Spray Dried Cashew (Anacardium occidentale L.) Juice Ingredients as an Upcycling Strategy for Abundant Cashew Apple

Abstract

Spray-dried yellow cashew juice ingredients produced under different inlet temperatures (140 and 150 °C) and gum arabic (GA) addition ratios (15% and 25% w/v) were evaluated for their physicochemical and phytochemical attributes and storage stability for 56 days. All spray-dried cashew juice particles showed high solids recovery (>70%) and solubility (>90%), low water activity (<0.3), and low hygroscopicity (<10%). Spray-dried particles prepared with 15% w/v GA showed spherical shapes with a semi-crystalline structure and higher ascorbic acid concentration (>650 mg 100 g⁻¹) and total phenolic content (>330 mg GAE 100 g⁻¹). During storage, spray-dried cashew juice particles maintained their water activity levels within the microbiologically safe range and retained high solubility, in addition to high ascorbic (>68%) and phenolic (>55%) acid retention. Overall, we showed that spray-drying cashew juice is a feasible strategy to upcycle abundant and undervalued cashew juice into stable, phytochemical-rich ingredients for multiple applications.

1. Introduction

Cashews (Anacardium occidentale L.) are exotic tropical fruits native to South America, with a significant volume of production in Brazil, and are widely grown in Asian and African countries [1,2,3]. The volume of the world’s cashew production is about 4.27 million tons, and it is highly concentrated in developing countries, such as India, Brazil, and several other African countries. Because of this, it has relevant socio-economic importance [4].

While the cashew nut is the most profitable and desired part of the fruit, the cashew apple (pseudo fruit) consists of a juicy, fleshy peduncle from which cashew juice is obtained, representing 90% of the total cashew weight [5]. The economical exploitation of cashew apple is still incipient and considered as agricultural waste utilization [6]. Every year, large volumes of cashew apple are discarded due to its abundant production, but their its perishability, astringent taste, and low commercial value compromise its effective use [7]. Although part of cashew apple production is directed toward beverage, confectionery, and bioproduct manufacturing [8], more profitable end uses are required to develop financial benefits for the cashew production chain and to add value to this overlooked agricultural commodity [9]. Indeed, cashew juice is still considered to be an exotic product in most parts of the world [10].

Despite this, scientific reports have shown that the cashew apple is rich in ascorbic acid, carotenoids, phenolic, flavonoids, fibers and other relevant phytoactive compounds [11,12]. In addition to minerals such as iron, magnesium, sodium, phosphorus, copper, and calcium [13], the cashew apple also contains various organic acids, including gallic, cinnamic, and malic acids [14]. Due to the lack of knowledge on proper processing and repurposing technologies, in addition to not understanding the phytochemical value and market potential of the cashew apple, some producers still consider it as a mere by-product of the cashew nut industry [5]. There are several opportunities to develop cashew apple-derived functional products in a growing market that demands natural, plant-based foods and ingredients. As these emerging trends continue to evolve, manufacturers are challenged to establish innovative ways to incorporate fruit-based functional ingredients and their nutritional and health-promoting benefits into commercial formulations [15,16].

In this regard, shelf-stable dried fruit products have gained popularity due to their convenience, nutrient density, and versatility [11]. Our research group has already demonstrated that spray drying, the most popular drying technique in the food industry, can be successfully applied to produce dried fruit-derived particles with preserved bioactive compounds and extended storage stability [17,18,19]. Drying carriers, such as complex carbohydrates and proteins, are used to enhance the spray drying microencapsulation performance by improving the solids recovery and modulating the storage stability and physicochemical attributes of fruit-derived products [20,21]. For example, gum arabic is a tasteless biopolymer and popular carbohydrate-based drying carrier obtained from the exudate of Acacia trees. This odorless and tasteless carrier has a complex, highly ramified structure composed of carbohydrates with a content of 2–3% covalently bound protein. It presents functional, emulsifying, and film-forming properties with low viscosity, and represents a story of success in encapsulation applications [20,22].

Although the microencapsulation of cashew juice has been reported in the literature, many of these studies do not disclose the performance of the spray-drying process, and important aspects related to storage stability such as the influence of different packaging materials on the shelf-life of cashew particles are often overlooked [23,24]. Moreover, the type of drying carrier has a marked influence on the process, and several strategies remain to be investigated.

