Elaboration , Physicochemical and Sensory Analysis of a Sweet Bread Made with Buckwheat and Fruit Flours

The aim of this study was to evaluate the viability of new gluten free sweet bread, as well as their physicochemical features and acceptance. As more and more people become aware of coeliac disease, it is important to increase the options in terms of gluten free bakery products. The adaptation of bakery product-sweet bread-to gluten free versions can be justified for its role in preventing coeliac problems. Wheat flour was substituted by common buckwheat flour mixed with fruit flours and their physicochemical characteristics were evaluated, compared to standard sweet bread, with wheat flour in its composition. The passion fruit sweet bread had the highest percentage of humidity, with significant difference among the other formulations (p≤0.05). Ash and lipids had the highest amount in the banana sample and proteins showed its highest value in the standard sweet bread (p≤0.05). A sensory analysis was conducted, with good results. It was also evaluated the purchase intention, indicating that these products are not only viable, but worth buying.


INTRODUCTION
Gluten is an elastic, fibrous substance, formed by the combination of flours proteins (such as gliadin and glutenin) and water, resulting in hydration and formation of a protein complex by disulphide and hydrogen bonds.Its purpose is to retain gases that are formed by fermentation, turning the dough/batter expandable but resistant to cracks, which makes possible for it to grow during bakery.Its other purpose is to retain humidity from the batter even after baking, helping to ensure its elasticity and softness (Wieser, 2007;Gallagher et al., 2004).However, gluten comprises peptides, which cause autoimmune reactions on people with coeliac disease (Moore et al., 2006).Among the extra-intestinal manifestations, there are iron deficiency anemia, hepatic steatosis, psychiatric syndromes, dental enamel hypoplasia and arthritis (Mahan and Escott-Stump, 2004).
An alternative to wheat is the common buckwheat (Fagopyrum esculentum Moench), which lacks gluten in its composition.Although called buckwheat due to its chemical composition similarities to wheat (Silva et al., 2002), the buckwheat tends to the rice family.
It is a good source of fiber and, also contains flavonoids, such as rutin, which is known by its antioxidant properties (Silva et al., 2002;Yang et al., 2008), polyunsaturated essential fatty acids, fagopyratol and sterols.It has a high rate of vitamins, amino acids and minerals (Kalinova and Dadakova, 2009).It also has functional components, which assists in the cholesterol and blood sugar regulation, reduces high blood pressure and even helps to prevent the risk of cancer (Wojcicki et al., 1995;Kim et al., 2004).
Sweet bread is originary from Germany, where it is known as kuchen and was brought to Brazil by immigrants, who settled firstly in the Vale dos Sinos-Rio Grande do Sul, spreading later to other parts of the state.During the years, the recipe went through changes, being adapted to local conditions and available ingredients, until it became the current version, traditionally in Rio Grande do Sul.Among the ingredients of sweet bread, wheat flour is the main one.
Due to the fact that there is gluten in its composition, coeliac people are not able to consume such dish.There are a lot of products that are gluten free and buckwheat is becoming a very common ingredient in products such as pasta, bread, cookies, noodles and spaghetti (Manthey et al., 2004).
A sweet bread formulation bearing the characteristics of being gluten-free, easy to prepare and with a good acceptability would provide improvements in the life quality of such patients, offering a wider range of food choices in their diet.Thus, this study will endeavor to produce a sweet bread formulation that attends these features.

