Evaluation of the Soil Type Effect on the Volatile Compounds in the Habanero Pepper (Capsicum chinense Jacq.)

Abstract

The aim of this research was to evaluate the effect of soil on the concentration of the main volatile compounds in the Habanero pepper (Capsicum chinense Jacq.). Plants were cultivated in three soils named, corresponding to the Maya classification, as Chich lu’um (brown soil), Box lu’um (black soil), and K’ankab lu’um (red soil). The volatile compounds of the peppers were extracted by steam distillation, analyzed by gas chromatography, and reported on a fresh weight (FW) basis. The results indicated that the soil presented a significative effect on the concentration of the volatile compounds evaluated (1-hexanol, hexyl-3-methyl butanoate, 3,3-dimethyl-1-hexanol, cis-3-hexenyl hexanoate). The peppers cultivated in black soil exhibited the highest concentration of 1-hexanol (360.14 ± 8.57 µg g⁻¹ FW), 3,3-dimethyl-1-hexanol (1020.61 ± 51.27 µg g⁻¹ FW), and cis-3-hexenyl hexanoate (49.49 ± 1.55 µg g⁻¹ FW). In contrast, the highest concentration of hexyl-3-methyl butanoate (499.93 ± 5.78 µg g⁻¹ FW) was quantified in peppers grown in brown soil. This knowledge helps us to understand the role of the soil in the aroma of the Habanero pepper and could be used by farmers in the region (Yucatan Peninsula) to select the soil according to the desired aroma characteristics.

1. Introduction

The Habanero pepper (Capsicum chinense Jacq) of the Yucatan Peninsula is regarded as one of the most representative peppers of Mexico due to its cultural, gastronomic, and economic value, and its high potential for export and industrialization [1]. The Habanero pepper is highlighted by its high content of capsaicinoids. Capsaicinoids classifies the Habanero pepper as one of the spiciest peppers in the world [2], which is also distinguished by its aroma and flavor [3]. These are considered attributes that contributed to the designation of origin by the Mexican Institute of Intellectual Property in 2010 (“Chile Habanero de la Peninsula de Yucatan”) [4].

Organoleptic characteristics, such as flavor and aroma, have been shown to play an important role in the acceptability of food products by consumers [5]. The Habanero pepper is not an exception, because one of the most attractive properties of the pepper is the typical aroma, which has been considered a critical quality parameter [6,7]. These organoleptic characteristics that make the Habanero pepper unique, are the result of the concentration and profile of volatile compounds produced in the fruit. In a previous study, Sosa-Moguel et al. [8] reported between 53 and 102 volatile compounds in the Habanero pepper of the Yucatan Peninsula. In this sense, (E)-2-hexenal, 3-methylbutanoate, (Z)-3-hexenyl, hexadecanoic acid, 3,3-dimethylcyclohexane, hexyl-3-methylbutanoate, and hexyl pentanoate are considered as the largest constituents [9]. Therefore, it is important to know the factors that affect the production of these compounds in the Habanero pepper.

The content of metabolites such as capsaicinoides, vitamins, carotenoids and polyphenols in the Habanero pepper is mainly related to the degree of ripeness, the type of soil, and the genetic variety of the pepper [10,11,12]. Previous works have reported only the effect of the genetic variety and degree of ripeness on the profile and concentration of volatile compounds. It was found that the aroma of the Habanero pepper depends on ripeness (unripe or ripe), variety (Jaguar or Mayapan) and method of isolation (simultaneous distillation solvent extraction or headspace solid-phase microextraction) [13]. Despite this, other factors such as soil type have not been previously reported, even though this is a condition that has shown to influence the concentration of certain metabolites in the Habanero pepper, such as capsaicinoids and polyphenols [11,14].

In the region of Yucatan, there have been reported three main soils used for the cultivation of Habanero pepper, called, corresponding to the Maya classification, Chich lu’um (brown soil), Box lu’um (black soil), or K’ankab lu’um (red soil) [15]. These soils are distinguished by being stony, shallow, and highly heterogeneous [16]. However, there are also differences; for example, the black soil has the highest percentage of organic matter (10.93 ± 0.23%) and concentration of nitrogen (52.01 ± 7.05 mg kg⁻¹) and presents the highest electrical conductivity (2.32 ± 0.16 d Sm⁻¹) [11]. On the other hand, the red soil exhibits the highest concentration of calcium (2075.28 ± 29.70 mg kg⁻¹) and iron (6.27 ± 0.21 mg kg⁻¹), while the brown soil stands out for having intermediate chemical characteristics, which make it different from the two other soils [11].

For this reason, the purpose of this study was to analyze the effect of the main soils used in the Yucatan Peninsula for the planting of Habanero peppers on the concentration of the major volatile compounds. The experiment was performed with two Habanero pepper varieties (Mayapan and Jaguar) to two different degrees of ripeness (unripe and ripe). The knowledge generated could help us to understand the role of the soil on the aroma of the Habanero pepper. In addition, this information would help farmers in the region (Yucatan, Peninsula) to select the best soil type according to the desired aroma characteristics.