Therefore, this work presents an upcycling strategy for the abundant yet undervalued cashew juice produced from cashew apple. The spray drying of cashew juice using gum arabic as a drying carrier was evaluated and the final product was assessed regarding its physicochemical characteristics and phytochemical attributes. Prioritized treatments were investigated regarding their storage stability using different packaging materials. This research evaluates spray-dried cashew ingredients produced by means of scalable and realistic strategies as an alternative to diversify the portfolio of cashew products and promote a value-added use of this abundant phytochemical-rich tropical resource.

2. Materials and Methods

2.1. Materials

Whole cashew fruits (yellow variety, early dwarf clone EMBRAPA 50) were donated by a local producer (Fortaleza, CE, Brazil). The fruits were received in several batches, screened for uniformity, and the cashew nuts were manually separated. Then, the fruits were sanitized (250 ppm NaOCl, 15 min), homogenized into a single batch, and frozen until further use (no longer than two weeks). Finally, frozen cashew apples (herein referred to as cashews) were thawed (12 h, 4–5 °C) and processed in a commercial juicing machine (model Compacta, Itametal, Brazil) to obtain the cashew juice (a_w = 0.981 ± 0.001; moisture content = 87.7 ± 0.1%; pH = 4.5 ± 0.1; soluble solids = 11.3 ± 0.5 °Brix). The gum arabic (GA; Instant Gum BB®) used in this study was donated by Nexira Brazil (Sao Paulo, Brazil). Folin–Ciocalteau reagent, 2,6-dichlorophenolindophenol (DCFI), metaphosphoric acid, ascorbic acid, and acetone were acquired from Sigma-Aldrich (St. Louis, MO, USA) and used without further purification.

2.2. Production of Spray-Dried Cashew Juice

The production of spray-dried cashew particles was evaluated using GA as a drying carrier at 15% w/v and 25% w/v addition rates (conditions defined in preliminary tests, Table S1). Prior to drying, GA was thoroughly homogenized in the cashew juice (standardized batch of 100 mL of cashew juice) for 15 min at room temperature until complete dissolution. The spray-drying process was performed using a lab-scale spray drier (model LM MSD 1.0, Labmaq, Brazil) with inlet temperatures (IT) of 140 °C and 150 °C (outlet temperature 90–98 °C), a feed flowrate of 0.6 mL min⁻¹, a compressed air flowrate of 45 L min⁻¹, a drying air flowrate of 38 m³ min⁻¹, and a 1.0 mm diameter atomizing nozzle. The feed solution was stirred during the entire spray drying process. In total, four experimental groups were prepared and evaluated: C1: 15% w/v GA, 140 °C inlet temperature; C2: 15% w/v GA, 150 °C inlet temperature; C3: 25% w/v GA, 140 °C inlet temperature; and C4: 25% w/v GA, 150 °C inlet temperature.

After spray drying, particles were collected from the powder collection vessel only, weighed, immediately sealed, and kept under refrigeration. The performance of spray drying was evaluated in terms of solids recovery, calculated according to Hoskin et al. [19], as the ratio between the total solids in the final spray-dried product and the total solids in the feeding mixture prior to spray drying.

2.3. Physicochemical Characterization of Spray-Dried Cashew Particles

2.3.1. Particle Size, True Density, Water Activity (a_w), and pH

The average particle size of spray-dried cashew particles was determined using a particle size analyzer with laser diffraction (model Cilas 1090, Cilas, Orleans, CVL, France) according to the procedure described by the manufacturer. A gas pycnometer (model AccuPyc 1340, Micromeritics, Norcross, GA, USA) was used to measure the true density of spray-dried cashew particles at 25 °C following the protocol determined by the manufacturer. Water activity (a_w) was determined using a digital water activity meter (model Aqualab 4 TE, Decagon Devices, Pullman, WA, USA) and the pH (model Q400AS, Quimis, São Paulo, SP, Brazil) of powdered samples was determined in 10% w/v dispersions in distilled water.

2.3.2. Solubility and Hygroscopicity

Solubility was determined in 1% w/v dispersions according to Correia et al. [25] prepared via vigorous stirring for 5 min. Solutions were centrifuged at 3000× g for 5 min (model Universal 320R, Hettich, Tuttlingen, BW, Germany) at 20 °C and aliquots of the supernatant where dried at 105 °C to constant weight. Solubility was calculated as the ratio between the weight of the dried supernatant (g) and the total solids in the initial sample (g), expressed as a percentage (%) [26]. Hygroscopicity was determined by placing samples (1 g) in Petri dishes that were kept at room temperature (22–23 °C) in a desiccator containing a NaCl saturated solution (relative humidity 75%) for 90 min. The results were calculated as the weight (g) of water absorbed per 100 g of solids and expressed as a percentage [27].

