The Effect of Buckwheat Flour on the Taste and Texture of Pumpkin Bread Carissa Dixon, Kayla Ballard, and Cynthia Rawley Nutr 453, Thursday 9:30am lab November 19, 2012
Title: The Effect of Buckwheat Flour on the Taste and Texture of Pumpkin Bread Abstract: Buckwheat flour is used in place of other flours as a gluten-free alternative, and it is also used because of its high nutritional content. Buckwheat flour has become an item of interest in the food industry because of its potential and usefulness in gluten-free cooking and baking. As gluten-free foods are a growing interest of consumers, using buckwheat flour instead of all-purpose flour could make it possible for Celiac patients and gluten intolerant individuals to enjoy many baked goods that they otherwise could not have. In this experiment buckwheat flour replaced all-purpose flour completely in one of the samples of pumpkin bread. Another sample contained 50 percent buckwheat flour and 50 percent all-purpose flour. These samples were compared to the control, which contained only all-purpose flour. The comparison was done by determining differences in water activity, using the water activity meter; color, using the Hunter Colorimeter; and texture, using the texture analyzer. The hypothesis is that substitution of buckwheat flour for all-purpose flour in pumpkin bread will result in a final product that is firmer in texture, darker in color, and that is altered in taste. Results from the texture analyzer showed no statistically significant differences between the three samples for any of the three trials. Results for water activity of the three samples were not significantly different for any of the three trials. Results for color showed there were significant differences in the L, a, and b values for all three samples. Results for the subjective texture analysis showed there was a significant difference between 100 percent all-purpose flour and 100 percent buckwheat flour. Results for the subjective taste analysis showed there were no significant differences between the three different samples. Therefore, this experiment showed that buckwheat flour can be a good substitute for all-purpose flour when baking pumpkin bread. Introduction: The only treatment for Celiac Disease or a gluten intolerant individual is to eliminate or reduce gluten in the diet. Unfortunately, the availability of such foods without gluten is very little, and the cost is much higher than that of regular foods. Therefore, many Celiac or gluten intolerant patients do not receive adequate nutrient intake due to the limited amount of foods they have to choose from. A study was recently done to assess the availability of such foods in retail supermarkets, and the researchers found that there is an extremely limited availability of these foods along with much higher prices (Singh 2011). Therefore, it is important to find a good alternative to regular all-purpose flour in baked goods that is gluten-free and has a high nutrient content so that the consumers will not miss out on essential nutrients. A recent study was performed to find a healthy alternative ingredient in cereal for individuals with gluten intolerances. Cereals are typically made out of wheat, barley, or rye; however, celiac patients cannot consume these grains. Tests were then performed to determine which gluten-free grains had the most nutritional benefits. Oats, rice, sorghum,
corn, teff, buckwheat, and quinoa were all analyzed. The results showed that corn and rice had low nutritional value, which included low amounts of protein, fiber, and folate. Teff, quinoa, and buckwheat showed to be the most beneficial. They had high contents of protein and folate (Hager, 2012). Similar to the previous findings, a study was conducted to test the nutritional benefits of buckwheat flour incorporated into a bread recipe. The study was performed to find a healthy alternative to gluten-free flours that lack vitamins and minerals. This study tested how incorporating buckwheat by 10-40% would alter the physical properties of the bread. The measurements of weight, volume and height were all recorded. The protein content and micronutrient data was also collected. Based on the results, the addition of buckwheat flour increased the overall quality of the bread. There was an increase in size, proteins, and micronutrients (Krupa-Kozak, 2011). In this experiment, the changes in dimension of each loaf of pumpkin bread will be observed. Buckwheat is a preferred alternative to other flours because of the nutritional benefits it supplies. According to the Whole Grains Council, buckwheat enhances the nutritional components of food because it provides vitamins, minerals, and antioxidants. Buckwheat is an alternative to other gluten-free flours. Research has also shown that buckwheat lowers blood pressure and blood glucose levels (Whole Grains Council, 2011). Recent studies evaluating the health benefits of buckwheat flour have proven that it has potential usefulness as a functional ingredient in the future of the food industry. Not only is this flour useful in gluten-free baking and cooking, it has a high protein content that has shown to suppress hypercholesterolemia and obesity in rats and mice eating a poor diet. The high protein buckwheat flour also decreased cholesterol in mice in this same experiment while the mice were fed diets extremely high in cholesterol. These results were due to the low protein digestibility of the buckwheat flour (Tomotake 2006). Buckwheat flour is not only substitute flour for gluten intolerant individuals, but may also in the future be regarded as a functional ingredient to help manage and maintain weight and cholesterol. Concerns for the acceptability of the pumpkin bread with buckwheat flour are an increase in density, harsh taste, color, and an overall firmer texture. The color of the buckwheat grain and products that contain it remain dark since the fragments of the grain have not been removed in the milling process. A recent study was performed to determine the characteristics of a cookie made from rice and a cookie made from buckwheat flour. The cookies made from buckwheat flour were darker, while the rice cookies were more yellow. When the researchers raised the content level of buckwheat from 10% to 20%, the sensory scores for flavor and chewiness also increased (Torbica, 2012). The quantity of buckwheat flour used is a potential gap in research. That study increased buckwheat flour content to 20% but in this experiment 50% and 100% buckwheat flour were used to replace all-purpose flour. Through this experiment with pumpkin bread, the goal was to determine if the higher percentages of buckwheat flour have the same sensory and textural appeal as the lesser amounts. The structure of buckwheat flour is somewhat different than all-purpose flour because of its disulfide bonds. The globulins contain lower levels of free cysteine residues. These exist as disulfide linkages that connect polypeptides, while in all-purpose flour there are more free sulfide hydrogen groups (Vallons, 2011). The result of baking with flour with this
particular structure is a batter that is higher in viscosity and a final product that is more dense. The purpose of this experiment is to substitute all-purpose flour with buckwheat flour in pumpkin bread to create a gluten-free product that is rich in essential nutrients. The independent variable in this experiment is the amount of buckwheat flour replacing the all-purpose flour in each sample of pumpkin bread. The first sample will be the control, which is the original recipe with only all-purpose flour. The second sample will be made using the same amount of flour, but replacing 50 percent of the all-purpose flour with buckwheat flour. The final sample will contain 100 percent buckwheat flour. The dependent variables in this experiment will be water activity, color, and texture of the final baked product. The tools selected to measure the dependent variables are the texture analyzer, water activity meter, and the Hunter Colorimeter. The texture analyzer will assess the firmness of each of the variations of the pumpkin bread. The water activity meter will measure the difference in water binding capacities of the 3 different flour variables, and the Hunter Colorimeter will measure the differences in color of the final products. Consumer acceptability and preference will be measured as well. The panel of judges will be asked to rate the texture on a 9-point Hedonic scale, ranging from extremely soft to extremely hard. The panel will also be asked to choose which sample of the three variations they prefer the most. Three trials of this experiment will be done, and objective and subjective testing will be done for each trial. Methods: Three experimental trials were all completed in one week. There were three independent variables used: 100% all-purpose flour, 50% all-purpose flour and 50% buckwheat flour, and 100% buckwheat flour. The same procedure was used for each trial and the same recipe was used for each sample except for the type of flour used. Three trials were done because replication is important in confirming results. The recipe was found on allrecipes.com and is in metric units below: Sample 513 145 g all-purpose flour 160 g canned pumpkin puree 1-1/4 eggs 80 ml vegetable oil 55 ml water 200 g white sugar 3 g baking soda 3 g salt 0.8 g ground cinnamon 1 g ground nutmeg 0.4 g ground cloves 0.2 g ground ginger
Sample 920 72.5 g all-purpose flour and 72.5 g buckwheat flour 160 g canned pumpkin puree 1-1/4 eggs 80 ml vegetable oil 55 ml water 200 g white sugar 3 g baking soda 3 g salt 0.8 g ground cinnamon 1 g ground nutmeg 0.4 g ground cloves 0.2 g ground ginger Sample 623 145 g buckwheat flour 160 g canned pumpkin puree 1-1/4 eggs 80 ml vegetable oil 55 ml water 200 g white sugar 3 g baking soda 3 g salt 0.8 g ground cinnamon 1 g ground nutmeg 0.4 g ground cloves 0.2 g ground ginger The oven was preheated to 350 degrees F (175 degrees C). Three 7x3 inch loaf pans were greased and floured and also labeled for each of the three different types of flour that was used. In a large mixing bowl at room temperature, the pumpkin puree, eggs, oil, water, and sugar were mixed together using an electric mixer until well blended. In a separate bowl, the flour, baking soda, salt, cinnamon, nutmeg, cloves, and ginger were whisked together. The dry ingredients were stirred into the pumpkin mixture until just blended. This procedure was done three different times using a different flour each time. The three different batters were poured into the loaf pans and baked for 45 minutes. To keep the other variables stable in the experiment, the water needed to be at the same temperature for each of the loaves, the vegetable oil and pumpkin puree were held at room temperature, and the eggs were taken right out of the refrigerator. Objective Tests The first dependent variable tested was texture using the Texture Analyzer. A 1.5 inch piece of pumpkin bread was centered under the cone probe and the bread setting was
chosen. For each variable, three measurements were taken and then averaged. See Table 1, Figure 1, and Figure 1a for the results of this objective test. The second dependent variable tested was water activity using the Water Activity Meter. Pieces of pumpkin bread were placed in the container to the top, but not over-filled. One measurement was taken per trial per variable. See Table 2 and Figure 2 for the results of this objective test.the third dependent variable tested was color using the Hunter Colorimeter. Pieces of pumpkin bread were placed in the container to completely fill it so that no light could get through. For each variable, three measurements were taken to get the L, a, and b values and then averaged. The L value is where the color falls on the white to black axis, the a value is where the color falls on the green to red axis, and the b value is where the color falls on the blue to yellow axis. See Table 3, Table 3.1, and Figure 3 for the results of this objective test. Subjective Test The panel of judges was randomly selected and they participated willingly. They were not told the purpose of the experiment or the differences between the samples. Randomization is important to help prevent bias. The panel of judges for each trial consisted of eight people. Each person tasted each variable and then filled out the sensory scorecard. The dependent variables that were assessed were texture and taste preference. The texture was rated using a 9-point hedonic scale with 1= extremely soft and 9= extremely hard. The taste preference was rated on a scale of 1 to 3 with 1 being the one they liked the least and 3 being the one they liked the most. The results from each trial were tallied, averaged, and analyzed. See Table 4, Figure 4a, and Figure 4b for the results of the subjective tests. Three digit numbers were assigned to each variable, which are listed below. 513 100% all-purpose flour 920 50% all-purpose flour and 50% buckwheat flour 623 100% buckwheat flour Pumpkin Bread Sensory Evaluation Please taste each sample and rate the texture on a 9-point hedonic scale. Sample 623: Texture Extremely Very Moderately soft Slightly Neither or Slightly Moderately Very Extremely
Sample 920: Texture Extremely Very Moderately soft Slightly Neither or Slightly Moderately Very Extremely Sample 513: Texture Extremely Very Moderately soft Slightly Neither or Slightly Moderately Very Extremely Please rank the samples in order of preference. 3 being the one you like the most and 1 being the one you like the least. 623 920 513
Results: Table 1: Texture Analyzer Average Values (g) for Trials 1, 2, and 3, Consisting of 100% All-Purpose Flour, 50% All-Purpose Flour with 50% Buckwheat Flour, and 100% Buckwheat Flour 100% AP 50% AP 50% Buckwheat 100% Buckwheat Trial 1 23.03 26.46 29.26 Trial 2 30.9 26.53 32.53 Trial 3 Average Std Dev. 30.96 28.30 a 3.29 34.76 29.25 a 4.1 30.3 30.70 a 2.57 Averages bearing the same superscript are not statistically significant, p > 0.05. 40 35 30 Force (g) 25 20 15 10 5 Trial 1 Trial 2 Trial 3 0 100% AP 50% AP 50% Buckwheat 100% Buckwheat Figure 1: Effect of 100% all-purpose flour, 50% all-purpose flour with 50% buckwheat flour, and 100% buckwheat flour based on the average texture analyzer values for trials 1, 2, and 3.
Figure 1a: Overall averages for texture analyzer Table 2: Water Activity for Trials 1, 2, and 3, Consisting of 100% All-Purpose Flour, 50% Buckwheat Flour with 50% All-Purpose Flour, and 100% Buckwheat Flour. 100% AP 50% AP 50% Buckwheat 100% Buckwheat Trial 1 0.835 0.853 0.859 Trial 2 0.901 0.889 0.886 Trial 3 0.883 0.855 0.848 Average.873 a.866 a.864 a Std Dev..034.020.019 Averages bearing the same superscript are not statistically significant, p > 0.05.
Water Activity (a w ) 0.92 0.9 0.88 0.86 0.84 0.82 Trial 1 Trial 2 Trial 3 0.8 100% AP 50% AP 50% Buckwheat 100% Buckwheat Figure 2: Effect of 100% all-purpose flour, 50% all-purpose flour with 50% buckwheat flour, and 100% buckwheat flour based on the water activity values for trials 1, 2, and 3. Figure 2a: Overall averages for water activity
Table 3: Hunter Colorimeter results for 100% All-Purpose Flour, 50% All-Purpose Flour with 50% Buckwheat Flour, and 100% Buckwheat Flour Pumpkin Bread with Averages and Standard Deviations. 100% AP 50% AP 50% Buckwheat 100% Buckwheat L a b L a b L a b Trial 1 32.28 5.33 10.31 23.42 2.83 3.87 22.97 2.21 3.07 Trial 2 32.32 5.56 11.18 23.0 2.73 10.52 22.67 2.17 2.8 Trial 3 32.01 5.65 11.06 23.27 3.17 3.67 22.66 2.10 2.78 Average 32.20 5.51 10.85 23.23 2.91 6.02 22.77 2.16 2.88 Std Dev. 0.1686 0.1650 0.4715 0.2128 0.2307 3.8984 0.1762 0.0557 0.1620 Table 3.1: Hunter Colorimeter Result Averages with Statistically Significant Data L-Values a-values b-values 100% AP Flour 32.20 A 5.51 c 10.85 e (Control) 50% BW and 50% 23.23 b 2.91 cd 6.02 e AP 100% BW flour 22.77 b 2.16 d 2.88 f Averages not bearing the same superscript are statistically significantly different, p < 0.05.
Hunter Colorimeter Values 40 35 30 25 20 15 10 5 0 a c e 100% AP Flour (Control) b cd e 50% BW and 50% AP 100% BW Flour Figure 3: Overall Hunter Colorimeter Averages for the Control of 100% All-purpose, 50% All-purpose flour with 50% Buckwheat flour, and 100% Buckwheat flour with error bars for L, a, and b. b d f L a b Table 4: Subjective Results for trials 1-3 consisting of 100% All-Purpose Flour, 50% All-Purpose Flour 50% Buckwheat Flour, and 100% Buckwheat Flour, including averages and standard deviations for texture and taste preference. The texture was tested with a sensory scorecard using a 9-point hedonic scale with 1= extremely soft and 9= extremely hard. Taste preference was tested with a sensory scorecard rated on a scale of 1 to 3 with 1 being the one they liked the least and 3 being the one they liked the most. Trial Sample Texture Taste Preference 1 623 2.63 2.38 920 2.50 1.63 513 3.13 2.00 2 623 5.25 1.13 920 3.88 2.38 513 2.38 2.50 3 623 4.00 1.88 920 4.50 1.75 513 2.75 2.38 Average 623 3.96 b 1.79 a 920 3.63 ab 1.92 a 513 2.75 a 2.29 a Std Dev. 623 1.68 0.78 920 1.58 0.78 513 0.99 0.86 Averages not bearing the same letter are statistically significantly different, p < 0.05
Figure 4a: Effect of 100% All-purpose flour, 50% All-purpose flour 50% Buckwheat flour, and 100% Buckwheat flour on subjective results for texture, shown as averages for all three trials. Figure 4b: Effect of 100% All-purpose flour, 50% All-purpose flour 50% Buckwheat flour, and 100% Buckwheat flour on subjective results for taste preference, shown as averages for all three trials.
Discussion: The Hunter Colorimeter was used to evaluate the color differences between the variables in each trial. The Hunter Colorimeter gives L, a, and b values. The L value signifies lightness and darkness of the color, a higher value representing a lighter color. The a value evaluates the sample on the red to green spectrum, and the b value measures from yellow to blue. To determine differences in colors between samples, it is necessary to find the difference between these values. To find the change in the L value, the L value of the standard must be subtracted from the L value of the sample being compared. It is the same equation for the a and b values. L= Lsample-Lstandard. If the change in L is positive the sample is lighter than the standard. If the change in a is positive then the sample is more red than the standard. If it is negative than the sample is greener. If the change in b is positive it is yellower than the standard. Referring to table 3 and table 3.1, for all three trials the L values for the 50% Buckwheat variable and the 100% buckwheat variables were lower than the L values for the 100% all-purpose variable, indicating a darker color of the loaves with buckwheat flour. The average L values of the 50% buckwheat and the 100% buckwheat were both statistically significantly different from the 100% all-purpose variable. The a value averages for all of the variables were statistically different from each other. The more buckwheat flour added to the sample, the lower the a value, indicating a greener color in the buckwheat variables rather than red. For the b average values, 100% buckwheat variable was statistically significantly different than the 100% all-purpose variable. The more buckwheat added to the samples, the lower the b value, indicating a more blue color in the buckwheat samples rather than yellow. The replacement of buckwheat flour for allpurpose flour statistically significantly affected the color of the pumpkin bread as hypothesized. The change in color with use of buckwheat flour is most likely due to the fragments of grain that are not removed by milling of buckwheat (Torbica, 2012). The texture analyzer was used with the cone probe to measure the amount of force needed to penetrate the pumpkin bread variables. As seen in Table 1 and Figure 1, the average values for grams of force by the texture analyzer were similar for all three variables in all three trials. None of the results for this test were statistically significantly different, which is shown in Figure 1a. This result suggests that the textures of the 100% all-purpose, 50% buckwheat, and 100% buckwheat variables all had a similar texture or firmness. This result is not what was hypothesized, but it is a good result because it means that texture is not significantly affected by the replacement of buckwheat flour in pumpkin bread. Although buckwheat flour has a high protein content that aids in structure of the bread, it does not contain gluten, which is normally what gives the structure to the pumpkin bread. Perhaps the absence of the gluten in the buckwheat flour allows for the high protein content of this flour to be structurally comparable to allpurpose flour after baking. The water activity meter was used to measure the water activity of the three variables. The disulfide bonds in buckwheat flour differ from the free sulfur-hydrogen bonds in all-purpose flour. This led to the hypothesis that the buckwheat flour would have less water-binding capacity. The results for all three trials, however, indicated no
statistically significant differences in water activity for any of the three variables. This can be seen in Table 2, Figure 2, and Figure 2a. This is also another positive result, indicating that buckwheat flour is a good replacement for all-purpose flour on the contents of the moistness of the pumpkin bread. The sensory scorecard was used to get subjective data on texture and taste. The texture results showed that there was a significant difference between 100 percent allpurpose flour and 100 percent buckwheat flour, as shown in Table 4 and Figure 4a. The combination of 50 percent all-purpose flour and 50 percent buckwheat flour was not significantly different from the control of 100 percent all-purpose flour. This means that adding 50 percent buckwheat did not affect the texture. The taste results showed that there were no significant differences between the three different samples, as shown in Table 4 and Figure 4b. This means that any amount of buckwheat added does not have a significantly different taste than the control. The sources of error that we encountered during our experiment with pumpkin bread could have altered the objective data as well as subjective data. The cooking time for each trial was slightly different. Trial 1 took 50 minutes, trial 2 took 40 minutes, and trial 3 took 80 minutes. We performed all three trials on the same day. Therefore, trial 2 took less time because the oven was already hot from being heated for the first trial. We had other complications in regards to trial 3. After we started baking the pumpkin bread for trial 3, we noticed that the batter was not cooking at all. It turned out that the oven was not on or working properly. Therefore, we had to extend the cooking time because we switched to a different oven. This may have altered the color of the bread, as well as the softness. As for the batter itself, there could have been other sources of error. The measurement of ingredients could have been slightly different among all three trials. This could have enhanced or reduced the sensory results for each of the breads. In regards to the machines we used, there could have been errors through inaccurate use or function of the machines. This could have produced results with inaccurate data. After analyzing all of the results from the objective and subjective tests, it can be concluded that adding 50 percent buckwheat flour to pumpkin bread does not show a statistically significant difference in texture or water activity for the objective tests or texture and taste for the subjective test. The color test did show statistically significant difference between the variables. The added buckwheat flour made the product a darker brown color. This could have caused bias for the panel of judges because most of them probably had eaten pumpkin bread before and knew what color it should be. The future research in this area is needed because of the high prevalence of individuals interested in a gluten-free diet and those with Celiac Disease. More research would be needed to determine the most appropriate ratio of buckwheat flour to allpurpose flour. This would alter the objective and subjective data in a positive way in order to obtain the most nutritionally beneficial product that can be produced. If this pumpkin bread was used as a strictly gluten-free product by using 100 percent buckwheat flour, complementary ingredients may be used along with the buckwheat flour to enhance the texture and color.
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