Spray Drying of Jackfruit (Artocarpus heterophyllus Lam.) Seeds Protein Concentrate: Physicochemical, Structural, and Thermal Characterization

Abstract

Jackfruit seeds (Artocarpus heterophyllus Lam.) are a viable option for supporting a sustainable protein supply. The objective was to obtain protein powder from jackfruit seeds protein concentrate (JSPC) by spray drying. A central composite design was used; the independent variables were inlet temperature (110, 115, and 120 °C) and the solids of the JSPC solution (5, 7.5, and 10%). With the desirability function, the optimal drying parameters to maximize the process yield and achieve a low moisture content were 7.5% solids in the JSPC solution and an inlet temperature of 115 °C, resulting in a process yield of 71.51 ± 1.21%. Moisture (5.33 ± 0.11%), water activity (0.15 ± 0.02), bulk density (0.40 ± 0.01 g/mL), and color (L*: 70.56 ± 0.38, a*: 7.80 ± 0.11 and b*: 15.18 ± 0.15) were measured; these parameters are within the allowed ranges for stable food powders. Hydrosolubility (82.46 ± 1.68%), foaming capacity (48.33 ± 1.66%), and emulsifying activity (105.74 ± 10.20 m²/g) were evaluated. Glass transition temperature (129.49 °C) of the JSPC powder enables the establishment of optimal storage and processing conditions for the protein. JSPC powder could be applied to the elaboration of food products with nutritional and functional value.

1. Introduction

Currently, increased protein consumption has been attributed to global population growth. According to reported figures, it is estimated that the global population will surpass 9.9 billion by the year 2050 [1]. The proteins used in the food industry are predominantly sourced from animal origins [2], which has an adverse environmental impact by producing higher levels of greenhouse gas emissions [1]. Consequently, alternative sources of protein are sought. Plant protein production offers a more sustainable and environmentally friendly alternative to animal-based proteins. It is necessary to know that it requires significantly fewer resources, such as land, water, and non-renewable materials. This shift not only helps our planet but also supports a more responsible approach to food production [3]. Thus, byproducts of the agro-industrial sector are a potential source for producing proteins, such as waste seed meals from the processing of plant-based foods [4]. Therefore, plant-based proteins derived from agro-industrial byproducts could be included among the available sources of protein for utilization, coordinating with dietary and cultural requirements and preferences, and being an encouraging solution from an environmental standpoint [5]. This also contributes to ensuring food availability and promoting sustainable agricultural practices. In this case, in the production of food protein powder.

The fruit “Jackfruit” (Artocarpus heterophyllus Lam) is a big tropical fruit that comes from South and Southeast Asia. Today, it is found in Africa, Asia, and Central and South America. Jackfruit is part of the Moraceae family, which thrives in warm, humid climates [6]. It has been introduced to various tropical nations, including Mexico, particularly in the state of Nayarit [7]. Jackfruit seeds account for approximately 10–15% of the fruit’s overall weight and are rich in carbohydrates and protein, presenting potential uses in the food sector [8].

In addition, proteins have various applications in the formulation of food systems due to their techno-functional properties, such as emulsifying, foaming capacity, gelling agents, stabilizers, and increased hydrosolubility [9]. Therefore, obtaining jackfruit seeds protein concentrate in powder form is interesting, as it leverages these properties.

The process of spray drying is the most widely used and effective technique for creating protein powder, as it is a continuous and low-cost process that yields powders with good stability and ease of handling [10]. A spray dryer is mainly integrated of three key components: a drying chamber, an atomizer, and a dust collector [11]. In spray drying, a liquid formulation (such as a solution, emulsion, or suspension) is processed and moved through a hose with the help of a peristaltic pump at a set feed rate. The liquid is atomized at the inlet of the drying chamber. This atomization is achieved using a spray mouthpiece that turns the liquid formulation into small droplets, which then come into contact with the inlet hot gas. It is during this contact that phenomena related to mass and thermal transfer are observed, leading to the evaporation of the liquid [12].

The quality of the dry powder product directly depends on operating parameters, which are inlet feed temperature, liquid solution concentration, inlet air flow rate, and feed flow rate [13]. Therefore, optimizing drying conditions is essential to maximize process yield, maintain necessary physicochemical properties, preserve functional and nutritional qualities, and ensure stability during storage. In experimental designs, the central composite design offers a quadratic model for the response variables. The response surface methodology is employed to identify optimal spray-drying conditions, as it is a comprehensive and efficient approach [14]. Spray drying has the advantage of allowing control over particle size, shape, and morphology [15], as well as extending the shelf life of the food product due to increased powder stability by the microbiological control [11], offers greater ease and lower transportation costs, as well as the flexibility that dehydrated foods give to consumers [16].To assess the quality of spray-dried food powder, it is important to evaluate various properties, including moisture content, water activity, water solubility, hygroscopicity, apparent density, color, particle size distribution, and particle morphology, among others [17].

