WHEAT BRAN (TRITZCUM AESTWUM): COMPOSITION, FUNCTIONALITY AND INCORPORATION IN UNLEAVENED BREAD ABSTRACT

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1 WHEAT BRAN (TRITZCUM AESTWUM): COMPOSITION, FUNCTIONALITY AND INCORPORATION IN UNLEAVENED BREAD ARCHANA SHENOY H. and JAMUNA PRAKASH' Department of Studies in Food Science and Nutrition Universiry of My sore, Manasagangotri Mysore INDlA Accepted for Publication February 20, 2001 ABSTRACT High fiber Chapathi, an Indian unleavened bread incorporating different levels (515%) of wheat bran to wheat flour was prepared and evaluated for acceptability and farinograph characteristics. Whole wheat flour, wheat bran and its differently milled fractions were analyzed for chemical composition and fwtctional properties. The water absorption capacity of bran was slightly lower than that of jlour and did not increase as a function of time. The bran incolporated doughs were dificult to knead and sticky with no change in rolling properties. Farinograph characteristics revealed an increase in dough development time and a decrease in mixing tolerance index as the level of incolporation of bran increased. Wheat bran incorporatedproducts scored lesser for the sensoly quality attributes than controls. The differences were statistically significant forproducts prepared with 10% and 15% bran and not significant for products prepared with 5% level of bran. It can be concluded that wheat bran can be incorporated up to a level of 5% for preparation of high fiber phulkas or chapathis without affecting sensory quality. INTRODUCTION Among food grains, wheat is one of the most extensively produced and consumed cereals. Wheat, mainly as flour, is utilized for the preparation of a wide range of products like bread, leavened and unleavened, cakes, biscuits, cookies, etc. Wheat and wheat products contribute substantially towards proteins, vitamins and minerals when consumed as a major component of diet (Ortho and Shellenberger 1971). Wheat bran is an important byproduct of the wheat milling industry. Wheat bran forms a good source of proteins and ' Correspondent author: Dr. (MIS.) Jamuna Prakash. jampr55@hotmail.com Journal of Food Quality 25 (2002) All Rights Reserved. "Copyright 2002 by Food & Nutrition Press, Inc., Trumbull, Connecticut. 197

2 198 A. SHENOY H. and J. PRAKASH minerals apart from being a rich source of dietary fiber. The fiber in wheat bran is mainly the insoluble type (Kent 1974). Use of wheat bran in the treatment and prevention of certain western diseases due to its physiological effects are being viewed with great interest (Burkitt 197 1). Fiber from wheat bran is an effective fecal bulking agent (Anderson 1985). Coarse wheat bran is found to be more effective than fine bran as a fecal bulking agent due to its higher water holding capacity (Anderson and Eastwood 1986). Wheat bran can be used in the treatment of constipation and other related disorder (Burkitt 1977). Incorporation of wheat bran into bread is a commonly used method for increasing the dietary fiber content (Pomeranz ef al. 1977). Addition of wheat bran in products induces certain rheological changes like increased dough water absorption and reduced loaf vohme, thus bringing about major changes in quality characteristics of end products (Finney ef al. 1985). Pretreatment of wheat bran like grinding or presoaking helps obtain a dough with enhanced quality characteristics (Lai et al. 1989). The present study was planned with an objective to incorporate wheat bran in chapathi (an unleavened bread used as a staple throughout India) at various levels and evaluate its organoleptic quality. The bran samples were also analyzed for composition and functional properties. Materials MATERIALS AND METHODS For the entire study, medium strong variety of Aestivum wheat (Triticum aesfivum) was purchased in one lot. It was subjected to milling in a roller mill and the bran was separated from flour. Whole wheat bran obtained by roller milling was dried in a hot air oven and powdered in a grinder to pass through 40 mesh to reduce coarseness. This was used for preparation of products. A portion of wheat bran was further milled in a Quadramat mill to obtain three fractions, namely coarse, medium and fine with particle size of 150 p, 195 p and 275 p, respectively. All the differentially milled bran samples along with whole wheat bran and flour were used for determination of chemical composition and functional properties. All the samples were stored in airtight containers in refrigerator till used. Analysis Whole wheat flour, whole wheat bran and bran fractions were analyzed for moisture, protein, fat and total ash by standard methods (AOAC 1984). Other constituents like calcium (Bernard and Hawks 1965), phosphorous (Taussky and Shorr 1953), iron (NIN 1984), insoluble and soluble dietary fiber by enzymatic-