MATERIALS AND METHODS
The physical and sensory analysis were conducted in the Dietetic Technique Laboratory of the Nutrition course in the Medicine School (FAMED) of Universidade Federal do Rio Grande do Sul (UFRGS).
The sweet bread loafs were elaborated with wheat flour being replaced by common buckwheat flour mixed with passion fruit, apple or banana flour, resulting in three different gluten free formulations.Some changes had to be made to the original formulation in order to adapt the recipes to those flours during the tests.The ingredients used can be found in Table 1.
All ingredients were weighed using a Plenna ® precision scale.The common buckwheat, passion fruit, apple or banana flours were available at the Dietetic Technique Laboratory of the Nutrition course in the Medicine School (FAMED) of Universidade Federal do Rio Grande do Sul (UFRGS).All the ingredients were bought at a local market, as was the standard sweet bread, made with wheat flour, which was used as control sample.
The elaboration consisted in firstly preheating the Dako ® oven, Luna model.Then, egg whites were beaten with a Top Mixer mixer, Sield ® brand.Using the same mixer, sugar, vegetable oil and the yolks were mixed until a cream was formed.Common buckwheat flour, each fruit flour, yeast and milk, were added to this cream, which was being mixed all along.When the batter was homogenized, the beaten egg whites were added, mixed slowly with a spreader.The batter was, then, poured on a greased baking dish and the sugar crust was added on top of it.The batter with the sugar crust was then taken to the Dako ® oven, Luna model, at 180°C, for approximately 1 h.
For the sugar crust, the ingredients were homogenized in a metal bowl and mixed with the fingertips till it turned into many irregular "lumps".
The physical analyses occurred at the Dietetic Technic Laboratory, where depth was measured with a scale in three different spots of each formulation already on their respective baking dish, before and after baking.The formulations were also weighted, three times each, before and after baking, using a precision scale.
The chemical analyses were conducted at the Bioactive Compounds Laboratory of the Institute of Food Science and Technology (ICTA) of Universidade Federal do Rio Grande do Sul (UFRGS).Moisture, ash, lipids, proteins analyses were performed following Adolfo Lutz Institute's protocols (2008), with three samples.For comparison parameters, a standard sweet bread loaf was used, bought at a local market.
The sensory analysis was conducted at the Dietetic Technic Laboratory and was performed by 36 nontrained, non-coeliac people, after signing an informed consent form.The participants of the survey were students and teachers from the university.The sweet bread loafs were evaluated in terms of global acceptance, texture, color, flavor and appearance.The sensory analysis was conducted isolated with each evaluator, at ambient temperature, using white plastic dishes, numbered with three random digits, which corresponded to each respective flours (passion fruit, apple, banana and wheat flour).The evaluators received water to drink before evaluating each sweet bread sample.A hedonic scale of 9 points was used, each point meaning: The statistical analyses were made using the program ESTAT, version 2.0, with the Tukey's test, considering a 5% error probability.The results are given as means±standard deviation based on three measurements for each sample.There were considered as being statistically significant the results that had differences with p≤0.05.

Physical analysis:
The physical analysis showed that the raw and baked sample composed by the combination of common buckwheat flour and passion fruit flour was the heaviest (p≤0.05),followed by the apple sweet bread loaf and the banana sweet bread loaf (Table 2).
The depth analysis of the raw samples suggests that the passion fruit flour sample also obtained more volume (3.06 cm), followed by the banana flour (2.63 cm) and the apple flour (2.50 cm) samples.However, no significant differences were found (p>0.05).The depth analyses of the baked products are as follows: passion fruit flour sample (4.53 cm) and apple flour sample (4.43 cm), without significant differences between them (p>0.05),but presenting a significant difference in relation to the banana flour sweet bread loaf (3.63 cm-p≤0.05).
The baking time also presented significant statistic difference: 72 min for the passion fruit flour sample, 64 min for the apple flour one and 60 min for the banana flour one, with an average of 65.3 min baking time.

Chemical analysis:
The chemical analysis (Table 3) suggests that the passion fruit sample had a higher moisture percentage (46.57%),with statistically significant difference (p≤0.05) in regard to the other samples.The banana sample indicated a higher ash percentage (1.08%),although without significant difference (p>0.05) when compared to the passion fruit sweet bread loaf.The fat test showed the banana sample as having the highest percentage of all (11.30%), with statistically significant difference in regard to the other samples (p≤0.05), which did not have a significant difference among themselves (p>0.05).Proteins percentage indicated the standard sweet bread loaf as having the highest value (2.18%), with significant differences in regard to all the other samples (p≤0.05).
Fibers (total, insoluble and soluble) were also evaluated.The highest amount was found in the passion fruit one, which total fiber (14.51%)overcomes more than two times apple sweet bread (5.8%).The commercial sample presented the lowest percentage (2.37%) and there were significant differences among each other (p≤0.05).Insoluble fibers kept the ranking, with the passion fruit one showing 12.72%, followed by the apple one (5.1%), the banana sweet bread (4.49%) and the commercial sample (0.8%), again, all with significant differences (p≤0.05).The passion fruit loaf and the commercial sample scored 1.79 and 1.57%, respectively, in soluble fiber.Both showed statistically significant differences (p≤0.05).

