1. Introduction
India is the largest producer of millets in the world, and sorghum production accounted for a 7.21% share in the world production of millets in 2022 [
1]. In 2018, cereal grain production was 9.2 billion tons globally, due to rapid changes in demographics, economic development, and lifestyle [
2]. Millets are nutritious foods loaded with energy, unsaturated fatty acids, iron, phosphorus, and alkaline phenolic phytochemicals, and can be used to combat malnutrition. They are also cheaper and affordable for everyone, regardless of the class they belong to in society [
3]. Consumer demand for readily available healthy, exotic, and unique foods encourages the food industry to invest in new products and process development in functional foods and functional food ingredients [
4].
Over the decades, the demand for instant beverage premixes has increased globally because of changes in lifestyle and dietary choices. These premixes have nutritional value and can be prepared with the addition of water or milk and in less time than other products [
5]. Various types of sports drinks and premixes are becoming increasingly popular among athletes and those who are physically active because they contain water, electrolytes, and energy. Sports drinks are a class of beverages containing a suitable proportion of carbohydrates and electrolytes. The main motive behind the concept of sports drinks is to provide hydration and carbohydrates that can easily pass through the stomach to the small intestine for its rapid absorption. A sports drink can be used before exercise to top up glycogen levels in muscles, during exercise, and recovery, as it assists in rehydration [
6]. The consumption of sports drinks has increased over time owing to increased awareness of the need for fluids and nutrients in athletes. Conventional sports drinks or premixes are characterized by high contents of added sugars (sucrose and dextrose), chemical additives, caffeine, and artificial flavors, which have raised concerns about their potential negative effects on health and performance [
7,
8,
9]. This has necessitated the development of more natural and enriched products, including millet-based SDP.
Food scientists are working relentlessly to create new generation multigrain foods and beverages, which can provide a good base for achieving the right nutritional standard and enhancing the acceptability factors. Proper formulation of mix combinations for a variety of grains, such as cereals, pseudo-cereals, legumes, and millets, can enhance appetizing, satisfactory, wholesome, and palatable products like grain-based beverages [
10]. Research has particularly focused on drinks from cereals and legumes, which are known to have high contents of antioxidants, proteins, carbohydrates, vitamins, minerals, and other natural nutrition values [
11,
12,
13]. Despite the fact that many researchers are studying millet-based multigrain products [
5,
11,
12], only a few have investigated the appropriate formulation of SDP that would be beneficial in meeting the recommended dietary allowances (RDA) for moderately active women and men and according to the guidelines given by the International Olympic Committee (IOC) and Food Agriculture Organization (FAO) [
13].
The major millet,
Sorghum bicolor (L.) Moench (sorghum), is considered to be a nutrient-rich source of complex carbohydrates, protein, fiber, B vitamins, minerals, and antioxidants, which make it a perfect choice as a batter or base ingredient. Pre-processing, i.e., popping, involves heating the grains with salt until they expand in size. This process improves the bioavailability of minerals, creates a crispy texture, increases the shelf life of the grain, and finally reduces anti-nutrient factors such as phytic acid compared to raw sorghum (from 4.42 to 1.84) [
3,
14,
15]. Popping tends to increase starch digestibility by decreasing resistant starches naturally present in sorghum grains. Sorghum protein is less digestible because of the presence of non-kafirin proteins, which glue together in the matrix. During popping, the cell wall is disrupted and kafirin is damaged, making the proteins soluble and easily digestible [
16]. Additionally,
Cicer arietinum L. (bengal gram) contains proteins, dietary fiber, and complex carbohydrates which qualify the pulse as a component to be added to sports drinks to provide energy and rehydration. Roasting, one heat treatment, promotes protein denaturation and hence improves the digestibility of grains [
17]. The proper combination of carbohydrates derived from these ingredients can be useful for improving an active lifestyle, enhancing and maintaining performance, and facilitating recovery. The inclusion of seeds such as pumpkin seed powder and flax seeds also adds nutritional value to sports drinks, such as omega 3 fatty acids, which help boost the general health and performance of athletes [
18].
The purpose of this study was to create a nutrient-dense SDP using popped sorghum, roasted Bengal gram, and other ingredients such as pumpkin seed powder, flax seed, chicory root powder, dehydrated carrot, beetroot, and banana powder. The main objective of including popped sorghum in SDP was to provide a source of easily digestible carbohydrates and plant-based proteins [
16]. In this study, nutritional composition, antioxidant capacity, and bioactive compounds of the SDP were determined; these help in replenishing energy reserves, electrolytes, and nutrients in the body. By exploring the benefits of natural ingredients, this research will lead to the formulation of healthier and more effective sports drink alternatives for athletes and health-conscious consumers.
