Effect of Turmeric Powder Addition on the Quality and Colour Properties of Wheat Bread

Key

A = (Control) 100 g wheat flour

B = 100 g wheat flour + 1.5 g turmeric powder

C = 100 g wheat flour + 3.0 g turmeric powder

D = 100 g wheat flour + 4.5 g turmeric powder

E = 100 g wheat flour + 6.0 g turmeric powder

Table 2: Recipe Formulation for Bread

Preparation of Bread from Wheat Flour and Turmeric Powder Blends

Breads were produced from the composite of wheat flour and turmeric powder based on the recipe formulation shown in Table 2. The breads were baked in accordance with the modified method of Joseph et al. [16]. The composite flour, butter, sugar, yeast, salt and other baking ingredients with water after scaling were manually mixed together in a bowl. The mixtures were kneaded using the kneading machine until the dough was developed then moulded and allowed to proof in pans for an hour. The doughs were baked at a modified temperature and time (250 ^oC for 45 mins) in the oven and were allowed to cool then packaged for further analyses. The production of wheat and turmeric composite bread is shown in Figure 2.

Figure 2: Production of Wheat flour and Turmeric Powder Bread (Source: Joseph et al. [16] with modification).

The method described by Onwuka [17] was used. One (1 g) of the flour sample was weighed into a 15 mL centrifuge tube and suspended in 10 mL of water. It was shaken on a platform tube rocker for 1 minute at room temperature. The sample was allowed to stand for 30 min and centrifuged (Model SM 800B Uniscope Surgifriends Medicals, England) at 500 rpm for 30 min. The volume of free water was read directly from the centrifuge tube. Density of water was taken to be 1 g/cm³.

Loose bulk density and packed bulk density (g/ mL)

Loose bulk density of the flour samples was determined by the gravimetric method described by Kakar et al. [18]. A weighed sample (10g) was put in a calibrated 25 mL measuring cylinder and the volume was recorded as the loose volume. The bottom of the cylinder was tapped repeatedly on a firm pad on a laboratory bench until a constant volume was observed. The packed volume was recorded. The loose bulk density (LBD) and packed bulk densities (PBD) was calculated as the ratio of the sample weight to the volume occupied by the sample before and after tapping.

Where

pb = Bulk density

M = Weight of powder

V = Volume of powder

Swelling capacity (%)

The swelling capacity % of the flour determined based on method described by Kakar et al. [18]. One gram of the sample was transferred into a weighed graduated 50 mL centrifuge tube. Distilled water added to give a total volume of 40 mL. The suspension stirred uniformly with a stirrer avoiding excessive speed, in other not to cause fragmentation of the starch granules. The sample heated at 85°C in a thermostatically regulated temperature bath (Grant instruments, England Ltd.) for 30 min with constant stirring. The tube was removed, wiped dry on the outside and cooled to room temperature, then centrifuged for 15 min at 560 g (Mistral 3000i, UK). The solubility determined by evaporating the supernatant in a hot air oven (BS Gallen Kamp, England) and the residue weighed. The swelling volume was obtained by directly reading the volume of the swollen sediment in the tube. The sediment paste weighed. The swelling capacity % determine by formula.

Determination of the Proximate Composition of Wheat and Turmeric Powder Bread

The proximate composition of bread from composite of wheat flour and turmeric powder was determined according to the methods of AOAC [19] and Carbohydrate content was determined by difference according to Ihekoronye and Ngoddy [20].

Moisture content determination

Moisture content was determined using the air oven dry method described by AOAC [19]. A clean dish with a lid was dried in an oven at 100 ⁰C for 30 min. It was cooled in desiccators and weighed. Two (2) grams of sample was then weighed into the dish. The dish with its content was then put in the oven at 105 ⁰C and dried to a fairly constant weight. The loss in weight from the original sample (before heating) was reported as percentage moisture.

