Characterization of Starch from Jinicuil (Inga jinicuil) Seeds and Its Evaluation as Wall Material in Spray Drying

Abstract

Jinicuil seed starch (JSS) was partially characterized and then evaluated as wall material. JSS showed higher content of proteins, lipids, and resistant starch than commercial corn starch (CCS). JSS granules presented both oval-spherical shapes and heterogeneous sizes (~1–40 µm) and exhibited a crystallinity lower than CCS with an A-type X-ray diffraction pattern. Both gelatinization peak and final viscosity values in the pasting profile were higher in JSS than in CCS. At 90 °C, the water solubility was 22% and the swelling power was 17 g g⁻¹. Under refrigeration and freeze-thaw, the JSS gel showed high stability. JSS showed a significant presence of protein and small particles; therefore, it was evaluated as wall material in spray drying. The results showed the formation of spherical aggregates and encapsulation efficiencies of L-ascorbic acid of 14.97–81.84%, with process yields of 19.96–27.64%, under the conditions evaluated. JSS has a potential application in the food industry but also as wall material for microencapsulation by spray drying.

1. Introduction

Starch is a biological macromolecule used in foods as a stabilizer, thickener, and gelling agent [1,2]. The isolation and characterization of native starch granules from unconventional botanical sources in terms of thermal [3,4], rheological [4,5], morphological [6,7], structural [7,8,9,10], functional [10,11], and/or physicochemical [10,12,13] properties allow for the detection of native starches with possible industrial applications and the identification of new research directions in the area of food.

Encapsulation is used to protect substances that are susceptible to degradation of their functionality due to hydrolysis, oxidation, or other reactions [14,15,16]. Some native or modified starches are used as wall material to protect compounds against the effects of oxygen, pH, temperature, humidity, and other components that could affect the core material [15,16,17]. Spray-drying encapsulation is a common process due to its versatility and scalability and because it allows a continuous process while the temperature of the core material is maintained around the saturation temperature, i.e., at a lower value than the inlet temperature of dry air [15]. Some native starches tend to form spherical aggregates during encapsulation by spray drying [16,18] due to the presence of both small starch granules and proteins [19], and this structure allows for significant encapsulation of the core material [18,19,20]. Therefore, a characterization of native starches is necessary to identify their possible application as wall material in the encapsulation of bioactive compounds by spray drying.

Inga spp. (Leguminosae) have been recommended as shade trees for coffee plantations, and their presence is registered from Mexico to South America [21,22]. The pods from Inga jinicuil Schltdl. (jinicuil) trees are usually exploited as a food source; however, the jinicuil seeds are generally discarded after consuming their cover [22,23]. Jinicuil seeds represent an unconventional source of starch. Therefore, in this study, the isolation and morphological and physicochemical characterization of native starch from jinicuil (Inga jinicuil) seeds were carried out. The information can be correlated with possible agroindustry applications, inclusive with the potential application as wall material in encapsulation by spray drying.

2. Materials and Methods

2.1. Materials

Pods of the jinicuil (Inga jinicuil) trees were collected in June 2019 from local cultivars (located at 17°56′44.736″ N and 96°10′15.348″ W; San José Chiltepec, Oaxaca, Mexico). Both resistant starch (K-RSTAR) and total starch (K-TSTA) assay kits were used (Megazyme International; Wicklow, Ireland). Chemicals (reagent grade) and solvents (analytical grade) were purchased from Sigma Chemical Co. (St. Louis, MO, USA) and JT Baker (Mexico City, Mexico), respectively. A commercial native starch from corn (CCS) (Sigma-Aldrich Química, S.A. de CV; Toluca, Mexico State, Mexico) was used as a reference in the characterization analyses due to this starch being widely studied and used for these purposes.

2.2. Starch Isolation

Jinicuil starch was obtained from jinicuil seeds by adapting the method reported by Flores-Gorosquera et al. [24] and Vázquez-León et al. [17]; the use of citric acid was omitted. The jinicuil seeds (250 g) were ground with water (1.5 L) in an industrial blender (Waring Commercial CB15; Torrington, CT, USA). Then, the product obtained was sieved through different meshes (40, 100, 200, 325 US). The final liquid fraction was precipitated at 20 °C for 12 h, and the sediment was washed by resuspension in water and then was sieved through 100 US mesh [17]. The sieved suspension was centrifuged (Thermo Fisher Scientific Inc., Heraeus Megafuge 16 R; Waltham, MA, USA) at 20 °C and 4000× g for 10 min. This procedure was carried out twice. The fraction resulting from the final centrifugation was dried at 40 °C and 1.5 m s⁻¹ for 24 h. The dried starch was ground and sieved through 100 US mesh [17]. Jinicuil starch was stored in airtight containers until further analysis. Starch extraction performance was evaluated as the ratio between the final mass of jinicuil seed starch (JSS) and the mass of jinicuil seeds used for isolation [17].

