Cultivars and Fruit Part as Differentiating Factors of Physicochemical Characteristics of Mango Starches

Abstract

Fruit production has increased, which has led to an increase in fruit wastage, opening up new opportunities for the use of non-standard fruits as starch sources. Herein, the physicochemical properties of mango starches isolated from the pulp and kernel of four cultivars were investigated. The pulp starches showed higher purity with total starch ranging from 97.84 to 98.09% (dry basis). The kernel starches had a higher percentage of other components (ash, fiber, lipids, protein, sugars). The main mineral in the starches was potassium (0.37 to 1.32 g/kg). Pulp starches were circular and smaller (15–79 to 16.70 µm) and kernel starches were oval and larger (19.75 to 25.33 µm). Differential scanning calorimetry and rapid viscosity studies showed that the kernel starches had higher gelatinization properties. The mango starches were A-type with varying crystallinity levels (28.37–32.35%). PCA analysis showed the greater impact of gelatinization properties on the grouping of cultivars. These findings would be useful for adding commercial value to mango agricultural and industrial waste and for industries in terms of using the starch as an ingredient in food products and other industrial applications.

1. Introduction

The starch market is continuously growing owing to the intrinsic characteristics of the applications of this polymer in different industrial sectors. According to Mordor Intelligence, the global industrial starches market was valued at USD 51,496.8 million in 2021, and it is projected to reach USD 70,469 million in 2027, registering a CAGR of 5.40% during the forecast period (2022–2027) [1]. Associated with this growth is the search for starches with different properties, which, in large proportion, have been met by different modification techniques. However, more attention has been paid to starches obtained from non-conventional sources owing to the issue of clean label food products and sustainability aspects, including fruits and residues of industrial processing [2,3].

The starch market for the food industry involves the differentiation of chemically modified starches as additives, and physically modified or natural starches as ingredients. Therefore, in parallel with the growth of the starch market, the clean label food ingredients market is expected to reach $47.50 billion by 2023 with a compound annual growth rate of 6.8%, which values natural starches with differentiated properties [3].

Mango (Mangifera indica L.) is an important tropical commercial fruit. Brazil stands out among the world’s major producers, with the production of 1.57 million tons of fruit harvested in an area of 71,800 hectares in 2020. In Brazil, mango is cultivated in 21 states, with the Northeast region responsible for 78.5% of national production, followed by the Southeast with 20.7%. The states of Pernambuco (624.6 thousand tons), Bahia (470.5 thousand tons), and São Paulo (217.2 thousand tons) are the three largest national producers [4].

Mango is a highly perishable fruit, and this characteristic, combined with improper handling of the product during its production, harvest, transport, storage, and handling conditions until the product reaches the final consumer, has generated great losses for Brazilian mango agribusiness. Fruits that do not meet the quality requirements due to skin blemishes, small size, and damage are left in the orchards, causing pollution problems, and resulting in a significant decrease in profits [5].

In addition to these losses, considerable amounts of waste are generated during mango processing; between 40% and 60% of the raw material, of which 15 to 20% are seeds. The kernel can vary from 45 to 85% of the total seed weight, representing about 20% of the fruit [6,7].

The pulp of immature mango fruits has high starch content (30–45%, dry basis) and the kernel has about 77% of starch (d.b) [7]. Thus, in the context of sustainability, unripe fruits that were disqualified for the fresh market and processing residues may be potential starch sources.

Starch is a glucose polymer composed of branched amylopectin and linear amylose chains, and its structure and physicochemical properties are fundamental to the quality of starch products. The structural characteristics and physicochemical properties of starch are dependent on several factors linked to the plant of origin, as well as the plant’s growth environment and the conditions under which starch is isolated [8].

In Brazilian and international mango markets, cultivar diversification is important for agronomic aspects, for meeting the different requirements of post-harvest quality attributes, as well as for parameters related to consumer preference. However, characterization of starches from different cultivars and different portions of the fruit is essential for the possible use of unqualified green fruits as a starchy raw material. This study aimed to analyze the physicochemical properties of starches isolated from the pulp and kernels of four mango cultivars. The findings will help broaden the understanding of the properties of mango starches, considering the possibility of industrial processing of the whole fruit or its parts.

2. Materials and Methods

2.1. Mango Cultivars and Location of the Orchard

The mango cultivars used were Keitt, Palmer, Parwin, and Tommy Atkins. The fruits of the four mango cultivars were harvested at the immature stage from mango trees in the experimental orchard of the School of Agriculture, UNESP, in São Manuel city, São Paulo State, Brazil (22°44′28′′ S, 48°34′37′′ W; 740 m a.s.l). The predominant climate type is temperate mesothermal, with rain in the summer and dry climate in the winter, an average temperature of the warmest month above 22°C and an average annual rainfall of 1377 mm. The soil of the area is classified as dystrophic Red Yellow Latosol [9].

The pulp/seed ratios of mango fruits were 6.2 for ‘Keitt’, 4.4 for ‘Palmer’, 4.5 for ‘Parwin’ and 5.89 for ‘Tommy Atkins’.

2.2. Isolation of Starches from Mango Pulp and Kernel

After harvesting the immature fruits (4 to 6° Brix) of the four mango cultivars, approximately 40 kg of fruit per cultivar was selected. These were separated into four batches consisting of repetitions for the isolation and characterization of the starches.

Starch extraction was started by washing the fruits in water, peeling, and separating the pulp and kernel manually. The extraction of starches from the pulp and kernel of the mango fruit followed the methodologies of Bello-Perez et al. [10] and Ferreira et al. [11] respectively, with few modifications.