2.3.3. Instrumental Color

Color parameters were measured using a reflectance spectrophotometer (model CR-400, Konica-Minolta, Tokyo, Japan) previously calibrated with white and black standards. The color parameters L* (lightness), a* (greenness −a* or redness +a*), and b* (blueness −b* or yellowness +b*) were used to calculate the browning index (BI = [100 (x − 0.31) / 0.17; where X = (a* + 1.75L) / (5.645L + a − 3.012b*) and the total color difference (ΔE = (L² + a*² + b*²)^1/2) according to Pathare et al. [28]. Color parameters from cashew juice prior to spray drying were used as a reference to calculate the total color difference.

2.3.4. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM)

The microstructure of spray-dried particles was evaluated using a high-resolution X-ray diffractometer with Cu Kα radiation (λ = 1.5406 Å; model XRD 7000, Shimadzu, Tokyo, Japan) over a 2θ range between 5° and 80° and a scan step of 5° min⁻¹. Spray-dried particles’ morphology was observed via SEM (model SEM TM3000, Hitachi, USA) with Au metallization operating at 5 kV and 15 kV in 300× and 600× magnifications [26].

2.4. Phytochemical Characterization

2.4.1. Total Phenolic Content (TPC)

Total phenolics were extracted from spray-dried particles using water, according to a extraction protocol previously established by our research group [29]. Briefly, spray-dried particles (1 g) were dispersed in 50 mL of distilled water, stirred for 1 h at room temperature, and filtered under vacuum (vacuum pump model NOF 650, New Pump, Campinas, SP, Brazil). The filtrate was centrifuged (3600× g, 10 min, 4 °C; model Universal 320R, Hettich, Tuttlingen, BW, Germany) and kept at 4 °C in the dark until use. TPC was determined by means of the Folin–Ciocalteau method [30]. Samples’ absorbance was measured at 765 nm using a microplate reader (model UVM340, Biochrom, Cambridge, UK), and results were expressed as mg gallic acid equivalent (GAE) 100 g⁻¹ DM (dry matter) using an external calibration curve (0–200 mg L⁻¹).

2.4.2. Ascorbic Acid Determination

Ascorbic acid was determined via a modified protocol [31] based on 2,6-dichlorophenolindophenol (DCFI) titration (method 967.21, AOAC 2005). Briefly, 0.5 g of spray-dried particles was mixed with 50 mL of 1% w/v metaphosphoric acid and titrated with a solution of 0.5 mg mL⁻¹ DCFI in water, and the results were expressed as mg 100 g⁻¹ DM, based on the ascorbic acid standard.

2.4.3. Carotenoid Quantification

Carotenoid content was determined using a spectrophotometric (model Genesys 10s VIS Spectrophotometer, Thermo Scientific, Waltham, MA, USA) method [32]. For this method, 0.3 g of spray-dried cashew particles was extracted with 18 mL of acetone for 30 min and filtered under vacuum (vacuum pump NOF 650, New Pump, Campinas, Brazil). The absorbance of filtrates was read at wavelengths of 470 nm, 645 nm and 662 nm, and the results were expressed as mg 100 g⁻¹ DM according to Equations (1)–(3).

$$\mathrm{Total} \mathrm{carotenoids}\left({\displaystyle \frac{\mathrm{mg}}{\mathrm{mL}}}\right)={\displaystyle \frac{1000 \times { \mathrm{A}}_{470} - 1.90 \times \mathrm{Ca} - 63.148 \times \mathrm{Cb}}{214 \times 1000}}$$

(1)

$$\mathrm{a}\left({\displaystyle \frac{\mathsf{\mu }\mathrm{g}}{\mathrm{mL}}}\right)=11.24 \times { \mathrm{A}}_{662} - 2.04 \times {\mathrm{A}}_{645}$$

(2)

$$\mathrm{Cb}\left({\displaystyle \frac{\mathsf{\mu }\mathrm{g}}{\mathrm{mL}}}\right)=20.13 \times { \mathrm{A}}_{645} -4.19 \times {\mathrm{A}}_{662}$$

(3)

where A₄₇₀, A₆₄₅, and A₆₆₂ are the absorbance results at wavelengths of 470 nm, 645 nm and 662 nm, respectively.

