Non-GMO-high oleic soybean meal value addition and studying the functional and reconstitution behavior

ABSTRACT

Soy meal, a substantial byproduct of soy-oil processing, is rich in crude protein (44–49%), crude ash (5.2–9.1%), minerals, and vitamins. Only 2% of the total soy meal is consumed by humans, while 97% is utilized for animal feed and other industrial purposes. In this study, we use soy meal from non-genetically modified high oleic (Non-GMO-HO) soybean oil processing to develop value-added food products. In this study, soy meal was spray-dried using 5–15% maltodextrin and gum Arabic as a drying aid because trial investigations revealed that the sticky behavior of soy meal powder, which impacts product yield. The physical properties, such as colour, flowability (m³/h), moisture content (%), water activity (Aw), hygroscopicity (%), reconstitution properties, viscosity (mPa-s), thermal degradation behavior, and particle size distribution, were investigated to analyze the impact of drying aid on the quality of soy meal powder. JMP 14.0.0 Pro software was used to conduct the statistical analysis. Spray-dried soy meal powder can be used in reconstituted beverages, infant formulas, soy-based cookies, meat analogs, carrier agents, and more.

GRAPHICAL ABSTRACT

KEYWORDS:

• Soy meal (SM)
• SEM (scanning electron microscopy)
• Rheological property
• DSC (differential scanning calorimetry) and DLS (dynamic light scattering)

Introduction

Malnutrition and obesity are the two most common health issues in the present scenario. According to the CDC, 2017–2018 data, approximately 42.4% of the total adult population in the USA is obese with no major significant difference between males and females.^[1] WHO states that 1.9 billion of the world’s adult population are overweight and about 462 million are underweight.^[2] Although these two problems are quite opposite to each other, they both have a common link with nutrition imbalance, causing an adverse effect on the human body. The major consequences of obesity are cardiovascular disease (CVD), musculoskeletal disorders, and some cancers (gallbladder, kidney, ovarian, and endometrial.^[1] On the other hand, low weight, stunting, nutritional deficiency, and wasting are majorly caused by malnutrition.^[2] Furthermore, protein calorie malnutrition (PCM) is another major health concern that affects about 1 billion people worldwide.^[3] Protein deficiency can lead to metabolic disorders that impair the function of the pancreas, gastrointestinal tract, and tissue repair, which can lead to chronic inflammation and cancer.^[4] Therefore, a sustainable protein-rich food source with a reasonable cost could be helpful for fulfilling the nutritional requirements of malnourished populations.

The soybean has significant levels of protein (35–45%), fat (15–25%), carbohydrate (33%), and soluble sugar (16.6%).^[5] Over the past few years, there have been more than a thousand new soybean cultivars developed worldwide. Non-genetically modified high oleic (Non-GMO-HO) soybean is one of the recently developed varieties of soybean. The traditional varieties of soybean are highly rich in protein and fat (saturated fat: 15%, oleic acid: 25%). Highly saturated fatty acids are not recommended for a healthier diet. In contrast, non-GMO-HO soybeans are highly rich in oleic acid (72–75%) and less in saturated fatty acids (7%), which is recommended for good health.^[6] In addition, Non-GMO-HO soybeans have high-temperature tolerance and avoid the chemical process that adds artery-clogging trans fats.^[7] Non-GMO-HO soybeans are potentially more sustainable than the traditional variety of soybeans. Consuming this variety of soybean in the diet lowers the risk of cardiovascular disease, obesity, metabolic syndrome, certain types of cancer, such as prostate, breast, gastric, and other chronic diseases.^[8] Over and above, non-GMO HO soy isoflavones show promising effects on some diseases; they act as antiestrogenic, antiproliferative, insulinotropic, antiinflammation, and cholesterol-lowering agents.^[9,10]

There are some by-products generated during soybean processing that are very rich in proteins, lipids, fibers, and micronutrients. Soy meal is a major by-product of the soy oil processing industry, used in animal feed, protein supplements, energy metabolization, industrial soap, and biodiesel production. However, overall, only 2% of the total soy meal is used for human consumption. On the other hand, a huge amount (approx. 97%) of soy meal is used as animal feed and for some other industrial purpose.^[11] Soy meal contains a high amount of crude protein, 44–49% (protein content in soybeans is approximately 40%), and low in crude fat, 0.55–3% (soybean 15–24%), and crude ash, 5.2–9.1% (soybean 4.86%).^[12] Fully extracted soy meal contains a very low amount of lipid but mechanically expelled soy meal contains enough fat. The value addition in soy meal could aid in the development of low-cost plant-based food products. Soy meal costs about $0.38 per kilogram (soybeans cost about $5–10 per kilogram), making it very affordable for people of all income levels to consume. The usability of any food product depends on three major factors, such as nutrient profile, availability, and cost of the product. Based on some prior cost analysis, even after the value-added cost of soy meal is not going to exceed the commercially available whey protein and egg protein isolates, the United States and Brazil are the world’s top producers of soybeans, followed by Argentina and Asian countries. Soybean processing industries in these countries generate a huge amount of soy meal as a by-product every year. By using some processing methods, soy meal could be utilized to produce tofu, soy milk, soy protein isolates, textured soy protein, and a variety of other human consumable food products.^[13]

In the current study, soy meal produced by the non-GMO-HO soybean oil processing industry is spray-dried by using 5% of maltodextrin and gum Arabic as a drying aid. In the trial experiments, a higher amount (20–50%) of soy meal was reconstituted in the aqueous solution, but due to its high protein content and colloidal behavior, the achieved consistency of the sample was very thick. For these reasons, 15% soy meal was thoroughly mixed with water before being centrifuged and vacuum filtered to prepare the feed solution for spray drying. Initially, 15% of the soy meal was spray-dried at some modified drying conditions, but it was observed that most of the powder particles got stuck in the cyclone separator area. Even though these powder particles were easily scrapable by using a soft plastic spatula, due to the complicated structure of the cyclone separator, it was hard and tedious to recover all the powder samples, which highly impacted the product yield (%) and cost affectability of the spray drying process. With the addition of a small amount of drying aid, such as maltodextrin and gum Arabic, the process productivity increased many folds, with little or no powder accumulation in the cyclone separator. Soy meal feed solution was spray-dried at an optimized set of drying parameters at 140°C inlet temperature, 90% aspirator, and 15% feed rate. Collected soy meal powder with and without drying aids is utilized for analyzing physical (colour, flowability, moisture content (%)), water activity, hygroscopicity (%), and reconstitution (wettability, solubility, and viscosity) properties. To determine the quality of soy meal powder with and without drying aids, its thermal degradation behavior, particle shape, and particle size distribution were analyzed.

