptance with the flavor. Putting avocado into everyday foods is a good way to increase fiber and healthy fat intake (increases HDL cholesterol), while decreasing LDL cholesterol. Increasing the amount of avocado consumed by the population can help reduce cardiovascular disease and promote colon health. In the future more work could be done to find the level that avocado can be substituted for oil without negatively affecting consumer acceptance. Avocados can be introduced into other foods to see if it can provide functional components without compromising the flavor. Foods that it could be used in include cakes, cookies and other baked goods. Results: Table 1: Reflectance values of brownies measured by the Hunter Colorimeter Hunter Colorimeter Trial 1 Trial 2 Trial 3 Averages SD Variable L a b L a b L a b L a b L a b Control 14.65 6.09 4.86 11.94 6.74 5.97 14.68 7.48 6.56 13.76 a 6.77 c 5.80 e 1.42 0.62 0.77 50% 17 8.3 6.68 17.37 9.08 7.5 18.63 10.44 10.11 17.67 b 9.27 d 8.10 f 0.75 0.94 1.56 100% 21.18 9.61 9.12 19.78 9.91 8.95 16.74 8.75 7.8 19.23 b 9.42 d 8.62 f 1.97 0.63 0.63 Note: Averages not bearing the same superscript are statistically significantly different, p < 0.05
25 Hunter Parameter Value 20 15 10 5 0 L Value a Value b Value Hunter Parameter Figure 1: Average Reflectance Values of Brownies Control 50% 100% Table 2: Compression of brownies measured by Texture Analyzer Texture Analyzer Variable Trial 1 Trial 2 Trial 3 Averages SD Control 14.7 15.6 253.6 94.63 148.85 50% 10.6 51.3 19.3 27.07 55.57 100% 39.87 50.4 12.6 34.29 20.24 Note: Post tests were not calculated because the P value > 0.05 (0.3534) 300 250 Force (g) 200 150 100 50 0-50 -100 Fat Replaced Figure 2: Average Compression of Brownies Control 50% 100%
Table 3: Water Activity of brownies measured by Water Activity Machine Water Activity Variable Trial 1 Trial 2 Trial 3 Averages SD Control 0.656 0.718 0.622 0.665 a 0.05 50% 0.676 0.706 0.822 0.735 b 0.07 100% 0.755 0.791 0.823 0.790 b 0.04 Note: Averages not bearing the same superscript are statistically significantly different, p < 0.0.5 Water Activity 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Fat Replaced Control 50% 100% Figure 3: Average Water Activity of Brownies Table 4: Average values from Sensory Evaluation based on overall flavor, texture and appearance Sensory Evaluation Variable Trial 1 Trial 2 Trial 3 Averages SD Control 8.5 8.4 8 8.3 a 0.8 50% 7 7 7.8 7.27 b 1.45 100% 5.75 6.4 7 6.38 c 1.43 Note: Averages not bearing the same superscript are statistically significantly different, p < 0.0.5
Average Value 10 9 8 7 6 5 4 3 2 1 0 Control 50% 100% Fat Replaced Figure 4: Average Overall Satisfaction of Brownies References: 1) Davenport, A., Dreher, M., & Fulgoni, V. 2013. Avocado consumption is associated with better diet quality and nutrient intake, and lower metabolic syndrome risk in US adults: results from the National Health and Nutrition Examination Survey (NHANES) 2001-2008. Nutritional Journal, 21:1. 2) Leon, K., Mery, D., Pedreschi, F., & Leon, J. 2005. Color measurement in L* a* b* units from RGB digital images. Science Direct. 3) Mendis, S., Samarajeewa, U., & Thattil, R.O. 2001. Coconut fat and serum lipoproteins: Effects of partial replacement with unsaturated fats. British Journal of Nutrition, 85 (5), 583-589. 4) Weaver, C, & Daniel, J 2003, Equipment guide. In F Clyesdale (Ed.), the food chemistry laboratory: A manual for experimental foods, dietetics and food scientists. 2 nd edition. Boca Raton: CRC Press. 107-132. 5) Wekwete, B. and Navder, K.P. 2008, Effects of Avocado Fruit Puree and Oatrim as Fat Replacers on the Physical, Textural and Sensory Properties of Oatmeal Cookies. Journal of Food Quality, 31:131-141.