Where: W₁=weight of empty crucible,  W₂= weight of crucible+sample before ashing, W₃= weight of crucible+content after ashing

Ash Content Determination

AOAC [20] was used in determining the ash content of the bread samples. Two (2) gram of sample was weighed into an ashing dish which had been pre-heated, cooled in a desiccator and weighed soon after reaching room temperature. The crucible and content were then heated in a muffle furnace at 550 oC for 6 h. The dish was cooled in a desiccator and weighed soon after reaching room temperature. The total ash was calculated as percentage of the original sample weight.

Where: W1=weight of empty crucible,  W2= weight of crucible+sample before ashing, W3= weight of crucible+content after ashing

Crude Fibre Determination

Method described by AOAC [19] was used to determined crude fibre content of the bead samples. Two (2) grams of the sample was extracted using Diethyl ether. This was digested and filtered through the California Buchner system. The resulting residue was dried at 130 0C for 2 hrs., cooled in a dessicator and weighed. The residue was then transferred into a muffle furnace and ignited at 550 0C for 30 min, cooled and weighed. The percentage crude fibre content was calculated as:

Crude Fat Determination

Fat was determined using Soxhlet method described by AOAC [19]. Samples were weighed into a thimble and loose plug fat free cotton wool were fitted into the top of the thimble with its content inserted into the bottom extractor of the Soxhlet apparatus. Flat bottom flask (250 mL) of known weight containing 200 mL of hexane was fitted to the extractor. The apparatus was heated and fat extracted for 8 hrs. The solvent was recovered and the flask (containing oil and solvent mixture) were transferred into a hot air oven at 105 oC for 1 hr to remove the residual moisture and to evaporate the solvent. It was later transferred into desiccator to cool for 15 min before weighing. Percentage fat content was calculated as 

Crude protein determination

The Kjeldahl method recommended by AOAC [19] was used to determine the percentage crude protein. Exactly, two (2) grams of sample was weighed into a Kjeldahl digestion flask using a digital weighing balance. A catalyst mixture weighing 0.88 g (96 % anhydrous sodium sulphate, 3.5 % copper sulphate and 0.5 % selenium dioxide) was added. Concentrated sulphuric acid (7 mL) was added and swirled to mix content. The Kjeldahl flask was heated gently in an inclined position in the fume chamber until no particles of the sample was adhered to the side of flask. The solution was heated more strongly to make the liquid boil with intermittent shaking of the flask until clear solution was obtained. The solution was allowed to cool and diluted to 25 mL with distilled water in a volumetric flask. Ten (10) mL of diluted digest was transferred into a steam distillation apparatus. The digest was made alkaline with 8 mL of 40 % NaOH. To the receiving flask, 5 mL of 2 % boric acid solution was added and 3 drops of mixed indicator was dropped. The distillation apparatus was connected to the receiving flask with the delivery tube dipped into the 100 mL conical flask and titrated with 0.01 HCl. A blank titration was done. The percentage nitrogen was calculated from the formula:

Where  S = sample titre, B = blank titre, S-B = corrected titre, D=diluted factor % Crude Protein=% Nitrogen ×6.25 (conversion factor)  

Carbohydrate determination Carbohydrate content was determined by difference according to Ihekoronye and Ngoddy [20] as follows % Carbohydrate =100-(% Moisture + % Ash + % Fibre +% Fa t+ % Protein) [9].

Energy content (kcal/100g) determination The values obtained for protein, fat and carbohydrate were used to calculate the energy content value of the samples. The proportion of protein, fat and carbohydrate were multiplied by their physiological fuel values of 4, 9 and 4 kcal/100g, respectively and the sum of the product was taken [22].

Protein content (%)=P Fat content (%)=F Carbohydrate content (%)=C

Determination of the Physical Characteristics of Bread

Determination of oven spring

Oven spring of the loaves was determined according to the method of Onwordi et al. [22]. The dough height was measured before baking using a straight edge metric rule and height was measured again after baking. The difference in height equals the oven spring.

                                       Oven Spring (cm) = Height after baking-Height before baking                                                     (11)

Determination of loaf volume was by seed displacement method as described by the modified bof Cotovanu and Mironeasa [23]. A container (126.44 g) of fixed dimensions (18 cm³ × 12.7 cm³ × 12.4 cm³) of internal volume 2834 cm³ was filled with rice grain; a straight edge ruler was used to cut off all grains above the container rim. The grains were poured out and weighed (W₁). A weighed loaf was placed in the container and the weighed seeds were used to fill the container and levelled off as before. The overspill was weighed (W₂) and from the weight obtained, volume of rice displaced by the loaf was calculated using the following equation.

Determination of loaf volume was by seed displacement method as described by the modified bof Cotovanu and Mironeasa [23]. A container (126.44 g) of fixed dimensions (18 cm3 × 12.7 cm3 × 12.4 cm3) of internal volume 2834 cm3 was filled with rice grain; a straight edge ruler was used to cut off all grains above the container rim. The grains were poured out and weighed (W1). A weighed loaf was placed in the container and the weighed seeds were used to fill the container and levelled off as before. The overspill was weighed (W2) and from the weight obtained, volume of rice displaced by the loaf was calculated using the following equation.

W1 = Weight of rice grains that filled the container W2 = Weight of rice grains displaced by the loaf samples

Determination of loaf weight The bread samples were weighed (g) using a weigh balance (model: Sliding Harvard Trip balance, 2 kg-51 b capacity) as described by Onwordi et al. [23].

Determination of specific volume The specific loaf volume was determined by dividing the loaf volume by its corresponding loaf weight (cm3/g) as described by Araki et al. [24]. The specific volume is the ratio between loaf volume and loaf weight expressed in cubic centimetre per gram.

The bread samples were weighed (g) using a weigh balance (model: Sliding Harvard Trip balance, 2 kg-51 b capacity) as described by Onwordi et al. [23].

Determination of specific volume

The specific loaf volume was determined by dividing the loaf volume by its corresponding loaf weight (cm³/g) as described by Araki et al. [24]. The specific volume is the ratio between loaf volume and loaf weight expressed in cubic centimetre per gram.

Colour Determination (L*, a* and b* Values)

L, a and b parameters were determined using a colourimeter (Minolta Chroma Meter (CR200, Minolta, Japan). In detail, it assessed the following colour traits: L (lightness) axis – 0 is black, while 100 is white; a (red-green) axis – positive values are yellow, while negative values are blue and 0 is neutral. Multiple measurements (triplicate) of L*, a* and b* parameters were determined using the colourimeter on the sample. From the data obtained, deltachroma (∆C), colour intensity (∆E), hue angle and degree of whiteness were calculated according to equations 1, 2, 3 and 4, respectively [25].

 Note: W is the degree of whiteness of the sample

Sensory Evaluation of Bread

Sensory evaluation of the bread samples was carried out according to the method described by Ochelle et al. [26]. A panel of thirty [30] members consisting of students and members of staff from the Department of Food Science and Technology, Joseph Sarwuan Tarka University, Makurdi, Nigeria was selected based on their familiarity and experience with wheat based breads for sensory evaluation. Breads produced from each flour blend, along with the reference sample were presented in coded form and were randomly presented to the panellists. The panellists were provided with potable water to rinse their mouth between evaluations. A questionnaire describing the quality attributes (crumb appearance, taste, aroma, crumb texture and overall acceptability) of the bread samples was given to each panellist. Each sensory attribute was rated on a 9-point Hedonic scale (1 = dislike extremely and 9 = like extremely).

Statistical Analysis

Data obtained were subjected to analysis of variance (ANOVA) and means were separated using Duncans multiple range test (D M R T) with significance difference tested at 5 % level of probability.

RESULTS AND DISCUSSION

Effect of Turmeric on the Functional Properties of Wheat-Turmeric Composite Flour

Table 3 shows the effect of turmeric powder addition on the functional properties of wheat-turmeric dough. Generally, the result showed a significant difference in the functional parameters of the wheat-turmeric dough. The water absorption capacity (71.00-81.33 %), swelling capacity (4.01- 5.50 %), loose bulk density (0.43-0.48 %) and packed bulk density (0.71-0.85 %) increased progressively with increased level of turmeric powder addition.