Protein powders are considered for the development of biomaterials, primarily in the food industry, for example, to create encapsulating materials or food preservatives [18]. The literature search revealed various applications of protein powders in biotechnological processes, primarily in the development of foods and beverages for the food sector [19]. Protein powder can be added to solid (bakery products) or liquid food matrices, used in industrial food formulations, applied as an emulsifier or encapsulating material, and enhances preservation and storage.

Due to the need to promote sustainable food production, such as obtaining protein powder from agro-industrial byproducts, this contributes to the circular economy and minimizes the negative environmental impact; this research aimed to optimize the operating parameters for obtaining protein powder from jackfruit seed protein concentrate through the spray drying process, as the most widely utilized drying process in the food sector. This continuous, scalable, and easy-to-handle process results in a stable and functional powder product. To ensure the quality and functionality of jackfruit seed protein powder, its physicochemical and functional properties were evaluated. As an alternative and innovative protein powder, it was essential to assess the particle size distribution, the amino acid profile to identify its protein quality, a thermal analysis by differential scanning calorimetry (DSC) to report thermal stability, and analysis by Fourier transform infrared spectroscopy (FTIR) to identify the characteristic bands of proteins. Detailed protein characterization is of vital importance for future applications in food matrices or functional foods.

2. Materials and Methods

2.1. Vegetal Material and Chemical Substances

Fresh jackfruit seeds were washed and dried at 60 °C in a convection oven (Novatech, HS60-AID, Guadalajara, Jalisco, Mexico) during 24 h. The arils and brown spermatoderms were then manually taken off from the seeds and milled in an electric pulverizer mill (Gutstark 2000 g, Mexico City, Mexico). The resulting powder was sieved through a 100-mesh sieve (ASTM: 100; 150 μm). The product, named jackfruit seed flour (JSF), was saved at 4 °C for the next protein extraction.

2.2. Jackfruit Seeds Protein Concentrate Obtention

The extraction of jackfruit seeds protein concentrate (JSPC) was carried out using the procedure described by Miss-Zacarías et al. [20] with modifications. Jackfruit seeds flour was mixed with 1 M NaOH (1:20, w/v) at pH 12 and stirred on a plate with a magnetic shaker at 25 °C and 350 rpm for one hour. It was then subjected to sonication using the JP-4820 equipment (Kendal, FL, USA) at 42 kHz for 20 min, followed by centrifugation (Thermo Fisher Scientific Inc., Osterode am, Harz, Germany) at 3745 g for 20 min at 25 °C. Once collected, the supernatant underwent isoelectric precipitation, for which the pH was adjusted to 4.0 with HCl (1 M). The precipitate was allowed to stand for 24 h and recovered by centrifugation at 3745× g for 15 min at 25 °C. Protein concentrate was then recovered at pH 7.0 for drying.

2.3. Spray Drying of the Jackfruit Seeds Protein Concentrate (JSPC) Optimization

A central composite design (CCD) with two factors and three levels was employed to assess the impact of independent variables on the response. The independent variables were the inlet temperature Ti (110, 115, 120 °C) and the solids percentage of the JSPC solution (5, 7.5, 10%). The inlet temperature and solids percentage levels were chosen based on initial teamwork. These temperatures were selected because very high temperatures can influence protein functionality. The solids percentage was set at a moderate level to ensure efficient atomization and to minimize issues such as poor yield or thermal degradation. Samples with volumes of 110 mL were processed. Six replications of the center point were conducted to determine the repeatability of this method. The JSPC solutions were dried in a laboratory-scale Mini Spray Dryer (Büchi B-290; Flawil, Switzerland), equipped with a 0.7 mm diameter feed nozzle, under a constant flow rate (35 m³/h) and air pressure (0.6 MPa) throughout the process. The solutions were kept under constant agitation at 25 °C and 350 rpm. The peristaltic pump supplied the dryer at a rate of 4.5 mL/min. The powder was recovered from the product collection vessel and stored in propylene tubes at 25 °C in a desiccator for further analysis. Process yield was calculated with Equations (1) and (2). The moisture content and hydrosolubility percentage were also determined for each treatment.

$$Yield \left(\%\right)={\displaystyle \frac{m_1 }{m_2}}\ast 100$$

(1)

$$Theoretical={\displaystyle \frac{total solids}{100}}\ast solution volume$$

(2)

where $m_1$ is the mass (g) of the recovered powder. $m_2$ was calculated with Equation (2).