2.3. Total Starch Content and Proximal Analysis

Total starch content of JSS and CCS was measured with a Megazyme assay kit (K-TSTA, actually available as AA/AMG, Bré, Ireland) [17]. For this analysis, the manufacturer’s recommendations were followed. Proximal analysis of JSS and CCS was carried out in accordance with AACC International methods [25] for proteins (46-13.01), lipids (30-25.01), moisture (44-16.01), and ash (08-01.01).

2.4. Morphological Analyses

The starch granules were analyzed in a microscope with transmitted light and polarized light (Eclipse 80i, Nikon, Tokyo, Japan), according to the procedure described by Vázquez-León et al. [17]. In addition, the granules’ morphology was examined by scanning electron microscopy (JEOL, JSEM 35CX; Tokyo, Japan) at 20 kV [26]. First, the granules were directly deposited over a conductive copper tape, and then they were covered with a layer of coal. The samples were covered with gold to provide conductivity.

Finally, the granule size distribution (PSD) of the starches was evaluated according to Vázquez-León et al. [17] on a laser diffraction particle size analyzer (Malvern Instruments Ltd., Mastersizer 3000; Malvern, UK) equipped with a dip-in wet sample dispersion unit (Malvern Instruments Ltd., Hydro EV; Malvern, UK) at 90% ultrasound power. Starches were dispersed in water until an obscuration of 3–5%.

2.5. Physicochemical Properties

2.5.1. Pasting Properties

A Discovery HR-2 Hybrid Rheometer (TA Instruments; New Castle, DE, USA) for pasting profile determination was used. Three cycles of scanning on water-dispersed starch (10% w/v) were used according to Vázquez-León et al. [17]: (1) from 30 to 90 °C at 15 °C min⁻¹; (2) at 90 °C for 360 s; and (3) from 90 to 30 °C at 30 °C min⁻¹. The results were registered with the equipment software Trios V.4 (TA Instruments, New Castle, DE, USA) [17].

2.5.2. Thermal Properties

A Discovery DSC250 Calorimeter (TA Instruments; New Castle, DE, USA) was used to evaluate the gelatinization onset ($T_O$), gelatinization peak ($T_P$), gelatinization conclusion temperatures ($T_C$), and gelatinization enthalpy ($\Delta H$) [17,27]. First, 2 mg of the starch sample were inserted into an aluminum pan cell, then 7 $\mathsf{\mu }$L of distilled water were added. Each sample was hermetically sealed and then equilibrated for 1 h. Under nitrogen flow (50 cm³ min⁻¹), each sample, with a reference aluminum pan cell, was heated from 30 to 140 °C at 10 °C min⁻¹. The results were registered with the equipment software Trios V.4 (TA Instruments, New Castle, DE, USA) [17].

2.5.3. X-ray Diffraction

A D8-Advance Diffractometer (Bruker AXS; Billerica, MA, USA) was used to examine the diffraction patterns of starches according to Vázquez-León et al. [17]: 2θ scanning region, from 5 to 60°; scan rate, 1° min⁻¹. The samples were not conditioned prior to the analysis due to their moisture content (<15%) and also because they were deposited as powder. With both the peak area and the total area of diffraction pattern, the crystallinity percentage was calculated [9,28].

2.5.4. Apparent Amylose Content

A spectrophotometric method (λ = 600 nm) described by Hoover and Ratnayake [29] was used to evaluate the amylose content. A Genesys 10 S Spectrophotometer (Thermo Scientific; Waltham, MA, USA) was used.

2.5.5. Resistant Starch Content

A method based on the AACCI [25] 32-40.01 procedure to determine the resistant starch content was used. For this analysis, a spectrophotometer at λ = 510 nm was used, and the K-RSTAR Megazyme kit manufacturer’s recommendations were followed [17].