2.4.4. Antioxidant Activity

Antioxidant activity was determined based on the DPPH (2,2-diphenyl-1-pricrylhydrazil) radical scavenging activity using a microplate-adapted protocol [33]. Briefly, 200 µL of 40 mg mL⁻¹ methanolic DPPH solution was mixed with 40 µL of sample eluates and left standing in the dark at room temperature for 25 min. Absorbance was read at 517 nm (model UVM340, Biochrom, Cambridge, UK) and the results were expressed as µmol Trolox equivalents (TE) g⁻¹ DM using a Trolox calibration curve (10 µmol L⁻¹–200 µmol L⁻¹ ).

2.5. Evaluation of Storage Stability

Spray-dried groups C1 and C3 were selected for the evaluation of storage stability at room temperature (25 °C) under controlled humidity (RH 43%) for 56 days. Samples (25 g) were stored in two types of plastic packaging (biaxially oriented polypropylene (transparent, T) or metallized biaxially oriented polypropylene (opaque, O)) and sealing (under vacuum (V) or not (N)). As a result, four experimental groups were evaluated: TV—packaged in transparent plastic and sealed under vacuum; TN—packaged in transparent plastic and sealed without vacuum; OV—packaged in opaque plastic and sealed under vacuum; and ON—packaged in transparent plastic and sealed without vacuum. Samples were collected after 0, 7, 21, 35, and 56 days and were analyzed for their a_w, solubility, TPC, and ascorbic acid content. Phytochemical (TPC and ascorbic acid content) retention (%) was calculated as follows: (parameter result after n days of storage time)/(parameter result at day 0) × 100.

2.6. Statistical Analyses

The results are shown as the average ± standard deviation for triplicate values (n = 3). Data were analyzed using one-way ANOVA followed by Tukey’s post hoc test at 95% of significance (p < 0.05) using the software Statistic 7.0 (StatSoft, Tulsa, OK, USA). GraphPad Prism version 10.0.0 (GraphPad Software, San Diego, CA, USA) was used to create data graphics.

3. Results and Discussion

3.1. Spray Drying Performance: Solids Recovery

Solids recovery, also referred to as spray-drying yield, is an important index to assess the spray-drying performance, as it relates to the success of the operation and potential scalability of the process. This parameter is even more relevant for fruit-derived products that contain high concentrations of low-molecular-weight sugars and organic acids, such as cashew juice, since their low glass transition temperature (Tg) usually leads to excessive stickiness of the dried particles that adhere to the dryer walls and compromise productivity [34,35,36,37]. Drying carriers are often needed to improve spray-drying performance and to produce spray-dried fruit-derived particles with enhanced physicochemical and phytochemical stability [20,38]. In this study, when no GA carrier was added, no powder could be produced and recovered, which highlights the importance of drying carriers.

High solids recovery (>70%,

Table 1. Solids recovery, physicochemical properties, and color attributes of spray-dried cashew particles.

Samples	C1	C2	C3	C4
Solids recovery, %	88.8 ± 4.5 a	88.8 ± 4.4 a	70.1 ± 1.5 b	71.8 ± 5.8 b
Average diameter, µm	17.9 ± 0.4 bc	15.1 ± 0.1 c	20.4 ± 1.1 b	29.5 ± 1.5 a
Density, g cm3	1.434 ± 0.001 b	1.458 ± 0.000 a	1.370 ± 0.001 c	1.374 ± 0.001 d
aw	0.262 ± 0.014 a	0.296 ± 0.009 a	0.266 ± 0.008 a	0.245 ± 0.018 a
pH	4.2 ± 0.0 a	4.3 ± 0.0 a	4.2 ± 0.0 a	4.2 ± 0.0 a
Solubility, %	97.1 ± 0.5 a	95.5 ± 1.0 a	94.9 ± 0.5 a	97.5 ± 0.9 a
Hygroscopicity, %	7.4 ± 0.4 ab	7.5 ± 0.2 a	6.0 ± 0.4 c	6.5 ± 0.1 bc
ΔE	22.3 ± 0.2 b	22.2 ± 0.1 b	23.9 ± 0.1 a	23.7 ± 0.2 a
BI, %	7.3 ± 0.1 c	7.7 ± 0.0 b	7.7 ± 0.0 b	8.1 ± 0.2 a

Results are shown as the average ± standard deviation (n = 3). Different letters (a, b, c, d) in the same line indicate statistical difference determined Tukey’s test (p < 0.05). Legend: a_w: water activity; ΔE: total color difference; BI: browning index. Sample identification: C1: spray-dried cashew juice with 15% w/v GA, IT 140 °C; C2: spray-dried cashew juice with 15% w/v GA, IT 150 °C; C3: spray-dried cashew juice with 25% w/v GA, IT 140 °C; C4: spray-dried cashew juice with 25% w/v GA, IT 150 °C. GA: gum arabic; IT: inlet temperature.

) was obtained for all experimental groups, at above 50%, which is considered as satisfactory performance for lab-scale spray-drying protocols [39]. The highest solids recoveries were observed for groups with 15% w/v GA (groups C1 and C2; p < 0.05), independent of the inlet temperature (Table 1). The solids recovery results were higher than those reported for spray-dried cashew particles obtained from cashew apple juice with maltodextrin and chemically modified starch (38.1–69.8%) [24], spray-dried particles obtained from probiotic cashew apple juice with maltodextrin (60%) [40], and spray-dried elderberry particles obtained from elderberry juice with tapioca starch (62.18 ± 2.47%) [17].

Treatments with a higher addition of GA (25% w/v, groups C3 and C4) showed lower solids recovery (p < 0.05) compared to C1 and C2 (Table 1), independent of the inlet temperature, indicating that the drying carrier addition ratio was the main factor affecting solids recovery. Likewise, when eggplant peel extract was spray-dried with GA and maltodextrin as drying carriers, it was observed that eggplant particles obtained with higher GA concentrations showed lower solids recovery compared to groups obtained with maltodextrin (MD) or an MD–GA 1:1 w/w blend at the same inlet temperature [41]. Moreover, when date fruit extracts were spray-dried with an MD–GA 1:1 w/w blend, response surface statistical models showed that the carrier addition ratio had a positive impact on solids recovery up to 45% w/v, above which it compromised powder productivity [20]. This behavior was attributed to the increased viscosity of spray drying feed solutions with higher GA concentrations, which leads to coarse droplets that compromise the drying efficiency due to higher agglomeration [20,38,41].

3.2. Physicochemical Attributes of Spray-Dried Cashew Particles

The average diameter of spray-dried cashew particles varied from 15.1 µm to 29.5 µm (Table 1), which falls within a typical range for atomized particles (10–100 µm) and allows them to be classified as microparticles [42,43]. Overall, particles obtained with a higher concentration of GA (groups C3 and C4, Table 1) showed a higher average diameter, which agrees with the hypothesis that feed solutions with higher GA concentrations generate coarse droplets during spray drying, leading to lower solids recovery and a higher average particle diameter [20,41]. Moreover, at higher GA concentrations (25% w/v, groups C3 and C4), the inlet temperature significantly (p < 0.05) affected particle average diameter (Table 1). At higher temperatures, the faster drying process may lead to immediate particle formation and avoid particle shrinkage [44], which may have also contributed to group C4 (GA: 25% w/v, IT: 150°C) showing the highest average diameter (29.5 ± 1.5 µm).

Spray-dried cashew particles had similar (p > 0.05) and low a_w, typical for spray-dried samples [38,45], and within the range considered as safe against microbial deterioration (below 0.6) [46,47]. As expected, all treatments showed a similar pH (p > 0.05), within the acidic range (4.2–4.3; Table 1), and the results are comparable to those of a previous report on freeze-dried cashew powders [48]. Powder density influences products’ processing, packaging, and transportation. A lower density was observed for spray-dried powders with a higher drying carrier concentration (Table 1). A similar trend was reported by Saikia et al. [49] and Goula and Adamopoulos [50] and might be related to reduced adherence between particles. The density of spray-dried cashew particles was in the same range as that of spray-dried elderberry particles obtained from elderberry juice with tapioca starch (1.415 ± 0.007 g cm³) [17], but was higher than that reported by Saikia et al. [49] for fiber-rich mix fruit particles obtained from pineapple, carambola, and watermelon mixed with maltodextrin (0.291–0.456 g cm³).

Remarkable water solubility was registered for all spray-dried cashew particles (>94%, p > 0.05) due to the inherently high solubility of GA [20,51]. High solubility is a desirable attribute, because it directly influences the acceptability of food ingredients and their performance in food formulations [43]. The results obtained here are better than those reported for spray-dried blackberry juice with an arrowroot starch and GA mixture (58.39–79.37%) [44], spray-dried citron (Citrus medica L. var. sarcodactylis Swingle) extract with GA, modified starch, whey protein, and maltodextrin carriers (70.09–91.26%) [43], and spray-dried elderberry particles obtained from elderberry juice and pomace extract using tapioca starch as a drying carrier (49.4–51.1%) [17].

Low hygroscopicity is a desirable feature for powdered matrices because hygroscopic materials require special packaging and handling conditions to avoid the excessive absorption of moisture, which can lead to quality deterioration, agglomeration, and caking [52]. The hygroscopicity of spray-dried cashew particles ranged from 6.0% to 7.5% (Table 1), and it was not affected by the inlet temperature (p > 0.05). Although particles obtained with higher GA concentrations (groups C3 and C4, 25% w/v) were less hygroscopic, all spray-dried cashew particles can be classified as non-hygroscopic (<10%) according to previously established classifications (hygroscopic: 15–20%; slightly hygroscopic: 10–15%; and non-hygroscopic: <10%) [53].

Aragüez-Fortes et al. [54] reported higher hygroscopicity for spray-dried guava particles obtained with maltodextrin (21.9–27.8%), but similarly observed that higher drying carrier concentrations led to lower hygroscopicity. It has been reported that hygroscopic behavior is influenced by physicochemical attributes such as composition and particle size [55]. We hypothesize that the lower hygroscopicity of spray-dried groups C3 and C4 might be attributed to the higher GA concentration (25% w/v), providing a higher glass transition temperature [41] and delivering spray-dried particles with a bigger average particle size, thus decreasing the overall surface area and, consequently, the hygroscopicity of the powdered matrices [55].

The concentration of GA influenced the total color difference ΔE of spray-dried cashew particles (p < 0.05). The results for ΔE were in the range of 22.2–23.9 (Table 1), and for ΔE > 5, color differences between the original solution and the final spray-dried particles are noticeable by the human eye [56]. A higher ΔE reflects increased variations in the L*, a*, and b* color parameters [57]. Groups C3 and C4 had higher L* values resulting from the higher concentration of GA (naturally white–light beige) and the consequent loss of the yellowish tones typical of cashew juice [20,58,59]. No clear effect of the inlet temperature or GA concentration was observed for BI values, which ranged from 10.5% to 14% and are lower than the results registered for spray-dried blackberry with GA (33.76 to 41.72%) [60].

3.3. Microstructure and Morphology

Figure 1 shows the XRD spectra of GA (Figure 1A) and spray-dried cashew particles (Figure 1B–E). Diffuse, broad peaks indicate an amorphous state typical of randomly oriented structures, while sharp, well-defined peaks are typical of crystalline materials with highly ordered molecular structures [26]. According to the XRD spectra, GA and spray-dried cashew particles presented predominantly amorphous structures, although spray-dried cashew particles (Figure 1B–E) showed a noisy, relatively more defined peak around 2θ = 20°, which is characteristic of semi-crystalline materials. The higher crystallinity of spray-dried particles, when compared to GA, is desirable because crystalline properties are associated with lower water absorption and retention in powdered matrices, which can increase storage stability and shelf-life [20]. The similarities among the spectra of all spray-dried groups C1-C4 indicate that the different spray drying conditions assessed in this study (inlet temperature and GA concentration) did not significantly alter the microstructure of spray-dried cashew particles. Similar trends were reported by Bastos et al. [61] for spray-dried cashew particles obtained with whey protein isolate–chitosan blends, and by Arumugham et al. [20] for spray-dried date fruit particles with MD–GA blends.

The SEM micrographs in Figure 2 show that spray-dried cashew particles mostly consist of spherically shaped structures (Figure 2B–E), as expected for spray-dried fruit products [20,45]. GA (Figure 2A) had irregularly shaped and larger structures when compared to spray-dried cashew particles. It was also observed that when a lower GA concentration was used (15% w/v, groups C1 and C2), smaller particles with more adhesion were produced (Figure 2B,C), while larger, more spherical, and more dispersed particles were obtained at higher drying carrier addition rates (25% w/v, groups C3 and C4; Figure 2D,E). These findings correlate with the particle size and hygroscopicity results of the group C3 and C4 samples (Table 1). Previous reports have demonstrated that particle morphology directly affects the stability of spray-dried phytochemicals [62]. Fissures, holes, and excessive surface roughness may weaken the protective role of the outer structure created by the drying carrier, either by promoting gas permeation or facilitating oxidation reactions [63,64]. In our study, all groups yielded particles with a smooth surface and the absence of cracks, which is an indication of the potentially efficient protection of the encapsulated material.

3.4. Phytochemical Attributes

Phytochemicals, health-promoting compounds with potential applications in functional foods, are generally susceptible to degradation under industrial food processing conditions, affected by factors such as temperature and the presence of oxygen and light [65]. Thus, identifying the phytochemical composition is important to assess the potential applications of the spray-dried cashew particles.

