Pumpkin Puree as a Fat Replacer in Brownies

Transcription

1 Pumpkin Puree as a Fat Replacer in Brownies Michelle Wang Jacquie Sullivan FN 453 Written Report 11/22/2010

2 ABSTRACT: Levels of obesity have reached epidemic proportions in the United States. Obesity can primarily be attributed to unhealthy dietary habits, including the overconsumption of high fat foods. Given these circumstances, researchers have begun to focus on ways to reduce the fat content of popular high calorie foods. In particular, several have studied the effectiveness of fruit-based fat replacers. The purpose of this experiment was to evaluate the feasibility of pumpkin puree as a fat replacer in brownies and to determine effects of varying degrees of fat replacement on taste, texture, appearance, and consumer acceptability. Three variations of brownies were baked using a full fat recipe, a recipe that used half fat and half pumpkin puree, and a recipe in which all the fat was replaced with pumpkin puree. Objective measurements were taken to examine the effects on water activity, texture, and color. In addition, subjective testing was also performed to determine the acceptability of the brownies in regards to their taste and appearance. Overall, the brownies with pumpkin puree had a higher water activity and a tougher texture than the full fat control. All of the brownies were significantly different in regards to color. In general, consumers preferred the taste and appearance of the full fat control more so than the variations with pumpkin puree. These findings suggest that although % replacement of fat with pumpkin puree would produce a healthier product, this may not be feasible due to its negative effects on quality. Further research must be done to determine if mixtures of fruit-based fat replacers or alterations in the recipes using fruit purees would produce more acceptable products. INTRODUCTION: Over the last three decades, obesity has become increasingly more prevalent in the United States. Currently, over million Americans are considered to be overweight or obese (American Heart Association 2009). The incidence of obesity can primarily be attributed to unhealthy eating behaviors, such as frequent overconsumption of high fat, energy dense foods (American Dietetic Association 2005). Ultimately, these dietary patterns can lead to increased risk for numerous health problems, including diabetes mellitus and coronary heart disease. In attempts to improve the weight status and overall health of the population, many researchers have focused on developing methods to reduce the fat content of popular high calorie foods (Romanchik-Cerpovicz and others 2002; Swanson and others 2003; Wiese and others 2003).

3 Unfortunately, many baked goods are made healthier while compromising overall quality and consumer acceptability, since fat contributes to both flavor and texture of the final product. In baked goods, fat acts primarily by providing qualities such as tenderness, flakiness, volume, and moisture (Miraglio 1995). When baked goods are mixed, the fat lubricates the batter and coats the proteins glutenin and gliadin to reduce the formation of gluten (Sanchez 1995). The result is a product that is both tender and moist. In addition to contributing to texture, fat also provides flavor that enhances overall palatability of baked goods (Miraglio 1995). Although fat has these desired properties in baked goods, it also contributes substantially to their caloric content by providing 9 kcals for every gram used. Since this can have an unfavorable impact on energy intake, many have attempted to find healthier fat alternatives that can mimic its functions in baked goods without the caloric burden. Fruit-based fat replacers are often used in baking because they are nutrient-rich and have high water content. The water in these foods contributes to moisture and causes aeration during the baking process, which increases volume (Figoni 2010). Given these favorable properties, several researchers have analyzed the effectiveness of using fruit purees as fat replacers. In particular, Wiese and colleagues (2003) and Swanson and colleagues (2003) have assessed the feasibility of using applesauce, prune, and pawpaw fruit purees in various baked goods. Although this research has provided valuable information concerning the use of fruit-based fat replacers, little remains to be known about the feasibility of using other types of purees. The purpose of this experiment was to evaluate the feasibility of pumpkin puree as a fat replacer in brownies and to determine effects of varying degrees of fat replacement on taste, texture, appearance, and consumer acceptability. It was hypothesized that pumpkin would be appealing as a fat replacer due to its physical properties and nutritional benefits. Its creamy texture and high water content may be able to simulate the sensory properties of fat without the excess calories. In addition, pumpkin provides a variety of nutrients and is an excellent source of fiber and the antioxidant β-carotene. Brownies were specifically chosen in this study because they are a sweet indulgence with a high fat content and low nutritional value. Since brownies have a strong chocolate taste, dark color, and dense texture, it was thought that replacement of fat with pumpkin puree would reduce their caloric content while having relatively little impact on their sensory properties. In order to study this hypothesis, three variations of boxed brownie mixes were made with full fat content, half fat and half pumpkin puree, and by completely