2.5.6. Swelling Power ($SP$) and Water Solubility ($WS$)

Both $WS$ and $SP$ patterns were obtained according to Pérez-Pacheco et al. [1] and Vázquez-León et al. [17]. Starch weights were recorded ($W_0$) and were then suspended in water (1% w/v). The suspensions were heated at different temperatures (60, 70, 80, or 90 °C) for 30 min under agitation. Subsequently, the suspensions were centrifuged at 4000× g and 20 °C for 10 min. The supernatants were dried at 120 °C (Shel Lab, Mod. 1425; Cornelius, NC, USA) until constant weight ($W_2$, soluble solids). The sediment weights ($W_1$, gel) were recorded. Both $SP$ and $WS$ were estimated with Equations (1) and (2), respectively [1,10].

$$SP (g/g)=W_1/\left(W_0-W_2\right)$$

(1)

$$WS (\%)=\left[W_2/W_0\right]\times 100$$

(2)

2.5.7. Refrigeration and Freeze-Thaw Stability

Syneresis rates under refrigeration (4.0 °C) and freeze-thaw (−12.0 °C) cycles of water starch suspensions (5% w/v) that were gelatinized (85 °C for 30 min) were determined according to Eliasson and Kim [5], for 5 cycles of 24 h (total time: 120 h). After each cycle, the samples were heated until 25 °C, and the weights were recorded ($W_{gct}$). Subsequently, the samples were centrifuged at 4000× g and 25 °C for 10 min. The supernatants were decanted and weighed ($W_{sw})$. The syneresis percentage was estimated with Equation (3) [5].

$$Syneresis \left(\%\right)=\left[W_{sw}/\left(W_{gct}-W_{ct}\right)\right]\times 100$$

(3)

2.6. Microencapsulation by Spray Drying

A B-290 Spray Dryer (Büchi; Flawil, Switzerland) was used to evaluate the JSS as wall material for microencapsulation of ascorbic acid (AA). Suspensions at 20% w:w of solids were prepared with a starch:AA ratio of 4:1 w:w. Different inlet (Tin: 130, 140 and 150 °C) and outlet (Tout: 60 and 70 °C) air temperatures were evaluated. The atomization air flow and the atomization pressure were 667 L h⁻¹ and 6 × 10⁵ Pa, respectively. The aspirator rate was maintained at 100% operating capacity [30]. The spray-drying treatments were performed in duplicate. Both the total recovered product mass and the total solids mass of the feed mixture were used to estimate the process yield [30].

2.7. Characterization of Microparticles

2.7.1. Water Activity, Particle Size Distribution, and Morphological Analysis

An AquaLab vapor absorption analyzer (Decagon Devices, Inc., AquaLab VSA; Pullman, WA, USA) was used for the water activity determination at 25 °C of the products obtained by spray drying [17]. Both particle size distribution (PSD) and morphology of the dried samples were analyzed according to Section 2.4, described previously.

2.7.2. Encapsulation Efficiency (EE)

The EE was evaluated according to Vázquez-León et al. [17]. A total of 200 mg of spray-dried particles were suspended in 25 mL of distilled water for 15 s to wash the superficial ascorbic acid (AA_S) [17]. Then, 100 µL of the mixture were gauged to 10 mL with the diluent (4:120:876 v:v:v ratio of sulfuric acid:acetone:Milli-Q water) and filtered [17]. An ion chromatography system (Metrohm, 930 Compact IC Flex, Gallen, Switzerland) with a conductivity detector and a Metrosep Organic Acids—250/7.8 column (Metrohm AG, Gallen, Switzerland) were used to quantify the ascorbic acid [31]. The eluent used was a mixture of 0.4 mmol L⁻¹ of sulfuric acid and 12% of acetone at an isocratic flow of 0.4 mL min⁻¹ for 20 min [31]. The total ascorbic acid (AA_T) was determine from aqueous suspensions of spray-dried particles (200 mg in 25 mL) that were sonicated (Bandelin, SONOPULS HD 3200; Berlin, Germany) for 10 min at 15 °C [17]. A calibration curve for ascorbic acid (1–100 mg L⁻¹) was carried out [17]. The EE was calculated as described in Equation (4) [17].

$$EE \left(\%\right)=\left[\left({AA}_T-{AA}_S\right)/{AA}_T\right]\times 100$$

(4)

2.8. Statistical Analyses

1W-ANOVA followed by Tukey’s pairwise test to identify significant differences (p < 0.05) was carried out. A factorial design 3 × 2 with two replicates was used to evaluate the JSS as wall material during spray drying. Three inlet (Tin) and two outlet (Tout) air temperatures were studied (Tin: 130, 140 and 150 °C; Tout: 60 and 70 °C). Multivariate analysis of variance (MANOVA) to identify significant factors (p < 0.05) was carried out followed by Tukey’s pairwise test (p < 0.05) for each response variable.