3 WHEAT BRAN IN UNLEAVENED BREAD 199 gravimetric method (Prosky et at. 1992; Lee et al. 1992) were also determined. Bioavailable iron in wheat flour and whole wheat bran were estimated using the Narasingha Rao and Prabhavati s (1978) method. Certain functional properties of wheat flour and bran samples were also determined namely bulk density (Wang and Kinsella 1976), water absorption capacity (Janicki and Walczak 1954) and fat absorption capacity (Sosulski et al. 1976). Water absorption capacity was also determined as a function of time at 30, 60, 120 and 240 min. For determination of the water absorption property a weighed amount of sample was taken in a preweighed centrifuge tube and mixed well with 5.0 ml of water. This was allowed to stand a room temperature for a specified length of time and centrifuged at 3000 rpm for 20 min. The unabsorbed water was decanted carefully taking care not to disturb the sample. The tube was weighed again. The difference in weight was taken as the water absorbed by the sample. Preparation of Product A popular form of unleavened bread made from whole wheat flour used as a staple item in diet throughout India was selected as a product for incorporating wheat bran. The product was prepared by replacing 5%, lo%, and 15% of whole wheat flour with wheat bran (milled to pass through 40 mesh). Whole wheat flour with no added wheat bran served as control. Two types of unleavened bread were made for the study, namely, Chapathi with oil and Phulka without oil. A dough was prepared with flour, water and salt, kneaded well by hand (30 strokes) and allowed to develop for 1 h. Small portions (25 g) of dough were rolled into flat round sheets to make chapathi or phulku and roasted on a hot pan. A small amount of vegetable oil was smeared on both sides of chapathis while roasting. The amount of water, flour and bran used for different products are given in Table 1. Dough Development Characteristics The dough development properties of all the doughs prepared were studied. The doughs were observed for certain physical characteristics like kneading properties, rolling properties, elasticity and stickiness. A scale was developed for objective determination of properties indicating very good (+ + +), good (+ +) and fair (+). Farinograph characteristics of the flour were studied using a Brabender farinograph (AACC 1988). The various parameters studied were water absorption (amount of water required by a given weight of flour to yield a dough of a given consistency), dough development time (time from addition of water to the development of dough s maximum consistency), dough stability (difference in time between the time when the curve first intercepts the 500 Brabender unit line and the time when the curve leaves the 500 line), mixing

4 200 A. SHENOY H. and J. PFL4KASH tolerance index (the difference in Brabender unit from the top of the curve at the peak to the top of the curve measured 5 min after the peak). TABLE 1. COMPOSITION OF PRODUCTS Product Variation Flour (g) Water (ml) Wheat bran (g) Salt (g) Oil (ml) Chapathi A (control) B I C D Phulka A (control) B C D Sensory Analysis Sensory analysis of the prepared products was done by a panel of 75 members to judge the acceptable level of incorporation of whole wheat bran for various attributes like appearance, color, texture (hardness or softness, degree of coarseness, moistness), flavor and overall quality. A score card was developed based on hedonic scaling with a maximum score of 10 (IS1 1972). The quality grade description indicative of scores given were excellent (9 - lo), good (6-8), fair (4-5) and poor (1-3). Coded samples of the products were presented to panel members with a carrier: coconut chutney. The analysis of chapathi and phulka were done on different days. The sensory analysis data were subjected to statistical analysis. Mean and standard deviation were calculated individually for scores obtained for all quality attributes of each product. Analysis of variance was also carried out to determine significant differences among the quality attributes of products. A post test Bonferroni P value was applied to bring out differences between the attributes of two products. Bonferroni P value indicates the level of significance obtained between 2 products. Unlike analysis of variance which determines level of significance in all the attributes of all the products together, this value gives the comparison only between 2 products (P < 0.05).