Functional properties of a food material are parameters that determine its application and end use [27]. They are those physico-chemical properties of food proteins that determine their behaviour in food system during processing, storage and consumption. It usually shows that the food materials under investigation will interact with other food components directly o indirectly affecting processing applications, food quality, and ultimate acceptance [28].

Water absorption capacity is the ability of product to incorporate water and water inhibition is an important functional trait in food such as sausages, custard and dough [29]. It also refers to water retained by a food product following filtration and application of mild pressure of centrifugation [30]. The increment in water absorption capacities may be attributed to the high carbohydrate contents recorded in 100 % wheat bread, as carbohydrates have been reported to greatly influence the water absorption capacity of foods [31]. Also, wheat flour and turmeric powder may have contained more hydrophilic constituents which gave rise to higher water absorption capacity of the composite flours [32]. The lower moisture content in wheat bread flour may have contributed to its higher water absorption capacity, as flour with lower initial moisture content tends to absorb more water during mixing and processing [32]. Water absorption of flours is dependent mainly on the amount and nature of the hydrophilic constituents and to some extent, on pH and nature of the protein [33]. It has been suggested that flours with high water absorption capacity as seen in this study will be very useful in bakery products and this could prevent staling by reducing moisture loss [34] and also, help maintain the freshness of bread, cakes and sausages and could favour their use as soup thickener [30]. WAC is important in foods where water will be absorbed without dissolution of protein, thus increasing their viscosity and body thickening [35]. Thus, this implies that the addition of turmeric powder improves the reconstitution ability.

The results of both loose and packed bulk densities are used to evaluate flour heaviness, handling requirements, and the type of packaging materials suitable for storage and transportation of food materials [36]. These findings suggest that flour samples may require different packaging spaces and materials. Bulk density reflects the load the samples can carry when allowed to rest directly on one another [37]. The loose and packed bulk densities of the composite flours increased as the incorporation level of turmeric powder increased, indicating that turmeric powder contributes to densification. Similar trends in bulk density increases have been reported for composite flours enriched with natural additives, such as turmeric and pumpkin powder, which contribute hydrophilic and structural components [38]. Generally, the bulk density of food materials is affected by the particle size and the density of the food. It is therefore an important factor in food packaging [39]. Also, it has been reported that bulk density is influenced by the structure of the starch polymers and loose structure of the starch polymers could result in low bulk density [40]. Low bulk density of flour as observed in this study is a good physical attribute when determining transportation and storability [41]. Low bulk density is also important in infant feeding where less bulk is desirable. However, the higher bulk density of the flours would be a disadvantage in the use of the flour for preparation of complementary foods [32,42]. The range of bulk density obtained in this study is higher than 0.586 – 0.693 g/mL and 0.86 – 0.72 g/cm³ obtained for wheat – pigeon pea blends by Arukwe [43] and wheat and acha by Ubbor et al. [42], respectively.

The result of the swelling index as shown in Table 3 indicated that addition of turmeric powder significantly increased the swelling index of the flour samples. Swelling capacity is a function of process conditions, nature of material and type of treatment. The high swelling capacity could be an advantage in production of bakery products. The highest value of swelling index recorded for the composite flours indicates that the flours possess higher starch content than other flour samples [44], and can be used for the formulation of variable products [42]. The result of the increasing trends of functional properties of wheat-turmeric flour presented in this study is similar to that reported by Lim et al. [45] in their study on the quality and antioxidant properties of bread containing turmeric cultivated in South Korea.