Experimental data for the responses of interest (hydrosolubility, moisture, and yield) were analyzed using response surface methodology to evaluate the effects of spray drying conditions. Inlet temperature, as well as linear and quadratic JSPC solution solids percentage, did not significantly affect the hydrosolubility response. Therefore, it was discarded for optimization. The spray-drying process was optimized using the response surface methodology in combination with the desirability function. To this end, 14 experimental treatments were designed to evaluate the effect of the solids content in the JSPC solution (%, X₁) and the inlet temperature (Ti, X₂) to identify the conditions that maximize the analyzed responses. The validity of the second-order quadratic model was verified using Equation (3).

$$Y={\beta }_0+\sum _{i=1}^k{\beta }_i{X}_i+\sum _{i=1}^k{\beta }_{ii}{X}_i^2+\epsilon$$

(3)

where $Y$ represents the response variables (Y₁ = % yield and Y₂ = % moisture content), $X_i$ is the coded values for factors (X₁ = % JSPC solution solids and X₂ = inlet temperature), ${\beta }_0$ is a constant, ${\beta }_i$ is the primary effect coefficients for each independent variable, and ${\beta }_{ii}{X}_i^2$ represents the second-order or non-linear effects of each variable.

The optimal JSPC powder was subjected to physicochemical characterization, functional properties, amino acid profile, FTIR, and thermal analysis.

2.4. Physicochemical Analysis and Functional Properties of Jackfruit Seeds Protein Concentrate (JSPC) Powder

2.4.1. Moisture Content

A thermobalance (Sartorius MA 35, Göttingen, Germany) was used to measure the moisture content of the spray-dried JSPC powder. One gram of the JSPC powder was placed on aluminum plates and dried at 105 °C until a consistent moisture level was achieved.

2.4.2. Water Activity

A hygrometer (Aqualab series 4TEV, Decagon Devices, Inc., Washington, DC, USA) was used to determine water activity (a_w). A total of 2 g of the JSPC powder was placed, and the dew point principle was used to determine the water activity.

2.4.3. Bulk Density

The volume occupied by 2 g of the JSPC powder in a 10 mL graduated cylinder was recorded and used to determine the bulk density (ρB) with Equation (4).

$$\rho \mathrm{B}={\displaystyle \frac{sample weight \left(\mathrm{g}\right)}{volume \left(\mathrm{m}\mathrm{L}\right)}}$$

(4)

2.4.4. Color

The color of the powder was determined using a Minolta Chroma Meter CR-400 (Minolta Co., Ltd., Osaka, Japan). L* (Brightness, white to black), a* (red-green), and b* (yellow-blue) were registered.

2.4.5. Hydrosolubility

One percent (1%) solutions of JSPC powder were prepared. The solutions were stirred for 30 min at 100 rpm and 25 °C and then centrifuged at 18,626× g for 15 min using a centrifuge (Hettich MIKRO 200/200R; Kirchlengern, Germany). According to the Bradford procedure [21], the protein content was calculated, and a calibration curve with bovine serum albumin (BSA) was necessary. The absorbance was measured at 595 nm using a spectrophotometer (Cary 50 Bio UV Visible Varian; Mulgrave, Australia). The percentage of hydrosolubility was calculated with Equation (5).

$$Hydrosolubility\left(\mathrm{\%}\right)={\displaystyle \frac{Protein content in the supernatant}{Total protein content in the sample}}\times 100$$

(5)

2.4.6. Foaming Properties

Adapted from Calderón-Chiu et al. [7], the foaming properties were evaluated [foaming capacity (FC) and foaming stability (FS)]. To do this, 0.2 g of powder JSPC was dissolved in 20 mL of distilled water. The samples were then poured into tubes, homogenized, and aerated at 16,000 rpm for 2 min at 25 °C using an IKA T10 basic Ultra-Turrax (IKA; Staufen, Germany). The total sample volume was measured immediately (t₀) and again after 30 min. FC and FS were calculated using Equations (6) and (7).

$$FC\left(\mathrm{\%}\right)={\displaystyle \frac{B-A}{A}}\ast 100$$

(6)

$$FS\left(\mathrm{\%}\right)={\displaystyle \frac{C-A}{A}}\ast 100$$

(7)

where A is the initial volume (mL) before aeration (homogenization), B is the foam volume (mL) after homogenizing (t₀), and C is the foam volume (mL) after 30 min of homogenization.