Materials and methods

Sample preparation

To prepare the feed solution, 15% of (W/V) fully pressed soy meal powder (obtained from the Missouri Soybean Merchandising Council, USA) generated during processing of non-GMO-HO soybean oil was used for spray-drying. The 15 g of soy meal was dissolved in 100 mL of distilled water and mixed well by homogenization (IKA EUROSTAR 40 digital) for 15 min at 500 rpm. The mixed feed solution was centrifuged at 5000 rpm for 15 min. The supernatant was vacuum filtered using filter paper (Fisherbrand P8 grade). To achieve a higher product yield (%) and analyze the effect of other drying aids on the physicochemical properties of soy meal powder, maltodextrin (MD), and gum Arabic (GA) were added at different concentrations (5%, 10%, and 15%). To calculate the product yield of the collected powder, the total solid (%) content of the feed solution was recorded which was 6 ± 0.34 g for soy meal solution (15%).

Spray-drying parameters

Spray drying of the soy meal solution was performed by using a BUCHI-290 mini spray dryer. Based on the higher product yield (%) and thermal efficiency (%) of drying process, drying parameters were optimized at inlet temperature (140°C), aspirator (35 m³/h), and feed rate (5 mL/min) for a similar variety of soybean (Non-GMO-HO).^[14] The inlet temperature (140°C), aspirator (35 m³/h), and feed rate (5 mL/min) were maintained throughout the drying process. The drying chamber, cyclone separator, and collection chamber of the spray dryer are made up of 3.3 borosilicate glass to prevent the equipment from thermal shock. These glass chambers are also coated with perfluoro alkoxy polymer to prevent any contamination and acidic reactions. The nozzle, heater, and connection pipes are made up of stainless steel, titanium, and alloy to prevent the metal from any acidic reactions. The product feed tube and seal of the product collection vessel are made up of silicon. Other technical parameters, such as the dimension of the drying chamber, were 65*110*70 cm, nozzle diameter 0.7 mm, nozzle orifice size 150 µm, heating capacity 2300 W, and connection voltage 200–230 V. To maintain the peristaltic flow inside the drying chamber, a 0.7 cm peristaltic pump was attached to it, which was covered by a titanium nozzle tip.^[15]

Thermal efficiency of spray drying process

A thermocouple sensor was used to measure the outlet temperature (OT) of the B-290. According to Santos et al., the reflected OT indicates the maximum temperature that powder was exposed to during spray drying. It also reflects the temperature that resulted from all mass and heat transfers during spray drying.^[16] The thermal efficiency can be described as the difference between the amount of heat applied and the amount utilized, according to Cheng.^[17]

(I) $\text{Thermal}\text{efficiency}\%\left(\eta \right)=\frac{Tx1-Tx2}{Tx1-Ta}$(I)

Where ɳ is the thermal efficiency of spray dryer in %, Tx¹ is IT °C, Tx² is OT °C, and T_a is the surrounding temperature °C

Total product yield % (TPY)

The total product yield (%) of spray-dried soy meal powder was calculated by measuring the % total solid content in the feed solution and recovered powder after spray-drying process.^[18] Total product yield is the total recovered mass after spray drying from the collection chamber as well as the drying chamber and cyclone separator area. To measure the consistency of the product yields, 100 ml of the feed solution was passed through the spray dryer process during each run (n = 4). Spray-dried soy meal powder was stored in glass vials at room temperature (25°C) to perform the physicochemical characterization of the powder.

(II) $\mathrm{\%}\mathrm{T}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}\mathrm{S}\mathrm{o}\mathrm{l}\mathrm{i}\mathrm{d}=\frac{Finalweightofdriedsoymeal}{Initialsoymealcontentinthesuspension}\times 100$(II)

(III) $\mathrm{P}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\left(\mathrm{\%}\right)=\frac{\mathrm{R}\mathrm{e}\mathrm{c}\mathrm{o}\mathrm{v}\mathrm{e}\mathrm{r}\mathrm{e}\mathrm{d}\mathrm{s}\mathrm{o}\mathrm{y}\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{l}\mathrm{p}\mathrm{o}\mathrm{w}\mathrm{d}\mathrm{e}\mathrm{r}\mathrm{a}\mathrm{f}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{s}\mathrm{p}\mathrm{r}\mathrm{a}\mathrm{y}\mathrm{d}\mathrm{r}\mathrm{y}\mathrm{i}\mathrm{n}\mathrm{g}\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{c}\mathrm{e}\mathrm{s}\mathrm{s}}{\mathrm{I}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{c}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{o}\mathrm{f}\mathrm{s}\mathrm{o}\mathrm{y}\mathrm{m}\mathrm{e}\mathrm{a}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{h}\mathrm{e}\mathrm{f}\mathrm{e}\mathrm{e}\mathrm{d}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{u}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}\times 100$(III)

Powder characterization

Colour values

A colorimeter (Konica Minolta® CR-410, Ramsey, New Jersey, USA) was used to analyze the colour profile of spray-dried soy meal powder. Each sample’s colour profile (L*, a*, and b*) was measured to calculate the colour difference (delta E), chroma, and whitening index (WI).^[19] A white calibration plate was used to calibrate the colorimeter prior to recording the colour values to ensure that the reflected x, y, and z values were similar to the calibration values. To minimize the experimental error, all the values were measured five times.

(IV) $\mathrm{\Delta }E=\sqrt{{\left(\mathrm{\Delta }\mathrm{L}\ast \right)}^2+{\left(\mathrm{\Delta }\mathrm{a}\ast \right)}^2+{\left(\mathrm{\Delta }\mathrm{b}\ast \right)}^2}$(IV)

(V) $Chroma=\sqrt{a^2+b^2}$(V)

L* value varies between 0 and 100, here 0 represents black and 100 represents white. Chromaticity values a* and b* varies between positive to negative here a* = red, -a* = green, b* = yellow, and – b* = blue.^[20]

Flowability and cohesiveness

To analyze the flowability and cohesiveness of spray-dried powder, bulk density, and tapped density were measured. To measure the bulk density, approximately 2 g soy meal powder was transferred to 10 ml graduated cylinder, and bulk volume was recorded. To measure the tapped density graduated cylinder was tapped against smooth and padded surface for 50 times and a new volume was recorded. Calculate both tapped density and bulk density by dividing mass by voume (bulk density) and tapped volume (tapped density).^[21] Based on the bulk density and tapped density outcome, Carr Index (CI) and Hausner ratio (HR) were calculated to determine the flowability and cohesiveness o,f spray-dried soy meal powder.