3. Results

3.1. Starch Isolation Yield

The isolation yield of JSS was 7.63% in a wet basis (wb) and 7.90% in a dry basis (db). This yield value was lower than corn (79.5%), rice (75.8%), and wheat (71.9%) starches [32]. Therefore, to promote Inga jinicuil pods as a secondary source of starch, other isolation strategies should be studied to improve the process yield. However, its characterization is essential to define its potential applications and then evaluate whether an isolation optimization study is essential.

3.2. Chemical Composition of Jinicuil Seed Starch (JSS)

Table 1. Physicochemical properties of jinicuil seed starch.

Parameter	Jinicuil Seed Starch	Commercial Corn Starch
Moisture (g 100 g−1 db)	7.82 ± 0.24 b	8.94 ± 0.08 a
Total starch (g 100 g−1 db)	76.71 ± 1.54 b	83.97 ± 2.82 a
Protein (g 100 g−1 db)	20.93 ± 1.54 a	1.01 ± 0.02 b
Fat (g 100 g−1 db)	2.08 ± 0.05 a	0.25 ± 0.05 b
Ash (g 100 g−1 db)	0.27 ± 0.04 b	0.97 ± 0.03 a
Resistant starch (g 100 g−1 db)	15.73 ± 2.52 a	0.38 ± 0.02 b
Apparent amylose (%)	21.00 ± 2.23 b	26.65 ± 0.55 a
$T_O$ (°C)	84.53 ± 0.05 a	69.16 ± 0.18 b
$T_P$ (°C)	87.85 ± 0.05 a	74.62 ± 0.48 b
$T_C$ (°C)	98.02 ± 0.14 a	80.69 ± 0.18 b
$∆H$ (J g−1)	15.27 ± 0.33 a	12.19 ± 0.39 b

The values are reported as the mean ± standard error (n = 3). Means in rows that share a letter are not significantly different (p > 0.05). $T_O$, gelatinization onset temperature; $T_P$, gelatinization peak temperature; $T_C$, gelatinization conclusion temperature; $∆H$, gelatinization enthalpy.

shows the chemical composition of JSS. The moisture of JSS was <15% wb, which is an acceptable value for dried products to be used as starches [33], so it could be classified as physiochemically stable and microbiologically safe. The total starch content in JSS is lower than that of a commercial corn starch (CCS) because both protein and lipid contents are high in comparison to CCS and other starches [1,33], thus an additional purification treatment for removing protein may be necessary. The ash value indicates a scarce mineral content in JSS and moreover was not higher than the recommended maximum value of 5 g kg⁻¹ in starches [33]. According to Moore et al. [34], who classified the starches depending on the amylose content, the JSS is a normal type starch (18–30% amylose), but the amylose value in JSS was lower than that of CCS. The resistant starch content of JSS was lower than that of banana starch (65.8 ± 0.43%) [11] or common bean starch (72.1–78.3%) [12] but was higher than in CCS (Table 1) and Brazilian pine seeds (3.0–9.0%) [9].

3.3. Morphological Properties of JSS

Figure 1 shows the morphological properties of the JSS granules. Both white and polarized light microscopy showed intact starch granules (Figure 1a) with a well-defined Maltese cross (Figure 1b), and smooth surfaces with no cracks were observed through SEM (Figure 1c), so the granule structures were not damaged by the isolation process [12,17]. JSS granules displayed a polymodal particle size distribution (PSD) (Figure 1d); this result suggests a formation of agglomerated granules of ~40 µm, as was observed by SEM (Figure 1c). In addition, peaks at 6.5 µm and <1 µm were observed. The larger size obtained stemmed from the JSS showing oval-spherical granules; this characteristic is similar to the starch granules from Brosimum alicastrum Swarts seeds [1], common bean starches [12], and kithul palm (Caryota urens) [35]. Figure 1c shows some spherical structures surrounding the JSS granules (red circles); these structures could correspond to protein remnants, as Estrada-León et al. [36] suggest. This is in agreement with the high protein value observed for JSS (Table 1).