Mango pulps were immersed in a sodium sulfite solution (1 g/L) and then macerated for 2 min in a low-speed blender (1:1 pulp/solution). The homogenate was sieved (0.250 mm and 0.088 mm) and the residue retained on the sieves was washed with distilled water and sieved. This step was repeated three times. The solid residue was discarded. The starchy juice was decanted for 12 h at 4 °C and the supernatant was discarded. The surface of the decanted starch was scraped with a spatula and the settled starch was dehydrated in a convection oven at 40 °C for 48 h.

Kernels were cut into pieces (1 cm³) and then submerged in a 0.5% sodium bisulfite solution for 24 h (1:2 kernel: solution) at 4 °C. After this period, the extraction and purification of the starch proceeded as described for the isolation of starch from the pulp. The dry starches were ground carefully with a mortar and pestle and sieved (0.088 mm). The starches were stored at room temperature (20 to 25 °C) in a glass container.

2.3. Starch Analysis

2.3.1. Chemical Composition

The chemical composition of the starches was determined according to the AOAC methods [12]. Moisture (method 934.06), ash (method 923.03), protein (method 920.152), fiber (method 920.86), lipids (method 923.05), total sugars (method 968.28), and total starch (method 996.11) were measured.

The levels of calcium, zinc, nitrogen, potassium, phosphorus, magnesium, and iron were analyzed in the starches according to the methodologies described by Malavolta et al. [13]. The N concentration was determined via sulfur digestion and subsequent distillation in a semi-micro Kjeldahl steam distiller. The P, K, Ca, Mg, and Fe contents were determined via nitroperchloric digestion with subsequent atomic emission spectrometry with argon plasma.

The amylose content of the starch was determined using the method described by Williams et al. [14].

2.3.2. Morphology and Granule Size

The shapes of the starch granules were analyzed using a scanning electron microscope (Quanta 200 model, FEI Company, Hillsboro, OR, USA), as described by Mesquita et al. [15]. The powdered samples were sprinkled on double sided sticky tape placed on aluminum stubs and covered with a thin layer of gold in metallizer BAL-TEC SCD 050 for 220 s. The images were viewed, selected and saved by the software coupled to the equipment.

The size of the starch granules was determined using laser diffraction spectroscopy (Mastersizer 2000, Laser Scattering Spectrometer Mastersizer S, model MAM 5005—Malvern Instruments Ltd. Malvern, UK). Starch samples (0.10 to 0.15 g) were collected with the tip of a spatula and placed at the bottom of a glass test tube. About 10 mL of distilled water were slowly added and the samples were shaken in a tube shaker at 1750 rpm for 10 s. About 1.5 to 2 mL of the diluted sample was pipetted for analysis. Volume size distribution of the particles was obtained using a computer program supplied by the manufacturer (Malvern Application, version 5.60) and the average particle size was expressed as volume mean diameter (D _{[4, 3]}) in micrometer.

2.3.3. Color

Instrumental color was determined by direct reading using a digital colorimeter (CR 400, Konica Minolta, NJ, USA). It was used the illuminant D₆₅. The color of starches was expressed as the average of three L*, a*, and b* readings, where L* stands for brightness, +a* redness, −a* greenness, +b* yellowness, and −b* blueness. A white calibration plate was used to standardize the equipment prior to color measurements. The yellowness index was derived from the L* and b* measurements (YI = 142.86 (b*)/L*). It was used the illuminant D₆₅ [16].

2.3.4. X-ray Diffraction Pattern

The diffraction patterns of the starch samples were measured using an X-ray diffractometer (Rigaku Miniflex 300, Tokyo, Japan) with Cu monochromatic radiation, line K, L = 1542 Å, using glass sample port. Starches samples were preconditioned in a desiccators for 10 days with a saturated solution of BaCl₂ (Barium chloride, 25 °C, aw = 0.9). Samples were analyzed from 3° to 40° in 2θ with a scanning speed of 1°/min and the conditions of use were 30 kV and 10 mA [15]. The relative crystallinity was quantitatively determined according to the method of Nara and Komiya [17] using Origin software version 7.5 (version 7.5, Microcal Inc., Northampton, MA, USA). The plots were smoothed using the ‘Adjacent Averaging’ method.

2.3.5. Swelling Power (SP) and Solubility (SS)

The swelling power and solubility of the starches were analyzed following the methodology described by Schoch [18]. The swelling power and solubility of starches were analyzed following the methodology described by Schoch [18] with adaptations. Briefly, 0.2 g of starch was weighed into centrifuge tubes and 20 mL of distilled water added. The tubes were shaken and covered with plastic caps. The tubes were heated in a water bath for thirty minutes at temperatures of 55, 65, 75, 85 and 95 °C. The cooled samples were then centrifuged (2500 g, 20 min). The precipitated slurry was separated from the supernatant and weighed. Both phases were dried at 105 °C for 24 h and the dry solids in the precipitated slurry and supernatant were calculated.

SP (g/g) = Weight of the wet sample/Weight of the sample—weight of the dried supernatant

SS (%) = Weight of the dried supernatant/Weight of the sample × 100.

2.3.6. Pasting Properties

The pasting properties of mango starches were analyzed using a Rapid Visco Analyzer (RVA), 2122792 series (RVA-4500, Newport Scientific Pty. Ltd., Warriewood, Australia), using Thermocline for Windows, version 3.0. For the analysis, 3 g of each sample was weighed according to their respective moistures, adding approximately 25 g of water to reach a concentration of 10% starch, and were placed in the sample holder of the equipment. For approximately 10 s, the mixture was stirred at 960 rpm (160 rpm during the test). The temperature program used was STD 1. The samples were held at 50 °C for 1 min, followed by heating from 50 °C to 95 °C at a rate of 6 °C min⁻¹; holding at 95 °C for 5 min, and cooling at 50, at 6 °C min⁻¹. The equipment generated viscosity in Rapid Visco Units (RVU), in which one unit is equivalent to 12 cP.