GA concentration was the most significant factor influencing TPC and ascorbic acid content (p < 0.05) in spray-dried cashew particles (

Table 2. Phytochemical characterization of spray-dried cashew juice obtained under different conditions.

	Ascorbic Acid (mg 100 g−1)	Carotenoids (mg 100 g−1)	TPC (mg GAE 100 g−1)	DPPH Antioxidant Activity (µmol TE g−1)
C1	673.2 ± 37.3 a	0.4 ± 0.1 a	393.4 ± 23.8 a	16.4 ± 0.2 a
C2	656.9 ± 43.0 a	0.2 ± 0.0 b	330.9 ± 7.4 b	14.8 ± 0.3 ab
C3	496.0 ± 65.0 b	0.5 ± 0.0 a	233.6 ± 22.2 c	13.0 ± 0.7 b
C4	468.0 ± 42.6 b	0.4 ± 0.0 a	229.3 ± 11.9 c	16.0 ± 1.5 a

Results are shown as the average ± standard deviation (n = 3). Different letters (a, b, c) in the same line indicate statistical difference according to Tukey’s test (p < 0.05). Legend: TPC: total phenolic content; GAE: gallic acid equivalents; DPPH: 2,2-diphenyl-1-pricrylhydrazil; TE: Trolox equivalent. Sample identification: C1: spray-dried cashew particles with 15% w/v GA, IT 140 °C; C2: spray-dried cashew particles with 15% w/v GA, IT 150 °C; C3: spray-dried cashew particles with 25% w/v GA, IT 140 °C; C4: spray-dried cashew particles with 25% w/v GA, IT 150 °C. GA: gum arabic; IT: inlet temperature.

). Spray-dried particles prepared with 15% w/v GA presented a higher TPC (330.9–393.4 mg GAE 100 g⁻¹) and ascorbic acid content (656.9–673.2 mg 100 g⁻¹) than their counterparts with 25% w/v GA, which we hypothesize to be related to the diluting effect of the higher carrier addition ratio [38]. The TPC and ascorbic acid results reported here are higher than those previously reported for freeze-dried cashew particles (TPC: 65.32–67.64 mg GAE 100 g⁻¹; ascorbic acid: 72.83–96.46 mg 100 g⁻¹) [48] and spray-dried cashew particles obtained from cashew pomace extract (TPC: 215.45 ± 2.94 mg GAE 100 g⁻¹) [11], highlighting the success of our spray-drying protocol in preserving valuable phytochemicals. A low carotenoid content was found in all spray-dried cashew particles (0.2–0.5 mg 100 g⁻¹, Table 2), similar to that previously reported for freeze-dried cashew particles (0.38–0.41 mg 100 g⁻¹) [48].

The inlet temperature affected the TPC of particles prepared with 15% w/v GA (groups C1 and C2, Table 2). For these groups, the inlet temperature increasing from 140 °C to 150 °C led to a significant (p < 0.05) decrease in TPC from 393.4 ± 23.8 mg GAE 100 g⁻¹ to 330.9 ± 7.4 mg GAE 100 g⁻¹ for C1 and C2, respectively. This effect was not observed for groups C3 and C4 prepared with 25% w/v GA. Our hypothesis is that GA provided better protection to phenolics against heat degradation at the 25% w/v addition ratio when compared to 15% w/v [66,67]. A similar effect was reported by Maia et al. [24] for spray-dried cashew particles produced with an MD–starch 1:1 w/w blend that showed higher TPC retention (p < 0.05) at a 15% w/v addition ratio (92.5 ± 5.4%) than at a 10% w/v addition ratio (67.7 ± 6.5%).

The antioxidant activity of spray-dried cashew particles, assessed as DPPH radical scavenging activity, was in the range of 13.0–16.4 µmol TE g⁻¹ (Table 2), which is comparable to previously reported results for spray-dried elderberry particles (17–25 µmol TE g⁻¹) [17] and spray-dried coconut shell extracts (8–12 µmol TE g⁻¹) [68]. No clear influence of the tested parameters (GA concentration and inlet temperature) was found in the antioxidant activity results.

3.5. Storage Stability

Considering that GA concentration was the parameter that showed the greatest influence on the process performance (solids recovery; Table 1) and particle attributes (particle size, hygroscopicity, ΔE, and phytochemical content; Table 1 and Table 2), one group from each GA addition ratio was selected for storage stability evaluation. Furthermore, considering that a lower inlet temperature (140 °C) yielded higher TPC preservation for spray-dried particles with 15% GA w/v, groups C1 and C3 (both prepared at 140 °C) were prioritized for the study of storage stability. The effects of light (storage under light in transparent (T) or opaque (O) packaging materials) and oxygen (sealed under vacuum (V) or without a vacuum (N)) on a_w, solubility, and TPC and ascorbic acid retention were evaluated over the course of 56 days.