3.4. Pasting Profile and X-ray Diffraction Pattern of JSS

Figure 2 shows the pasting profile and the X-ray diffraction pattern (XRD) of the JSS. According to the peaks observed in 2θ (15°, 17°, and 23°), the XRD pattern of JSS is an A-type pattern, which is similar to those of CCS (Figure 2a) and other starches [32,35,37]. The relative crystallinity of the JSS was found to be 23.15%, i.e., in the value range of native starches (15–45%) [32]. However, this value was lower than crystallinity from CCS (41.00%).

According to Figure 2b, the JSS has a peak viscosity of 2230 cP and a final viscosity of 3425.4 cP. Both values are higher than the viscosity values of CCS (PV, 1750 cP). The increases of the viscosity values start in JSS at 90 °C, while those in CCS start at 80 °C, so the JSS requires a higher heating temperature to gelatinize. This could be related to the high lipid and protein content presented by JSS (Table 1) [3,38,39].

3.5. Gelatinization Properties of JSS

Gelatinization properties for both JSS and CCS are presented in Table 1. These results are in agreement with the pasting profile (Figure 2b), because the gelatinization temperatures of JSS were higher than those of CSS. The T_p value for JSS is also higher than those reported for Brosimum alicastrum Swarts seeds (83.05 °C) [1], common bean starches (63.1–74.0 °C) [12], lintenerized and native banana starches (77–80 °C) [11], and Litchi chinesis Sonn. seed starch [10].

3.6. Water Solubility ($WS$) and Swelling Power ($SP$) of JSS

Figure 2c,d show the $WS$ and $SP$ patterns, respectively, for JSS and CCS. When the starch granules are heated in water, the double helices that form part of the crystalline zone of the amylopectin unfold, exposing the hydroxyl groups that interact with water through hydrogen interactions, so an increase in the $SP$ and $WS$ values can be observed [6,35]. For JSS, these properties show that the granules did not swell and are appreciably soluble at temperatures below 80 °C.

3.7. Stability under Freeze-Thaw and Refrigeration of JSS Gel

Figure 3 shows the stability under five cycles of freeze-thaw and refrigeration of both JSS and CCS gels. In the first cycle, under both refrigeration (56.68%) and freeze-thaw (15.43%) processes, the highest values of syneresis were obtained; but above the second cycle, the syneresis values were not changed, which was different from other works [1,9]. Pérez-Pacheco et al. [1] reported that both corn and Brosimum alicastrum seeds starches increased the syneresis values under different cycles of refrigeration (56.00–73.67%; 76.33–80.00%) and freeze-thaw (70.33–78.00%; 72.33–76.33%). Zortéa-Guidolin et al. [9] reported an increase in the syneresis values (34.1–73.0%) of Brazilian pine seeds starch gel under freeze-thaw. In this manner, JSS gel is more stable in both the refrigeration and freeze-thaw processes than the samples cited.

3.8. Spray Drying Process Yield and Encapsulation Efficiency

Table 2. Effects of spray-drying conditions (inlet and outlet air temperatures) on the process yield and encapsulation efficiency of ascorbic acid using the jinicuil seed starch as wall material.

Inlet Air Temperature (°C)	Outlet Air Temperature (°C)	Process Yield (%)	Encapsulation Efficiency (%)
130	60	19. 96 ± 0.18 b	79.29 ± 1.84 a
140	60	20.62 ± 0.63 ab	81.84 ± 0.73 a
150	60	21.95 ± 1.55 ab	27.54 ± 1.04 b
130	70	21.18 ± 2.79 ab	14.97 ± 0.48 d
140	70	27.64 ± 0.64 a	65.74 ± 1.48 b
150	70	20.76 ± 0.23 ab	71.48 ± 0.80 b

The values are reported as the mean ± standard error (n = 2). Means in columns that share a letter are not significantly different (p > 0.05).

shows the process yields and encapsulation efficiencies obtained under different spray drying conditions with JSS as wall material. A higher process yield indicates more benefit for the industries [40]. Therefore, some variables should be adjusted to increase or obtain a feasible value of spray-drying yield; for example, the solids content, the inlet (Tin) and outlet (Tout) temperatures of drying gas, the atomization conditions, and the feed rate [40,41]. In the present study, neither Tin nor Tout have a significant effect on process yield (p > 0.05) according to MANOVA; instead, the interaction Tin-Tout showed a significant effect (p < 0.05) on this response variable. In Figure 4a, it can be observed that at 140-70 °C (Tin-Tout), the higher process yield was obtained, even if this treatment in fact only showed a significant difference (p < 0.05) with the spray drying at 130-60 °C (Tin-Tout); under this last treatment, the yield value was lower. However, the process yields obtained in this work (19.96 ± 0.26–27.64 ± 0.91%; Table 2) were < 50%, so the process with JSS as wall material was not feasible [40].