2.3.7. Thermal Properties

The thermal properties of the starches were determined using a differential exploration calorimeter (DSC Pyris 1, Perkin Elmer, Norwalk, CT, USA) [15]. Starch samples (2.0 mg, dry basis) were weighed into aluminum pans, mixed with deionized water (6 μL) and sealed in a universal press (Perkin Elmer, Norwalk, CT, USA). The sealed containers were held for 12 h at room temperature and then heated at a rate of 10°C min⁻¹ at 25 to 125 °C. An empty aluminum sample port was used as a reference. The equipment was calibrated with indium.

2.4. Data Analysis

Data were submitted to analysis of variance (ANOVA) and compared by using Tukey’s test at 5% significance level, with STATISTICA 8.0 software. Principal component analysis (PCA) was performed using MINITAB 17 software to correlate and discriminate the varieties and to identify the relationships among the different components.

3. Results and Discussion

3.1. Chemical Composition, Minerals and Amylose

Brazilian regulations for starches establish maximum moisture limits of 15% for cereal starch, 18% for cassava starch, and 21% for potato starch. In addition, legislation requires 80% as a minimum for the starch content and a maximum value of 0.5% for ash (wet basis). All mango starches had moisture and ash contents within the limits established by the Brazilian regulations (

Table 1. Chemical composition of mango starches from different cultivars.

Variables (g/100 g)		Keitt	Palmer	Parwin	Tommy Atkins
Moisture	Pulp	8.66 ± 0.14 Ba	8.67 ± 0.07 Ba	10.93 ± 0.02 Aa	8.91 ± 0.02 Bb
	Kernel	7.76 ± 0.17 Cb	8.94 ± 0.01 Ba	9.90 ± 0.03 Ab	9.87 ± 0.05 Aa
	Dry basis
Ash	Pulp	0.03 ± 0.00 Ca	0.04 ± 0.00 Ba	0.05 ± 0.00 Aa	0.03 ± 0.00 Ca
	Kernel	0.03 ± 0.00 Aa	0.03 ± 0.00 Ab	0.03 ± 0.00 Ab	0.03 ± 0.00 Aa
Fiber	Pulp	0.13 ± 0.04 Bb	0.19 ± 0.02 Ab	0.20 ± 0.01 Ab	0.21 ± 0.03 Ab
	Kernel	0.29 ± 0.02 Aa	0.27 ± 0.04 Aa	0.26 ± 0.02 Aa	0.31 ± 0.02 Aa
Lipids	Pulp	0.44 ± 0.01 Bb	0.44 ± 0.02 Bb	0.75 ± 0.08 Ab	0.41 ± 0.06 Bb
	Kernel	3.74 ± 0.02 Ca	4.26 ± 0.07 Aa	3.97 ± 0.06 Ba	4.36 ± 0.08 Aa
Protein	Pulp	0.47 ± 0.06 Bb	0.68 ± 0.06 Ab	0.61 ± 0.06 Ab	0.71 ± 0.02 Ab
	Kernel	1.57 ± 0.14 Aa	1.53 ± 0.04 Aa	1.48 ± 0.03 Aa	1.61 ± 0.04 Aa
Sugars	Pulp	0.79 ± 0.02 Bb	0.97 ± 0.03 Ab	0.85 ± 0.04 Ab	0.66 ± 0.02 Bb
	Kernel	2.57 ± 0.10 Ba	3.22 ± 0.03 Aa	2.97 ± 0.05 Aa	3.12 ± 0.06 Aa
Starch	Pulp	97.94 ± 0.08 Aa	97.64 ± 0.21 Aa	98.09 ± 0.15 Aa	98.03 ± 0.18 Aa
	Kernel	90.41 ± 0.08 Ab	89.46 ± 0.11 Ab	89.12 ± 0.17 Ab	89.84 ± 0.11 Ab
Amylose	Pulp	17.17 ± 0.09 Bb	16.20 ± 0.12 Cb	18.44 ± 0.04 Ab	18.95 ± 0.01 Ab
	Kernel	27.38 ± 0.13 Aa	25.82 ± 0.10 Ba	25.91 ± 0.03 Ba	27.98 ± 0.04 Aa
	Minerals (g/Kg)
P	Pulp	0.04 ± 0.00 Cb	0.13 ± 0.01 Bb	0.32 ± 0.02 Aa	0.06 ± 0.00 Cb
	Kernel	0.16 ± 0.01 Ca	0.16 ± 0.01 Ca	0.28 ± 0.01 Bb	0.35 ± 0.02 Aa
N	Pulp	0.02 ± 0.01 Cb	0.32 ± 0.01 Aa	0.27 ± 0.01 Ba	0.06 ± 0.01 Cb
	Kernel	0.14 ± 0.00 Ca	0.17 ± 0.01 Cb	0.27 ± 0.02 Ba	0.35 ± 0.02 Aa
K	Pulp	0.88 ± 0.01 Ba	0.78 ± 0.01 Ca	1.32 ± 0.01 Aa	0.99 ± 0.02 Ba
	Kernel	0.48 ± 0.00 Ab	0.51 ± 0.01 Ab	0.37 ± 0.01 Bb	0.43 ± 0.02 Bb
Ca	Pulp	0.08 ± 0.01 Cb	0.12 ± 0.01 Bb	0.17 ± 0.01 Ab	0.13 ± 0.02 Ba
	Kernel	0.15 ± 0.01 Ba	0.17 ± 0.01 Ba	0.22 ± 0.02 Aa	0.15 ± 0.02 Ba
Mg	Pulp	0.05 ± 0.00 Bb	0.04 ± 0.00 Bb	0.09 ± 0.00 Aa	0.06 ± 0.00 Bb
	Kernel	0.08 ± 0.00 Aa	0.08 ± 0.00 Aa	0.09 ± 0.00 Aa	0.08 ± 0.00 Aa
Fe	Pulp	0.006 ± 0.00 Aa	0.006 ± 0.00 Aa	0.004 ± 0.00 Ba	0.002 ± 0.00 Cb
	Kernel	0.004 ± 0.00 Bb	0.005 ± 0.00 Ab	0.004 ± 0.00 Ba	0.004 ± 0.00 Ba

Means followed by the different capital letter in the row and lowercase in the column for each component are significantly different (p < 0.05) by Tukey’s test.

