Addition of Pumpkin to Yogurt

Transcription

1 Brooks Pritchett F&N 453 Individual Project Written Report Addition of Pumpkin to Yogurt Abstract Both pumpkin and yogurt contain a wide variety of nutrients and compounds that aid in promoting health. The purpose of the current experiment was to create a more nutritious product using pumpkin and yogurt. Methods involved adding varying amounts of pumpkin to a standard amount of yogurt and then analyzing each sample for changes in color, texture, and consumer desirability. It was found that adding pumpkin to yogurt produced slight color and textural changes, but was still acceptable to consumers. Such sensory changes, however, did not impact the product s nutritional value. Therefore, the creation of pumpkin-yogurt resulted in a more nutritious product than either pumpkin or yogurt alone. Introduction Individually, both pumpkin and yogurt provide a wide variety of nutrients and health-promoting properties. Each food product by itself is used both in conventional cooking and to provide additional benefits to food. Pumpkin-pie or yogurt-based dips would be two such examples. The overall purpose of this experiment was to take two nutritionally dense foods, pumpkin and yogurt, and combine them to produce an even more nutritionally dense food product pumpkin yogurt. Pumpkin is very high in many important nutrients including potassium, magnesium, vitamins C and E, and pantothenic acid (Pratt and Matthews 2004). Aside from these essential nutrients, pumpkin contains a tremendous amount of the carotenoids

2 beta and alpha-carotene. Carotenoids are known to help ward off diseases such as heart disease, cancer, and diseases of the eye (Mayne 1996). It has been found by Seo and others 2005 that over 80% of the carotenoids in pumpkin exist as beta-carotene, with smaller amounts of lutein, lycopene, alpha-carotene, and cis-beta carotene. A few carotenoids, including alpha and beta-carotene, are precursors to vitamin A, and thus contribute as a source of vitamin A in the diet. Pumpkin is also high in fiber, which is inversely associated with several cardiovascular risk factors. Specifically, the fiber found in vegetables, such as pumpkin, is associated with lower blood pressure and homocysteine levels, which are known to increase risk for cardiovascular disease (Lairon and others 2005). In addition, a review by Trowell 1976 suggests that fiber also plays a role in reducing colonic disease, certain metabolic diseases, diabetes mellitus, and obesity. In addition to pumpkin, yogurt contains several important health-promoting benefits of its own. Not only does yogurt contain calcium, riboflavin, vitamin B12, potassium, magnesium, and zinc, it also contains probiotics, beneficial bacteria known to promote gastrointestinal health (Isolauri 2001). Probiotics also boost immune function as a result of their interactions in the gastrointestinal tract. Many diseases and/or conditions can be prevented or alleviated by consuming yogurt and the probiotics it contains. Cancer, lactose intolerance, ulcers, irritable bowel disease, and diarrhea are just a few (Pratt and Matthews 2004). Aside from these benefits, the consumption of dairy foods, such as yogurt, is inversely associated with body mass index (Mirmiran and others 2005) and metabolic

3 syndrome (Azadbakht and others 2005). Thus, yogurt may play a role in weight management as well. Although both pumpkin and yogurt contain several nutritional benefits, no effort has been made to combine the two into one product. Thus, it is unknown whether certain variables could affect the final outcome of the product. The overall design of the experiment involved adding varying amounts of pumpkin to a standard amount of yogurt and assessing the changes between samples. Three trials were completed to obtain the most valid data. Given the novelty of this experiment, the two dependent variables considered for the current purpose were viscosity and color, as measured by the Brookfield viscometer and Hunter colorimeter, respectively. A 9-point Hedonic scale was also used to assess consumer desirability. The independent variable involved varying the amount of pumpkin in each sample. The previously listed tools were all used to assess differences among samples. Because there is no previous research examining the addition of pumpkin to yogurt, this experiment will assess the possible changes and consumer desirability of a new food product. As mentioned previously, the purpose of this experiment is to create a more nutritious product by combining pumpkin and yogurt to create pumpkin-yogurt. Methods In each trial of pumpkin-yogurt, a different amount of pumpkin was added to a standard amount of yogurt. Three samples were prepared for each trial. The Hunter colorimeter and Brookfield viscometer were then used to test each sample for color and

