Effects of barley flour substitution on glycemic index, compositional, rheological, textural, and sensory characteristics of chickpea flour‐based flat bread

The present study investigated the impact of barley flour substitution (10%–40%) on chickpea flour‐based flat bread (CFB). The crude fiber content significantly increased on addition of barley flour, whereas a significant decline was observed in protein and fat contents. All chickpea flour doughs with and without addition of barley flour exhibited shear thinning with flow behavior index of less than one. The hardness of CFBs decreased, whereas elasticity increased with the increase in barley flour content suggesting improvement in texture of flat breads. Glycemic index of CFBs containing barley flour was significantly less than control flat bread made without any addition of barley flour. Sensory panelists also gave higher scores to CFBs prepared with barley flour, whereas in terms of flavor and overall acceptability, no significant difference was observed between control bread and CFBs containing up to 30% barley flour content. Thus, the textural, compositional, and digestibility of chickpea flour‐based breads can be greatly improved through barley flour substitution without significantly affecting sensory attributes of bread.

Chickpea (Cicer avientum L.) is the fifth and the cheapest form of legume protein that can be used as a substitute of animal protein (Man et al., 2015;Sofi et al., 2020). It grows both in tropical and subtropical areas of the world (Shirani & Ganesharanee, 2009). Among all pulses, chickpeas have excellent nutritional composition as it contains 50% available carbohydrate, 17%-22% protein, 6.48% fat, and 3.82% crude fiber (Alajaji & El-Adawy, 2006). The two main varieties of chickpea are kabuli and desi (Singh et al., 1991). The kabuli and desi varieties of chickpea are not only native to India but also cultivated in many parts of the world. The desi variety of chickpea is mostly grown in Asia and Africa (Pande et al., 2005), whereas the kabuli variety is widely grown in west Asia, North Africa, North America, and Europe (Jukanti et al., 2012). The protein of chickpea is considered a suitable source of dietary protein due to its excellent balance of amino acids composition (Zhang et al., 2007). In terms of mineral content, it is usually higher in zinc, phosphorous, and manganese compared with other legumes (Wang et al., 2010). Due to its higher lysine content, chickpea becomes tremendous enhancer of protein quality when mixed with cereal grain proteins, which are usually low in lysine but contain higher amount of sulphur-based amino acids (Iqbal et al., 2006).
Chickpea flat bread is a widely consumed unleavened flat bread of South Asia. The bread dough made primarily from chickpea flour, water, and salt is rounded followed by sheeting using a roller pin into 8-10 cm diameter bread. The bread is then cooked on iron griddle.
However, it lacks popularity among masses as it is harder compared with other breads, being devoid of gluten content. Therefore, the aim of the present study was to improve the textural (increased softness and elasticity), rheological, and sensory characteristics of chickpea flour-based flat bread by adding different levels of barley flour. The motive behind preference of barley flour for enriching chickpea-based unleavened flat bread was its health benefits associated with the presence of both soluble and insoluble fiber in barley. Thus, the idea was to make highly nutritious bread with improved organoleptic and textural characteristics.

| MATERIALS AND METHODS
Desi variety of chickpea flour with proximate composition of 46.49% total carbohydrate, 25.82% fat, 19.70% protein, 6.25% crude fiber content, and 1.74% ash content and barley flour with proximate composition of 85.52% total carbohydrate, 10.55% protein, 1.77% fat, 1.18% ash, and 0.98% crude fiber content were used to prepare flat breads. Corn oil, red chili, and salt were bought from the local market.

| Preparation of chickpea flat breads
Five blends of flour were prepared separately by mixing the chickpea flour with barley flour in the ratio of 100:0 (control bread), 90:10, 80:20, 70:30, and 60:40 (w/w), respectively. Based on flour weight, red chili (5%), corn oil (10%), and salt (2%) were added to the flour mixture. The dough was made using Braun Mixer (Model K650, Kornberg/Germany) by kneading for 5 min at room temperature at 3000 rpm while adding 50 g of water per 100 g of flour weight to form a uniform dough. Dough (50 g) was rounded to make a ball which was then spread out using a wooden roller pin into a thin circular sheet of 3 mm thickness. The dough sheet was subsequently trimmed into an 11.5 cm diameter round sheet using a petri plate. Immediately, after sheeting, the chickpea flour bread was placed on a hot iron griddle at a temperature of approximately 270 C. The bread was then cooked on both sides for 120 s. Before further analysis, breads were cooled and stored in desiccators (containing silica gel beads as desiccant to obtain a dry atmosphere).

| Textural analysis of chickpea flat bread
The textural characteristics of chickpea flour-based bread were performed by using Universal Testing Machine employing the method of Mehfooz et al. (2018). Chapatti was incised into bone type strips from center of bread. The strip was 10 mm long and 5.5 mm wide from edges and 3.5 mm wide at the center. The two clamps of Universal testing machine (Zwick/Roell, GmbH, Germany) were used to hold the strips of flat bread from each side. One clamp was connected to the moving arm, whereas the other was fixed on the platform. The load cell of 1 kilo Newton was used, and grip to grip separation was 50 mm. The upper moving clamp was 50 mm/min in speed, whereas force shutdown threshold was kept at 30%. The upper clamp stretched the chapatti strip until it broke from the center. The F max or maximum force required to tear the bread was measured in MPa, and extensibility was measured in mm. Test Xpert software was used to calculate all the parameters. were randomly coded with a three-digit number so as to carry out a blind trial. One freshly cooked bread of each sample at a temperature of 40-50 C was served to each panelist along with mineral water to clean the palate. The flat breads were rated in terms of appearance, flavor, grittiness, hardness, aroma, and overall acceptability.

| Glycemic index of chickpea flat bread
The method of Goñi et al. (1997) was used to determine the predicted glycemic index (pGI) of chickpea flour bread samples. Equation (2)

| Statistical analysis
One-way analysis of variance (ANOVA) followed by Duncan's multiple range test at p < .05 was used to determine significant differences between the means by using SPSS software (version 17, SPSS Inc., USA).

| Compositional characteristics of chickpea flat bread
It could be observed from the Table 1 that total starch content of chickpea flour-based breads (CFB) increased by increasing level of barley flour into chickpea flour. This increase could be due to the fact that legume flour has low level of total starch content as compared with cereal flour (Gómez et al., 2008). However, a significant decline was observed in protein, fat, and ash content of CFBs showing that barley flour contained lower level of protein, fat, and ash content as compared with chickpea flour (Bai et al., 2018). Rababah et al. (2006) reported

| Dynamic frequency sweep measurements of chickpea flat bread dough
It could be observed from Table 2 that G 0 and G 00 increased with the rise in frequency from 1.25365 to 125.367 rad/s. Similar results were also reported by Kahraman et al. (2018). This suggested that both viscous and elastic character simultaneously increased with higher frequency. Therefore, determination of phase angle was necessary to determine the comparative impacts of rising frequency on G 0 and G 00 .
Moreover, Figure 1 showed that values of storage moduli of all the doughs were higher than loss moduli for the entire range of frequency, suggesting elastic nature of dough with solid like properties.

| Textural characteristics of chickpea flat bread
It could be observed from Table 4

| Sensory analysis of chickpea flat bread
Sensory attributes of CFBs with and without addition of barley flour are presented in Table 5. Hardness was observed to decrease

T A B L E 3 Effects of barley flour on flow behavior index (n) and consistency coefficient (k) of chickpea flour bread doughs
Barley flour (%) significantly with the addition of barley flour, suggesting formation of softer breads compared with control due to development of gluten network. These are also in agreement with the results of hardness (

| Glycemic index of chickpea flat bread
The maximum hydrolysis extent or equilibrium concentration (C∞) defines the values of starch hydrolysis. It could be observed from  will not only increase daily fiber uptake values but will also include both cereal and legume proteins in daily diet that can cover all essential amino acids. Development of such flour blends would be beneficial to improve the nutritional value of bread and will reduce the spike of glucose and cholesterol in blood after ingestion. In future, availability of different composite chickpea-barley flour breads in the market will lead to increased barley flour consumption as breads are considered staple food in many countries around the world.

CONFLICT OF INTEREST
There is no conflict of interest to declare.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon request.

ETHICS STATEMENT
This article does not contain any in vivo studies with human participants (except flat bread sensory test) or animals performed by any of the authors.