(VI) $CarrIndex\left(CI\mathrm{\%}\right)=\frac{\left(\rho t-\rho b\right)}{\rho t}\times 100$(VI)

(VII) $Hausnerratio\left(HR\right)=\frac{\rho t}{\rho b}$(VII)

For good flowability, the CI value should be less than 20, if CI value exceeds than 25 it is an indication of the bad and unacceptable quality of soy meal powder.^[22] Similarly, HR values should be 1–1.4 for acceptable quality of soy milk powder, and if HR is more than 1.4, it means flowability of soy meal powder is bad.^[23]

pH, % brix, and water activity of spray-dried powder

The pH of soymeal (10%) reconstituted with DI water was analyzed using a digital pH meter (Mettler Toledo TM), and the electrode was the In Lab® Expert Pro-ISM. Before taking the actual reading, The pH meter was calibrated with a buffer solution with a pH of 7.00. Water activity is a powder property, which measures the amount of water present in food powder that directly affects microbial growth.^[24] The water activity (aw) of spray-dried soy meal powder was determined by using water activity meter (AquaLab CX-2) at 25 ± 1°C. To measure the water activity 2.0 ± 0.5 soy meal powder was evenly spread on the plastic disc, and water activity was recorded in triplicates.

Water solubility (%)

To measure the water solubility, 2 g soy meal powder was thoroughly mixed with 25 ml double distilled water. Soy meal sample was kept in a water bath at 37°C for 30 min, with intermittent stirring followed by centrifugation for 10 min at 5000 rpm. The supernatant was transferred to a petri dish (pre-weighted) then dried in a vacuum oven at 105°C. The weight of the remaining residue was recorded to calculate the water absorption index.^[25] The drying time of soy meal sample range 40–60 min (sample was observed at every 10–15 min to prevent overdying and under drying). When the sample reaches room temperature, then the weight of the dried sample is recorded to calculate the water solubility. The water solubility (%) is the percentage of dried supernatant with respect to the amount of soy meal sample taken.^[26]

(VIII) $WaterSolubility\left(\mathrm{\%}\right)=\frac{DriedWeightofSupernanant}{AmoutofSoymealPowdertaken}\times 100$(VIII)

Dispersibility

The dispersibility of spray-dried soy meal powder was measured by the Jinapong method with some modifications.^[27] To begin the experiment, 1 g of spray-dried soy meal powder was weighed and placed in a 50 ml beaker, followed by 10 ml of distilled water. The powder sample was thoroughly dissolved in the aqueous medium after being stirred continuously for 25 min and 15–20 s. The stirred sample was passed through the 212 µm mesh size sieve and collected on a pre-weighted aluminum disc. The supernatant/sieved liquid was dried in a vacuum oven at 105°C until it achieved the dried state (drying time: 15–20 min). Spray-dried soy meal powder’s moisture content (%) was measured using a moisture analyzer (METTLER TOLEDO HE53). Dispersibility was calculated using the formula given below.

(IX) $Dispersibility=\frac{\left[\left(10+x\right)\times \mathrm{\%}TS\right)]}{x\left[\frac{100-y}{100}\right]}$(IX)

where x is indicating the powder content added (g), y is moisture content (%) present in the spray dried powder and %TS = Total solid in the filtered soy meal.

Hygroscopicity

Hygroscopicity is defined as the ability of a material to absorb moisture from the atmosphere as a function of relative humidity. The hygroscopicity of spray-dried soy meal was measured according to the Wang et al. method with some modifications.^[28] To assess the hygroscopic behavior of soy meal powder, 0.5 g of the powder was thoroughly spread on 0.9 mm Petridis and placed inside a desiccator for 24 h at room temperature (25°C) and 75% relative humidity. To maintain the saturated humidity inside the desiccator, NaCl was mixed with the DI water in a 1:2 ratio (w/v). The resulting hygroscopicity is expressed in terms of the moisture content of the sample absorbed after 24 h of storage.

Scanning electron microscopy (SEM)

Scanning Electron Microscope (FEI Quanta 600 F ESEM) operated in high vacuum was used to determine the particle shape, size, and morphology of spray-dried soy meal powder. Soy meal sample was mounted with carbon adhesive and sputtered with 10 nm platinum for imaging. Imaging was performed at 5KV, 30 μm objective aperture, 3.5 spot size, and 8 mm working distance.

Thermal analysis of soy meal powder

Thermal analysis of spray-dried soy meal powder was conducted by using TA Instruments Q20 Differential Scanning Calorimeter (Q20 DSC) attached to the refrigerated cooling system 90 (RCS 90). Before starting the experiment, the system was stabilized to a flange temperature (<-70°C) RCS 90 cools the system up to −80°C, but chiller cannot hold beyond 400°C. The Q series (Q20-0985-DSC Q20) software was used to analyze the onset temperature, glass transition temperature, and thermal degradation behavior soy meal powder. Soy meal powder (8 ± 1 mg) was sealed in aluminum pan and subjected to heating from −60 to 400°C, at rate of 10°C/min with n nitrogen flow rate was maintained 50 mL/min.

Rheological behavior of reconstituted soy meal powder

The viscosity of the reconstituted soy meal powder (10%) was determined using an Anton-Paar MCR-302 rheometer at room temperature (25°C) with a cone plate measuring system. The measured diameter of the cone was 50 mm, and it made a 1° angle with the surface of the plate. A total of 0.75 ml of soy meal sample was carefully poured onto the plate using a micropipette. Different combinations of spray-dried soy meal powder with drying aids MD and GA (5%, 10%, and 15%) were reconstituted with DI water and compared soy meal powder without any drying aids. Experiments were performed in triplicate at shear rates between 0.1 and 100 s-1.

Particle size distribution and zeta potential of soy meal powder

The DLS (Dynamic Light Scattering) Delsa Nano Submicron Particle Size and Zeta Potential Particle Analyzer, recruited from Beckman Coulter, California, USA, was used to measure the particle size distribution of spray-dried soy meal samples. The sample is placed in the instrument, and the particles are subjected to an electric field. Particle distribution and zeta potential of soy meal powder were analyzed at room temperature (25 ± 1), 0.15–0.2 ml of 1000-fold diluted with distilled water. Particle size evaluation were performed at room temperature (24 ± 1), refractive index value 1.3328, viscosity, 0.8878 mPa-s, scattering angle 15°, and at signal intensity of 3700 ± 500 counts per second (cps).