4 viscosity, respectively. Finally, a 9-point Hedonic scale was used as a subjective analysis of consumer desirability. Recipe for Each Trial of Pumpkin-Yogurt Sample Amount Yogurt (grams) Amount Pumpkin (grams) 1 (control) Procedure: 227 grams of yogurt was measured out and poured into a medium mixing bowl. The specified amount of pumpkin for the given sample was then measured out and added to the yogurt. Using a spoon, the pumpkin was stirred into the yogurt until fully mixed. Half of the mixture was then poured into a separate beaker for objective analysis. Finally, the remaining mixture was spooned into individual custard cups for subjective sampling. Design In order to reduce bias, random three-digit numbers were assigned to each variable in each trial. The number assigned to each variable was as follows: Control Sample 1 Sample 2 Trial Trial Trial Three trials were conducted in order to obtain the most accurate data. The experiment was replicated using exactly the same procedures each time. Averages values were used when analyzing the final results. To measure color, a small amount of sample was spooned out of the prepared recipe to cover the bottom of a Petri dish. The Hunter colorimeter was then used to determine the L, a, b values of the particular sample. After the values for all nine

5 samples were obtained, the average values of the Control variable, Sample 1, and Sample 2 were calculated. To measure viscosity, the remaining mixture left after the Hunter colorimeter test was used on the Brookfield viscometer. Spindle 5 was used for all trials and samples. The chosen speeds were 6, 12, 30, and 50 rpm and viscosity was recorded in units cps. When values were obtained for all samples and trials at all speeds, the average values for the Control variable, Sample 1, and Sample 2 were calculated. To determine the viscous nature of each sample and the averages, viscosity was plotted versus speed. The resulting graph revealed whether pumpkin-yogurt exhibited Newtonian or non-newtonian behavior. A 9-point Hedonic scale was used for subjective evaluation. Test subjects were given three samples, all from the same trial, and rated each variable s overall desirability, based on personal preference. Six different test subjects volunteered for each trial. The scorecard follows below. PRODUCT: Pumpkin-yogurt DATE: SAMPLE NUMBER: Please judge each sample for its overall desirability. Place a mark beside the statement that you most agree with. Like extremely Like very much Like moderately Like slightly Neither like nor dislike Dislike slightly Dislike moderately Dislike very much Dislike extremely

6 Results Objective Analysis Table 1 Hunter Colorimeter Values for All Trials and Samples of Pumpkin Yogurt Sample L a b Trial Trial Trial Table 2 Hunter Colorimeter Average Values for All Three Trials of Pumpkin Yogurt L a b Control Sample A Sample B Table 3 Hunter Colorimeter Standard Deviations for All Three Trials of Pumpkin Yogurt L a b Control Sample A Sample B Table 4 Viscosity (cps) of Pumpkin Yogurt As Measured by the Brookfield Viscometer Speed 6 rpm 12 rpm 30 rpm 50 rpm Sample Trial Trial Trial *Spindle 5 was used for all trials and all samples

7 Table 5 Average Viscosity (cps) of Pumpkin Yogurt Measured by the Brookfield Viscometer Speed 6 rpm 12 rpm 30 rpm 50 rpm Control Sample A Sample B Table 6 Standard Deviation (cps) of Pumpkin Yogurt Measured by the Brookfield Viscometer Speed 6 rpm 12 rpm 30 rpm 50 rpm Control Sample A Sample B Viscosity (cps) Figure 1 6 rpm 12 rpm 30 rpm 50 rpm Speed (rpm) Average Viscosity vs. Speed of Control Variable Using the Brookfield Viscometer Viscosity (cps) Figure 2 6 rpm 12 rpm 30 rpm 50 rpm Speed (rpm) Average Viscosity vs. Speed of Sample 1 Using the Brookfield Viscometer

8 Viscosity (cps) Figure 3 6 rpm 12 rpm 30 rpm 50 rpm Speed (rpm) Average Viscosity vs. Speed of Sample 2 Using the Brookfield Viscometer Subjective Analysis Table 7 Tally of Subjective Results of Pumpkin-Yogurt Using a 9-point Hedonic Scale Neither Like Like Like Like Like Dislike Dislike Dislike Dislike Extremely Very Much Moderately Slightly nor Disklike Slightly Moderately Very Much Extremely Sample Trial Trial Trial Discussion The addition of pumpkin to yogurt resulted in slight changes in color, texture, and consumer desirability. The most drastic changes occurred with the addition of the most pumpkin. However, such changes did not affect the nutritional value of the new product, and thus pumpkin-yogurt can be considered a more nutritious product than either pumpkin or yogurt individually.