2. Materials and Methods

2.1. Growing Conditions

The crop of Habanero pepper (Capsicum chinense Jacq.) was established in a greenhouse in CIATEJ Southeast Headquarters (Sierra Papacal, Yucatán in Mexico). The cultivation began on 24 May 2021. For this, seedlings of Habanero pepper from a local nursery in Suma de Hidalgo, Yucatan, Mexico (characterized to use certified seed) with 48 germination days were used. Thirty seedlings per variety/soil type were used, giving a total of 180 seedlings. These were transplanted into polyethylene bags containing 12 kg of the soils from Yucatan: (1) Chich lu’um (brown soil), (2) K’ankab lu’um (red soil), or (3) Box lu’um (black soil). The three soils used in the experiment were acquired from a local distributor from the municipality of Suma de Hidalgo in Yucatan, Mexico. This distributor is responsible for the collection and distribution of these soils to farmers of Habanero pepper. Harvest was carried out at 98 PTD (post-transplant day). Data loggers were positioned throughout the crop to monitor relative humidity, light, and temperature.

Irrigation frequency was maintained twice a week (1 L/bag) during the first 15 days after post-transplant; afterwards, the irrigation frequency was maintained every third day (2 L/bag), in both cases, with water from local well. After 10 PTD, the fertilizer Triple 18 Ultrasol (SQM, Santiago, Chile), composed of potassium (18%), nitrogen (18%) and phosphorus (18%), was used [17]. In addition, a commercial product (Bayfolan^® Forte, Bayer CropScience, Mexico City, Mexico) to supplement micronutrients (Zn, Mg, Ca, Fe, Cu, B, Mn, Co, and Mo) was sprayed on the leaves once a week (1.5 mL L⁻¹). A growth regulator with gibberellin, cytokinin, and auxin (Biozyme^®-TF, Arysta LifeScience, Guatemala City, Guatemala) was also sprayed once a week, after 20 PTD and before floral initiation, at a concentration of 1 mL L⁻¹. Biweekly, the leaves of the lower part of the plant were pruned (under the first knot forming a Y shape).

2.2. Soil Analysis

The cation exchange capacity, permanent wilting point, bulk density, and field capacity of the three soils were evaluated; determinations were conducted in triplicates. The methods used are shown below.

The cation exchange capacity was performed according to the method reported by Chapman [18] with some changes. For this, 10 g of soil was mixed with 250 mL of sodium acetate 1N; subsequently, the sample was washed with 200 mL of isopropanol. Then, the wash was diluted to a volume of 100 mL with ammonium acetate 1N, and then, the displaced sodium was determined by atomic absorption.

Bulk density is defined as the weight of dry soil divided by its volume. It was measured according to the methodology reported by Blake [19]. This was performed using a sampling cylinder of known volume, in which the soil to be analyzed was placed and weighed with a triple-beam balance.

Field capacity is defined as the amount of water that remains in the soil after it has been thoroughly saturated with water and allowed to drain freely [20]. It was determined using the methodology reported by Cassel et al. [20]. The field capacity was determinate using a sandbox at −10 kPa of tension. To make this, the soils samples were previously saturated in a solution of CaCl₂ (5 mmol L⁻¹).

Soil wilt point is defined as the minimum moisture point at which a plant cannot continue to extract water from the soil and cannot recover from water loss even if the ambient humidity is saturated [21]. The measurement of the soil wilt point was calculated using the method reported by Norton [22]. It was determined using the traditional pressure plate apparatus at −1500 kPa of tension.

2.3. Sample Preparation

The peppers were harvested and classified by soil (brown, black, and red), degree of ripeness (unripe and ripe), and variety (Jaguar and Mayapan). The peppers were selected according to the degree of ripeness represented by the color of the fruit; the color parameters used to determine the degree of ripeness are presented in

Table A1. Average color values (L*, a*, b*, and Chroma) of Habanero pepper samples.

Variety	Grade of Ripeness		Soil	L*	a*	b*	Chroma
Jaguar	Unripe		Red	44.8 ± 1.3 b	−12.7 ± 0.6 c	27.8 ± 2.3 de	30.6 ± 2.3 d
			Brown	43.4 ± 1.5 b	−11.8 ± 0.5 c	26.6 ± 2.0 e	29.1± 2.0 d
			Black	43.1 ± 1.5 b	−11.5 ± 0.8 c	26.9 ± 4.2 e	29.2 ± 4.2 d
	Ripe		Red	56.0 ± 0.4 a	26.4 ± 1.4 a	46.7 ± 1.3 a	53.6 ± 1.6 a
			Brown	54.7 ± 1.0 a	19.3 ± 4.4 b	42.4 ± 2.5 b	46.7 ± 3.4 b
			Black	51.9 ± 1.0 a	24.6 ± 2.0 a	42.0 ± 1.2 b	48.7 ± 1.6 b
Mayapan	Unripe		Red	43.6 ± 3.2 b	−12.0 ± 0.4 c	33.0 ± 0.3 d	35.1 ± 0.4 c
			Brown	40.6 ± 4.1 b	−11.3 ± 0.9 c	24.9 ± 2.4 e	27.4 ± 2.5 d
			Black	44.0 ± 1.3 b	−11.8 ± 0.2 c	31.1 ± 2.0 d	33.3 ± 1.9 cd
	Ripe		Red	51.1 ± 3.6 a	19.8 ± 1.5 b	39.4 ± 2.6 bc	44.1 ± 2.9 b
			Brown	54.1 ± 1.3 a	20.8 ± 1.0 b	38.2 ± 0.8 c	43.5 ± 1.2 b
			Black	54.4 ± 0.8 a	24.3 ± 3.5 a	39.7 ± 3.2 c	46.6 ± 4.5 b