Sensory analysis:
The sensory analysis of the sweet bread samples showed a good acceptability rate of the ones made with common buckwheat flour and fruit  4).Both apple and banana samples had good results in global acceptability (6.20 and 6.28, respectively, which means "like slightly", according to the hedonic scale), with no significant differences between them or even in comparison to the standard one, which still had the best result of all (7.22-like moderately).
The apple sweet bread was the one with the best score in terms of appearance (7.50-like moderately), with no significant differences (p>0.05) in relation to the standard commercial sample (6.66-like slightly).The color evaluation presented a good score for all samples, with no significant differences (p>0.05)among the samples with the exception of the banana one, which had the lowest result.
The standard commercial sweet bread had the best result in the taste assessment (7.5-like moderately), with significant differences (p≤0.05) in relation to the other sweet bread loafs.The apple and banana samples had the following results: 5.80 (neither like nor dislike) and 6.19 (like slightly), respectively, with no significant differences (p>0.05) between them.
The results concerning texture indicated the banana sweet bread loaf as the best one (7.11-likemoderately), but without significant differences (p>0.05) in relation to the apple sweet bread loaf (6.97-like slightly) and the standard sweet bread one (6.77-likeslightly).
Evaluator's purchase intention: Table 5 presents the evaluator's purchase intention test, which indicated the standard commercial sweet bread as the most likely of being bought (4.11), with significant differences (p≤0.05) in relation to the other sweet bread loafs, followed by the banana (3.31) and the apple samples (3.30).