Encapsulation of bioactive compounds is important in designing functional foods because a wall material protects the active principle against light, moisture, oxygen, and other extreme conditions [15,18,41]. Moreover, encapsulation enhances the targeting precision of bioactive compounds and their bioavailability and controls their release [15,18]. Starch as a wall material in spray drying is very used, but the capsule formation also depends on the process conditions [18,30]. In the present work, Tin, Tout, and the Tin-Tout interaction showed significant effects (p < 0.05) on the encapsulation efficiency of ascorbic acid, according to MANOVA. An increase from 60 to 70 °C in Tout reduced the encapsulation efficiency of ascorbic acid, except for the process at 150-60 °C (Tin-Tout) (Table 2). These results suggest a thermal degradation of the bioactive compound. The treatment at 130-70 °C (Tin-Tout) showed lower values for the encapsulation, so an increase in Tin (140-70 °C; Tin-Tout) was necessary to obtain the highest values (Table 2). Vázquez-León et al. [30] indicated that an increase in Tin with the fixed Tout improve the encapsulation efficiency of ascorbic acid with maltodextrin, but this could be feasible up to a point, as the results at 150-70 °C (Tin-Tout) and 150-60 °C (Tin-Tout) suggest in the present work. Table 2 shows that the encapsulation efficiencies of ascorbic acid with JSS were above 60% for some treatments.

3.9. Morphological Properties and Water Activity of Dried Particles

Water activity ($a_w$) is an important factor for describing the microbiological safety and physicochemical stability of powders [41]. High $a_w$ values (>0.5) could favor the degradation reactions and then reduce the shelf life and increase the capsules’ collapse during storage [40,42]. In the present work, according to MANOVA, the factors evaluated (Tin, Tout, interaction Tin-Tout) did not show a significant effect (p > 0.05) on the $a_w$ of dried products, as others’ works about spray-dried products have reported [30,40]. The spray-dried particles with JSS presented $a_w$ values from 0.32 to 0.43, which are in a desirable range to ensure both the physicochemical and microbiological stabilities of spray-dried powders [41].

For SEM and PSD analyses, the sample obtained at 140-60 °C (Tin-Tout) was selected, as it showed higher encapsulation efficiency (Table 2). According to the image obtained by SEM (Figure 4a), the particles showed the shape and surface aspects of spray-dried particles. For a microencapsulation process, particles with uniform and smooth surfaces with a slightly spherical shape and minimum cracks on their walls are preferred [30]. Figure 4a shows that the small particles obtained with JSS as wall material have continuous walls with no cracks, which suggest that the starch granules were not damaged during the drying process [41], in accordance with other works that reported that the starch’s granular structure did not change during the spray drying [18]. In addition, some spherical aggregate particles are also observed (Figure 4a).

Figure 4b shows a higher population of particles at ~10 µm in spray-dried particles than in JSS and without the presence of agglomerates at 40 µm, as is observed in Figure 1d. The size of spray-dried particles with JSS was lower than spherical aggregates obtained with taro starch (20.8 µm) and L-ascorbic acid capsules based in taro starch (16.4 µm), as informed by Hoyos-Leyva et al. [26], and the L-ascorbic acid capsules obtained with hydrolyzed corn starch in blends with Arabic gum (1087.44–1245.43 µm) reported by Leyva-López et al. [42]. A peak at 1 µm was also observed and could be related to small starch granules that were not affected by the drying process and that did not form spherical aggregates, as was observed by SEM (Figure 4a). According to the PSD, the particles obtained in the present work could be considered microcapsules [15,41].

4. Discussion

4.1. Characteristics, Properties, and Potential Applications of Jinicuil Seed Starch

In general, the chemical composition of starches depends on the botanical source and the extraction process [1,36]. The resistant starch value found in the present work indicates a nutritional benefit of JSS, because resistant starch can prevent health problems such as obesity, diabetes, and metabolic syndrome and promotes other positive physiological effects [9,12,28].