5 WHEAT BRAN IN UNLEAVENED BREAD 20 1 Chemical Composition RESULTS AND DISCUSSION The proximate composition of wheat flour and bran sample is given in Table 2. The moisture content of sample varied from 2.17% to 8.5%. The whole wheat bran had a lesser moisture content because it was dried in an oven for further milling. The protein content of whole wheat flour and whole wheat bran ranged from 14 to 15% but on fractional milling of bran the protein content increased progressively as the particle size of the bran decreased. For example, the coarse fraction had 15% protein but the fine fraction had 20% protein. Whole wheat bran also had a higher content of fat (4.08%) in comparison with wheat flour (1.57%). Coarse fraction also had a higher fat content which decreased in medium and fine fractions. Generally bran is supposed to be a rich source of mineral and here also it exhibited a very high content of total ash in whole bran sample as well as in the coarse fraction. The medium fraction and the fine fraction of wheat bran exhibited a progressive decrease in mineral content. The dietary fiber fractions of wheat flour and wheat bran samples presented in Table 2 indicate that wheat contains more of insoluble fiber than soluble fiber. Most of the fiber is present in the bran fraction and gets separated in the roller milling of the wheat. The whole wheat bran in the present study had a very high content of insoluble dietary fiber (42.8%). On fractional milling of wheat bran the coarse fraction as expected showed a very high content of insoluble dietary fiber in comparison with the medium and fine fractions of wheat bran. Although wheat contains more of insoluble fraction of fiber as stated earlier, in milled wheat flour sample the soluble fiber fraction comprised 19% of total fiber whereas in all the wheat bran samples the soluble fiber fraction ranged from %. This clearly indicates that bran samples were richer in insoluble fiber fraction. The higher mineral content of bran samples as reported earlier are also reflected in the iron, phosphorus and calcium content of samples as estimated in the laboratory. Whole wheat flour had 8 mg iron/loo g of flour whereas wheat bran sample had a very high content of 15.1 mg/loo g. On fractional milling of bran a progressive decrease was observed. The phosphorus content of whole wheat bran was higher than flour and exhibited an increase in the fractions. The calcium content of flour was lower than the bran samples which showed a range of mg/loo g. Bioavailable iron was 1.83 and 3.16 mg/loo g for whole wheat flour and whole wheat bran, respectively.

6 ~ 202 A. SHENOY H. and J. PRAKASH TABLE 2. CHEMICAL COMPOSITION OF WHEAT FLOUR AND BRAN SAMPLES* Constituent (per Whole Whole Bran fractions 1wz) wheat flour wheat bran Coarse Medium Fine Moisture (8) Protein (g) 14 O+O Fat ( Carbohydrate(g) (by dilference) Total ash (8) g.001 Insoluble fiber (g) Soluble fiber (g) Iron (mg) Phosphorous (mg) Calcium (mg) Bioavailable iron (mg) *:Values indicate means of duplicate determinations. Proximate composition of wheat bran samples aid effect of differential milling on the composition have been studied by many.workers. Ranhotra er al. (1994) reported an increase in the protein content of wheat bran with a reduction in particle size as observed in the present study. They As0 reported a reduction of total ash content of coarse fraction which ranged fron %, whereas the fine fractions had an ash content of %. Halverson and Zeleny (1988) found the protein content of wheat bran to be in the rmge of 14-16%. Functional Properties The bulk density, water absorption capacity and oil absorption capacities of wheat flour as well as the wheat bran samples are given in Table 3. Bulk density of the samples varied from 4.2 g/ml to 16.8 g/ml. Among the samples whole wheat flour had the least bulk density value of 4.2 g/ml and the coarse wheat bran fraction had the highest value of 16.8 g/ml,. A gradual decrease in the bulk density of the samples was observed with decreases in the particle size of the bran samples.