DISCUSSION
Sweet bread loafs made in this study presented lower growth rate when compared to the standard commercial one.Ács et al. (1996a, 1996b) studied the viability of using various binding agents, such as guar, xanthan, tragant and locust bean gum as substitute for gluten in gluten-free corn starch bread.These tests showed a significant increase in those products' loaf volume.It is possible that a gluten-free sweet bread formulation added of such binding agents could improve its growth rate.Bonafaccia and Kreft (1994) also had similar results while experimenting bread formulations blended with increasing amounts of buckwheat flour.By the photographs showed in that study, it is clear that, as the percentage of buckwheat flour increases in the blending, the height gradually decreases, due to the decrease of the gluten matrix in the composition.
Moisture percentage was higher in all buckwheat sweet bread samples than in the standard one.This can be due to the higher water-binding feature of the buckwheat starch, which is superior to wheat (Wijngaard and Arendt, 2006).Also, Hager et al. (2012), in a study to investigate the quality, sensory and ultra structure characteristics of gluten-free bread, found that the moisture content was related to the amount of water added to the dough samples.This could be attributed to the extra milk volume added to the passion fruit sweet bread batter.On the other hand, moisture content is very important when regarding deterioration of baking quality, which is less in lower moisture percentage due to decrease in activity and respiration of microorganisms (Staudt and Zeigler, 1973).This could jeopardize the shelf life of the glutenfree sweet breads made in this study.
The gluten-free sweet bread loafs presented an increase in ash percentage in relation to the control sample.Bilgiçli (2008) also found an ash amount increase in buckwheat flour, corn starch and rice flour pasta formulations when compared to wheat flour control pasta.As the buckwheat flour amount increased from 40 to 60 g, so did the ash amount.Another study by Bonafaccia and Kreft (1994) also noticed higher ash percentage in 100% buckwheat flour pasta in comparison to 50% buckwheat flour+50% wheat flour pasta.Nevertheless, ash percentage could also be related to the fruit flours, as the apple sweet bread sample presented lower ash percentage than the standard commercial one.Filipcěv et al. (2011) using increasing amounts of buckwheat to substitute wheat flour in 30, 40 and 50%, respectively in ginger nut biscuit, found higher rates in fat percentage, although with no significant difference (p>0.05).This could partially explain our findings in fat content being higher in gluten-free sweet bread samples than in the standard commercial one, as the first ones were made with whole milk.Jozinović et al. (2012) added different amounts of buckwheat flour to corn meal (ratio meal: flour = 70:30, 50:50 and 30:70), in order to determine its effects in extruded and nonextruded samples.There was an increase in fat percentage in non-extruded samples following buckwheat flour ratio.
Levels of protein were lower in all buckwheat flour sweet bread samples.Although wholegrain buckwheat flour contains higher protein percentage when compared to wheat flour (Bonafaccia et al., 2003), it is also known that refined buckwheat flour has lower protein content than refined wheat flour.Rayas-Duarte et al. (1996), while studying the quality of spaghetti containing buckwheat, amaranth and lupin flours mixed with durum flour, found that the higher the percentage of buckwheat, the lower the amount of protein the pasta would have.Unfortunately, there are few reports on the technological quality of buckwheat (Ikeda et al., 1997).
It is already well known that dietary fiber plays an important role in reducing the risks of nontransmissible chronic diseases, such as cardiovascular diseases (Marlett, 2001).High percentage of fiber were also found by Chau and Huang (2003), in passion fruit seeds-which is used to produce the passion fruit flour used in one of the sweet breads-specifically insoluble fiber.In another study, apple fiber was compared to wheat and oat bran (Chen et al., 1988).The total dietary fiber in apple was 61.9%, while wheat bran was 38.00%.Fruit flours usually have high levels of fiber.Although they were blended with buckwheat flourwhich has significant more fiber than wheat flour (USDA, 2007), it is clear they help to improve the volume of fiber in one's diet.Bilgiçli (2008), when studying the use of buckwheat flour in the production of gluten-free egg noodle, noticed that the color acceptability of the control sample was better than the buckwheat samples' one.That was not the case in this study, where the passion fruit and apple samples had the highest acceptability rates.This could be related to color changing due to the fruit flours, which caused a darker appearance to the sweet bread loafs.Nowadays, dark colored food tends to attract consumers' attention, since it is usually attributed to higher amounts of dietary fiber, as noticed by Chillo et al. (2008), when adding buckwheat flour and durum wheat bran to spaghetti.Lin et al. (2009) reported that buckwheat improved wheat bread's color because it contains more phenolic compounds, which could inhibit the browning processes during baking.Baljeet et al. (2010) also had low score in tasting evaluation of cookies incorporated with buckwheat.The authors suggest that this probably happened due to higher concentrations of rutin, which gives a bitter taste to buckwheat flour products.On the other hand, according to Chlopicka et al. (2012), sensory quality analysis of bread samples made with pseudo cereal flours (especially buckwheat) blended with wheat flour may increase acceptability attributes such as taste, color and odor.These observations suggest that the addition of buckwheat flour to bread can improve not only antioxidant but also sensory properties of bread.
Purchase intention suggests that the commercial standard sweet bread is more likely to be bought.However, there could be an assessment bias since the evaluators were all non-coeliac people and, therefore, could have considered a gluten product more to their liking.Nevertheless, the banana and apple sweet bread samples received a good purchase intention score.The passion fruit sample, on the other hand, received the lowest score, which suggests that more research can be done to improve its acceptability.

CONCLUSION
Changing wheat flour for common buckwheat flour demanded a few adaptations on products formula.Sweet bread formulations usually include candied fruit or fruit jelly, which made us consider adding fruit flour to the recipe a viable option.This also helped to give a different flavor to each sweet breads and made it possible for us to elaborate more than one recipe.The results were satisfactory, with good batter growth, good taste and overall acceptability.Although more research is necessary to improve these products, we believe that this gluten-free sweet bread loafs are viable products.

Table 2 :
Physical analysis of gluten free and standard commercial sweet breads Same superscript in same columns indicate that there is no significant difference between the results, for p≤0.05

Table 3 :
Mean chemical composition of gluten free and standard commercial sweet breads in g % Same superscript in same columns indicate that there is no significant difference between the results, for p≤0.05

Table 4 :
Sensory analysis of gluten free and standard commercial sweet breads Same superscript in same columns indicate that there is no significant difference between the results, for p≤0.05It was also evaluated the purchase intention, using the following scale: • Would certainly not buy it • Would probably not buy it • Not sure if would buy it • Would probably buy it • Would certainly buy it This study was approved by the Ethics Committee of Universidade Federal do Rio Grande do Sul (UFRGS), process number 20556.

Table 5 :
Evaluator's purchase intention of gluten free and standard