4 replacing the fat with pumpkin puree. Objective measurements were taken to measure the effects on texture, water activity, and color. Using a sensory panel, subjective measurements were also used to determine the impact on taste, appearance, and overall acceptability. METHODS: Materials: 3 boxes Duncan Hines Premium Milk Chocolate Brownie Mix (540 g each) 6 eggs (approximately 50 g each) ml water ml Crisco Vegetable Oil 1 (15 oz.) can Libby s 100% Pure Pumpkin Preparation of Brownies: Brownies were prepared according to the instructions on the back of the box for Fudgy Brownies. The recipes are listed below. Three trials of the experiment were performed in one day (using one box of brownie mix for each), and testing was done the following day. Full Fat Control Recipe: 182 g Duncan Hines Premium Milk Chocolate Brownie Mix 33.3 g egg 19.7 ml water 39.4 ml Crisco Pure Vegetable Oil Half Oil/Half Pumpkin Puree Recipe: 182 g Duncan Hines Premium Milk Chocolate Brownie Mix 33.3 g egg 19.7 ml water 19.7 ml Crisco Pure Vegetable Oil 20.3 g Libby s 100% Pure Pumpkin (canned)

5 Full Pumpkin Puree Recipe: 182 g Duncan Hines Premium Milk Chocolate Brownie Mix 33.3 g egg 19.7 ml water 40.6 g Libby s 100% Pure Pumpkin (canned) To begin with, the oven was preheated to C (350 F). Three brownie box mixes were combined and then separated into nine portions of 182 g each. The six eggs were beaten and measured on a scale, then divided into nine equal portions using a graduated cylinder. Then, the following procedure was performed for each of the trails. For the full fat control brownies, 39.4 ml of vegetable oil was added to a portion of brownie mix. For the half pumpkin brownies, 19.7 ml of vegetable oil and 20.3 of pumpkin puree were added to another portion of brownie mix. Finally, for the full pumpkin variation, 40.6 g of pumpkin puree was added to a portion of brownie mix. For each bowl, 19.7 ml of water and 33.3 g of egg were also added. To ensure that all brownies were prepared the same way, all mixtures from the 3 trials were stirred by hand 20 times and then separated into individual loaf pans (5-3/4 x 3-1/4 x 2-1/4 each). All pans were then placed in the oven and removed after 55 minutes (when toothpicks inserted into all the brownies came out clean). After cooling, the brownies were cut to the same size pieces and separated onto plates for objective and subjective analysis. Objective Analyses: Texture, water activity, and color were tested for the objective analysis. A brownie piece from each trial was tested, and the average of the measurements from the three trials was taken. First, the Stable Micro Systems Texture Analyzer was used to measure the grams of force needed to penetrate the brownies. A cone probe was used with a setting of cake. After analyzing texture, the difference in moisture and water content between the brownies was measured using a Water Activity system. Lastly, the Hunter colorimeter was used to assess the differences in color between the three variations. Subjective Analyses For the subjective analyses, the brownies were evaluated using sensory testing. The