Experimental design and statistical analysis

In the current study total six sets of the combination were developed with GA (5%, 10%, and 15%) and MD (5%, 10%, and 15%) and soy meal was set as control sample. Experiment was designed using the full factorial model of 2³ categorical variable (Table 2). To analyze the product yield and interaction drying aids with soy meal the physicochemical properties were measured. Based on the trial experiments and optimized parameters for non-GMO-HO soy milk powder set inlet temperature (140°C), feed rate (5 mL/min), aspirator (35 m³/h) was kept constant throughout the drying process to obtain optimal quality of the spray-dried powder.^[29] A one-way analysis of variance (ANOVA) was used to determine the significant difference between the mean values of physical, reconstitution, particle, and thermal properties of spray-dried soy meal powder. All the statistical analysis was done using the JMP 14.0.0 software (FEAST lab), and all the results were expressed in average ± standard deviation (n = 3).

Table 1. The physicochemical properties of spray-dried soy meal powder with and without gum Arabic (GA) and maltodextrin (MD) as a drying aid.

Combinations	SM	SM + 5% MD	SM + 10% MD	SM + 15% MD	SM + 5% GA	SM+ 10% GA	SM + 15% GA	P value	R^2 value
Colour profile
L	93.57 ± 0.01	95.86 ± 0.00	96.65 ± 0.02	97.09 ± 0.01	94.49 ± 0.04	94.96 ± 0.01	95.51 ± 0.02	<0.0001	0.92
a	−2.07 ± 0.01	−2.56 ± 0.00	−2.58 ± 0.01	−3.4 ± 0.01	−1.94 ± 0.02	−1.83 ± 0.02	−1.4 ± 0.01	<0.0001	0.95
b	19.58 ± 0.01	16.77 ± 0.00	16.09 ± 0.00	17.83 ± 0.01	17.07 ± 0.13	15.45 ± 0.05	14.89 ± 0.01	<0.0001	0.71
Delta E	0.02±0.00	3.65±0.00	4.68±0.01	4.14±0.00	2.67±0.14	4.36±0.05	5.11±0.01	<0.0001	0.96
Chroma	19.68 ± 0.01	16.96 ± 0.00	16.3 ± 0.00	18.15 ± 0.01	17.18 ± 0.13	15.56 ± 0.05	14.95 ± 0.01	<0.0001	0.72
WI	79.29 ± 0.00	82.54 ± 0.00	83.36 ± 0.00	81.61 ± 0.00	81.96 ± 0.14	83.65 ± 0.05	84.39 ± 0.01	<0.0001	0.72
Flowability
Bulk Density (g/cm^3)	0.22 ± 0.00	0.25 ± 0.01	0.31 ± 0.03	0.37 ± 0.02	0.28 ± 0.00	0.37 ± 0.03	0.37 ± 0.00	<0.0001	0.87
tapped density	0.29 ± 0.00	0.29 ± 0.01	0.33 ± 0.02	0.40 ± 0.02	0.30 ± 0.00	0.39 ± 0.03	0.39 ± 0.00	<0.0001	0.82
Carr Index (%)	21.64 ± 0.50	12.51 ± 1.72	6.95 ± 2.37	6.86 ± 1.25	6.16 ± 0.85	7.31 ± 0.59	5.52 ± 0.06	<0.0001	0.71
Hausner Ratio	1.28 ± 0.01	1.14 ± 0.02	1.08 ± 0.03	1.07 ± 0.01	1.07 ± 0.01	1.08 ± 0.01	1.06 ± 0.00	<0.0001	0.71
Porosity	82.08 ± 0.14	80.25 ± 0.74	76.82 ± 2.5	73.18 ± 1.46	77.58 ± 0.4	70.23 ± 2.29	70.72 ± 0.14	<0.0001	0.87
Reconstitution Properties
Dispersibility	88.17 ± 1.02	89.35 ± 0.66	88.60 ± 1.51	86.88 ± 1.71	86.12 ± 0.22	85.39 ± 2.34	83.58 ± 2.58	0.0004	0.59
Solubility (%)	94.08 ± 2.03	90.45 ± 1.15	90.75 ± 0.55	89.4 ± 0.4	71 ± 0.3	74.4 ± 1.2	76.65 ± 0.35	<0.0001	0.72
MC (%)	7.44 ± 0.14	5.9 ± 0.25	6.43 ± 0.54	6.29 ± 0.12	6.15 ± 0.13	6.18 ± 0.11	6.26 ± 0.21	<0.0001
Hygroscopicity (%)	4.83 ± 0.34	5.07 ± 0.10	5.64 ± 0.20	5.94 ± 0.55	3.80 ± 0.17	4.84 ± 0.16	3.83 ± 0.15	<0.0001	0.97
Viscosity (m Pas)	3.75 ± 0.10	4.68 ± 0.37	5.65 ± 0.30	5.15 ± 0.19	6.55 ± 0.11	9.28 ± 0.14	11.06 ± 0.48	<0.0001	0.97
Brix (%)	9.53 ± 0.05	9.33 ± 0.06	9.07 ± 0.12	8.63 ± 0.12	7.53 ± 0.06	7.57 ± 0.06	7.83 ± 0.06	<0.0001	0.72
pH	6.78 ± 0.01	6.78 ± 0.00	6.92 ± 0.01	6.74 ± 0.01	6.26 ± 0.02	6.03 ± 0.01	5.89 ± 0.01	<0.0001	0.95
Aw	0.42 ± 0.00	0.39 ± 0.00	0.41 ± 0.00	0.5 ± 0.00	0.28 ± 0.00	0.24 ± 0.00	0.22 ± 0.00	<0.0001	0.89

Table 2. Particle size distribution properties of spray-dried soy meal powder.

