Biochemical and nutritional profile of maize bran‐enriched flour in relation to its end‐use quality

Abstract The core objective of current research was determined to nutritional and bioactive profile of maize bran (MB)‐enriched flour in relation to its end‐use product quality. Furthermore, rheological properties of MB‐enriched flour at different levels (5%, 10%, and 15%) were explicated through farinograph and mixograph. Moreover, bread was prepared with the addition of MB‐enriched flour and was characterized for nutritional and textural properties. Results showed that MB‐enriched flour having high water absorption and water retaining potential up to 4%–7% as compared to wheat flour (WF). Moreover, dough height gradually decreased with the addition of MB due to water‐binding ability of bran which causes a decrease in gas retention during fermentation. This resulted in bread volume decrease (4%–7%) as compared to WF. Furthermore, the moisture content and hardness increased with the addition of MB. The water activity of bread slightly increased with the addition of maize bran after 4‐day storage. Conclusively, MB‐enriched flour improved nutritional, textural, and sensorial properties of final product.

Among different cereal products, bread has much importance and is usually prepared from wheat flour, sugar, yeast, water, salt, and fat (Okafor et al., 2012). Bread is primarily prepared with wheat flour, but it has low mineral and dietary fiber as well as low vitamins and proteins (Lu et al., 2018). With the supplementation of nutrients, it becomes an excellent food product that will ultimately improve nutritional condition of consumers (Alamu et al., 2018). Arabinoxylans (Saeed et al., 2016), alhydwan seeds (Ammar et al., 2016), dietary fiber (Packkia-Doss et al., 2019), Pumpkin seed flour (Agu et al., 2010), banana, aonla and sapota powder (Rajeswari et al., 2018), and protein concentrates (Alzuwaid et al., 2020) have been incorporated into bread to increase its quality and nutritional composition. Boita et al. (2016) described the rheological properties of wheat flour dough and bread with the addition of wheat bran. Fortifying staple foods such as bread and maize bran are a particularly accessible and economical source of dietary fiber, protein, and phytochemicals, as its excellent insoluble dietary fiber content, and antioxidants including ferulic acid, diferulic acid, and p-coumaric acid (Bento-Silva et al., 2018).
However, the bran addition in bread contributes to practical and functional improvements in the cycle of bread making and organoleptic properties including crumb softness and reduction in bread loaf volume (Hemdane et al., 2018). In addition to diluting gluten when bran is incorporated in bread, the maize bran properties play a crucial role in potential interactions between bran and flour components . It has several functions like enhancing water absorption, lowering tolerance for dough strength, mixing, fermentation, and dough stickiness improved, when maize bran is incorporated into the flour. Thus, the incorporation of cereal bran leads to lower loaf volume, crumb softness, specific volume, and causes darker crumb color and coarser crumb texture (Özkaya et al., 2018).
Hypothesis: Maize bran may or may not have positive impact on biochemical, nutritional and rheological characteristics of wheat flour. Objective: In this research work, the effects of maize bran on biochemical composition, water-holding capacity, farinographic and mixographic characteristics of MB-enriched flour were determined. In the end, bread was prepared with the addition of different levels of MB and was analyzed for its textural and sensorial characteristics. Ltd. Faisalabad, Pakistan. Maize bran was commercially micronized (particle size <250 µm) by using milling process.

| Total dietary fiber of MB-enriched flour
Total dietary fiber, soluble, and insoluble dietary fibers of all the treatment groups WF, MB5, MB10, and MB15 were analyzed by the following method no. 32-05, AACC (2000).

| Water-holding capacity of MB-enriched flour
Water-holding capacity (WHC) of wheat flour (WF) and branenriched flour (MB5, MB10, and MB15) was measured according to Hemdane et al. (2018) protocol. 1 g sample was weighed in a 50 ml centrifuge tube and 10 ml distilled water was added to the solution. Then, the sample was stirred by using a vortex mixer and left for 40 min at room temperature and centrifuged at 10,000 RPM for 10 min. The supernatant was gently separated, and a drainage process of 15 min was done to remove excess water that was not retained. Weighed the centrifuge tube, and declared the WHC as g water retained per g of dry matter.

| Farinographic Analysis of MB-enriched flour
The farinographic characteristics including water absorption capacity, dough development time, dough stability, mixing tolerance index, and dough softness of dough obtained from various blends of wheat flour with maize bran treatments (WF, MB5, MB10, and MB15) were analyzed through farinograph by following method no. 54-21.01 of AACC (2000).

| Mixographic characteristics
Mixographic properties such as mixing time and peak height of the dough obtained from various blends of wheat flour with maize bran treatments (WF, MB5, MB10, and MB15) were analyzed through mixograph by following method no. 54-40.02 of AACC (2000).

| Preparation of bread
The ingredients, MB-enriched flour, milk powder, compressed fresh yeast, sugar, salt, improver, shortening, and water were mixed with mixer and prepared bread with straight dough bread baking method no. 10-10.03 (AACC, 2000). Comparison of dough height after molding and bread height after baking was measured to estimate fermentation effects on MB samples.

| Moisture content
The moisture content of fresh-baked bread was measured by using a hot air oven at 105 ± 5°C temperature by following the AACC (2000) method no. 44-15.02.

| Textural analysis of bread
The hardness of the bread was measured by some modification of the bread compression test described by Saeed et al. (2016). In this method, the sample of bread was compressed twice by up to 50%.
Deformation and rehabilitation behavior under stress demonstrated crumbs of firmness.
The fracturability of bread was evaluated by a cylindrical ball die that penetrates the bread slices up to 40% followed by method no.

| Bread loaf volume
After baking, the bread was cool down for 15 min, and the loaf volume was estimated by the rapeseed replacement method by following the AACC method 10-05.01 (AACC, 2000).

| Water activity of bread
The water activity of bread samples was indicated by using the Hygropalm Water Behavior Meter (Retronic, Rotronic Instrument Corp., UK) followed by the method illustrated by Piga et al. (2005).

| Sensory characteristics of bread
Bread treatments WF, MB5, MB10, and MB15 were prepared for sensory evaluation. Sensory acceptance of bread was tested by twenty panelists (Ph.D. scholars and some faculty members of

Department of Food Sciences Government College University
Faisalabad, Pakistan). Each panelist was presented with four coded samples in a sensory booth and asked to evaluate for appearance, color, taste, flavor, texture, and overall acceptability on a 9-point hedonic scale, where 1 was disliked extremely and 9 was like extremely. Statistical analysis of data was carried out using SPSS statistics 21. The F test value was obtained, and a multiple comparison test was performed on the means, using Duncan's Multiple Range Test at 0.05 levels.

| Statistical analysis
All experiments were carried out in three replicates. Analysis of variance (ANOVA) was conducted by using the SPSS statistics 21. The F test value was obtained, and a multiple comparison test was performed on the means, using Duncan's Multiple Range Test at 0.05 levels.

| Nutritional composition of MB-enriched flour
The flour samples were analyzed for moisture content, crude protein, crude fat, crude fiber, NFE, and ash content. The nutritional composition of different flour samples and their mean values are mentioned in Table 1.
Moisture content is important aspect to control physiochemical properties of flour. Moisture is important in determining the shelf life of the flour. The mean value of moisture content was 12.48 ± 0.04 in WF (control) sample. The moisture content in MB5, MB10, and MB15 treatments was 12.32%, 12.16%, and 11.69%, respectively.
According to Turkish Food Codex (1999) and Codex Alimentarius standards, maximum moisture should be 14.5% and 15.5%, respectively. When the moisture content of flour rises above 14%, it is more susceptible to fungal growth, flavor change, and enzymatic activity (Batool et al., 2012).
The ash content of the flour represents the inorganic residues after the combustion of organic material which contains a small amount of minerals. Elawad et al. (2016) explored that the ash content of cereal/legume bran composite flour ranged between 0.8% and 2.3%. The mean value results of Ash content in WF, MB5, MB10, and MB15 were 0.35 ± 0.01%, 0.66 ± 0.02%, 0.78 ± 0.02%, and 1.02 ± 0.05%, respectively.

| Total Dietary Fiber (soluble and insoluble dietary fiber)
The total dietary fiber content in flour treatments WF, MB5, flour with wheat bran incorporation at different levels 6.25%-25% was 3.67% to 12.08%. MB is identified as a good source of several bioactive compounds as well as dietary fiber (Sharma et al., 2016). Therefore, MB-enriched flour has high total dietary fiber content due to maize bran addition. Dietary fiber helps against cardiovascular diseases, obesity, cancer, and diabetes type II (Cui et al., 2019).