7 WHEAT BRAN IN UNLEAVENED BREAD 203 TABLE 3. FUNCTIONAL PROPERTIES OF WHEAT FLOUR AND BRAN SAMPLES* Properties Whok wheat Whole wheat Bran fractions flour bran Coarse Medium Fine Bulk density (#mi) Water absorption capacity (mu100g) Fat absorption capacity (mu100g) 18.~ k Water absorption capacity 8s a function of time (mv100g) 60 min , min L w min , *: Values indicate means of triplicate determinations. The water absorption capacity of wheat flour was 86.5 ml/loo g, whereas that of wheat bran was 74.5 ml/100 g. Wheat bran seemed to have lesser water absorption in comparison with wheat flour. On fractional milling of wheat bran, the coarse fraction was found to have the least amount of water absorption, which increased significantly in medium and fine fractions. This could be related to compositional differences in the samples. Water absorption capacity of wheat flour and wheat bran samples as a function of time did not show a significant effect. Decrease in the water absorption of the wheat bran and wheat flour sample was observed after 120 min even though a slight increase was observed from 30 to 60 min. The fat absorption capacity of wheat flour was comparatively much lower. Only 18 ml of fat was absorbed by 100 g of flour; whole wheat bran absorbed only 23 ml of fat. The coarse fraction of wheat bran had high fat absorption of 46.5 ml/100 g, which decreased to 30 and 20 ml/loo g, respectively for medium and fine fraction. In the bran samples, the water and fat absorption exhibited an inverse relationship. As mentioned earlier, this could be related to their compositional differences.

8 204 A. SHENOY H. and J. PRAKASH Farinograph Characteristics of Different Dough Used for Product Formulation Farinograph characteristics of dough used for the products are shown in Table 4 and Fig. 1. Water absorption, dough development time, stability of the dough and mixing tolerance index of the dough were studied. From the table it is clear that there was no difference in the water absorption of dough on addition of wheat bran, i.e., water absorption of control sample was about 70% and that of 15% level of incorporation was 71.4%. However, the dough development time recorded a progressive increase with increasing levels of wheat bran to the dough, The value for control was 6.5 min whereas that of dough with 15% wheat bran was 10 min. Dough stability did not show a predictable pattern. It was 6 min for control, 6.5 min for dough with 15% wheat bran, 5 min for dough with 10% wheat bran and 3.5 min for dough with 5% wheat bran. The mixing tolerance index was unlike that reported by other authors. It was 50 BU for control and showed a decrease with 10% (30 BU) and 15% (20 BU) bran. With 5% bran the value was 60 BU. Zang and Moore et al. (1997) reported an increase in mixing tolerance index with a higher level of bran. For the control the value was 26 BU whereas it increased to 30.9, 32.9 and 40.6 BU with 5, 10 and 15% bran in the dough, respectively. They also reported a higher water absorption in dough with an increase in wheat bran. Physical Properties of Dough Prepared for Products Physical characteristics of dough prepared for products such as kneading property, rolling property, dough elasticity and stickiness of dough were analyzed using the grading scale shown in Table 4. Dough with 5 % added wheat bran had a very good rolling property and dough elasticity and was comparable to the control, while with 10% added wheat bran there were slight changes in kneading and rolling properties, i.e., the dough was slightly hard to knead and showed slight resistance to rolling. Elasticity was not affected but the dough was slightly sticky in nature. With 15% wheat bran addition there was considerable change in the physical characteristics except for the dough elasticity, which remained unchanged. Kneading and rolling of the dough was difficult compared with other variations. Stickiness of dough was very prominent. It can thus be concluded that addition of wheat bran influenced dough characteristics to a certain extent. The changes were more prominent with addition of higher percentages of wheat bran.

9 WHEAT BRAN IN UNLEAVENED BREAD 205 Sensory Analysis The mean scores obtained for the sensory attributes of both the products are given in Table 5. There was a remarkable difference observed in sensory attributes of products incorporated with higher level of bran in comparison with the control. Appearance and color ofphulkus scored lower with increasing levels of bran. With a 5% level of incorporation the differences were statistically not significant but at 10% and 15% level they were extremely significant. The different qualities of texture tested in the products were hardness or softness (Texture I), degree of coarseness (Texture 11) and moistness or dryness (Texture 111). The texture of product B (5% wheat bran) was similar to A (control) but that of product C (10% wheat bran) and D (1 5 % wheat bran) showed significant differences. A similar trend was also seen for the attributes of flavor and overall quality. On ANOVA extremely significant differences were found in all the quality attributes. Hence a post test Bonferroni 'P' value was also applied. As can be observed from the Table, quality wise, there is no statistical difference in product A (control) and B (5 % wheat bran), hence phulkas incorporated with 5% bran can be recommended. TABLE 4. DOUGH DEVELOPMENT PROPERTIES OF BRAN INCORPORATED DOUGH Properties Control With 5% With 10% With 15% bran bran bran Farinograph characteristics Water absorption (%) Dough development time (min) Dough stability (min) Mixing tolerance index (BLJ)' Physical characteristicsb Kneading property t+e t Rolling property +tt tee ++ * Dough elasticity +t+ tee $-H +++ Dough stickiness t+e t a: BU - Brabender units b: Grading scale: +-I+ - very good ++ -good + -fair