6 brownies were assigned the random numbers 547 (full fat control), 869 (half oil/half pumpkin puree), and 103 (full pumpkin puree) to reduce any bias. After being cut to the same size, the brownies were then placed on white paper plates with corresponding labels and were arranged in a triangular formation. Each trial was placed for tasting in approximately 1 hour increments and each panel contained 10 people. The brownies were tasted by fellow students as well as other faculty members present. The sensory evaluation form was presented as follows: Please describe the kind of brownie you prefer: Please circle the phrase or number that applies (5 being the highest, 0 being the lowest for # ratings): Sample 103 Texture Very Dry, Fairly Dry, Slightly Dry, Not Dry or Moist, Slightly Moist, Fairly Moist, Very Moist Not Chewy, Slightly Chewy, Fairly Chewy, Very Chewy Taste Appearance Sample 547 Texture Very Dry, Fairly Dry, Slightly Dry, Not Dry or Moist, Slightly Moist, Fairly Moist, Very Moist Not Chewy, Slightly Chewy, Fairly Chewy, Very Chewy Taste Appearance Sample 869 Texture Very Dry, Fairly Dry, Slightly Dry, Not Dry or Moist, Slightly Moist, Fairly Moist, Very Moist Not Chewy, Slightly Chewy, Fairly Chewy, Very Chewy Taste Appearance Please rank the samples based on overall preference (1= most preferred, 3=least preferred). Sample 103 Sample 547 Sample 869

7 RESULTS: Objective Analyses: Table 1: Effect of Fat Replacement with Pumpkin Puree on the Water Activity of Brownies Full Fat Control Half Pumpkin Puree Full Pumpkin Puree Trial Trial Trial Average a a,b b Standard Deviation Water Activity (Aw) a,b b a Full Fat Control Half Pumpkin Full Pumpkin Brownie Variation Figure 1: Average Water Activity Measurement for Each Brownie Variation

8 Table 2: Effect of Fat Replacement with Pumpkin Puree on the Texture of Brownies as Measured by the Texture Analyzer (g of Force) Full Fat Control Half Pumpkin Puree Full Pumpkin Puree Trial Trial Trial Average 32.2 a 36.8 a 69.4 b Standard Deviation (Averages not bering the same superscript are statistically significantly different, p<0.05) Force (g) b a a Full Fat Control Half Pumpkin Full Pumpkin Brownie Variation Figure 2: Average Texture Analyzer Measurement (g of Force) for Each Brownie Variation

9 Table 3: Effect of Fat Replacement with Pumpkin Puree on the Color of Brownies as Measured by the Hunter Colorimeter Full Fat Control Half Pumpkin Puree Full Pumpkin Puree Average L Value a c b L Value SD* Average a Value 5.65 d 8.68 f 7.26 e a Value SD Average b Value 5.07 g 9.83 i 7.81 h b Value SD *SD=standard deviation Hunter Parameter Value c b a i f e h d g Full Fat Control Half Pumpkin Full Pumpkin L value a value b value Brownie Variation Figure 3: Average Hunter Parameter Values for Each Brownie Variation

10 Subjective Analyses: Table 4: Distribution, Average, and Standard Deviation of Taste Rating Scores by Brownie Variation Taste Rating* Full Fat Control Half Pumpkin Full Pumpkin Average Rating 4.09 b 3.16 a 2.88 a Standard Deviation * Taste Rating is from 0 to 5 with 5 being the highest and 0 being the lowest. 5 4 b a a Taste Rating Full Fat Control Half Pumpkin Full Pumpkin Brownie Variation Figure 4: Average Subject Taste Rating* for Each Brownie Variation * Taste Rating is from 0 to 5 with 5 being the highest and 0 being the lowest.

11 Table 5: Distribution, Average, and Standard Deviation of Appearance Rating Scores by Brownie Variation Appearance Rating* Full Fat Control Half Pumpkin Full Pumpkin Average Rating Standard Deviation * Appearance Rating is from 0 to 5 with 5 being the highest and 0 being the lowest. 5 b Appearance Rating a a 0 Full Fat Control Half Pumpkin Full Pumpkin Brownie Variation Figure 5: Average Subject Appearance Rating* for Each Brownie Variation * Appearance Rating is from 0 to 5 with 5 being the highest and 0 being the lowest.