9 Table 1 and Table 2 summarize the L, a, b values as obtained from the Hunter colorimeter. Average L values decreased, a values increased, and b values increased in each trial as more pumpkin was added to yogurt. Compared to the control samples, this indicates a notable change in color with the addition of pumpkin to yogurt. Variability among trials was low (Table 3), so the change in color is likely a valid trend. Although this does not affect the nutritional value of the product, it may alter consumer acceptability. More pumpkin produced a darker orange product, which may or may not be desirable to consumers. Texture also changed as more pumpkin was added to yogurt. Table 4 lists the viscosity of each sample as measured by the Brookfield viscometer in each trial (in cps) at speeds 6, 12, 30, and 50 rpm. Table 5 lists the average values for the control variable and samples 1 and 2. These results reveal that viscosity increased as more pumpkin was added to yogurt. Therefore, pumpkin produces textural changes in yogurt proportional to the amount added. From Figure 1, which graphs the average viscosity of the control sample vs. spindle speed, the viscous behavior of plain yogurt can be characterized as pseudoplastic (Daniel 2007). Thus, plain yogurt is a non-newtonian shear-thinning fluid. Figures 2 and 3, which graph the average viscosity of Samples 1 and 2 vs. spindle speed, also reveal that pumpkin yogurt can be characterized as a pseudoplastic fluid. However, the resulting values for viscosity at each speed increased as more pumpkin was added (Table 5). Although pumpkin yogurt exhibited the same viscous flow as plain yogurt, it did produce notable textural changes. The standard deviations for each sample at each speed were not significantly high (Table 6), thus it can be inferred that such textural changes in pumpkin-yogurt were legitimate. As with the color changes, textural changes

10 did not affect the nutritional value of pumpkin-yogurt, but such changes may or may not be desirable to consumers. In comparing the sensory properties of soy yogurt to probiotic-enhanced soy yogurt, a study by Donkor and others 2007 found that consumers preferred plain soyyogurt, which was less viscous and provided better mouth feel. Probiotic yogurts also exhibited greater pseudoplastic properties. This coincides with the results from the current experiment, which further confirm the pseudoplastic behavior of yogurt, in addition to textural changes that occur when ingredients are added. Therefore, it is important to consider these characteristics when adding ingredients to new yogurt products. Subjective evaluation of pumpkin-yogurt (Table 7) indicated that consumers tended to prefer the samples with less pumpkin added. The lowest score occurred in samples 475, which had the most pumpkin added. The highest scores occurred in 649 and 901, which were the control variable and Sample 1, respectively. Most consumers marked within the range of Like Very Much to Like Slightly. It can be inferred from these results that consumers find pumpkin-yogurt desirable, although perhaps certain improvements could be made in the product. Although the values obtained during data collection in this experiment tended to follow certain trends, error could still have occurred. Sources of error could have included improperly calibrating the equipment, not being consistent in measuring out ingredients for all trials, or being careless in collecting data. Given the novelty of pumpkin-yogurt, it is difficult to determine whether error actually occurred.

11 Future experiments involving improving the nutritional value of yogurt products could proceed in many directions. For instance, Ann Bartoo and Badrie 2005 experimented with the addition of dwarf golden apple to plain yogurt, which was found to be acceptable to consumers. Different types of foods or ingredients could be added to yogurt to create more nutritious products, aside from just pumpkin. Other considerations for future research could involve uncovering methods to minimize textural, color, or any other changes that might occur as a result of adding a new ingredient to yogurt. Overall, the current experiment successfully resulted in the creation of a more nutritious product. Although some changes occurred as pumpkin was added, pumpkinyogurt provided improved nutritional value in a form still desirable to consumers. References Ann Bartoo S, Badri N Physicochemical, nutritional and sensory quality of stirred dwarf golden apple (Spondias cytherea Sonn) yoghurts. International Journal of Food Science and Nutrition 56(6): Azadbakht L, Mirmiran P, Esmaillzadeh A, Azizi F Dairy consumption is inversely associated with the prevalence of the metabolic syndrome in Tehranian adults. American Journal of Clinical Nutrition 82: Daniel, JR Food Chemistry Lecture Notes. Donkor ON, Henriksson A, Vasiljevic T, Shah, NP Rheological Properties and Sensory Characteristics of Set-Type Soy Yogurt. Journal of Agricultural Food Chemistry Nov 3; [ahead of print]. Isolauri E Probiotics in human disease. American Journal of Clinical Nutrition 73:1142S-1146S. Larion D, Arnault N, Bertrais S, Planells R, Clero E, Hercberg S, Boutron-Ruault M Dietary fiber intake and risk factors for cardiovascular disease in French adults. American Journal of Clinical Nutrition 82(6): Mayne ST Beta carotene, carotenoids, and disease prevention in humans. The FASEB Journal 10:

12 Mirmiran P, Esmaillzadeh A, Azizi F Dairy consumption and body mass index: an inverse relationship. International Journal of Obesity (London) 29: Pratt S, Matthews K Superfoods Rx. New York, NY: HarperCollins Publishers Inc. 336 p. Seo JS, Burri BJ, Quan Z, Neidlinger TR Extraction and chromatography of carotenoids from pumpkin. Journal of Chromatography 6: Trowell H Definition of dietary fiber and hypotheses that it is a protective factor in certain diseases. American Journal of Clinical Nutrition 29: