Physicochemical properties and sensory attributes of cookies prepared from sorghum and millet composite flour

Abstract Sorghum and millet are rich in nutrients and bioactive compounds. They can enhance nutrition and health. This study was aimed to develop sorghum–millet gluten‐free cookies from sorghum and millet composite flour. Cookies were made using 100% wheat WF100%, sorghum SF100% ,and millet MF100% flours and composite flours of 25% sorghum–75% millet (SF25%–MF75%), 50% sorghum−50% millet (SF50%–MF50%), and 75% sorghum–25% millet (SF75%–MF25%). The physicochemical, nutritional, bioactive, and sensory quality attributes of the developed cookies were evaluated. The results of flours displayed that the highest values of peak viscosity and final viscosity were observed in SF100%, breakdown and pasting temperature were observed in WF100%, setback viscosity in composite flour of SF25%–MF75%, and hardness and chewiness in WF 100%. Regarding cookies analysis results, the highest values of hardness were shown in WF100% and SF100% cookies, and the highest water activity was observed in the cookies of (SF25%–MF75% and SF50%–MF50%), and the (SF75%–MF25%) cookies had the best diameter and thickness. The lowest water‐holding capacity (WHC) and oil‐holding capacity (OHC) were found in (WF100%) cookies, while they were high in the cookies of SF and MF flours and their combinations (p ≤ .05). The cookies made using the composite flour of SF25%–MF75% appeared to have the uppermost values of moisture, protein, fat, total phenolic content (TPC), and antioxidant activity. They have the highest contents (p ≤ .05) of potassium, sodium, magnesium, and calcium. The scores of all sensory attributes of all cookie types were higher than the cutoff score (5). Overall, the incorporation of sorghum and millet flour in cookies formulation enhanced the physicochemical, nutritional, and bioactive properties without major effect on the sensory attributes of the product, which make it excellent nutritive and healthy sorghum–millet gluten‐free cookies.


| INTRODUC TI ON
Sorghum and millet are important sources of protein and energy for many people in arid and semiarid regions (ICRISAT/FAO, 1996).
These cereal grains are rich in nutrients such as proteins, minerals, bioactive compounds, and cholesterol-lowering waxes (Taylor et al., 2006). They are also considered as the best food crops for future human use due to their high tolerance to drought and hot temperature and their little input requirements during growth (Taylor et al., 2006). These vital cereal grains are used for the preparation of various foods and beverages in developing countries; however, they are still majorly used as animal feed in developed countries (Mohamed et al., 2019;Taylor et al., 2006). Due to global warming, water shortage, population growth, and health concerns about gluten-containing foods, the popularity and importance of sorghum and millet products are greatly increased in recent decades. Glutenfree foods are highly required for the treatment of celiac disease, an immune-mediated enteropathy activated by the consumption of gluten-containing foods of wheat, barley, and rye origins (Brites et al., 2018). In recent years, the production and consumption of snacks are highly increased due to urbanization, speedy work, and fast food, and increased numbers of working women (Rao et al., 2018). Among snacks, cookies are considered an important food as they have high acceptability, a wide range of crispiness, digestibility, shapes, flavors, and tastes, low cost, and long shelflife (Sudha et al., 2007). The development of gluten-free bakery products, such as bread, pastas, noodles, cookies, pizza, and biscuits from sorghum and millet, represents a major challenge for the food industry because the absence of gluten affects the structure of the developed products (Torbica et al., 2012). Currently, glutenfree bakery products deliver lower protein, fiber, and mineral content and elevate glycemic index (GI) than gluten-containing foods.
The currently low mineral content can be increased with the use of mineral-rich ingredients such as amaranth, buckwheat, or flaxseed flour (Sophie & Luca, 2018).
Gluten-free cookies from sorghum and millet could be nutritious and healthy due to their richness of chemical constituents (dietary fibers, proteins, fatty acids, and minerals) and bioactive compounds (Brites et al., 2018;Taylor et al., 2006;Torbica et al., 2012).
Due to the high content of micronutrients and dietary fiber, in addition to the low GI and the lack of gelatin, the development of gelatin-free products from corn and millet is considered a necessity for the prevention of diseases related to gelatin, diabetes, obesity, and other diseases related to high glycemic factors. They also contain significant amounts of phytochemicals that make them a therapeutic food for the prevention and treatment of many chronic diseases. Accordingly, this study aimed to develop cookies using sorghum and millet flour and their blends and to evaluate the physicochemical, nutritional, bioactive, and sensory quality attributes of the developed cookies.

| Row materials
All ingredients (sorghum and millet flour, wheat flour, refined sugar, guar gum, shortening, baking powder, cinnamon powder, salt, and eggs) used to prepare cookies were purchased from local markets in Riyadh, Saudi Arabia.