12 Table 6: Distribution of Preference Ranking Results Preference Ranking Full Fat Control Half Pumpkin Full Pumpkin 1 st nd rd Number of Subjects st 2nd 3rd Preference Ranking Full Fat Control Half Pumpkin Full Pumpkin Figure 6: Distribution of Preference Ranking Results DISCUSSION: The objective data shows that replacing vegetable oil for pumpkin puree in brownie mix recipe resulted in substantial changes in water activity, texture, and color. The average water activity measurement for each variation can be seen in Table 1. The full fat control had the lowest water activity of 0.719, and the full pumpkin puree variation had the highest at As shown in Figure 1, there is an increasing trend in water activity as the fat is replaced with pumpkin. This is logical since pumpkin puree has high water content and more moisture was present when more puree was added. In addition to impacting water activity, fat replacement with pumpkin puree also affected texture. Table 2 and Figure 2 demonstrate this relationship. In Figure 2, grams of force required to penetrate the brownie was significantly lower in the full fat control brownies (32.2 g)

13 compared to the full pumpkin brownies (69.4 g). However, no significant difference was found between the full fat control brownies and the half fat/half pumpkin brownies (36.8 g). This suggests that the full pumpkin brownies were tougher due to lack of fat, which contributes tenderness to the food product. As mentioned previously, fat tenderizers baked goods by decreasing the interaction of gluten-forming proteins. Along with impacting texture and water activity, replacement of fat with pumpkin puree altered the color of the brownies. Table 3 shows that there were significant differences between the variations in terms of the L, a, and b values obtained from the Hunter colorimeter. The L values were for full fat control, for half fat/half pumpkin, and for full pumpkin. Their a values were 5.65, 8.68, and 7.26 for full fat, half fat/half pumpkin, and full pumpkin, respectively. Finally, their b values were 5.07 for full fat, 9.83 for half fat/half pumpkin, and 7.81 for full pumpkin. Overall, the brownies were noticeably different in terms of color, appearance, and consistency. The full fat control brownies had a chocolate brown color with a dense, fudge-like consistency. The half fat/half pumpkin brownies had a medium brown color with a cake-like consistency. The full pumpkin brownies had a burnt brown color with a spongy, crumbly consistency. Dutta and others (2006) investigated the reasons for the change in color and consistency of pumpkin puree as it is heated. The initial orange color of pumpkin is due to its β- carotene content, which becomes darker as it is heated due to geometric isomerization and nonenzymatic browning. The full pumpkin brownie had a darker burnt color because of the higher amount of β-carotene that was degraded. With research, Dutta and others (2006) also determined that pumpkin puree behaves as a pseudoplastic fluid that is structurally weakened upon heating. This may explain why the full pumpkin brownie became a darker color and had a crumblier consistency. Given the changes that occurred with texture and color, it was not surprising that there were also differences in subjective measurements. As expected, the subjective data showed that most people preferred the taste of the full fat brownies, while less people preferred the full pumpkin brownies. Table 4 shows that the majority of subjects rated the full fat control with a taste score of 4 or 5 (with 5 being the highest rating). The half fat/half pumpkin and full pumpkin variations were most often rated with a score of 3 or 4. Figure 4 show the average rating for each variation. As more fat was replaced with pumpkin, the average taste score