2. Materials and Methodology
2.1. Procurement of Raw Material
Sorghum variety CSV-23 was selected for this study because of its good popping yield and local availability. All ingredients, such as sorghum, Bengal gram, pumpkin seeds, flax seeds, chicory root powder, carrot, beetroot, and banana were procured from the local market.
2.2. Pre-Processing and Product Formulation
Popped Sorghum Flour: Sorghum grains were cleaned and popped using a traditional salt popping method at 240–250 °C. Popped grains were ground using a grain grinder (Prestige Grain Grinder PGG01-180 Mixer Grinder) to form flour and sieved using a 3.5 mm strainer to obtain a uniform particle size.
Bengal Gram Flour: Bengal gram was continuously roasted at 180–200 °C and ground to form roasted Bengal gram flour, and sieved (3.5 mm strainer) [
19].
Seed Mix Powder: Seeds (pumpkin seeds and flax seeds) were dry roasted at 70–80 °C and powdered to form seed mix, and sieved. Chicory root powder was added because of its prophylactic and phytobioactive properties [
20].
Flavor Mix: Carrot, beetroot, and banana were cut into thin slices and dried using a tray dryer (Model No.MSW-216, MAC, New Delhi, India) for 72 h at 50–60 °C. Dried carrots, beetroots, and bananas were ground to obtain a fine powder. This powder is used as a flavor mix because it acts as a natural colorant and adds a flavor to the formulation.
A total of 46 trial samples were prepared using a specific amount of each powdered ingredient. All formulated samples were tested to obtain the optimized product. All prepared popped sorghum sport premix were stored in air-tight containers.
Figure 1 shows the process of preparation of popped sorghum SDP.
2.3. Optimization of Sports Drink Premix (SDP)
For optimization of SDP, five independent variables viz., sorghum flour, Bengal gram flour, seed mix, chicory root powder, flavor mix and two dependent variables viz., carbohydrate and overall acceptability, were selected. According to the guidelines of the International Olympic Committee (IEC) and FAO, a sports drink premix should contain 6% carbohydrates per serving [
13]. Overall acceptability is an important parameter for new product development; thus, these two parameters were selected as the dependent variables.
The Box–Behnken study design using Design Expert Software (version 13.0; StateEase 2023) was applied for the optimization. The total carbohydrate content of SDP was estimated using the anthrone reagent method [
21]. Briefly, 0.1 g premix was mixed with 5 mL 2.5 N HCL. The mixture was heated for 3 h in water bath at 90 °C. The solution was left to cool, and sodium carbonate was added until effervescence stopped. The extract was filtered, and the volume was made up to 100 mL. Then, 0.5 mL of this extract was mixed with 4 mL anthrone solution (0.2% anthrone reagent was prepared with 95% conc. sulfuric acid) and absorbance was measured at 630 nm [
21]. Overall acceptability was calculated using 9-point Hedonic rating scale.
2.4. Physicochemical Analysis
pH was measured using digital pH meter (Labman Scientific Instruments Pvt. Ltd., Chennai, India). A 5% solution of the SDP was prepared using distilled water and the pH was measured at 25 °C [
22]. The color index of the formulated SDP was measured using a colorimeter (3nh portable spectrophotometer, Foshan, China) with a D65 illuminant and a standard observer angle of 10°. The sample brightness is represented by the symbol L*, where 100 represents flawless whiteness and 0 represents blackness. An increased L* value indicates a lighter or brighter sample. Moreover, the values a* and b* represent red–green and blue–yellow chromatically, respectively. Water activity (a
w) was measured using digital water activity meter (Rotronic 8303 Bassersdort with rortronic HW4 software). Titratable acidity was determined using the trimetric method using phenolphthalein indicator to change colorless solution to pink [
23].
2.5. Nutritional Analysis of SDP
Macronutrients were estimated using AOAC methods [
24]. Moisture was estimated by the hot-air oven drying method at 100 ± 1 °C for 10 h. The moisture percentage was calculated from the difference between the original and the final dried samples. A moisture-free sample was used for total ash estimation. Crude ash content was determined using a muffle furnace at 400–450 °C for 3 h. A moisture-free sample was used for fat estimation using Soxhlet extraction. The fat was extracted with 99 percent ethanol. Protein was estimated using the Kjeldahl method and the percentage protein was calculated by multiplying the percentage nitrogen by power factor. Crude fiber was estimated by acid and alkali wash method [
25] and total energy was determined by summation method by following equation.