Parameters	SM	SM +5%MD	SM + 5%GA
PDI	1.44	2.069	4.155
Mean diameter (µm)	2.31 ± 3.70	2.17 ± 3.47	2.55 ± 3.15
Span	6.58	6.60	7.92
Zeta potential (mV)	−23.96	−29.71	−27.78

Results and discussion

Product yield (%)

Product yield (%) is regarded as one of the most critical determining elements in determining the economic effectiveness of the drying process. From the current study, it was observed that spray drying of soy meal at a set inlet temperature, aspirator, and feed rate gave a 66.83 ± 1.66 (%) product yield. During the drying process, most of the soy meal powder accumulated in the cyclone separator area due to its sticky nature and high fat content (Figure 2). To calculate the product yield (%), soy meal powder was recovered by scraping it from the cyclone separator. To avoid this problem, a small amount of drying aid (MD and GA) was added into the feed solution. Visual observation as well as experimental data showed that even adding a small amount of drying aid improved the process efficiency, and product powder was collected into the collection chamber (Figure 2). The obtained product yield of soy meal (15% w/v) without any drying aid was 66.83 ± 1.66%, which dramatically increases with the addition of even 5% of MD (85.76 ± 2.19%) and GA (85.67 ± 2.69%) as drying aids (Figure 1a). However, increasing the concentration of drying aids in the feed solution has no significant effect on process product yield. Statistical evidence shows that 0.0029 P values, 0.50 R², and 0.42 R² adj (Figure 1b). Supporting data was obtained during the spray drying of waxy rice starches at different temperatures.^[30] The obtained product yield of soy meal powder is close to spray-dried goldenberry powder^[31] and appears closer to the value of soybean hydrolysate.^[32]

Figure 1. (a) Bar graphs and (b) regression plots for product yield (%), thermal efficiency (%), and outlet temperature (°C) of spray drying process for soy meal with and without drying aids.

Figure 2. Image of powder accumulation in cyclone separator and collection chamber of a spray dryer during drying (a) 15% Soy meal (b) 15% Soy meal + 5% Maltodextrin and (c) 15% soy meal + 5% Gum Arabic.

Spray drying parameters

The cost-effectiveness of the drying process is influenced by spray drying parameters, including the inlet temperature, outlet temperature, thermal efficiency, airflow rate, consistency of the feed solution, feed flow rate, nozzle diameter, size of the drying chamber, pressure drop, and relative humidity.^[33] In addition, the drying conditions have a significant influence on the characteristics that define the quality of spray-dried powder, such as stickiness, water activity, moisture content, hygroscopic behavior, particle size, and shape.^[34] Spray drying parameters including the inlet temperature (140°C), aspirator (90%), feed rate (15%), and nozzle size (150 µm) were maintained throughout the operation. In addition to the above parameters, other drying parameters, such as relative humidity (55 ± 5%), pressure drop (−70 ± 10 m bar), run time (18 ± 2 min), and airflow (45 ± 5%) slightly flatulated during the drying process, which influences the outlet temperature and thermal efficiency (%) of the process. The outlet temperature is the maximum temperature to which the product is exposed. It is directly dependent on the inlet temperature and indirectly influences the moisture content in the final product.^[35] The outlet let temperature during the soy meal drying process varied from 41.67 ± 0.52°C to 70 ± 2.65°C. It increased with increases in the concentration of GA in the feed solution, but a complex trend was recorded with MD (Figure 1a). In general, outlet temperature decreases as feed solution concentration increases,^[35] but in the current study, a more intricate pattern of outlet temperature was observed. The reason for the complex behavior of outlet temperature could be the change in fluctuations in relative humidity, pressure drop, and blockage in the filter.^[36] On the other hand, the thermal efficiency of the spray drying process reversely changes with outlet temperature. As the outlet temperature increases, the thermal efficiency of the drying process decreases. In the present study, the thermal efficiency (%) of the process decreased with increases in the solid content of the feed solution. The thermal efficiency (%) calculated throughout the drying process was increased from 59.04 ± 4.02% to 83.48 ± 5.4% (Figure 1a). High thermal efficiency and low outlet temperature are desired conditions for a cost-effective spray drying process.^[37]

Colour value profile

The colour value of food powder indicates a change in quality attributes, such as freshness, nutritional value deterioration, microbial contamination, and the physicochemical properties of spray-dried powder. The colour profile of spray-dried soy meal powder is a critical quality factor that influences consumer acceptance. The colour value of spray-dried soy meal powder was determined based on the degree of lightness (L), degree of redness/greenness (a), and degree of yellowness/blueness (b).^[38] These parameters are used to calculate the colour difference between two samples (Delta E), chroma, and whitening index (WI). Colour value L of spray-dried soy meal powder ranged from 93.57 ± 0.01 to 97.09 ± 0.01 and increased with the addition of maltodextrin powder (Table 1). As the concentration of maltodextrin increases, the colour value L also improves. The measured L value for soy meal powder was 93.57 ± 0.01, but when MD was added, it increased from 95.86 ± 0.00 to 97.09 ± 0.01 (5–15% MD in soy meal) (Table 1). This shows a statistical significance with avalue of <0.0001 and an R² value of 0.92. However, the addition of GA to the soy meal powder resulted in a slight increase in lightness value, with no significant difference in concentration change. Colour profile profilesprofiles added with soy meal added with MD and GA showed similarities with the whole and skim milk powders (96–97^[39]), maltodextrin mixed with sapodilla (93–94,^[40]) and spray-dried camel and cow milk powder (93–97^[41]). An alike lightness value pattern was recorded for spray drying the avocado using maltodextrin as a drying aid.^[42] Furthermore, colour value “a,” which indicates the change in colour products from red to green, ranged from −1.4 ± 0.01 to −3.4 ± 0.01. If the colour value is positive, it indicates that the product falls under the “redness” category. However, a negative “a” value is a sign that the product is slightly greenish.^[41] In the current study, colour value “a” slightly decreases with the addition of maltodextrin aid (−2.07 ± 0.01 to −3.4 ± 0.01) but it increases with the incorporation of gum Arabic (−2.07 ± 0.01 to −1.4 ± 0.01) (Table 1). Since the colour values “a” are very close to zero, it is difficult to distinguish between the different combinations with the bare eye. Colour value “b” is the representation of the yellow-to-blue colour of the product. The positive value of “b” is an indication that the product falls under the yellow category, and the negative value expresses that the product is bluish in colour. In this study, colour value “b” changed from 14.89 ± 0.01 to 19.58 ± 0.01, for soy meal colour value “b” was 19.58 ± 0.01, which decreased with the addition of MD (17.83 ± 0.01 with 15% MD) and GA (14.89 ± 0.01 with 15% GA) (Table 1). It revealed that spray-dried soy meal was slightly yellowish in colour, but the yellowness was masked by the addition of MD and GA as drying aids, which were close to the colour value of spray-dried cheese powder.^[43] In addition, delta E is the representation of the difference in colour between two samples; chroma is the indication of purity of colour; it depends on the degree of change in colour; and the whitening index (WI) is the value that represents the closeness to the reflecting surface. The obtained value of chromatic index ranged from 19.68 ± 0.01 to 14.95 ± 0.01. It was reduced with the addition of MD and GA. The value of WI changed from 84.39 ± 0.01 to 79.29 ± 0.00, which improved with the addition of GA and MD. Based on experimental outcomes and statistical evidence, it was observed that soy meal falls below the whitish to slight yellowish range, but after the addition of MD and GA, the colour value shifted to whitish. There was a significant change in the colour profile of soy meal powder and soy meal added with maltodextrin and gum Arabic, which was recorded with a P value <.0001.