Effect of Turmeric on the Physical Properties of Wheat-Turmeric Based Bread

Table 4 presents the physical properties of bread products formulated from blends of wheat and turmeric powder composite flour. There was significant difference in the physical properties of the formulated breads from wheat and turmeric powder. The oven spring, loaf volume, moisture loss and specific volume of the bread samples decreased progressively from 0.50 to -1.50 cm, 621.43- 473.19 cm³, 12.07-2.33 and 3.39-2.38 cm³/g in the control sample and in the 100:6.0 g wheat and turmeric powder bread respectively with increased level of turmeric powder substitution. The loaf weight increased with increased level of turmeric powder addition and it ranged from 183.3-199.5 g in 100:0g wheat bread and 100:6.0 g wheat and turmeric powder bread respectively.

Physical properties are properties that can be measured or observed without changing the chemical nature of the substance. The dilution effect on gluten was the reason for the observed decrease in oven spring, loaf volume and specific volume with increased turmeric powder addition. The gluten fraction is responsible for the elasticity of the dough by causing it to extend and trap the carbon dioxide generated by yeast during fermentation. When gluten coagulates under the influence of heat during baking, it serves as the framework of the loaf, which becomes relatively rigid and does not collapse [46]. The decrease is also attributed to the lower levels of gluten network in the composite doughs and consequently, less ability of the dough to rise due to weaker cell wall structure [47]. According to Yusnita and Wong [48], addition of dietary fibre rich substances in baking products reduce loaf volume. It is ultimate that bread samples with reduced volume will also have reduced specific volume [49]. The observed increase in weight of composite bread samples with increased turmeric powder is as a result of less retention of carbon-dioxide gas in the blended dough, hence providing dense bread texture. Also, the higher moisture contents of the composite flour could have contributed to the higher loaf weight relative to 100 % wheat bread [50]. The results of this study are in- line with the findings of Sengev et al. [51]; Igbabul et al. [52] and Ufot and Inemesit [50], who reported increased bread loaf weight but decreased oven spring, loaf volume and specific volume with the increased substitution of wheat flour with sweet potato, maize/orange fleshed sweet potato and unripe plantain, respectively.

Effect of Turmeric Powder on the Proximate Composition (%) of Wheat Based Bread

The proximate composition of wheat and turmeric powder breads is presented in Table 5. The moisture, ash, fibre, fat and protein contents increased progressively with increased level of turmeric powder substitution while the carbohydrate contents and energy values showed decreased values with an increased level of turmeric powder substitution. Differences in the proximate contents of the bread from various flour blends were significantly. The moisture, ash, crude fibre, crude fat and protein contents ranged from 23.78-30.83 %, 1.03-4.41 %, 1.54-3.59 %, 8.61-8.98 5 and 14-90-15.74 % in the 100 % wheat bread and 100:6.0g wheat and turmeric powder composite breads respectively. The carbohydrate contents decreased from 73.93 % to 67.28 % with increased level of turmeric powder addition. Differences in the carbohydrate contents of the various blends were significant (p < 0.05). The energy values of the wheat-turmeric powder bread decreased from 432.77 kcal/100g – 412.86 kcal/100g for the control sample and the 100:6 g wheat: turmeric powder bread respectively. The differences in the energy values across the five samples were significantly different. The lowest energy value was recorded in the 100:6.0 g wheat and turmeric powder bread (412.86 kcal/100g).

The increase in the moisture content could be attributed to the greater water holding capacity of the composite flours as seen from the water absorption capacity of flour samples. This trend is similar to the findings reported by Amandikwa et al. [53]; Ufot and Inemesit [50]; Ochelle et al. [54] Ayo et al. [58] for wheat-yam flour composite breads, wheat-unripe plantain, wheat-water yam, and soybean, respectively.

The ash contents of the bread samples increased significantly with increased levels of turmeric powder. Ash content gives an insight to the mineral content of food; hence, turmeric can be described as a good source of minerals hence the relatively high-value of minerals recorded in the wheat and turmeric composite breads. The results obtained in this study are in agreement with the work of Abdellatif et al. [55].

Table 3: Effect of Turmeric Addition on the Functional Properties of Wheat-Turmeric Flour