| Water-and oil-holding capacity
The water-holding (WHC) and oil-holding capacity (OHC) for all flour samples were assessed following the method described by Berton et al. (2002) with some modifications. The method was based on the AACC method no. 88-04 (AACC, 2000). Briefly, 1.0 g from the flour samples (W0) was dissolved in 5 ml of water or oil and vortexed for 10 s. The sample was left standing for 30 min at room temperature (25 ± 2°C), then subjected to centrifugation at 2000 × g for 10 min, and the sediment was weighed (W1). The WHC or OHC was calculated as the grams of water or oil absorbed per gram of flour samples, according to the following equation: WHC or WOH (g/g) = W1-W0/W0. Where: W0 represents the initial weight (g) of samples and W1 represents the final weight (g) of samples. The results are expressed as the mean values of three replicates.

| Pasting properties of composite flour dispersions
The wheat flour and the blends of composite (sorghum and millet) flour with 2% guar gum were prepared. The measurement of pasting properties for wheat and composite flours was done by using the Rapid Visco Analyzer (RVA) (Newport Scientific). The moisture content of the samples was adjusted to 14%, and then 3.5 g of each sample was weighed into aluminum canisters, and then distilled water was added to adjust the weight to 28 g. The sample was mixed, and the obtained slurry was poured into an aluminum pan, loaded into the RVA chamber, and held for 50 s at 50°C. After that, the temperature was raised to 95°C at 13.15°C/min in 3.42 min and then kept for 3.30 min at this temperature. The samples were subjected to cooling to 50°C at a rate of 12.93°C/min in 3.48 min and then held for 2 min at this temperature. The samples were measured in triplicate, and the data were processed by using Thermocline window software. Peak viscosity (PV), final viscosity (FV), peak time (Pt), peak temperature (PT), setback (SB), and breakdown (BD) were the main parameters measured.

| Gel texture analysis
After the RVA tests, the gel was subjected to overnight storage at 25°C in a beaker (25 ml volume) with the height and internal diameter of 35 mm and 30 mm, respectively. A Brookfield CT3 Texture Analyzer (Brookfield Engineering Laboratories, Inc.) was used for texture analysis. In the analyzer, the gel was compressed at a speed of 0.5 mm/s using two penetration cycles to a distance of 10 mm using 12.7 mm (width) × 35 mm (length) cylindrical probe. Thereafter, the texture parameters of the gels such as hardness, cohesiveness, adhesiveness, and springiness were measured. The harness and cohesiveness results were used to calculate the gumminess as reported previously (Hussain et al., 2013).

| Cookies preparation
The preparation of cookies was done according to the AACC method no. 10-50 (AACC, 2000), with slight modifications. The ingredients used for cookies are mentioned in Table 1. Five flour samples (wheat, sorghum, millet, sorghum 25% with 75%millet, sorghum 50% with millet 50%, and sorghum 75% with 25%) with 2% addition of gum for each flour except the wheat flour. To the mixing bowl, the materials were added in a specific order. Sugar, egg, and shortening were initially added to the bowl and then subjected to 2 min mixing at a low speed. Perfectly mixed flour sample, baking powder, cinnamon powder, and salt were added and subjected to 1 min mixing at low speed. In the end, dextrose and distilled water were added and continually mixed until homogenization. After that, the rolling pins were used to shape the dough into cookie sheets of 5-mm thickness.
Then, the sheeted cookies were sliced into cookie shapes, placed on baking trays, and subjected to the baking process (225°C for 8 min) in a cooking oven. After cooling to room temperature, the cookies were sealed in plastic bags and stored at room temperature for further analysis.

| Cookie physical analysis
The diameter of cookies, thickness, and spread ratio were assessed as described previously (Kaur et al., 2015). Briefly, a digital Vernier caliper was used to measure the average thickness (mm) of six cookies. The same for diameter, six cookies were lined edge to edge, and the average width (mm) was calculated by rotating the cookies at 90 degree angle. The ratio between the thickness and the diameter was considered as the spread factor of cookies.

| Water activity measurement
AquaLab Series 3 Water activity meter (Decagon Devices) was applied for the determination of water activity of cookies water activity (aw) at 25°C (Inglett et al., 2015).

| Cookie color analysis
Cookie color was measured at room temperature in terms of L* (lightness), a* (redness), and b* (yellowness) values in triplicate using a color grader (Satake, NCGA, Japan) with a D65 light source.

| Minerals' analysis
The minerals were evaluated in cookies samples after acid digestion of the samples. Briefly, to 0.5 g of samples in a Teflon tube 1.6 ml of 37% HCl and 1.7 ml of 65% HNO3 were mixed with the sample, and after standing for 30 min at room temperature (RT), 1.7% of H2O2 (30%) was added and mixed well. The digestion proceeded with heating in a microwave, a temperature ramp-up to 170°C for 20 min, and then it was sustained at the same temperature for

| Total phenols and radical scavenging activity determination
Initially, 1 g of cookies was extracted in ethanol (25 ml) in a shaker for 24 h and then centrifuged for 15 min at 10,000 × g. The mixture was filtered by using filter paper (Whatman #41), and the transparent supernatant was separated. The volume of the collected supernatant was readjusted to 25 ml and kept at 4°C for the estimation of phenolic and radical scavenging activity. The cookie extract was estimated for total phenolic content following the method described by Wu et al. (2007) with minor modifications. A gallic acid standard curve was prepared for comparison, and results were presented as equivalents of gallic acid per unit weight (g) of cookies. For the measurement of radical scavenging activity, the DPPH method was adopted (Akillioglu & Karakaya, 2010).