A lipid content >1% in starches could indicate the presence of lipid–starch complexes, and therefore their physical and chemical properties could be affected, such as by reducing the swelling of the granule, increasing the gelatinization temperature, and decreasing the digestibility of the starch [3,43]. Despite this, it is important to consider that only saturated monoglycerides and free fatty acids can form a complex with amylose (linear component of starch) and some linear chains (long chains) of amylopectin [44]. Furthermore, it must be taken into account that lipids from starches are classified into two groups: surface lipids and integral lipids [44,45]. Surface lipids are particularly soluble in a cold chloroform/methanol mixture, for example, free fatty acids, free sterols, triglycerides, sterol esters, phospholipids such as phosphatidylcholine and lysophosphatidylcholine, and glycolipids such as mono- and digalactosylmonoglyceride [45]. On the other hand, integral lipids are generally soluble in a hot propanol/water solution, for example, free fatty acids, free sterols, and phospholipids [45]. Therefore, to reduce the lipid content of starches, the use of different solvents could be studied during the isolation process.

Based on the high protein content, the JSS could be used in the production of food supplements. Protein content could also protect the starch granules and thus increase the gelatinization temperature and prevent the entrance of water into the structure [38]. Vázquez-León et al. [17] suggest that both lipid and protein content could explain the differences in thermal properties of starches, as the CCS and JSS in this work (Table 1).

Maniglia and Tapia-Blácido [37] and Jiang et al. [39] suggest that proteins and starch granules tend to form agglomerates; therefore, more energy to affect their structure could be required. In this study, the JSS presented with the most significant and highest protein content (Table 1), and agglomerated starch granules were observed (Figure 1) [17,18,19]. This may thus explain why the ∆H in JSS was higher than that in CCS (Table 1). Du et al. [12] compared the ∆H values between common bean starches (13.1–14.9 J g⁻¹) and CCS (12.8 J g⁻¹) and identified the same behavior observed in this work. Moreover, the peak viscosity temperature of JSS (90 °C) indicates that JSS could be included in pasteurized products without gelatinization [17]. The starch gelatinization is determined by other aspects such as granule size [46], structural characteristics of amylopectin, starch composition, and granule architecture [29,43].

High protein and lipid content in JSS also affected its crystallinity [3,38,43]. Maniglia and Tapia-Blácido [37] compared the crystallinity values between babassu starch and its fiber residues and identified a similar behavior observed in this work. According to Hoover and Ratnayake [29], these differences between starches could also be related to the amount of crystalline regions, the crystallite size, the orientation of the double helices within the crystalline domains, or the extent of the interaction between the double helices.

JSS presented with a higher increase in final viscosity than CCS (Figure 2b); this behavior is related to the amount of amylose released, which tends to form a network with water [10,38]. Even though JSS has less amylose than CCS, the structural characteristics could be different. The amylose present in JSS could have shorter chains than CCS, as it tends to reorganize more quickly by crosslinking the chains, forming a network that must trap more water molecules, and is more stable. Furthermore, the content of lipids, proteins, sugars, and acids could affect the formation of the gel because the binding areas are modified by these components [8].

The presence of lipids in starch has an effect on the swelling of the individual granule because the amylose-lipid complexes require high temperatures to dissociate and, moreover, are insoluble in water [6,43]. The presence of proteins can also influence the water permeation in starch granules [38,39]. Thus, the differences in the $SP$ and $WS$ patterns of the starches evaluated in this work (Figure 2c,d) could be related to the fact that JSS showed higher lipid and protein content than CCS (Table 1). The pasting profile and thermal properties described above are correlated with these results. Despite both starches being evaluated to possess the same $SP$ at 90 °C (Figure 2), the $WS$ is higher for JSS at 90 °C (Figure 2c). This difference could be the result of the different amylose exudation rate of the swollen starch granules [1]. At >90 °C, the amylose could be completely extracted from starch granules; However, some amylose molecules are large and therefore do not leach easily or could also become entangled in the complex structure of starch granules [1,38]. Therefore, the lowest solubility values are associated with the compact structure of the starch granules and a high amylose content [37,38,43]. In this study, the solubility patterns (Figure 2c) are in accordance with the fact that CCS showed a higher amylose content than JSS (Table 1).

The stability results under different cycles of freeze-thaw and refrigeration suggest that JSS would be considered an ingredient for both refrigerated and frozen food applications, as ice cream, frozen batter, soup, sauce, cream-based products, and desserts [2,47]. Srichuwong et al. [47] reported that syneresis was not observed for starch gels of waxy and normal japonica rice and cassava up to the fifth, third, and first cycles, respectively. The authors suggests that the gels from starches with a high distribution of amylopectin branch chains with a degree of polymerization 6–12 (APC ratio: 0.432–0.457) and small apparent amylose content (AAC: 0–13%) are more resistant to syneresis than the others.