2.6. Micronutrient Analysis
2.6.1. Wet Digestion of SDP
A 1 g moisture-free SDP sample placed in a muffle furnace at 450 °C for 180 min to estimate the crude ash content. To the ash sample in the glass tubes, 3 mL nitric acid and 1 mL hydrochloric acid were added and heated on hot plate at 50–80 °C for 8–9 h until a colorless solution was obtained. The reagents were allowed to cool, and the volume of the contents of the tubes was adjusted to 50 mL with distilled water [
26].
2.6.2. Estimation of Microminerals by Atomic Absorption Spectroscopy (AAS)
Quantitative analysis of the digested sample of SDP was performed for calcium, iron, zinc, magnesium, manganese, and phosphorous using Atomic Absorption spectroscopy (AAS-Perkin Elmer, Delhi, India). Lamps of electrodes were used for each mineral. Standard solutions of each mineral were prepared and passed through the equipment to calibrate the instrument. The dilution factors for phosphorus, magnesium, and for other minerals were 10,000, 2500, and 100 respectively. The concentrations were given as ‘ppm’ then converted to mg [
26].
2.6.3. Estimation of Sodium and Potassium by Flame Photometry
The wet digested SDP sample solution was used for the estimation of sodium and potassium using Flame photometry (Electronic India Pvt. Ltd., Delhi, India). Working standards of 25, 50, and 100 ppm were employed for calibration. The concentrations of the elements were determined based on the degree of emission and subsequently qualified in terms of ‘ppm’ and then converted in terms of mg [
26].
2.7. Antioxidant Potential of SDP
2.7.1. Total Phenolic Content
In a 100 mL volumetric flask, add distilled water 50:1 and 1 g of premix based at the diluted ratio of 1:5. Then, mix in 5 mL of commercially available Folin–Ciocalteu reagent and 20 mL of sodium carbonate solution (20% w/v). Distilled water was measured and added to the solution to reach capacity of 100 mL. The contents were then agitated for homogenization. After the reaction, the mixture was allowed to stabilize, and the absorbance was measured at 750 nm.
2.7.2. Diphenyl-1-Picrylhydrazyl (DPPH) Radical Scavenging Assay
A total of 0.0125 g of DPPH was mixed with methanol (5 mL). Aliquots (1 mL) were mixed with 100 mL of a methanol solution and covered with silver foil. For extraction, 0.3 g of sample was mixed with 100 mL of methanol, followed by maceration and centrifugation at 5000 RPM for 10 min. The sample was then filtered, and the supernatant was collected. The mixture was then incubated for 30 min at 25–30 °C in the dark. The absorbance was measured at 517 nm [
27]. The extract concentrations yielding IC
50 inhibition values were determined from the percentage of scavenging effect against extract concentration by plotting the graph using nonlinear regression. IC
50 values were expressed in µg/g of sample extracts based on the potency of the sample extract.
2.7.3. Flavonoid Content
The flavonoid aluminum chloride colorimetric method was applied for flavonoid determination. The SDP extract was prepared (0.5 mL of 1:10
w/
v), and methanol was added to 1.5 mL of methanol, 0.1 mL of 10% aluminum chloride, 0.1 mL of 1 M potassium acetate and 2.8 mL and distilled water. Incubated at 25 °C for 30 min. The absorbance of the reaction mixture was determined at 415 nm using a double beam UV/Visible spectrophotometer (Perkin Elmer, Waltham, MA, USA) [
27].
2.8. Gas Chromatography Mass Spectrometry (GC-MS)
An ethanolic extract of SDP was prepared using a Soxhlet apparatus. The solvent used for this process was 99.9% ethanol. The complete extraction process required 6 hrs at 60 °C. The 5 mg ethanolic extract was dissolved in 1 mL of ethanol (99%), followed by shaking in vertex until dissolved [
28]. The GC system (8860, Agilent Technologies, Hyderabad, India) linked to a single quadrupole (stainless steel source) mass spectrometer and DB-5 capillary column (30 m × 0.25 mm ID, 0.25 μm film thickness) (J and W Scientific, New York, NY, USA) was used to identify bioactive compounds. The intake was maintained in venting mode, and helium was used as the carrier gas at a rate of 1 mL/min. The temperature was then maintained at 220 °C for five minutes. The relative percentage of the sample constituents was computed using the peak area normalization method, and unknown compounds were identified using the NIST Library [
28].
2.9. Statistical Analysis
All analytical methods were performed in triplicates. The overall analysis of all results is expressed in mean and standard deviation. To optimize the degree of significance of the model terms and model fitting, State-ease software was used to perform regression analysis and analysis of variance (ANOVA). The adequacy of the models was assessed using the lack-of-fit test, model, and R2 (coefficient of determination) analysis. The measure of the degree of fit is the R2, which is the ratio of the explained variance to total variation. The coefficient of variation (CV) displays the relative deviation of the experimental points from the model’s forecast.