Flowability

Flowability is another defining quality factor of spray-dried food powder that measures the ability to flow. The flowability of a powder sample is determined by its bulk density, tapped density, Carr index (%), Hausner ratio, and porosity. Many factors, such as particle size, particle morphology, moisture content, water activity, and drying conditions, resist and support the flowability based on certain conditions.^[44] Better-flowing powder samples are easy to process, handle, pack, fill, and transport.^[45] Bulk density measures the amount of interstitial air present, and reduction is the effect of interstitial air on the tapped density. The bulk density of spray-dried soy meal powder varied from 0.22 ± 0.00 to 0.37 ± 0.03 g/cm³ and tapped density 0.29 ± 0.00 to 0.40 ± 0.02 g/cm³ (Table 1). Both bulk density and tapped density values increase with the increase in concentration of drying aids MD and GA. The Carr index, which measures flowability, and the Hausner ratio, which measures cohesiveness, show a declining tendency as the concentration of MD and GA in soy meal increases. The Carr index value for soy meal powder was 21.64 ± 0.50 and it dropped to 12.51 ± 1.72% with the addition of 5% MD and 6.16 ± 0.85% with 5% GA (Table 1). The obtained value of the Carr index indicates that soy meal falls under the good-flowing category of powder, but it improved to “excellent” with the drying aids MD and GA. Similarly, the Hausner ratio value changed from 1.28 ± 0.01 to 1.06 ± 0.00 for soy meal and soy meal with MD and GA. Both the Carr index values indicate that spray-dried soy meal has “good flowing” characteristics. However, it improved to excellent with the MD and GA (Table 1). Statistical analysis data show a significant P value of <0.0001 and an R² value of 0.71. Flowability improved with an increased concentration of MD in the feed solution, but it did not show a significant difference with an increased concentration of GA. The Carr index value for the flowability of spray-dried soy meal powder was seen to be comparable to that of soybean hydrolyzate (19–21%),^[32] spray-dried pineapple peel (22–32%)^[46] and spray-dried eggplant peel^[45] with MD and GA as drying aids. Therefore, based on the findings, it can be stated that spray-dried soy meal powder has good flowability, which was improved further after the incorporation of MD and GA.

Solubility

The ability of a food powder to dissolve in water is determined by its water solubility. The water solubility of food powder influences the bioavailability of nutrient components present in food powder. The solubility of food powder is significantly influenced by many factors, such as chemical structure, ionic strength, pH, particle size, surface area, and temperature of the solvent. Solubility of spray-dried food powder also depends on drying conditions such as temperature, feed concentration, and airflow rate. However, in this study, the pH of the solution and drying temperature were kept constant for all sets of experiments. Soy proteins present in soy meal are highly soluble in water, which is directly related to their emulsion, gelling, and foaming properties.^[47] Soy protein is a globular protein made up of glycinin and conglycinin that is more than 80% soluble in water, and the highest solubility was observed at a neutral pH of solution.^[48] In the current study, the obtained solubility of soy meal was 94.08 ± 2.03%. The visible appearance indicates that spray-dried soy meal is completely soluble in water with no residue left behind (Table 1). The solubility of the spray-dried soy meal powder exhibited a similar behavior to that of soybean hydrolysate (94–97%).^[32] In general, polysaccharides, such as maltodextrin and gum Arabic, are highly soluble in water with a high degree of hydrolysis.^[49,50] However, soy proteins mixed with polysaccharides showed slightly reduced solubility. The obtained solubility of soy meal mixed with maltodextrin was approximately 90%, with no significant difference with an increase in concentration. Soy meal’s lowest solubility was recorded with 5% gum Arabic (71 ± 0.3%). This may be due to the polysaccharides forming a thick secondary layer on the outer surface of globular soy proteins, which might influence the solubility of soy meal solutions.^[47] Nonetheless, the solubility of spray-dried soy meal powder slightly improved with an increase in the concentration of gum Arabic in the feed solution, which might be due to the replacement of polysaccharides with soy protein.

Dispersibility

Dispersibility is an important powder parameter that indicates the separation of powder particles in the aqueous solution.^[51] Food powder dispersibility depends on the particle size, particle density, agglomeration, particle size distribution, and composition of the powder sample.^[52] The dispersibility of soy meal powder with and without drying aids ranged from 83.58 ± 2.58% to 89.35 ± 0.66%. The obtained dispersibility for soy meal powder was 88.17 ± 1.02%, which slightly decreased (86.12 ± 0.22% to 83.58 ± 2.58%) with an increase in the concentration of GA in the feed solution (Table 1). However, the addition of MD does not show any significant difference in powder dispersibility. Spray-dried soy meal as well as soy meal added with the drying aids MD and GA showed a similar range of dispersibility with spray-dried sugar cane juice with MD and GA as carrier agents (89%)^[51] and orange juice with MD as a drying aid (76–84%).^[53] The obtained R² value was 0.59, and the P value was 0.0004.

Moisture content, water activity, pH, and %brix

The moisture content of the food plays a significant role in determining its storage stability. The lower moisture content of the food powder prevents microbial contamination and improves the shelf life of the product. The moisture content of food powder depends on many parameters, such as inlet temperature, aspirator, particle size, particle surface area, and agglomeration properties. The moisture content of the soy meal powder varied from 5.9 ± 0.25% to 7.44 ± 0.14%. The MC % of the spray-dried soy meal decreased with the addition of carrier agents, such as MD and GA (Table 1). However, there was no significant difference in the moisture content that was recorded with the increased concentration of MD and GA. Spray-dried soy meal and soy meal added with MD and GA showed a very close range of moisture content (4–7%) with yogurt powder,^[54] Noni juice mixed with MD and Gum acacia.^[55] The water activity of soy meal powders ranged from 0.22 ± 0.00 to 0.49 ± 0.00, with the water activity decreasing as the concentration of GA in the feed solution increased (Table 1). However, MD does not show any significant change in the water activity of soy meal powder. Based on the existing study, it was observed that water activity below 0.6 indicates that the powder is least susceptible to microbial contamination.^[56] The pH of the reconstituted (10%) soy meal ranged from 5.89 to 6.78. The pH of the reconstituted solution shifted to a slightly acidic range with an increase in the concentration of GA in the spray-dried soy meal powder. Similarly, the %brix of reconstituted soy meal powder changed from 7.53 ± 0.06% to 9.53 ± 0.05%; it insignificantly decreased with an increase in the concentration of MD in the soy meal powder.