).

The purity of the starch is determined as the total starch content. Starches isolated from the pulp of mango cultivars had total starch from 97.84 to 98.09% and lower levels of other components (ash, fiber, lipids, protein, sugar) (1.86 to 2.46%) than those isolated from the kernel (8.20 to 9.43%), indicating higher purity (Table 1).

The moisture and starch contents of the kernel starches were similar to those presented by Guo et al. [19], who studying the physicochemical characteristics of starches isolated from kernels of different fruits (jackfruit, longan, loquat, litchi, and mango) observed 10.8% of moisture and 84.7% of starch (wet basis) for mango starch. Moisture plays an important role in determining the shelf-life of product.

The effects of cultivar on chemical composition have also been reported in other studies. Bello-Perez et al. [10] observed moisture of 6.4 and 9.0% for starch from two mango cultivars; ash, 0.4 and 0.26%; lipids, 0.2 and 0.8%; and protein, 1.8 and 2.6% (dry basis). Mango kernel starch differs from conventional starch in chemical composition, showing higher ash content (2.3 to 3.2%) than corn and cassava starches, less protein (2.1 to 3.1%) than corn and rice, and less lipids (5.3 to 5.5%) than corn, and higher than cassava and rice starches [20].

Endogenous proteins on the surfaces of starch granules and the inner walls of surface pores and channels are known as granule-associated proteins. Their presence affects the crystallinity, digestibility, and physicochemical properties of starch [21]. Sugars have significant effects on starch retrogradation, with disaccharides having a greater effect than monosaccharides [22]. Lipids mainly form complexes with amylose, while amylopectin hardly interacts with lipids [23].

The importance of the mineral content in starches has been discussed in terms of cross-linking reactions affecting paste properties, as well as starch being a possible carrier for minerals in food products (fortified starches). Mineral nutrients are essential, and the dietary intake of potassium, phosphorus, magnesium, calcium and iron is necessary for good health [24,25,26].

In general, the starches isolated from fruit kernels showed higher total mineral levels than those from mango pulp (Table 1). For both starches, the mineral present in greater amounts was potassium (K), with higher levels in the pulp starches especially that isolated from the Parwin cultivar.

Starches isolated from ‘Parwin’ (pulp and kernel) and ‘Tommy Atkins’ (kernel) had considerable phosphorus content. Phosphorus bound to starch alters the ability to bind with water due to its ionic organization, interfering with gelatinization and retrogradation properties [15].

Compared to potato starch, mango starch showed lower phosphorus content, but potassium levels were similar to those reported for some potato starches (P = 0.510–1.125 g/kg and K = 0.048–1.061 g/kg). Iron was the lowest mineral found in mango starch, with contents lower than those reported for potato starch (16 ppm). Industrial potato starches have varying levels of potassium (500 to 900 ppm), calcium (50 to 200 ppm) and magnesium (80 to 150 ppm) [26]. Therefore, mango starch contained considerable amounts of these minerals (Table 1).

In potato starch, an inverse relationship between the cation content (potassium, calcium, magnesium, and sodium) and starch granule size has been reported [24]. This relationship was also observed in this study for starches from mango pulp, with a smaller average size and higher potassium content (Table 1 and

Table 2. Granule size, color and crystallinity of mango starches.

		Keitt	Palmer	Parwin	Tommy Atkins
D [4, 3] (µm)	Pulp	15.79 ± 0.01 Cb	16.24 ± 0.01 Bb	16.07 ± 0.01 Bb	16.70 ± 0.01 Ab
	Kernel	24.40 ± 0.01 Aa	19.75 ± 0.01 Ba	24.39 ± 0.01 Aa	25.33 ± 0.01 Aa
L*	Pulp	88.24 ± 0.7 Aa	86.88 ± 0.5 Ba	81.70 ± 0.2 Ca	78.15 ± 0.3 Ca
	Kernel	80.32 ± 0.9 Ab	80.60 ± 0.3 Ab	78.88 ± 0.6 Aa	75.88 ± 0.3 Bb
a*	Pulp	3.41 ± 0.1 Cb	3.71 ± 0.1 Bb	4.08 ± 0.2 Ab	3.16 ± 0.1 Cb
	Kernel	5.23 ± 0.2 Aa	5.19 ± 0.1 Ba	5.49 ± 0.1 Aa	5.60 ± 0.1 Aa
b*	Pulp	0.55 ± 0.05 Bb	0.35 ± 0.02 Bb	0.11 ± 0.0 Cb	2.89 ± 0.13 Ab
	Kernel	2.72 ± 0.1 Ba	2.18 ± 0.13 Ca	2.99 ± 0.12 Ba	4.51 ± 0.1 Aa
Yellowness index	Pulp	0.89 ± 0.06 Bb	0.58 ± 0.12 Cb	0.19 ± 0.03 Db	5.28 ± 0.11 Ab
	Kernel	4.84 ± 0.04 Ba	3.86 ± 0.14 Ca	5.41 ± 0.13 Ba	8.49 ± 0.12 Aa
Crystallinity (%)	Pulp	31.70 ± 0.12 Aa	32.24 ± 0.20 Aa	32.35 ± 0.27 Aa	30.31 ± 0.26 Ba
	Kernel	28.37 ± 0.03 Cb	29.35 ± 0.34 Bb	30.45 ± 0.38 Ab	29.84 ± 0.13 Aa

Means followed by the different capital letter in the row and lowercase in the column for each component are significantly different (p < 0.05) by Tukey’s test.