2.4.7. Emulsion Properties

Adapted from Calderón-Chiu et al. [7], the emulsion activity index (EAI) and emulsion stability index (ESI) were determined. To formulate the emulsion, 2 mL of olive oil (oily phase) and 6 mL of a JSPC solution (1%) (w/v) were first mixed, then homogenized with an Ultra-Turrax at 20,000 rpm during 1 min at 25 °C. A volume of 50 µL was taken at time 0 and after 10 min and diluted in 5 mL of SDS solution (0.1%). After stirring for 10 s, the absorbance was measured at 500 nm using a UV Vis spectrophotometer. The absorbance values A0 and A10, estimated at 0 min and 10 min, respectively, were used to calculate the EAI and ESI using Equations (8) and (9).

$$EAI\left({\displaystyle \frac{m^2}{g}}\right)={\displaystyle \frac{\left(2\right)\left(2.303\right){(A}_0\left)\right(DF)}{(g protein)\left(0.25\right)\left(1000\right)}}$$

(8)

$$ESI\left(min\right)={\displaystyle \frac{A_{10}}{A_0-A_{10}}}\ast t$$

(9)

DF is a dilution factor (100), and 0.25 is the fraction of olive oil used to form the emulsion.

2.4.8. Particle Size Distribution of Jackfruit Seeds Protein Concentrate (JSPC) Powder

The particle size of the JSPC solution and the powder was determined by laser light scattering using a Master Size 3000 Hydro and Aero laser diffractometer (Malvern Instruments, Malvern, UK). Two grams (2 g) of JSPC powder was placed in the hopper; the vacuum extraction system was set to 50% vibration and a 1 mm outlet opening. The sample was then allowed to travel and fall into the primary feed mechanism under compressed air at 4 bars of pressure. The JSPC powder was passed through the tubing and fired into the air cell fitted to the Mastersizer 3000, which had a maximum refractive index of 1.432, measured and collected by the vacuum extraction system. The JSPC powder was measured five times in succession to obtain a mean-size distribution curve based on the distribution volume. It was characterized by the mean volume-mass particle diameter (D_4,3), as defined by Equation (10), and the polydispersity index (PDI), as determined by Equation (11).

$$D_{\mathrm{4,3}}={\displaystyle \frac{\sum n_i{D}_i^4}{\sum n_i{D}_i^3}}$$

(10)

$$PDI={\displaystyle \frac{d_{90}-d_{10}}{d_{50}}}$$

(11)

where $n_i$ is the number of particles of size i and $D_i$ is particle diameter. d₁₀, d₅₀, and d₉₀ are the respective diameters at 10, 50, and 90% of the cumulative particle distribution.

2.5. Amino Acids of Jackfruit Seeds Protein Concentrate (JSPC) Powder

According to what was reported by [20], the JSPC powder was treated with acid hydrolysis using 6 M HCl for 24 h at 110 °C, and then filtered. Next, 2 mL were transferred to microtubes and centrifuged at 18,626× g for 15 min. Then, 100 µL of the sample and 20 µL of Norleucine (0.2 mg/mL), which served as an internal standard, were mixed in a 2 mL vial. The samples were evaporated using a flow of N₂ until dry. The precipitate was dissolved in 200 µL of acetonitrile and 200 µL of N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA). The solution was heated at 100 °C for 2.5 h in a glycerol bath. The standards for the L-amino acid mixture were evaluated under the same conditions using a GC 7890A chromatograph (Agilent Technologies; Palo Alto, CA, USA) coupled with a mass spectrometer (MS) 240 Ion Trap. One microliter of the derivatized solution was injected in split mode (20:1) at 260 °C, and the free amino acids were separated using a capillary column. The retention times and linear retention index (LRI) enabled the identification of amino acids in the samples, which was confirmed by comparing the mass spectra using the NIST (version 2.3) software. The amino acids were reported as grams of amino acids per 100 g of protein (Table S1, Figures S1 and S2, Supplementary Materials).

2.6. Differential Scanning Calorimetry (DSC) of Jackfruit Seeds Protein Concentrate (JSPC) Powder

DSC was performed using a Discovery DSC 250 (TA Instruments, New Castle, DE, USA). Three milligrams (3 mg) of JSPC powder was placed in an aluminum pan (T-Zero, volume 40 μL) and hermetically sealed. The sample was heated −40 to 400 °C. The experiment was conducted under an inert atmosphere with nitrogen as the gas purge at a flow rate of 50 mL/min. An empty aluminum pan was used as a reference in the test. The thermogram was analyzed with TRIOS 5.0.0.44616 software (TA Instruments Universal Analysis; New Castle, DE, USA).

2.7. Fourier Transform Infrared Spectroscopy (FTIR) of Jackfruit Seeds Protein Concentrate (JSPC) Powder

A FTIR spectrometer (Thermo Scientific, Waltham, MA, USA) equipped with an iD7 ATR accessory featuring a ZnSe crystal (4000–400 cm⁻¹ at 25 °C) was used to obtain the FTIR spectrum. Signals were automatically collected over 16 scans at a resolution of cm⁻¹. The data were processed using the Bio-Rad KnowItAll version 8.2 (Bio-Rad, Hercules, CA, USA) software to compare and search for functional groups.

2.8. Statistical Analysis

Results are reported as the mean ± standard deviation from 3 replicates, and the experiment was performed three times. The optimal conditions for spray drying were obtained through the response surface methodology and desirability function.

Data from the remaining experiments were analyzed using a one-way analysis of variance (ANOVA). A Fisher’s least significant difference (LSD) post-hoc test (p < 0.05) was performed to compare means. Statistical analysis was conducted using STATISTICA version 12 software (StatSoft, Inc., Tulsa, OK, USA).

3. Results and Discussion

3.1. Spray Drying of the Jackfruit Seed Protein Concentrate (JSPC) Optimization

Regression coefficients were determined for yield (%, Y₁) and moisture content (%, Y₂). According to the ANOVA, the independent variables had both linear and quadratic effects on the responses Y₁ and Y₂. The linear-quadratic models for the yield Equation (12) and the moisture content Equation (13) were derived using the regression coefficients. The quadratic variable that did not influence response Y₂ was removed from the model. The analysis of variance (ANOVA) provided the R² and adjusted R² values corresponding to the dependent variables. The R² for yield and moisture content were 0.9642 and 0.8546, respectively. An adequately fitted model should have an R-squared value (R²) greater than 0.8. The adjusted R² for yield and moisture content were 0.9593 and 0.8344, respectively, showing a strong correlation between the predicted and experimental values for these two response variables (

Table 1. Central composite design layout and observed data for the measured responses.

Run No.	Independents Variables		Responses Variables
	Solids (%, X1)	Ti (°C, X2)	Yield (%, Y1)	Moisture (%, Y2)
1	5.0	110	58.18 ± 0.01 b	6.89 ± 0.0 e
2	5.0	120	65.45 ± 0.01 e	5.38 ± 0.03 bc
3	10.0	110	56.36 ± 0.01 a	6.81 ± 0.06 c
4	10.0	120	58.18 ± 0.01 b	5.31 ± 0.06 b
5 *	7.5	115	70.30 ± 0.01 g	5.37 ± 0.02 bc
6 *	7.5	115	70.30 ± 0.01 g	5.39 ± 0.06 bc
7 *	7.5	115	71.51 ± 0.01 h	5.44 ± 0.03 c
8	3.9	115	68.79 ± 0.00 f	5.38 ± 0.05 bc
9	11.0	115	59.31 ± 0.01 c	5.21 ± 0.06 a
10	7.5	107.9	58.18 ± 0.01 b	6.23 ± 0.01 d
11	7.5	122.0	63.03 ± 0.02 d	5.20 ± 0.07 a
12 *	7.5	115	71.51± 0.00 h	5.40 ± 0.05 c
13 *	7.5	115	70.30 ± 0.00 g	5.38 ± 0.07 c
14 *	7.5	115	72.72 ± 0.00 i	5.4 ± 0.04 c
	Optimal		Predicted
	7.5	115	72.08	5.22
			Experimental
			71.51 ± 1.21	5.33 ± 0.11

*: Central points of CCD. Different lowercase letters in the same column indicate significant differences (p < 0.05).

). According to the desirability function and response surface methodology (Figure 1), the optimal drying parameters to maximize process performance and achieve low moisture content were 7.5% solids in the JSPC solution and an inlet temperature of 115 °C, with a desirability value of 0.9496 (Table 1). (Figure S3, Supplementary Materials).

The process yield was 71.51 ± 1.21%, a crucial parameter for evaluating the process’s feasibility and potential scalability. Proteins enhance spray drying yield by migrating to the air-water interface due to their surfactant properties, which minimizes the excessive adhesion of the feed solutions to the dryer walls [22].

$$Y_1=-3152.76+9.03X_1-0.68X_1^2+55.16X_2-0.24X_2^2+0.97$$

(12)

$$Y_2=182.27-0.25X_1-2.94X_2+0.01X_2^2-0.17$$

(13)

3.2. Physicochemical Analysis and Functional Properties of Jackfruit Seeds Protein Concentrate (JSPC) Powder

The results of the physicochemical analysis and functional properties of JSPC powder under optimal drying conditions are presented in

Table 2. Physicochemical and functional properties of jackfruit seeds protein concentrate (JSPC) powder at the optimum.

Property	JSPC Powder
Moisture (%)	5.33 ± 0.11
Water activity (aw)	0.15 ± 0.02
Bulk density (g/mL)	0.40 ± 0.01
L* (Lightness)	70.56 ± 0.38
a* (redness)	7.80 ± 0.11
b* (yellowness)	15.18 ± 0.15
Hydrosolubility (%)	82.46 ± 1.68
Foaming capacity (%)	48.33 ± 1.66
Foaming stability (%)	46.11 ± 0.96
Emulsifying activity index (m2/g)	105.74 ± 10.20
Emulsifying stability index (min)	85.12 ± 8.06

. Moisture content is a key parameter that ensures the stability of powdered foods. Under optimal drying conditions, the JSPC powder exhibited a moisture content of 5.33 ± 0.11% and a water activity of 0.15 ± 0.02, ensuring stability during storage. The smaller droplets increase the surface area that interacts with the hot air stream, which accelerates water evaporation and results in low humidity and a dry environment. These results are below the deterioration threshold (aw < 0.5), which gives food powders better microbial stability [23]. High inlet temperatures cause rapid water evaporation, but they also promote crust formation, which inhibits additional moisture loss and produces a protein powder with elevated moisture levels. In contrast, low inlet temperatures enhance water evaporation before crust formation, resulting in a powder with lower moisture content [24].

It is important to recognize the role of bulk density in powders for understanding material properties and industrial processes, as it affects processing, storage, packaging, and distribution conditions [24]. The bulk density of JSPC powder was 0.40 ± 0.01 g/mL. Low bulk density is beneficial for weaning food formulation, especially for packaging and transportation. Apparent density values of 0.27, 0.47, 0.40, 0.35, 0.35, and 0.33 g/mL have been reported in protein isolates from safflower, soybean, sunflower, pea, fava, and rice, respectively. A bulk density lower than 0.4 may be linked to undesirable agglomeration [25].

The color of JSPC after the drying process is influenced by the nature of the sample, specific reactions that occur during the extraction process, and the parameters of the drying process, including temperature and sample time in the dryer column. The color parameters for the JSPC powder were L*: 70.56 ± 0.38, a*: 7.80 ± 0.11, and b*: 15.18 ± 0.15. The alkaline extraction medium is responsible for the color of the protein powder. The brown color of the products obtained is due to the reaction of carbohydrates with proteins. This behavior is similar to that reported by [7] with the protein concentrate from jackfruit leaves.

Color plays a crucial role for improving consumer approval of food and drinks. JSPC powders showed a light brown color. Incorporating JSPC powder into the development of food products can provide color and nutritional contribution.

Hydrosolubility is a vital property of food powders because it affects key production aspects like reconstitution and compatibility with other food matrices. High hydrosolubility is generally preferred, as it simplifies mixing and product formulation [22]. The JSPC powder had a hydrosolubility of 82.46 ± 1.68%. Reports for spray-dried vegetable proteins include sesame bran protein with a solubility of 71.9% [15], quinoa protein around 80% [3], and safflower protein at 41.61% [26]. Spray drying helps stabilize proteins by increasing hydrosolubility, mainly because it causes less denaturation due to lower temperatures and shorter processing times compared to traditional drying. The process also enhances hydrosolubility by producing smaller particles with lower surface tension [27], which boosts the surface area available for interaction with the solvent [13]. Additionally, the inlet and outlet temperatures are below the protein denaturation point, so hydrosolubility remains unaffected [3]. Protein hydrosolubility is crucial for its functional roles in food, including foaming and emulsification.

The foam-forming and foam-stabilizing abilities of proteins are essential for producing a wide range of food products, including soufflés, mousses, whipped creams, meringues, and beverages. These culinary systems depend on the trapping of air, created by films of protein. Besides adding volume to the foams, the air bubbles also help distribute flavors [9]. The foaming capacity and foaming stability of JSPC powder were 48.33 ± 1.66% and 46.11 ± 0.96%, respectively. Foaming capacity (35.83, 30.00, and 48.00%) and foaming stability (83.81, undetermined, and 92.00%) values were reported for safflower, sesame bran, and camelina proteins, respectively, which were dried by spray drying [15,26,27]. The formation of foam is influenced by the interfacial film created by proteins and their ability to sustain air bubbles within the suspension, thereby slowing down the rate of coalescence. Additionally, proteins with a smaller particle size may exhibit better foaming ability because they can be absorbed more quickly during whipping, resulting in a greater volume of foam [3]. Generally, high surface hydrophobicity and good protein solubility can contribute to better foaming properties [27].

Among the most interesting properties of proteins, their capacity to form and stabilize emulsions dictates their applications in various food products, including minced meats, batters, doughs, coffee and tea whiteners, ice creams, soups, cakes, and mayonnaise [9]. The emulsifying properties of legume proteins can be assessed using the emulsifying activity index (EAI) and the emulsion stability index (ESI) [28]. The EAI and ESI of JSPC powder were 105.74 ± 10.20 m²/g and 85.12 ± 8.06 min, respectively. The EAI refers to the protein’s ability to form an emulsion. At the same time, the ESI measures the balance of the diluted emulsion over a given time [24]. In cowpea protein, the EAI of 101.83 m²/g and ESI of 3656.10 min were reported, obtained by spray drying [29]. The different results in the EAI and ESI among various plant-based protein powders obtained by spray drying can be attributed to the plant source, extraction conditions, solubility, surface charge, and the balance of hydrophilic and hydrophobic properties [24]. Hydrophobic interactions dominate the oil-water interface, and the exposure of hydrophobic groups at the interface significantly contributes to the emulsifying properties of the system. A greater degree of surface hydrophobicity can result in enhanced interaction between the emulsifier and the oil droplet, which in turn leads to improved emulsifying characteristics of the protein [3].

3.3. Particle Size Distribution of Jackfruit Seeds Protein Concentrate (JSPC) Solution and Powder

The particle size distribution of JSPC solution (Figure 2A) and powder (Figure 2B) showed a bimodal distribution. The values of D_4,3 and PDI in the JSPC solution were 9.93 µm and 2.42, respectively, and in the JSPC powder, 2.69 µm and 2.11, respectively. The D_4,3 (2.69 µm) represents the volume or distribution of particle size. The PDI is 2.11, indicating the particle size distribution and reflecting the powder’s uniformity as well as the distribution of particles within it. A reduction in powder particle size is primarily attributed to the atomization stage, where the atomizer enables control over droplet size, also particle size, and morphology. Particle formation begins with the formation of droplets in the drying chamber. Consequently, to ensure the management of particle characteristics, it is crucial to regulate droplet formation throughout the atomization process [11]. Likewise, in the high-pressure nozzle, the droplet size is reduced, resulting in smaller particles. Process operating conditions also influence particle size. In this case, the inlet temperature was 115 °C, which is considered low compared to processes that have dried at temperatures greater than 150 °C. Then, if the inlet air temperature is low, greater contraction is achieved, and the particles stay more shrunken, with a smaller diameter [14]. Finally, this parameter is also related to the feed rate (4.5 mL/min), as a low speed enables fine atomization and generates smaller drops. Additionally, it is associated with the percentage of solids in the solution (7.5%). Particle size is a critical parameter, as it influences powder handling, flowability, and rehydration; therefore, it may be prioritized in the drying strategy [30]. In other vegetable proteins, particle sizes of 10 μm have been reported for quinoa protein [3] and 5.73 μm for common bean protein. This is attributed to the spray drying method, which enables the production of smaller and more homogeneous particles [31].

3.4. Amino Acids of Jackfruit Seeds Protein Concentrate (JSPC) Powder

The nutritional quality of a protein powder is primarily dictated by its amino-acid composition. Analysis showed the presence of seven indispensable amino acids—lysine, threonine, phenylalanine, valine, leucine, isoleucine, and methionine—whereas histidine and tryptophan were undetectable. Nevertheless, the essential amino acids identified collectively meet the adult intake levels recommended by the WHO/FAO [32]. In addition, some non-essential amino acids (or conditionally essential), such as serine, glycine, alanine, proline, tyrosine, aspartic, and glutamic acid, were identified (

Table 3. Amino acids of jackfruit seeds protein concentrate JSPC powder.

Amino Acids		JSPC Powder (g/100 g)	WHO/FAO * (g/100 g)
Essential amino acids	Valine (Val)	9.58	3.9
	Leucine (Leu)	10.42	5.9
	Isoleucine (Ile)	9.44	3.0
	Methionine (Met)	1.71	1.6
	Threonine (Thr)	9.67	2.3
	Phenylalanine (Phe)	13.12	3.8 **
	Lysine (Lys)	15.50	4.5
Non-essential amino acids	Alanine (Ala)	3.48
	Glycine (Gly)	5.63
	Proline (Pro)	6.57
	Serine (Ser)	9.61
	Aspartic acid (Asp)	14.21
	Glutamic acid (Glu)	13.46
	Tyrosine (Tyr)	19.25

JSPC powder: Jackfruit seeds protein concentrate. * Essential amino acids reported by WHO/FAO (2007) in adults. ** Tyrosine + phenylalanine.

) [20]. Figure 3 shows the identification of amino acids in JSPC powder by chromatography. It is important to note that the JSPC powder exhibited an elevated proportion of the branched-chain amino acids (isoleucine, leucine, and valine) found in JSPC powder, which are critical for muscle protein synthesis and growth. Moreover, these amino acids are a promising ingredient for formulating protein-enriched foods and dietary supplements [33].

Likewise, the amino acid lysine was also predominant, which is an essential amino acid from a nutritional standpoint, as its deficiency in children can affect their growth. Additionally, this indispensable amino acid has been suggested as a supplement to adjust the nutritional balance of proteins that are limited in lysine, such as corn protein [34]. Greater abundance was also identified in negatively charged amino acids. These aspartic and glutamic acids function as the leading free radical scavengers or metal cations that decrease due to a significant proportion of electrons easily donated by these amino acids [35]. Proteins rich in glutamic and aspartic acid can increase hepatic glycogen synthesis and enhance skeletal muscle protein balance. Proteins that contain a high level of aspartic acid are linked to the regulation of the nervous system by modulating hormonal levels [34].