Hygroscopicity

Hygroscopicity is the tendency of food powders to absorb the surrounding moisture content. The hygroscopic behavior of spray-dried soy meal powder with and without drying aids varied from 3.80 ± 0.17% to 5.94 ± 0.55% (Table 1). The hygroscopic behavior of spray-dried food powder significantly changes with the alteration of inlet temperature, which directly influences the outlet temperature and reduces the moisture content of the final product. As the moisture content (%) of the final product decreases, the hygroscopicity of soy meal powder increases because the chance of water absorbance capacity is greater for the powder with lower moisture content.^[57] Since the inlet temperature was kept constant throughout the spray drying process, the outlet temperature fluctuated, which influenced the water absorption capacity of the soy meal powder with drying aids like GA and MD. Based on the visual appearance and experimental value, the hygroscopicity of soy meal powder increases with the increasing concentration of MD in the feed solution. Measured hygroscopicity of spray-dried soy meal powder was 4.83 ± 0.34%, which increased from 5.07 ± 0.10% (5% MD) to 5.94 ± 0.55% (15% MD), but there was no significant change was observed with an increase in the concentration of GA from 5% (3.80 ± 0.17%) to 15% (3.83 ± 0.15%) in the feed solution (Table 1). A similar increase in hygroscopic behavior was obtained for spray-dried date powder^[58], orange powder,^[53] and chokeberry powder added with the MD as a drying aid (2–7%).^[37]

Rheological properties of reconstituted soy meal powder

The viscosity was measured at room temperature (25°C) using reconstituted soy meal powder (10% w/v) with and without carrier agents. The viscosity of a food sample is an important attribute that measures the flow property of a liquid sample; it is heavily influenced by the adhesive properties of the starch content in the food sample. The viscosity of the food sample changes with solid content, pH, temperature, and environmental conditions. Low viscous food is easier to swallow and poses fewer problems during handling, processing, and packaging, whereas highly viscous food may be a limiting factor for food samples.^[59] The viscosity of soy meal with different concentrations of carrier agents falls under the Newtonian fluid and low viscous food categories; the viscosity of the sample ranged from 3.75 ± 0.10 to 11.06 ± 0.48 m Pas. The obtained viscosity of the reconstituted soy meal sample was 3.75 ± 0.10 m Pas, and the viscosity of the resultant samples increased with the addition of carrier agents. The measured viscosity of soy meal with 5% MD was 4.68 ± 0.37 m Pas and it increased to 5.65 ± 0.3 m Pa for the soy meal with 10% MD. However, a slight decrease in viscosity (5.15 ± 0.19 m Pas) was recorded for soy meal with 15% MD, which indicates that the interaction of soy meal with a small amount (510%) of MD increases the viscosity of the sample. Further addition of MD to soy meal does not show any significant change in the viscosity. In addition, using GA as a carrier agent significantly influences the viscosity of the reconstituted liquid. Soy meal with 5% GA demonstrates a 6.55 ± 0.11 m Pas, which is almost double the viscosity of the soy meal sample. The viscosity of soy meal with 10% GA and 15% GA was 9.28 ± 0.14 m Pas and 11.06 ± 0.48 m Pas, respectively, after further addition of GA to the soy meal (Table 1) (Figure 3).

Figure 3. Viscosity (mPa.s) vs. shear rate (1/s) graph of reconstituted soy meal (SM) with and without varying concentrations of drying aids maltodextrin (MD) and gum Arabic (GA).

The viscosity ranges for the spray dried soy meal powder with and without the addition of maltodextrin and gum Arabic exhibited Newtonian behavior. The experimental data are similar to the findings for viscosity from spray dried chokeberry powder with MD and GA ranging from 5.6 to 12.2 mPa.s at lower levels of concentration. The rheological behavior of the spray dried powders with GA and MD showed an increase in viscosity with the increase in the concentration of GA and MD.^[37] Furthermore, soy protein isolates at different pH and temperature settings (~7 m Pas)^[59] showed a similar range of viscosity.

Particle size distribution of spray-dried soy meal powder

The maximum distribution of spray-dried soy meal powder was recorded with a particle diameter of 2.31 ± 3.70 µm at the peak of the particle distribution curve. However, a slightly lower range of powder particle diameter (2.17 ± 3.47 µm) was recorded after the addition of 5% MD as a drying aid. On the other hand, the particle diameter (2.55 ± 3.15 µm) range was marginally increased with the addition of 5% GA as a drying aid (Table 2) (Figure 4). The particle size distribution of soy meal powder was measured using a Polydispersity Index (PDI) value, which defines the degree of non-uniformity. The lower the value, the higher the homogeneity of powder particles in the aqueous solution. The results show that the spray-dried soy meal powder was unevenly distributed with a PDI of 1.44. The addition of 5% MD (2.07) and 5% GA (4.16) caused an increase in the particle size distribution. Span is another parameter that measures granularity, uniformity, and size consistency. The lower span value demonstrates the granular and uniform particle distribution. Among all the spray-dried powder samples, soy meal shows the lowest span value of 6.58. However, there was no significant difference in the span value that was recorded for soy meal with 5% MD (6.60), but soy meal with 5% GA (7.92) showed a slightly higher range of particle size distribution (Figure 4). The zeta potential determines the colloidal stability of the surface charge of a powder particle in an aqueous solution. The zeta potential technique is used to determine the surface charge of micro and nanoparticles in a colloidal solution. The zeta of spray-dried soy meal powder with and without ranged between-23.96 to-29.71, which indicates the dedicated to moderately stable nature of colloidal suspension (Table 2). The stability of spray-dried soy meal colloidal suspension was slightly improved with the addition of 5% MD and 5% GA as a drying aid.

Figure 4. Intensity (%) vs. diameter (µm) particle size distribution curve for spray-dried soy meal powder with 5% gum Arabic (GA) and maltodextrin (MD).