).

The presence of different minerals in starches can interfere with gelatinization properties. Additionally, calcium, magnesium, and other multivalent cations appear to cross-link phosphate ester groups on adjacent amylopectin chains by ion forces, changing the pasting properties. Lastly, a high level of iron in starch is related to low peak viscosity and breakdown [25,26].

The intrinsic characteristics of the chemical composition of the parts of the fruit that are sources of starch determined its purity and showed that kernel starches have a protein and lipid content closer to cereal starches and that pulp starches have a higher degree of purity. Lower contents of other components make the starch whiter, more neutral, and less prone to complexation.

Mango starches have a high mineral content, and this characteristic can be valued both for applications in fortified foods and can also determine uses by the chemical and pharmaceutical industries, due to the possibilities of different complexations. As consumers place more emphasis on their health, the demand for starch-based food products that help boost immunity is likely to increase.

Starches isolated from mango pulp had lower amylose content than those isolated from mango kernels. Specifically, starch from the pulp of the Palmer cultivar had lower amylose content (Table 1). The amylose content of mango starches varies from 12.9 to 35.06% for those isolated from the pulp [10,27] and from 15.2 to 33.6% [28] for kernel starches, which shows the interference of cultivars and fruit portion.

Compared to the levels of amylose from conventional sources, the starches isolated from mango pulp were similar to the levels of cassava (19.1%) [29] and white rice starches (18.61%) [16] and the kernel starches were similar to those corn starch (25.16%) [30].

The differences observed in amylose content add commercial value to mango starches. Starches with higher amylose content, such as those from ‘Tommy Atkins’ and ‘Keitt’ kernels, may favor its use in products for diabetics and may have special industrial applications, including films, coatings, and biodegradable flexible packaging. Starches with lower amylose contents is desirable to extend the shelf life and cold stability in food products and can also favor applications in animal feed

3.2. Morphology and Granule Size

Starch granules occur in different shapes and sizes. Starches isolated from mango pulp had a predominantly circular shape with elongated and oval granules. Starches from the kernel showed a mixture of granules of various shapes, with oval and ellipsoid shapes, regardless of the cultivar (Figure 1). However, some granules were irregularly shaped, semi-spherical, or truncated. The crinkle-surface observed for kernel starch might be due to the extraction method used [31].

The shapes of the starch granules are in agreement with those reported in previous studies, highlighting the influence of the cultivar, fruit portion, and isolation method [31,32,33].

Analysis of the average size of the starches showed the interference of two factors. Regardless of cultivar, starches isolated from mango kernels were larger, ranging from 19.75 to 25.33 µm. Starches from the pulp varied between 15.79 and 16.70 µm for all cultivars. ‘Palmer’ starches were differentiated by the smaller size of those isolated from the kernel, as well as by the smaller difference between the parts of the fruit, which is interesting for the processing of entire fruits (Table 2).

Studies showed different sizes for starches isolated from mango kernels and pulps, which is related to cultivars, fruit maturity stage, extraction methods and methodology of analysis [7,32,33].

The influence of the extraction methods of starches from mango kernels on the shape and size of granules was discussed by Bangar et al. [7]. Starches extracted by centrifugation were larger and oval-shaped; starches extracted by alkaline, sedimentation, and distillation methods were smaller and irregularly shaped.

Dhital et al. [34] studied the granule size characteristics of maize and potato and found that smaller granules are related to the physiological phases of different parts of the plant and indicate granules that are still able to develop.

Compared with traditional starches, mango pulp starches are similar to those isolated from cassava in terms of morphology and size. Starches isolated from kernels are similar to those isolated from potatoes but have a smaller average size. Wide variations in size for traditional starches have been reported, with corn starch ranging from 5.02 to 39.91 µm [35], rice from 1.11 to 19.5 µm [36], potato from 5 to 100µm [37] and cassava from 2 to 32 µm [38].

Differences in average granule size may suggest different applications for mango starch. It is important to emphasize that, in the industrial processing of unqualified fruits, the percentage of seeds and pulp of the cultivar may interfere with the size distribution of the starch granules when the entire fruit is processed.

3.3. Color

Starch quality and acceptance by the consumer market are mainly evaluated by the color of the products. Color data for mango starches showed that L, which reflects the relative lightness or darkness of the products, ranged from 97.94 to 98.09 for pulp starches and 89.12 to 90.41 for almond starches (Table 2). Among the cultivars, the starch from the pulp of the cultivar Keitt was the lightest, and those from the pulp and kernel of the ‘Tommy Atkins’ were less clear.

All starches had positive a* values, indicating the presence of red color, with a higher presence in kernel starches. Starches had a positive b*, with a higher value for kernel starch, which is due to the synthesis of carotenoids in mango seeds [39].

The yellowness index (YI) ranged from 0.89 to 5.28 for the pulp starches, with starch extracted from ‘Tommy Atkins’ having the highest value and that from ‘Parwin’ the lowest. Almond starch YI ranged from 3.86 to 8.49 with ‘Tommy Atkins’ starch showing the highest index.

Mango starches regardless of the part of the fruit had lower luminosity than starches isolated from different banana cultivars, which presented L* ranging from 92.55 to 95.71, but lower YI, which ranged from 8.09 to 9.67 for banana starches. This difference is due to banana starches having a higher b* (5.42 to 6.26) [40]. High lightness and low yellowness are desired color quality factors for starches.