On the other hand, the high protein content in some starches would be favorable for their application as wall materials in encapsulation by spray drying [16,17], since these macromolecules can be applied together to improve the encapsulation efficiency and/or promote the formation of spherical aggregates [18,19,48]. In general, the JSS granules without the presence of agglomerates could be considered small according to Singh et al. [6], who reported that the average size of individual CCS granules ranges from 1 to 7 µm for small and 15 to 20 µm for large granules. These results are interesting since the smaller size and the formation of spherical agglomerates during the spray-drying process could be factors that improve the encapsulation efficiency of bioactive compounds.

4.2. Evaluation of Jinicuil Seed Starch as Wall Material

JSS showed small granules and high protein content (Figure 1d and Table 1), so it could be useful for micro- or nano-encapsulation by spray drying of bioactive compounds [17,18,26]. For these reasons, it was decided to evaluate JSS as wall material during spray drying of ascorbic acid; this compound is thermolabile and is used commonly to evaluate high-temperature treatments [17,41].

Hoyos-Leyva et al. [26] suggest that protein values in starches of ~5–7% tend to flocculate feed mixtures, so the operation of the nozzle can be affected and hinder the formation of spherical aggregates. The proteins can form complexes with starch because they have functional groups with positive charges, while the hydroxyl groups of starch have negative charges, leading to the formation of aggregates, which in aqueous solutions are unstable and tend to precipitate. This phenomenon could affect the process yield, as the results obtained with JSS suggest, which has a higher protein content (20.93 ± 1.54% db). The proteins are polymers with interesting functional properties since they are capable of solubilizing in various solvents; they also are good emulsifiers and have the property of forming a film. However, protein values <5% w/w are sufficient to increase the product yield [40]. Therefore, a reduction of protein in JSS could be evaluated to understand its effect on the spray-drying process yield. Process yields could also be increased with the addition of a flow regulator (e.g., silicon dioxides) or conventional wall materials (e.g., maltodextrins), as suggested by the results obtained by Vázquez-León et al. [30]

The encapsulation efficiency values (65.74 ± 1.47–81.84 ± 0.68%) obtained with JSS in this work were higher than those reported by Hoyos-Leyva et al. [26], when taro starch was used to encapsulate ascorbic acid (20.9 ± 0.30%) by spray drying (Tin, 145 °C; Tout, 80 °C; starch:compound ratio, 10:1). The authors attributed the low value of encapsulation efficiency to the porous structure of taro starch spherical aggregates. Spherical aggregates more sealed with JSS may be obtained under the conditions evaluated, which avoid the thermal degradation of ascorbic acid during spray drying and allow less release in water dispersion [17,49].

Gonzalez-Soto et al. [20] and Romero-Hernandez et al. [49] suggest that the spherical aggregates from starches are structures with high potential application for encapsulation of bioactive components by spray drying. In this sense, some bonding agents have been used, e.g., carboxymethyl cellulose and gelatin [18]. Gonzalez-Soto et al. [20] reported that the content of protein (5–7%) in taro starch is sufficient to form spherical aggregates without the addition of binding agents. In the present work, JSS showed a higher protein content (20.93 ± 1.54% db); however, it did not show as high of a formation of spherical aggregates as taro starch. This suggests that the properties of the proteins from starches are important factors to consider. In JSS encapsulation, the addition of a binding agent may be necessary to increase spherical aggregates or to evaluate different levels of protein content in the starch to define a technical limit.

5. Conclusions

The partial characterization of JSS, an unconventional starch source, suggests that it may have potential applications as an ingredient in food systems and other industries. However, a study on the optimization of starch isolation is necessary to increase the recovery yield. Moreover, the presence of protein and small particles suggests that JSS could be used as a wall material for microencapsulation purposes. Due to the protein content, the spray drying of JSS produced spherical aggregates and allowed a high encapsulation efficiency of a thermolabile compound (L-ascorbic acid); however, low values in the process yield were also observed. Thus, a systematic study based on the protein:starch ratios to understand the synergism of these biological macromolecules and its impact during encapsulation by spray drying should be carried out. Spherical aggregates of JSS can be an alternative for the microencapsulation of substances used in the food and pharmaceutical industries, but bioavailability assays of the microcapsules must be considered to demonstrate their feasibility.