A higher amount of amino acids that contain hydrophobic functional groups, such as alanine, valine, isoleucine, leucine, phenylalanine, proline, methionine, and glycine, were identified. These amino acids represent the majority of the total amino acids in the sample (≤60 g). These amino acids contribute to the amphiphilic nature of the proteins, enhancing their ability to act as surfactants, which supports their potential for effective emulsification and oil retention [36]. The amino acid composition of JSPC powder suggests possible applications in the development of foods with deficiencies in specific amino acids.

3.5. Differential Scanning Calorimetry of Jackfruit Seeds Protein Concentrate (JSPC) Powder

The glass transition temperature (Tg) determined by DSC of the jackfruit seed protein concentrate powder was 129.49 °C (Figure 4). The Tg temperature is the temperature at which an amorphous material changes from a glassy state to a rubbery state [15]. Knowledge of this parameter is essential because dry foods require stability for long-term storage. If the storage temperature exceeds the Tg, the amorphous product may undergo structural changes, resulting in stickiness and agglomeration in the protein powder, as well as a loss of functional properties [37]. The first endothermic peak in the thermogram is attributed to the denaturation temperature of the protein (Td). The onset temperature (T_onset), maximum denaturation temperature (T_peak), and enthalpy change (ΔH) were 154.95 °C, 155.06 °C, and 17.61 J/g, respectively. Td is correlated with the breaking of hydrogen bonds and is generally used to measure the thermal stability of the protein [34]. Proteins with a significant fraction of β-sheet structure typically exhibit high denaturation temperatures and greater thermal stability. The ΔH is the enthalpy change and represents the energy required for this thermal event to occur (denaturation process), as well as show the extent of the ordered secondary structure of a protein [38]. It has been reported that strong hydrophobic interactions in proteins are related to a high denaturation temperature, which indicates better thermal stability [39]. Therefore, it can be attributed that part of the thermal stability of JSPC is due to the interactions of its hydrophobic amino acids. The second endothermic peak is associated with the melting temperature (Tm) of the protein. The T_onset, T_peak, and ΔH were 189.02 °C, 191.63 °C, and 90.69 J/g, respectively. This endothermic peak corresponds to the process of protein breakdown and degradation, which generally requires significantly more energy than the process of protein denaturation.

3.6. Fourier Transform Infrared Spectroscopy of Jackfruit Seeds Protein Concentrate (JSPC) Powder

The functional groups corresponding to the protein have been identified using FTIR (Figure 5). The N–H stretching bond was determined at 3350–3250 cm⁻¹. This frequency is primarily associated with O–H and C–H stretching vibrations, as well as signals from residual moisture. The most critical peaks are amide I vibrations (1680–1630 cm⁻¹) and amide II vibrations (1570–1515 cm⁻¹), because they are associated with carbonyl stretch bonds C=O and the deformation of C–N stretch bonds [40]. Bonds of amide III correspond to the region 1305–1200 cm⁻¹, suggesting that β-sheets are the predominant secondary structures. Secondary structure refers to the conformation of a protein during folding and is classified into two main types: α-helix and β-sheet. The first option is prevalent, straightforward, and adaptable, characterized by a right-handed structure with hydrogen bonds. In contrast, this secondary structure, known as the β-sheet, forms when extended polypeptide strands fold in such a way that residues far apart in the linear sequence are positioned nearby [13].

4. Conclusions

In this research, jackfruit seed protein concentrate was processed into protein powder using spray drying, a method commonly employed in the food industry and highly effective for producing vegetable protein concentrate powder. Spray drying provides the benefit of being a feasible process when the protein drying parameters are optimized to extend shelf life and maintain protein stability. The operating parameters of the process influenced the physicochemical properties, particle size, and thermal stability of the jackfruit seed protein concentrate powder. Higher yields (71.51%), better hydrosolubility (82.46%), and lower moisture content (5.33%) and water activity (0.15) were achieved with spray drying conditions of 115 °C inlet temperature and 7.5% protein solution solids. The inlet temperature, solution solids percentage, and feed rate affected the particle size of the protein powder. The inlet temperature was optimized to reduce moisture content and water activity in the powder, ensuring microbial stability. Additionally, the protein powder demonstrated high thermal stability. Based on physicochemical characterization, the protein powder falls within acceptable ranges for food powders. Protein powder obtained through spray drying can be utilized in various food applications. The production of protein powder from jackfruit seeds represents the valorization of agro-industrial byproducts and is considered a key component of sustainable food production.