3.4. X-ray Diffraction Pattern and Crystallinity

Mango starch granules from pulp and kernel have strong diffraction peaks near diffraction angles of 15°, 17°, 18°, and 23°, indicating an A-type crystalline structure (Figure 2). This crystallinity polymorph is commonly observed in cassava and cereal starches [35,36,38,41] and has also been observed in mango starches isolated from different cultivars [10,20,28]. The A-type polymorph is related to the presence of shorter amylopectin chains and has a greater number of branches than the B-type polymorph, forming a lower crystalline structure [41].

Except for starches isolated from the ‘Tommy Atkins’, the crystallinity of the pulp starches was higher than that of kernel starches, which is in agreement with the lower amylose content of these starches (Table 2). In addition to amylose contents, the differentiation of mango starches isolated from pulps and kernels may have been influenced by the contents of non-starch components that may interfere with the regular spatial arrangement of the macromolecules [16].

Saeaurng and Kuakpetoon [20] compared starches isolated from mango kernels with commercial starches and observed crystallinities higher than 40% for starches from three mango cultivars, which were higher than tapioca (22.52%), corn (19.32%), and rice (19.12 and 19.22%) starches.

Starch crystallinity affects the physical, mechanical, and technological properties of various starchy products, and is therefore important for product development, quality, and process control.

3.5. Swelling Power and Solubility

The swelling power (SP) and solubility (SS) show the magnitude of the interaction between the networks within the crystalline and amorphous areas of the starch granules. The SP and SS of mango starches increased with increasing temperature and decreased at higher temperatures, indicating disruption of the granules (Figure 3,

Table 3. Solubility and swelling power of mango starches.

		Keitt	Palmer	Parwin	Tommy Atkins
		Solubility (%)
55 °C	Pulp	16.76 ± 0.15 Aa	16.20 ± 0.12 Aa	16.43 ± 0.09 Aa	16.19 ± 0.18 Aa
	Kernel	15.76 ± 0.13 Ab	15.34 ± 0.11 Ab	15.26 ± 0.14 Ab	15.29 ± 0.10 Ab
65 °C	Pulp	22.58 ± 0.22 Aa	22.45 ± 0.19 Aa	22.25 ± 0.16 Aa	22.16 ± 0.13 Aa
	Kernel	18.70 ± 0.15 Ab	18.51 ± 0.13 Ab	18.13 ± 0.09 Ab	18.52 ± 0.17 Ab
75 °C	Pulp	23.19 ± 0.26 Aa	23.41 ± 0.21 Aa	23.86 ± 0.14 Aa	23.18 ± 0.20 Aa
	Kernel	23.44 ± 0.17 Aa	23.35 ± 0.16 Aa	23.86 ± 0.14 Aa	23.51 ± 0.11 Aa
85 °C	Pulp	16.70 ± 0.13 Aa	16.91 ± 0.15 Aa	16.36 ± 0.09 Aa	16.80 ± 0.08 Aa
	Kernel	16.07 ± 0.22 Aa	16.26 ± 0.24 Aa	16.29 ± 0.27 Aa	16.63 ± 0.18 Aa
95 °C	Pulp	15.39 ± 0.12 Aa	15.18 ± 0.13 Aa	15.74 ± 0.12 Aa	15.73 ± 0.15 Aa
	Kernel	13.42 ± 0.07 Ab	13.78 ± 0.03 Ab	13.84 ± 0.08 Ab	13.46 ± 0.04 Ab
		Swelling power (g/g)
55 °C	Pulp	2.06 ± 0.05 Aa	2.18 ± 0.01 Aa	2.25 ± 0.03 Aa	2.09 ± 0.04 Aa
	Kernel	1.74 ± 0.02 Ab	1.85 ± 0.04 Ab	1.52 ± 0.07 Bb	1.89 ± 0.09 Ab
65 °C	Pulp	8.40 ± 0.13 Aa	8.57 ± 0.18 Aa	8.51 ± 0.22 Aa	8.80 ± 0.32 Aa
	Kernel	3.79 ± 0.20 Ab	3.73 ± 0.17 Ab	3.22 ± 0.21 Ab	3.57 ± 0.19 Ab
75 °C	Pulp	14.86 ± 0.15 Ab	14.12 ± 0.14 Ab	14.35 ± 0.13 Ab	14.21 ± 0.08 Ab
	Kernel	15.39 ± 0.11 Aa	15.34 ± 0.09 Aa	15.20 ± 0.12 Aa	15.21 ± 0.05 Aa
85 °C	Pulp	14.41 ± 0.10 Aa	14.54 ± 0.09 Aa	14.63 ± 0.15 Aa	14.29 ± 0.16 Aa
	Kernel	13.72 ± 0.09 Ab	13.07 ± 0.07 Ab	13.08 ± 0.12 Ab	13.51 ± 0.11 Ab
95 °C	Pulp	12.16 ± 0.08 Aa	12.14 ± 0.15 Aa	12.07 ± 0.10 Aa	12.11 ± 0.13 Aa
	Kernel	9.94 ± 0.05 Ab	9.24 ± 0.07 Ab	9.16 ± 0.11 Ab	9.24 ± 0.09 Ab

Means followed by the different capital letter in the row and lowercase in the column for each component are significantly different (p < 0.05) by Tukey’s test.

).

Banana starches showed low swelling power (below 3 g/g) at temperatures of 55 °C and 65 °C [40]. Comparatively, mango starches are less resistant to swelling, indicating weaker associative forces.

The factor with the greatest effect was the part of the fruit, with kernel starches showing the lowest SP at the lowest temperatures. This result agrees with the higher levels of proteins, lipids, and amylose in these starches (Table 1), which are factors that restrict the initial swelling power.

The increase in the SP and SS of mango starches with increasing temperature has also been observed in other studies, including Bello-Perez et al. [10]. Their study analyzed pulp starches from three mango cultivars, and they observed that when the temperature increased, the swelling power and solubility increased, and that the starches had higher values than corn starch. Kalaivendan et al. [31] reported swelling power ranging from 5.81 to 10.18 g/g and solubility from 0.8 to 5.29% for mango kernel starches with increasing temperature from 70 to 90 °C.

3.6. Pasting and Thermal Properties

Data on the pasting properties of the mango starches showed that, in general, the starches isolated from the pulps started pasting at an earlier time and exhibited a lower pasting temperature than kernel starches (Figure 4 and

Table 4. Pasting and thermal properties of mango starches.

		Keitt	Palmer	Parwin	Tommy Atkins
	Pasting properties
Peak viscosity (cP)	Pulp	3619 ± 0.74 Ab	3171 ± 0.54 Bb	3373 ± 2.50 Ba	3648 ± 0,40 Ab
	Kernel	4081 ± 1.28 Aa	4040 ± 0.77 Aa	3554 ± 0.04 Ba	3884 ± 0.35 Aa
Breakdown (cP)	Pulp	2553 ± 1.47 Aa	2132 ± 0.60 Bb	2205 ± 2.94 Ba	2332 ± 3.13 Aa
	Kernel	2352 ± 2.65 Aa	2344 ± 1.12 Aa	1850 ± 1.53 Ba	2140 ± 2.08 Ba
Final viscosity (cP)	Pulp	1606 ± 1.32 Bb	1615 ± 0.57 Bb	1706 ± 1.26 Bb	1964 ± 2.46 Ab
	Kernel	2778 ± 0.10 Aa	2733 ± 0.62 Aa	2685 ± 0.24 Aa	2736 ± 3.18 Aa
Set Back (cP)	Pulp	540 ± 1.96 Bb	576 ± 0.86 Bb	538 ± 0.33 Bb	648 ± 0.00 Ab
	Kernel	1048 ± 1.21 Aa	1037 ± 1.16 Aa	981 ± 3.39 Ba	1031 ± 5.63 Aa
Peak Time (min)	Pulp	3.10 ± 0.00 Bb	3.30 ± 0.00 Ab	3.30 ± 0.00 Ab	3.30 ± 0.00 Ab
	Kernel	4.16 ± 1.13 Aa	4.16 ± 1.13 Aa	4.16 ± 1.13 Aa	4.10 ± 0.00 Aa
Pasting temperature (°C)	Pulp	69.42 ± 0.15 Bb	69.82 ± 0.96 Ab	71.07 ± 0.05 Ab	71.02 ± 0.00 Ab
	Kernel	74.32 ± 0.05 Aa	74.65 ± 0.76 Aa	74.65 ± 0.66 Aa	74.37 ± 0.05 Aa
	Thermal properties
To (°C)	Pulp	64.57 ± 0.07 Bb	63.70 ± 0.11 Cb	64.55 ± 0.62 Bb	65.75 ± 0.43 Ab
	Kernel	67.73 ± 0.40 Aa	66.75 ± 0.05 Ba	66.90 ± 0.09 Ba	67.03 ± 0.11 Ba
Tp (°C)	Pulp	68.22 ± 0.05 Bb	66.71 ± 0.29 Cb	67.99 ± 0.56 Bb	69.57 ± 0.47 Ab
	Kernel	72.31 ± 0.0 Aa	71.39 ± 0.05 Ba	71.57 ± 0.15 Ba	71.47 ± 0.22 Ba
Tc (°C)	Pulp	72.37 ± 0.14 Bb	70.34 ± 0.34 Cb	71.79 ± 0.43 Bb	73.40 ± 0.34 Ab
	Kernel	77.22 ± 0.41 Aa	76.29 ± 0.12 Ba	76.05 ± 0.0 Ba	76.22 ± 0.17 Ba
ΔT (°C)	Pulp	7.80 ± 0.07 Ab	6.64 ± 0.22 Cb	7.24 ± 0.19 Bb	7.65 ± 0.09 Ab
	Kernel	9.49 ± 0.82 Aa	9.54 ± 0.17 Aa	9.15 ± 0.08 Ba	9.19 ± 0.05 Ba
ΔH (J/g)	Pulp	12.60 ± 0.24 Aa	13.13 ± 0.69 Aa	11.26 ± 0.89 Bb	10.63 ± 0.20 Cb
	Kernel	12.58 ± 0.55 Ba	13.56 ± 0.88 Aa	12.70 ± 1.04 Ba	12.54 ± 0.17 Ba

Means followed by the different capital letter in the row and lowercase in the column for each component are significantly different (p < 0.05) by Tukey’s test.

). Low pasting temperatures indicated a lower degree of association in the amorphous zones of the granules, while high pasting temperatures have been applied to soups, gravies, baked products, and canned foods [7].

Kernel starches had a higher peak viscosity, final viscosity, and setback than pulp starches; granule size, amylose and phosphorus levels may be among the factors that influence these properties. The ‘Parwin’ kernel starch had a lower viscosity peak and higher heat resistance under stirring, differing from the others. A low setback can determine the applicability in desserts, sauces, yoghurts, emulsified products, and frozen foods, as retrogradation can destabilize and impair quality during storage due to water loss.

Except for the highest breakdown and lowest final viscosity, the variations observed in the pasting properties of starches isolated from mango kernels were close to those reported in a study with other cultivars: when the peak viscosity ranged from 3439 to 3932 cP, the breakdown from 894 to 1118 cP, setback from 823 to 1058 cP, and final viscosity from 3191 to 3952 cP [42].

The endodermal transition of starch can be understood as the influence of interactions between amylose, amylopectin, amylose-lipids, and amylose-amylose. The physicochemical parameters, onset temperature (To), peak temperature (Tp), conclusion temperature (Tc), and enthalpy change (ΔH), are influenced by the molecular architecture of the crystalline region.

Analysis of the thermal properties of mango starches showed variations in gelatinization temperatures and gelatinization enthalpy between cultivars as well as for pulp and kernel (Table 4). The initial temperature (To) of gelatinization of the starches isolated from pulps ranged from 63.70 to 65.75 °C, with the starch from ‘Tommy Atkins’ having the highest temperature. The starches of kernels regardless of cultivar had higher To, which ranged from 66.75 to 67.73 °C, with the starch from ‘Keitt’ having the highest initial temperature. The same behavior was observed at peak temperatures (66.71 to 69.57 °C for pulp and 71.39 to 72.31 °C for kernels) and conclusion temperatures (70.34 to 73.40 °C for pulp and 76.05 to 77.22 °C for kernels).

The initial gelatinization temperatures of the starches were in agreement with the most significant increase in swelling power of the starches between 65 and 75 °C. Similarly, it was possible to verify that the kernel starches had lower swelling power at lower temperatures and higher gelatinization temperatures.

Starches isolated from mango juice showed higher gelatinization temperatures (78.4 °C for ‘Palmer’ and 74.5 °C for ‘Haden’) and were higher than starches from maize (62–75 °C), potato (58–70 °C) and wheat (57–66 °C) [33].

The starches isolated from kernels had the highest temperature range (ΔT), and for the cultivars Parwin and Tommy Atkins, the highest enthalpy changes (ΔH). These results can be due to the higher levels of lipids and proteins in these starches. The formation of starch-lipid complexes with amylose alters the gelatinization properties of starch, decreasing ΔH. The protein-starch interaction results in an increase in the gelatinization temperature of starch [43,44].

The differences observed for the mango starches for enthalpy of gelatinization suggest differences in amylopectin structure. The gelatinization enthalpy reflects the crystalline order and double helix order level of amylopectin [43,44]. The lower ΔH for pulp starches can be attributed to the more homogeneous length of the short amylopectin chains.

Low gelatinization temperatures indicate a lower degree of association in the amorphous zones of the granules, and therefore, less resistance to swelling. Higher temperatures and enthalpy changes (ΔH) reflect stronger or more ordered crystalline molecular structures. Thus, starches with high gelatinization temperatures can be used as thickening and texturizing agents in sauces, soups, gravies, bakeries, and dairy products [7].

Amylopectin chains are divided into short (S) and long (L) chains, with differences in the molar ratio of S/L chains depending on the botanical source [8]. Espinosa-Solis et al. [27] observed for mango starch isolated from pulp of ‘Tommy Atkins’ average branch chain-length of amylopectin of 22.3, with 25.7% of DP 6–12, 46.1% DP 13–24, 11.6% of DP 25–36 and 16.6% of DP ≥ 37. The results of our study indicate that amylopectin in pulp starches may have a higher proportion of short chains, which may contribute to lower gelatinization temperatures and enthalpy.

The morphological, structural, and chemical composition differences of the mango starches affected the paste and thermal properties, and these results are important for the definition of mango cultivars, forms of starch extraction/purification, controls of process and products.

3.7. Principal Component Analysis

PCA was used herein to visualize the variations in the characteristics of the starches obtained from the mango pulp and kernel, accounting for >70% of the variation in the two starch types (Figure 4). In the PCA loading plot, the parameters that approach each other in pairs or groups are positively correlated, while those in opposite directions are negatively correlated, and those in orthogonal directions are independent of each other. The cultivars clustered together in the biplot have similar characteristics.

The pulp starch results showed that the first and second main components (Comp. 1 and Comp. 2) represented 43.67% and 33.01% of variation, respectively, with an accumulated variation of 76.68% (Figure 5a). Regarding the Comp. 1, moisture, starch, protein, and the minerals Ca, K and Mg, amylose, and pasting and thermal properties were located in Quadrants 1 and 2. Pasting and thermal properties contributed to the differentiation of pulp starches from ‘Tommy Atkins’. On the opposite side (Quadrants 3 and 4), Comp. 2 reflects the crystallinity, granule size, color, N, Fe and enthalpy range (ΔH) characteristics that contributed to the differentiation of pulp starches from ‘Palmer’ and ‘Keitt’.

In the PCA of mango kernel starches (Figure 5b), the overall PCA provided 70.01% of the cumulative variance, while Comp. 1 and Comp. 2 accounted for 41.73% and 28.28% of the variance, respectively. Comp. 1 was reflected in Quadrants 1 and 2 and was composed of factors that contributed to the differentiation of the ‘Keitt’ and ‘Palmer’ starches. Calcium level contributed to the differentiation of ‘Parwin’ starch. Starch from ‘Tommy Atkins’ was differed mainly by the yellowness index and phosphorus. Mango fruits are important sources of minerals, and it is interesting to highlight their role in the differentiation of starches.

The results of the PCA allowed identifying a way to identify the factors that could contribute to the choice of cultivars and possible mixtures of starches, which is very useful in the processing of mango fruits.

Based on the different characteristics of mango pulp and kernel starches, we assume that they can be used for different industrial uses, reducing waste and adding value to the crop.

4. Conclusions

Mango starches isolated from pulp and kernels differ substantially in physicochemical characteristics. Pulp starches show lower amylose content, pasting temperature, gelatinization temperature, and enthalpy. Additionally, starches from kernels have larger granules and higher levels of protein, lipids, total sugars, and minerals, with higher final viscosity and setback. Regardless of the part of the fruit in which the starches were isolated, they differed between cultivars, with starches from ‘Keitt’ and ‘Palmer’ being more similar, and ‘Parwin’ and ‘Tommy Atkins’ being more different.

Starch blends are emerging as ways to reduce the use of chemically modified starches. Thus, mango starches can be better explored in other studies in mixtures with traditional starches, as well as in mixtures themselves, mainly for fruits that are not valued for the pulp and juice market due to the bigger seeds.