10 206 A. SHENOY H. and J. PRAKASH h s

11 WHEAT BRAN IN UNLEAVENED BREAD 207 h Bp P v h a_ s 0 z a LL 0 h u_

12 TABLE 5. MEAN SCORES, STANDARD DEVIATION AND BONFERRONI 'P' VALUE a FOR SENSORY ATTRIBUTES OF PRODUCTS Products Appearance Colour Texture I Texture II Texture III Flavour Overall quality "' * * * I.68*** *** "s *** *** I W? ii Phulka A (control) B (with 5% bran) C (with 10% bran) D (with 15% bran) ANOVA 'F' ratio "' "' "s "" * * * * * * * * * * *** *** *** *** *** *** *** *** "' 5, * * * * ** ** > B * * z 0.e Chapathi A (control) B (with 5% bran) C (with 10% bran) D (with 15% bran) ANOVA 'F' ratio * * "' "' * * * * * * * ** * *** *** *** *** *** *** *** *** SO * * * * *** ** * * *** 6,32+1,49*** * * * *** v *** *** X *** a: Bonferroni 'P' value indicates level of significance in comparison with control product for all sensory attributes ns: not significant *: p **: p I 0.01 ***: p IO.001 Texture I = hardness or softness Texture I1 = degree of coarseness Texture I11 = moistness or dryness

13 WHEAT BRAN IN UNLEAVENED BREAD 209 Between phulkas and chapathis, chapathis seem to have a slightly higher score for all the quality attributes. This could be because of use of oil while preparing chapathis, which gives it a better texture, flavor and moist appearance. A progressively lesser score for the quality attributes of all the products were observed as the level of incorporation of wheat bran increased. For products C (10% wheat bran) and D (15% wheat bran) all the attributes were significantly different from the control product. In product B (5% wheat bran), significant differences were observed in the quality of appearance, color, texture and flavor (P ). There was no difference in Texture I and I1 in comparison with the control, whereas significant difference was seen in overall quality (P ). ANOVA revealed significant differences in all the attributes. It can be concluded that smaller levels of incorporation of bran to chapathi and phulka did not affect the sensory qualities adversely but higher levels lowered the acceptability significantly. Hence from the health benefit point of view, a smaller level of bran incorporation to either to chapathis or phulka can be recommended to increase dietary fiber in the diet. Incorporation of 5 % of wheat bran to the products increases the dietary fiber content by 2.3 g/100 g of product. This indicates an increase of 28% of total fiber. Considering that wheat is used as a staple cereal, consumption of g of wheat in a day is usual in an adult diet. Hence this can increase the fiber intake substantially by g/day. REFERENCES AACC Approved methods. The American Association of Cereal Chemists, Method: 54-21, St. Paul, Minnesota. ANDERSON, A. and EASTWOOD, M.A Flow characteristics and the water retention properties of wheat bran. J. Sci. Food Agri. 58, ANDERSON, J.W Dietary fiber in nutrition and management of diabetes. In Dietary Fiber: Basic and Clinical Aspects, (G.V. Vahouny and D. Kritcheveky, eds,) pp, , Plenum Press, New York. AOAC ojgicia1 Methods ofrlnalysis, 13th Ed. (S. Wiliams, ed.) pp. 144, Assoc. of Official Analytical Chemists. Arlington, VA. AOAC ojgicial Methodr oftlnalysis, 14th Ed. (S. Wiliams, ed.) pp. 162, Assoc. of Official Analytical Chemists. Arlington, VA. BERNARD, 0. and HAWKS, L Physiological Chemistry, 14th Ed., pp , Tata McGraw-Hill Publication Co. Ltd., New Delhi. BURKITT, D.P Epidemiology of cancer of the colon and rectum. Cancer 28, BURKITT, D.P Food fiber: Benefits from a surgeon s perspective. Cereal Foods World 22, 6-9.

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