A slight increasing trend was observed for the a_w of the C1 group over the 56 days of storage, regardless of packaging conditions (Figure 3A), which was not seen for C3 (Figure 3B). Spray-dried cashew particles produced with 25% w/v GA (group C3) displayed lower hygroscopicity (p < 0.05) than particles produced with 15% w/v GA (group C1; Table 1), which might have limited the water sorption over time. Despite the slight increase in a_w for the C1 samples, all spray-dried cashew particles retained a low a_w, below 0.4, throughout the 56 days of storage, indicating microbiological stability and a low risk of lipid oxidation or enzymatic degradation [69]. Similar behavior was reported by Kardile et al. [70] for vacuum-dried puran powder and by Upadhyay et al. [71] for spray-dried guava parties that showed an a_w increase in the range of 1.8–9.1% after storage for up to four months. Comparatively, the average a_w increases in this study were in the ranges of 9.6–22.6% and 0–5.3% for groups C1 and C3, respectively.

The solubility of spray-dried cashew particles was not affected by any of the storage conditions (Figure 3C,D), and remained high during the extended 56-day storage period (>90%). GA has been reported as being highly soluble in water [51,72], which might explain the observed results.

Transparent packaging led to higher ascorbic acid losses (p < 0.05; Figure 4A) in spray-dried cashew particles produced with 15% w/v GA (67.9–74.8% ascorbic acid retention after 56 days) when compared to opaque packaging (82.0–83.4% ascorbic acid retention after 56 days). Moreover, spray-dried particles produced with 25% w/v GA (group C3, Figure 4B) showed higher ascorbic acid retention (89.7–97.2%, p < 0.05) than group C1 after 56 days, regardless of the storage conditions. Group C3 (25% w/v GA) stored in transparent packaging (TN and TV) showed a significant (p < 0.05) and unexpected positive fluctuation in the ascorbic acid content at 21 days of storage. Similar behavior for ascorbic acid has been reported by Toledo et al. [73] when evaluating the storage stability of spinach. Although the mechanism that explains this behavior is not clear, authors have reported that light-induced reactions might have an influence on these results. Despite these during storage, at the end of the storage period (56 days), the samples displayed 94% and 90% ascorbic acid retention for C3-TN and C3-TV, respectively (Figure 4B). These results indicate that not only the packaging and storage conditions but also the protective effect resulting from higher GA concentrations during spray-drying microencapsulation influenced the shelf-life stability of ascorbic acid [74,75,76,77].

A notable TPC decrease was observed after 7 days of storage (p < 0.05) for both the C1 and C3 groups and regardless of storage conditions (Figure 4C,D), but after that, TPC remained virtually unchanged up to 56 days of storage. TPC fluctuations (degradation after 7 days of storage and a slight increase in TPC for group C3 after 56 days of storage) might be attributed to the oxidation of phenolic compounds or modifications of the phenolic profile under storage, which have also been reported for spray-dried cranberry juice [62] and spray-dried cantaloupe juice [78]. When analyzed altogether, spray-dried cashew particles retained between 55% and 76% of the initial TPC, which is similar to spray-dried horseradish particles produced with GA, MD, starch, and soy protein isolate that showed 56.4% to 79.9% TPC retention after 4 months of storage at room temperature, as reported by Tomsone et al. [79].

4. Conclusions

The concentration of GA had the most significant influence on the process performance (solids recovery) and particle attributes (particle size, hygroscopicity, ΔE and phytochemical content) for the spray drying of yellow cashew juice. Among the investigated conditions, 15% w/v addition of GA and a lower inlet temperature (140 °C) proved to be more beneficial for the preservation of phytochemicals in cashew juice particles. When cashew particles were stored under different conditions (transparent or opaque packaging material, under vacuum or not), despite some observed fluctuations, remarkable ascorbic acid retention (>90%) was observed at the end of the 56-day storage period. A significant phenolic content decrease was observed during the first week, with subsequent stabilization for all experimental groups. In a nutshell, all storage conditions led to the preservation of the key quality attributes of spray-dried cashew particles. Taken altogether, this work shows that the microencapsulation of cashew juice with GA is a feasible strategy to produce phytochemical-rich food ingredients from underutilized cashew apples for value-added food applications.