| Sensory evaluation of cookies
The panel was composed of 20 semitrained panelists of the male students and staff of the Department of Food Science and Nutrition, King Saud University. The cookie samples were coded using a threedigit number and randomly presented to the panelists. The sensory attributes (color, taste, aftertaste, texture, appearance, aroma, and overall acceptability) were assessed using a 9-point hedonic scale (1 = dislike extremely, 5 = neither dislike nor like, and 9 = like extremely) (Gat & Ananthanarayan, 2016).

| Statistical analysis
All data were collected in three replicates at least and analyzed by using the one-way analysis of variance (ANOVA) and Duncan's Multiple Range (DMR) test at sig ≤0.05 was used to compare means using SPSS (IBM Statistical Analysis Version 21).

| Pasting properties and texture profile of composite flour
The results showed significant (p ≤ .05) differences in the pasting and least values in cookies made using WF100% ( Table 3)  The water-holding capacity (WHC) and oil-holding capacity (OHC) were low in the cookies made using control flour (WF100%), and they were high in cookies made using SF and MF flour separately or in combinations (p ≤ .05). The values of these functional properties were insignificantly high in cookies made using high levels of SF (SF75%-MF25%) in the formulations suggesting the influence of SF on these properties. High WHC and OHC in cookies made using SF or MF and their combination could be attributed to the use of whole flour of sorghum and millet, which contain the bran that is rich in fiber and protein, and which are known to bind more water and oil in their structure (Paesani et al., 2020;Sharma et al., 2016).

| Chemical composition and bioactive properties of cookies
The results of the approximate composition, bioactive properties, and mineral contents of cookies made using different flour types are shown in Table 4. The highest values of moisture, protein, and fat were found in cookies made using composite flour of SF25%-MF75%, whereas the least values of moisture and protein were seen in cookies made using increased levels of SF in the composite flour (SF75%-MF25%), and the least value of fat content was seen in those made using pure sorghum flour (SF100%) (p ≤ .05). The ash content was high in cookies made using wheat flour (WF100%), and the lowest values were seen in those cookies made using MF100% and composite flours (SF75%-MF25% and SF25%-MF75%). The carbohydrate content was high in cookies of composite flour (SF75%-MF25%), and it was low in those made using (SF25%-MF75%). The variations in the chemical composition of cookies made with different flours could be attributed to the differences in the chemical composition of the raw materials. Similarly, previous studies showed differences in the chemical composition of the cookies made using different flours (Giuberti et al., 2018;Jan et al., 2015;Rai et al., 2014;Yildiz & Gocmen, 2021).
The bioactive properties (total phenolic content [TPC] and DPPH radical scavenging activity) of cookies indicate that the incorporation of sorghum and millet in the formulations significantly (p ≤ .05) enhanced these properties ( reaction with such melanoidins that possess antioxidant activity. In agreement with our findings, several studies indicated that the incorporation of gluten-free flours in cookies formulations significantly enhanced the total phenolic contents and the antioxidant activity of the cookies (Giuberti et al., 2018;Hussain et al., 2020;Jan et al., 2015;Yildiz & Gocmen, 2021).
Mineral analysis also showed significant variations among cookie samples ( Table 4). The highest (p ≤ .05) values of potassium, sodium, magnesium, and calcium were found in cookies made using the composite flour of SF75%-MF25% and the least values of these elements were seen in cookies made using wheat flour (WF100%).
The iron content was the highest in cookies made using wheat flour (WF100%), and the least value was found in cookies made using sorghum flour (SF100%) (p ≤ .05). The cookies made using SF100% showed the highest values of phosphorus, whereas those made using MF100% showed the least values (p ≤ .05). High levels of minerals in cookies made using composite flour of sorghum and millet are attributed to the use of whole flours of these grains, which contain the bran that is known for its richness of nutritional elements.
A previous study has shown that magnesium, phosphorus, and potassium were higher in cookies made using sorghum flour than those made using wheat flour (Rao et al., 2018), which is comparable to the findings of the current study.

| Sensory attributes of cookies
The sensory attributes of cookies made using WF, SF, MF, and composite flour of different levels of sorghum and millet flours are depicted in Figure 2. The scores of all sensory attributes of all cookie types were higher than the cutoff score (5), suggesting the accept- Another study showed no significant differences in the sensory attributes between the cookies made using gluten-free flours (Paesani et al., 2020).

| CON CLUS ION
This study concludes that cookies can be developed using millet and sorghum flour blends with acceptable physical and nutritional quality. The incorporation of sorghum and millet flour in cookies formulation improved the physicochemical, nutritional, and bioactive properties of the cookies without a major effect on the sensory quality. The developed gluten-free cookies can be good foods for people suffering from gluten intolerance and those with low income.
Based on this study, it is highly recommended that further research should be done to explore gluten-free cookies from sorghum and millet in nutritional properties and clinical studies are recommended.

CO N FLI C T O F I NTE R E S T
No potential conflict of interest was reported on behalf of all authors.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data used to support the findings of this study are included within the article.