| Mixographic characteristics
Results regarding means values of the peak height variation of wheat flour owing to maize bran addition showed a significant increase in peak height. In MB15 treatment, the highest peak height (67.72 ± 0.11 BU) was observed in flour with 15% maize bran. The peak height results were significantly increased with the addition of maize bran (Table 2).
Mean values regarding the effect of maize bran on the mixing time of wheat flour showed a significant decrease in mixing time by applying treatments (5%, 10% and 15% maize bran) as shown in Table 3. In WF, MB5, MB10, and MB15 treatments, mixing time was 6.23 ± 0.04, 6.08 ± 0.03, 5.88 ± 0.13, and 5.72 ± 0.01 min, respectively. The results regarding mean values revealed that the highest mixing time (6.23 ± 0.04 min) was observed in WF control treatment, whereas the lowest mixing time (5.72 ± 0.01 min) was exhibited by flour with MB15 (15% maize bran).

| Comparison of dough height and bread height
The bread dough height and after baking bread height mean values result were depicted in Figure 2a. to breakage, and that they develop a physical barrier around the gas cells, pressuring them to expand in a particular dimension . When the gas cells expand, the bran particles align with the gas cells, developing a physical wall that may hinder proper expansion of the gas cells.

| Bread loaf volume
The mean values of bread volume have been shown in Figure 1b. It is visible that volume was significantly affected by different treatments and storage periods. Likewise, a significant difference between treatments and day interaction was noticed. The size of the bran particle has a certain impact on the volume of the bread loaf.
This has been reported by many scientists that the bran particle size is associated with gas retention and the fine volume of the bread.
The mean values for loaf volume (Figure 1 b)

| Moisture content of bread
The moisture level of various food items is one of the most essential and widely measured properties. It is calculated for a multitude of reasons, such as legal and labeling criteria, economic importance, food quality, increased efficiency, and safety of storage. The mean values of moisture content in bread are described in Table 3. The water absorption property of dough improved with the addition of maize bran level, that is why the moisture content of bread was increased with high bran concentration. These results are equivalent to Pauline et al. (2020) reported that wheat bran-enriched bread has 30% moisture.

| Bread hardness and fracturability
The bran-enriched bread indicated higher water content but often higher hardness, indicating that the moisture content is not the only aspect affecting the hardness and may not have been sufficiently imperative to overcome the negative influence of bran fractions on texture (Boita et al., 2016). Chen et al. (2011) observed that the smaller size of the bran particles resulted in significantly greater hardness.
Other factors such as water molecular, redistribution, water dynamics, and gluten network changes (i.e., loss of plasticity) are reported to contribute to the increased hardness (Curti et al., 2015).
Hardness is a substantial qualitative parameter that affects the volume, water activity, and more hardness was also produced by the presence of the bran. In previous research, Curti et al. (2013) indicated that the incorporation of bran fractions with different particle sizes did not significantly affect the hardness of the samples.

| Water activity of bread
The water activity of bread indicates the lower limit of water availability for microbial growth. It is critical to regulating water activity to preserve the chemical stability of foods. Water activity plays a showed a gradual increase in water activity values for each trait but, meanwhile, the effect of the MB addition was also noticeable in the reduction of water activity of baked bread as a function of various levels.

| Sensory evaluation
Sensory evaluation of WF, MB5, MB10, and MB15 samples is presented in Table 4. The panelist scored the four bread on color and appearance of bread between "like moderately" and "like very much." Since the panelists were asked to score the bread individually and not compare between them, there were no statistically significant differences scores for color and appearance. Texture and taste scores for the four bread were between "like slightly" and "like moderately." Taste scores were low as no additional flavoring was added. Maize bran addition at 5%, 10%, and 15% level in bread did not significantly affect the overall acceptability scores. Based on the data in this study, it can be recommended that up to 15% of maize bran can be used in bread and bread-like products. Texture sensory "like slightly" by adding maize in the formulation, thus improving the overall acceptability of high-fiber bread containing finely milled MB.

| CON CLUS ION
Maize bran is rich in nutritional as well as bioactive profile than

CO N FLI C T O F I NTE R E S T
The authors declare no conflict of interest.