Thermal degradation behavior of soy meal

The thermal degradation behavior of soy meal with drying aids is demonstrated in this figure. Thermal scanning of all the samples was performed in a 20–180°C temperature range to obtain the endothermic peaks. Thermal degradation of the spray-dried soy meal powder was recorded at 77.17°C. Spray-dried soy meal powder’s thermal stability increases with the addition of drying aids 5% MD (81.01°C) and 5% GA (94.75°C) (Figure 5). A close peak was observed for Andes berries with MD and^[60] black mulberry juice with MD and GA.^[61] Thermally stable spray-dried powder requires a higher amount of heat flow to degrade the samples. The amount of heat flow needed to degrade the spray-dried soy meal powder (0.614 W/g) increases with the addition of 5% MD (0.83 W/g) and 5% GA (1.06 W/g). Glass transition behavior is one of the most important parameters that explains the loss of moisture, degradation of microparticles, and remaining organic matter present in the spray-dried soy meal powder.^[62] The glass transition began when powder properties changed from amorphous to soft/rubbery.^[55] The glass transition behavior of spray-dried soy meal powder started at 45.28°C and ended at 66.98°C, which moved to 58.99 to 71.42°C for soy meal with 5% MD and 57.54–85.86°C for soy meal with 5% GA. A similar pattern of glass transition temperature was recorded for the açai juice with MD and GA as carrier agents.^[63] The specific heat capacity ranged from 1.214 to 3.85 J/(g °C), with no significant difference with ingredient composition.

Figure 5. Differential scanning calorimetry heat flow (W/g) vs. temperature (°C) curve of spray-dried soy meal powder with 5% gum Arabic (GA) and maltodextrin (MD).

Scanning electron microscopic imaging of spray-dried soy meal powder

The microstructure of spray-dried soy meal powder is influenced by the drying temperature, feed rate, aspirator, nozzle size, rate of evaporation, viscosity of the feed solution, pressure drop, and relative humidity.^[64] The morphological behavior of spray-dried soy meal combined with MD and GA powder was determined using scanning electron microscopy imaging. The measured particle size of soy meal powder was 2.45 ± 1.79 µm and a similar range of particle size, 2.42 ± 2.89 µm was recorded for the soy meal with 5% GA. However, a slightly larger particle size of 3.45 ± 1.78 µm was observed for soy meal with 5% MD. A wide range of particle size distributions was documented for the soy meal powder with 5% GA (0.47–11.84 µm). However, the spray-dried soy meal powder had a particle size range of 0.65–8.07 µm. Similarly, 5% MD in soy meal embodied the particle size (7.7–1.39 µm) with a standard deviation (1.78 µm) (Figure 6). Spray-dried soy meal powder revealed a spherical particle with a smooth surface. In addition, a slight concavity on the surface of the particle was observed for spray-dried soy meal powder, and incurvation increases with the addition of GA as a drying aid (Figure 6). High temperatures and aspirations cause water vaporization, resulting in a smooth particle with wrinkles on the surface. Nonetheless, the microstructure of the MD-treated soy meal creased, spherical, and agglomerated on itself. Potential reasons for this could be the hygroscopic behavior of maltodextrin. Increased particle morphology was observed in spray-dried GA and MD at different sets of temperatures,^[37] which increased the concentration of MD for spray-drying bioactive component saffron.^[65]

Figure 6. Scanning electron images of spray-dried soy meal powder at magnification (a) 1000x (b) 5000x (c) 15000 x with drying aids gum Arabic (GA) (d, e and f) and (g, h, i) maltodextrin (MD).

Conclusion

Soy meal spray-dried with the drying aids showed a higher range of product yield (84–92%), which indicates the cost-effectiveness of the drying process. However, the thermal efficiency of the spray-drying process for the soy meal was 85.51%, which slightly decreased with the addition of drying aids but still showed a higher range of thermal efficiency (59.04–83.48%) and a low outlet temperature, indicating the process efficiency. Furthermore, powder characterization parameters such as lightening value of the colour profile (93.57–97.09) do not show any significant change, but powder flowability improved from poor to excellent with a CI value of 21.64–6.16 after the addition of drying aids. Spray-dried soy meal powder with and without drying aids showed a higher range of dispersibility (83–89%) with no significant change. Spray-dried soy meal powder was highly soluble in aqueous solution at 94.08 ± 2.03%, which slightly decreased with the addition of maltodextrin (~90%) but drastically decreased with the addition of gum Arabic (~71%) as a drying aid. Furthermore, spray-dried soy meal powder with maltodextrin as a drying aid showed highly hygroscopic behavior with a 5–6% moisture gain. However, there was a slightly lower hygroscopic nature shown by the soy meal powder (4.83%), with no significant change with the addition of gum Arabic (~6%) as a drying aid. Other characterization parameters, such as %Brix, pH, and water activity of the spray-dried soy meal decrease with the addition of drying aids. The viscosity, which is considered an important reconstitution property, increases with an increase in the concentration of drying aids in the soy meal powder. The viscosity of the reconstituted (10% w/v) soy meal (3.75 m Pas) slightly increases with an increase in the concentration of maltodextrin (5.65 m Pas), but it drastically increases in the case of soy meal added with gum Arabic (11.06 m Pas). The collected powder particle size falls in the microscopic range (0.47–11.84 µm), with a spherical, smooth, and slightly concave appearance. The thermal degradation peak was recorded at 77.17°C for spray-dried soy meal powder. It moved slightly to a higher range (81.01–94.75°C) with the addition of 5% maltodextrin and 5% gum Arabic. Overall, it can be concluded that spray-dried soy meal powder shows a good range of physicochemical and reconstitution properties. However, the addition of a small amount of drying aids (5%) improved the product yield significantly, and some improvement in other powder characteristics was also observed. This study could pave a new direction for utilizing soy meal in diverse applications, such as soy flour, breakfast cereal, soy-based cookies, soy milk, tofu, yogurt, reconstituted beverages, infant formula, and coffee whitener. It could also be used for soy protein isolates, soy protein concentrates, textured soy proteins, meat analog ground meat extenders, and extruded soy-based food products. Furthermore, it could be used as a wall material for encapsulating the bioactive components, fortified soy-based powder, and plant-based protein.

Acknowledgments

Special thanks to the Missouri Soybean Merchandising Council (MSMC) for funding this project. Funding for this project comes from MSMC Project No. MSMC00065151.

Author contribution

Priya Singh: Experimental design, spray drying, physicochemical characterization, data analysis, writing the original draft. Kiruba Krishnaswamy: Project administration, conceptualization, funding acquisition, supervision, reviewing, and editing.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The corresponding author, Kiruba Krishnaswamy, could provide proof to support the findings of this study.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by the Missouri Soybean Merchandising Council [MSMC00065151].