14 decreased. There was no significant difference between the average score of the half fat/half pumpkin brownies and the full pumpkin brownies (scores of 3.16 and 2.88, respectively), but both these variables were significantly different from the control (score of 4.09). These results are consistent with the data from the appearance rating test. Table 5 shows that most subjects rated appearance of the full fat control with a score of 4 or 5 (with 5 being the highest rating). Most subjects rated the half pumpkin/half fat and full pumpkin variations, however, with scores of 2 or 3. Figure 5 shows that the average score decreased with increasing fat replacement. The pumpkin variations were not significantly different from each other in terms of appearance (scores of 2.59 for half fat/half pumpkin and 2.38 for full pumpkin), but they were significantly lower than the control (score of3.97). The overall ranking preference of the brownies showed that the original brownie recipe most often received the best ranking. These results can be seen in Table 6 and Figure 6. Most people gave the full fat brownie the highest ranking (19 of 26 people ranked it as #1) and the full pumpkin brownie the lowest ranking (14 of 26 people ranked it as #3), while the half fat/half pumpkin brownie was in the middle (12 of 26 people). These data are consistent with previous studies experimenting with fruit purees as fat replacers. Oftentimes, substituting all the fat in a recipe decreases the acceptability of the final product, as shown by Swanson and Munsayac (2003). In their study, they examined the effects of partially substituting fat in different types of cookies with applesauce and prune puree. They found that substituting the fat in the cookies affected both texture and consumer preference. Using applesauce as a replacer made for a softer cookie, while prune puree made for a harder cookie. Both were perceived as being staler than the control. Overall, the cookies made with fruit substitutes tended to be less liked than their full fat counterparts. Similar results were found in a study by Wiese and Duffrin (2003), in which pawpaw fruit was used as a fat replacer in plain shortened cake. As increasing increments of fruit puree (25%, 50% and 75%) were substituted for butter, there was a decrease in preference. In particular, the replacement of fat for the pawpaw fruit led to a cake that was less fluffy and that had an undesirable color. Although the results from this study correlate with results from previous research, some unexpected variables may have affected the data collected from this experiment. In making smaller batches of brownie mix, loaf pans were used instead of the more commonly used 9 x

15 13 baking pans. This changed the cooking time of the brownies, as well as their thickness. While the brownies were all cut down to the same size (approximately 1 x 1 squares), they looked more like cake than brownies. The aesthetics of the brownies could possibly be different if baked in a 9 x13 baking pan. However, the water activity and color should stay the same. Other problems encountered were the layout of the sensory scorecard. Many people disregarded the texture portion (ranking dry, moist, and chewy) and failed to fill it out. Consequently, this was omitted from the results due to lack of information. Overall, this experiment showed that replacement of fat for pumpkin puree changes the texture, water activity, and color of brownies, as well as negatively affects consumer preference in taste and appearance. Replacing all the fat in the brownies with pumpkin puree produced an unacceptable product. Using a mixture of half fat/half pumpkin in the brownies resulted in greater preference, though it was still significantly different from the full fat brownies. These results suggest that although % replacement of fat with pumpkin puree would produce a healthier product, this may not be feasible due to its negative effects on quality. Often times, recipes utilizing fruit purees have different proportions of eggs and water compared to full fat recipes. Future experiments could analyze if changes in the amounts of these ingredients would improve the quality of brownies with pumpkin puree. Also further research should be done to determine if using a mixture of different fruit purees would be effective in mimicking the sensory properties that fat provides. REFERENCES: American Dietetic Association Position of the American Dietetic Association: fat replacers. Journal of the American Dietetic Association. 105: Dutta D, Dutta A, Raychaudhuri U, Chakraborty R Rheological characteristics and thermal degradation kinetics of beta-carotene in pumpkin puree. Journal of Food Engineering. 76: Figoni PI How baking works: exploring the fundamentals of baking science. 3 rd ed. Hoboken, New Jersey: John Wiley and Sons, Inc. p 481. Miraglio AM Nutrient substitutes and their energy values in fat substitutes and replacers. American Journal of Clinical Nutrition. 62: 1175S-1179S.

16 Overweight and obesity statistics. Dallas, TX: American Heart Association; 2009 [Accessed 2010 Nov 20]. Available from: Romanchik-Cerpovicz JE, Tilmon RW, Baldree KA Moisture retention and consumer acceptability of chocolate bar cookies prepared with okra gum as a fat ingredient substitute. Journal of the American Dietetic Association. 102: Sanchez C, Klopfenstein CF, Walker CE Use of carbohydrate-based fat substitutes and emulsifying agents in reduced-fat shortbread cookies. Cereal Chemistry. 72: Swanson RB, Munsayac LJ Acceptability of fruit purees in peanut butter, oatmeal and chocolate chip reduced-fat cookies. Journal of the American Dietetic Association. 99: Wiese TD, Duffrin MW Effects of substituting pawpaw fruit puree for fat on the sensory properties of a plain shortened cake. HortTechnology. 13: