Effects of carob substitution to unsalted pretzels on texture, bitterness, color, and consumer preference as a replacement for dark and milk

Transcription

1 Effects of carob substitution to unsalted pretzels on texture, bitterness, color, and consumer preference as a replacement for dark and milk chocolate-covered unsalted pretzels FN 453 Research Project Lisa Cool, Laura Wahl, Brittany Nikolich November 21, 2011

2 Abstract: Carob is known to have many health benefits in the human body. It is a popular substitute for chocolate. Carob powder is a non-dairy ingredient that is similar in taste to chocolate. This is very beneficial to those individuals who have a dairy allergy. Carob is also lower in fat, calories, and caffeine than regular chocolate. Carob chips were compared to milk and dark chocolate chips as a coating on pretzels in order to eliminate any risk of dairy allergens and to see if taste and consumer preference were affected. Three different chocolate coatings of milk chocolate, dark chocolate, and carob chocolate were prepared and dipped in pretzels. The chocolate coatings were objectively tested using the Brookfield viscometer and Hunter colorimeter. They were then tested subjectively to rate the products on bitterness, appearance, and overall consumer preference. The results of the subjective testing showed that more people preferred the dark chocolate and milk chocolate to carob. According to the objective measurements, the viscosity of carob was quite different from milk chocolate and dark chocolate. Also, the Hunter colorimeter values indicate that the hue, value, and saturation of carob are significantly different from milk chocolate and dark chocolate, thus impacting appearance of the final product. Introduction: Allergies are of serious concern in our society today. There are eight common food allergies and cow s milk is among these. This allergy affects mostly infants with 2-6% of young children having a cow s milk allergy. But, % of adults also suffers from the allergy (Crittenden and Bennett, 2005). For these people suffering from the allergy, the only option is to avoid the allergen completely. This is why it is important to find substitutes for dairy-containing products. One such dairy-containing product is milk chocolate. A popular substitute for chocolate is carob powder. Carob powder is a non-dairy ingredient that is similar in taste to chocolate. Carob powder also has more health benefits than regular chocolate. Most chocolate recipes call for added sugar. Because it is naturally sweeter than chocolate, there is no need for added sugar (Environmental Nutrition, 1993). Carob is much lower in fat and calories because it is naturally sweet, with a sugar content of approximately 41% (Mehmet et al., 2007). This is important for our society because many people are trying to watch their weight and carob could be a good alternative for them over chocolate. The fibers in carob have been shown to have hypolipidemic effects. Zavoral and colleagues found that in adults and children with familial hypercholesterolemia that were fed diets containing carob bean gum for three months, serum cholesterol was lowered 10-15%, and LDL cholesterol was lowered 11-19% (1983). It is believed that the fibers in carob gum bind bile acids and increase their excretion, which helps to decrease serum lipids (Zavoral et al., 1983). Furthermore, the addition of the carob gum to popular foods had no adverse effects on health or palatability (Zavoral et al, 1983). Thus, the substitution of carob for chocolate may have some potential for reducing serum cholesterol levels. Unlike chocolate, carob powder does not contain caffeine (Sahin et al, 2009). A diet low in caffeine can be beneficial. Caffeine is a stimulant that boosts energy, but it also can cause restlessness and delay sleep for some people. Too much caffeine can lead to headaches and a

3 faster heartbeat. It is also suggested that women who are pregnant should consume a diet low in caffeine (Hogan et al., 2002). People react differently to caffeine, with some people being more sensitive to its effects. Therefore, substituting carob powder for chocolate can be beneficial for those who are sensitive to the effects of caffeine. The purpose of this study was to substitute carob for chocolate coating on a pretzel in order to eliminate any risk of dairy allergens in the product, as well as to provide a snack that is lower in caffeine and sugar, without compromising taste or consumer preference. Suffering from a food allergy can be hard for people when they have to give up foods that they love and many people love chocolate. Offering carob as a substitute for chocolate allows people with a dairy allergy to continue eating their favorite chocolate recipes. And as mentioned, carob can also be a great substitute for people monitoring their calorie and caffeine intake. The independent variable in this experiment is the chocolate replacer used (milk chocolate, dark chocolate, or carob). The dependent variables that were measured include texture, more specifically the viscosity of the chocolate/carob, bitterness, color, and consumer preference. The hypothesis of this study was that substitution of carob for dark chocolate or milk chocolate on unsalted pretzels will have no effect on texture, bitterness, color, or consumer preference. Three separate trials were conducted. A taste panel was used to rate the products on bitterness, appearance, and overall consumer preference. The product was then tested objectively using the Brookfield viscometer and Hunter colorimeter. Methods: Sample Preparation The recipe for the carob/chocolate covered pretzels is a general recipe adapted from several recipe websites. The recipe is listed below. Milk Chocolate-Covered Pretzels: 1 bag (326 g) Nestle Toll House milk chocolate chips 15g vegetable shortening 78 unsalted small pretzel twists Dark Chocolate-Covered Pretzels: 1 bag (283 g) Nestle Toll House dark chocolate chips 15g vegetable shortening 78 unsalted small pretzel twists Carob-Covered Pretzels: 1 bag (283 g) SunSpire unsweetened carob chips

4 15g vegetable shortening 78 unsalted pretzels The shortening and chocolate or carob was heated in a double boiler until completely melted (1-2 minutes). The pretzels were individually dipped into the melted chocolate or carob and allowed to cool in a refrigerator for approximately 30 minutes on sheets of waxed paper, or until the coating was firm. Once cooled, the pretzels were evaluated by a sensory panel on bitterness, color, and overall preference. A total of 78 pretzels were dipped into each kind of melted chocolate or carob. To control for any confounding variables, all the utensils were used at the same temperature for each experiment. Chocolate and vegetable shortening were stored at room temperature (approximately 25 C) until they were needed for the trials. After the pretzels were dipped in their respective coatings, all samples were stored in the same refrigerator for 30 minutes. Subjective Testing Several sensory tests were performed with a consumer panel of 10 students in the FN 453 laboratory. Each sample was assigned a separate 3-digit number for each test. A 9-point hedonic rating scale was used to judge overall consumer preference for each sample. Overall appearance was ranked for each sample, with care taken to ensure that the pretzel chosen to be ranked from each group looked evenly coated and had a minimal amount of smudging and dripping. Finally, a triangle test was conducted to evaluate the bitterness of each sample. Figure 1 displays the scorecard that was given to each panelist for evaluating the carob- or chocolate-covered pretzels.

5 FIGURE 1 Sensory Evaluation Scorecard Sensory Evaluation Scorecard Product Date Please evaluate the product by looking at it and tasting it. Considering all the characteristics, please indicate your overall opinion by checking one box: Dislike Dislike Neither like Like Like Extremely moderately nor dislike moderately extremely Overall Appearance Ranking: Rank samples (931, 265, 567) in descending order for appearance on the three point scale below Bitterness Triangle test: Which sample (155, 734, or 490) differs from the other two in bitterness?

6 Objective Testing Objective methods for evaluating the quality of the chocolate included the Brookfield viscometer and the Hunter colorimeter. The methods were performed while the chocolate was still warm and not yet firm. To make sure results were consistent, each chocolate variable was held at approximately the same temperature of 113 o F. Brookfield Viscometer: The Brookfield viscometer was used to measure any changes in viscosity among the variables. A spindle size of 5 was used for each trial. The viscosity in centipoise (cp) of chocolate variable was taken at 6 repetitions per minute (rpm), 10 rpm, 12 rpm, and 20 rpm. The viscosity was recorded at each rpm three times and then the average viscosity was calculated. Hunter Colorimeter: The Hunter colorimeter was used to measure the color of each chocolate or carob variable. Standard procedure was carried out for utilizing the Hunter colorimeter. The Y, x, and y Hunter parameters were recorded three times for each variable. The average was then calculated and recorded. Replication, Randomization, and Sampling All three variables were replicated three times using the same methods. The method was performed the same way all three times in order to ensure that there were no confounding variables and to ensure uniformity. For the overall appearance in the sensory evaluation, three random numbers were used for each trial: 931, 265, and 567. For the triangle test, we assigned the random numbers 155, 734, ad 490 to the variables.

7 Results: TABLE 1 Average results for sensory evaluation of pretzel samples using hedonic evaluation on a scale of 1-9* Samples Consumer Preference Carob 3 Milk Chocolate 6 Dark Chocolate 8 *1= disliked extremely, very unpleasant flavor, and worst texture. 9= liked extremely, excellent flavor, best texture FIGURE 2 Figure 2. Hedonic ratings for carob, milk chocolate, and dark chocolate based on a 1-9 scale with 1= dislike very much and 9= like very much. TABLE 2 Measuring viscosity of milk chocolate by viscometer (g/cm) at various rpms Variable Trial 1 Trial 2 Trial 3 Average 6 rpm rpm rpm rpm

8 TABLE 3 Measuring viscosity of dark chocolate using a viscometer (g/cm) at various rpms Variable Trial 1 Trial 2 Trial 3 Average 6 rpm rpm rpm rpm TABLE 4 Measuring the viscosity of carob using a viscometer (g/cm) at various rpms Variable Trial 1 Trial 2 Trial 3 Average 6 rpm rpm rpm rpm TABLE 5 Comparing viscosity of milk chocolate, dark chocolate, and carob at various rpms Variable 6rpm 10 rpm 12 rpm 20 rpm Milk Chocolate Dark Chocolate Carob Average SD FIGURE 3 Figure 3. Comparing viscosity of milk chocolate, dark chocolate, and carob at different viscometer speeds.

9 TABLE 6 Hunter colorimeter Y values for carob, dark chocolate, and milk chocolate Carob Dark Chocolate Milk Chocolate Trial Trial Trial Average SD TABLE 7 Significance of Y-value comparisons Carob Dark Chocolate Milk Chocolate Carob x x x Dark Chocolate ** x x Milk Chocolate 3.65E-6** 2.33E-6** x **p<0.05 FIGURE 4 Figure 4. Column chart of Hunter colorimeter values for Y in each variable.

10 TABLE 8 Hunter colorimeter x values for carob, dark chocolate, and milk chocolate Carob Dark Chocolate Milk Chocolate Trial Trial Trial Average SD TABLE 9 Significance of x value comparisons Carob Dark Chocolate Milk Chocolate Carob x x x Dark Chocolate x x Milk Chocolate 0.005** 3.75E-5** x ** p<0.05 FIGURE 5 Figure 5. Column chart of Hunter colorimeter values for x in each variable.

11 TABLE 10 Hunter colorimeter y values for carob, dark chocolate, and milk chocolate Carob Dark Chocolate Milk Chocolate Trial Trial Trial Average SD TABLE 11 Significance of y value comparisons Carob Dark Chocolate Milk Chocolate Carob x x x Dark Chocolate ** x x Milk Chocolate ** x **p< FIGURE 6 Figure 6. Column chart of Hunter colorimeter values for y in each variable.

12 Discussion Our experiment disproved the null hypothesis, verifying that the different types of chocolate or carob used for the pretzel dip caused differences in viscosity, bitterness, appearance, and consumer preference. Since the carob used in this experiment was unsweetened, the taste was more bitter than expected. This may have been the reasons for the low scores on the sensory evaluation for consumer preference. All sensory panelists rated carob pretzels as bitterer than the other two chocolate-dipped pretzels. When examining the ingredient labels for each of the chocolate and carob chips, it was noted that carob chips had 0.47 g of sugar per each gram of carob. Milk chocolate chips had 0.57g of sugar per each gram of chocolate. Dark chocolate had 0.43g of sugar per each gram of chocolate. However, the discrepancy occured with the ingredient label for the carob chips, which claimed that 1 serving is 2 Tbsp, or 15 grams. Since 2 tablespoons is actually closer to 30g, this would bring the sugar content to 0.23g of sugar per gram of carob. More research needs to be done to determine the manufacturer s intentions for serving size and labeling for the carob chips. Future research with carob products might want to focus on controlling amounts of sugar across all variables, or experimenting with sweetened carob chips to see if the added sweetness impacts consumer preference. Carob was also rated lowest in appearance 60% of the time by the sensory panelists. Dark chocolate was rated highest 70% of the time. In fact, dark chocolate scored highest in both overall consumer preference and appearance in the sensory evaluations (Figure 2). Milk chocolate scored second highest in these areas, and carob received the lowest scores in each category. When judging the overall appearance of each variable, we tried to choose pretzels from each sample with the similar amounts of chocolate or carob dip, to minimize obvious differences as much as possible. However, the carob-dipped pretzels appeared to have a grainier texture that was less desirable to consumers. Future research working with carob dips might want to consider adding fats or gums to give the carob a smoother appearance. When analyzing the viscometer readings, milk chocolate had consistently higher values for viscosity, despite changes in rpm. This could be due to the addition of soy lecithin that is found in milk chocolate, but not in dark chocolate. However, soy lecithin was also found in the carob sample, which had the lowest viscosity. Dark chocolate was always less viscous than milk chocolate, but more viscous than carob, despite rpm speed. Finally, carob dip was always found to be the least viscous of the three variables, regardless of rpm. Dark chocolate had more fat per serving than the milk chocolate and carob. Despite this fact, dark chocolate was still less viscous than milk chocolate. Carob, which did not contain milkfat, was found to be less viscous in each trial. Ohene Afoakwa and colleagues (2007) noted that the addition of whey protein to chocolate generally increases viscosity. However, the addition of whey powder that was seen in the carob chips did not seem to produce the level of viscosity that was seen in the two chocolate variables. This could be due to the fact that the added fat and milkfat seen in the chocolate samples had

13 more of an impact on viscosity than the amount of whey protein added to the carob chips. As pointed out by Ohene Afoakwa, et al., other factors such as particle size, particle distribution, and lipid crystallization during manufacture also play a role in the rheological properties of chocolate (2007). Future research should take into consideration these properties when comparing viscosity of different types of chocolate. Results from the Hunter colorimeter readings show that milk chocolate, on average, has a higher Y- value (4.01), which makes sense, since milk chocolate is lighter in color compared to dark chocolate. Y values for dark chocolate (2.91) and carob (2.77) were similar to each other, yet statistically different from each other (p<0.0043), but much lower than Y values for milk chocolate. This makes sense, since both the carob and the dark chocolate were darker in color compared to the milk chocolate. The x-values for milk chocolate (0.4775), dark chocolate (0.4869), and carob (0.4867) were all very similar, indicating that they all have about the same balance of red and green color. In fact, carob and dark chocolate were not found to have statistically significant differences in x-values. The y-values for milk chocolate (0.3891), dark chocolate (0.3887), and carob (0.3944) were very similar, indicating that all samples had approximately equal balances of yellow and blue color. Dark chocolate and milk chocolate were found to have no statistically significant differences in y-values. Therefore, based on this data, the major difference in appearance due to color was seen in milk chocolate, which had a lighter color. Statistically significant differences were seen in other areas, but were not as obvious as the differences seen in Y values (Figure 4). Future trials with this experiment might involve using food dyes to darken the color of the milk chocolate to keep the color consistent across all samples. There were a few limitations to our experiment. Inexperience using the Hunter colorimeter may have provided inaccurate data for the Y, x, and y values. The fact that the market order for the carob chips did not specify for sweetened (as opposed to unsweetened) chips caused a greater difference among samples than what we had hoped to see originally. The dipping of the pretzels in carob or chocolate caused some pretzels to be coated more or less thoroughly than others, which might have affected the overall appearance results from the sensory evaluation. Although we tried to measure viscosity of each dip immediately after it had melted, due to the amount of time it took to measure the viscosity of each sample at 4 different rpms, the dip might have thickened somewhat during that time, causing viscosity measurements to be less accurate. References: Crittenden, RG, Bennett, LE Cow's milk allergy: a complex disorder. Journal of the American College of Nutrition. 24(5): It's hard to fudge on chocolate Environmental Nutrition. 16(2): 3.

14 Mehmet, MO, Derya, A, Harun, G Some compositional properties and mineral contents of carob (certaonia siliqua) fruit, flour and syrup. International Journal of Food Sciences and Nutrtion. 58(8): Ohene Afoakwa, E, Paterson, A, Fowler, M Factors influencing rheological and textural qualities in chocolate a review. Trends in Food Science and Technology. 18: Sahin H, Topuz A, Pischetsrieder M, Ozdemir F Effect of roasting process on phenolic, antioxidant and browning properties of carob powder. European Food Research Tecnology. 230(1): Zavoral, JH, Hannan, P, Fields, DJ, Hanson, MN, Frantz, ID, Kuba, K, Elmer, P, Jacobs, DR The hypolipidemic effect of locust bean gum food products in familial hypercholesterolemic adults and children. The American Journal of Clinical Nutrition. 38(2):