Note: L* = Lightness, a* = value relative to the green–red color, b* = value relative to the blue–yellow color (CIELAB color scale). Results followed by different letters (a–e) in the same row indicate statistically significant differences using minimum significant differences (MSD) test at p ≤ 0.05.

in Appendix B. After harvest, the peppers were stored in an ultrafreezer at a temperature of −40 °C until further analysis. These were crushed with the aid of a blender, weighed (approximately 100 g of chili per sample), and placed in a flask to perform the extraction process. Twelve combinations (soil type, degree of maturity, and variety) were analyzed in duplicate, giving a total of 24 samples analyzed.

2.4. Extraction of Volatile Compounds

It was carried out according to the conditions previously established by Pino et al. [7] to obtain the volatile compounds from Habanero pepper. The extraction was conducted with distillation solvent equipment by using heated water (to the boiling point) as a carrier solvent for one hour. The distillate obtained was mixed with dichloromethane and separated by liquid–liquid extraction. The organic phase (dichloromethane) was concentrated to 1 mL in the extraction hood. Finally, the sample was filtered throughout a 0.2 µm nylon membrane and, finally, injected (2 µL) to the gas chromatograph.

2.5. Analysis of Volatiles by Gas Chromatography

The implementation of the chromatographic method was carried out using, as a reference the method established by Bogusz-Junior et al. [23] with some modifications. The conditions used in this work are reported in

Table 1. Chromatographic conditions used for the analysis of volatiles compounds in Habanero pepper.

Chromatographic Conditions
Time of analysis:	65 min
Initial temperature:	40 °C
Ramp of temperature:	3 °C min−1
Final temperature:	240 °C
Type of injection:	Splitless
Temperature of the injector:	250 °C
Detector:	Flame ionization
Temperature of the detector:	250 °C
Flow of the carrier gas:	1 mL min−1

, and the equipment was a Thermo Scientific gas chromatograph, model Trace GC Ultra (Waltham, MA, USA).

The identification of the volatile compounds presented in the samples of Habanero pepper was made by the retention time of 9 standards signals (2,3-butadione, limonene, Isoamyl isobutyrate, trans-2-hexen-1-al, 1-hexanol, hexyl-3-methyl butanoate, 3,3-dimethyl-1-hexano l, linalool, and cis-3-hexenyl hexanoate) from Sigma Aldrich^® (Toluca, Mexico) analytical standard grade. The quantification was carried out with an external calibration curve of five levels in a concentration range of 80 to 670 µg mL⁻¹. The concentration of volatile compounds in the samples is expressed on a fresh weight (FW) basis.

2.6. Statistical Analysis

The factorial design (2 × 2 × 3) was conducted to analyze the effect of the three factors evaluated: degree of ripeness (unripe and ripe), variety (Jaguar and Mayapan), and type of soil (red, brown, and black). Minimum significant difference (MSD) and analysis of variance (ANOVA) at p < 0.05 were made to test significant differences in the volatile compounds. The interaction plots were performed with the factors (degree of ripeness (unripe and ripe) and kind of soil (brown, black and red)) to analyze the effect of these interactions on the concentration of volatile compounds. The software use for the statistical analyses was the Statgraphics Centurion XVII.II-X64 (Statgraphics Technologies Inc., The Plains, VA, USA).

3. Results

3.1. Soil Analysis

Results of the soil analysis used to produce Habanero pepper are in

Table 2. Analysis of the three soils (red, brown, and black) used to produce Habanero peppers (Capsicum chinense Jacq.).

	Red	Brown	Black
Cation exchange capacity (cmol kg−1)	27.00 ± 1.80 c	31.17 ± 1.15 b	38.50 ± 0.50 a
Bulk density (Tm−3)	0.97 ± 0.04 a	0.91 ± 0.07 b	0.80 ± 0.04 c
Field capacity (%)	45.94 ± 2.19 b	53.20 ± 1.55 a	30.57 ± 1.02 c
Permanent wilting point (%)	29.00 ± 1.62 b	34.36 ± 1.15 a	17.62 ± 0.75 c

Note: Values are the means ± standard deviation. Results followed by different letters in the same row indicate statistically significant differences using minimum significant differences (MSD) test at p ≤ 0.05.

. The red soil had the highest bulk density (0.97 ± 0.04 Tm⁻³) and the lower cation exchange capacity (27.00 ± 1.80 cmol kg⁻¹). Brown soil had the highest values of field capacity (53.20 ± 1.55%) and permanent wilting point (34.36 ± 1.15%). On the other side, black soil had the highest cation exchange capacity (38.50 ± 0.50 cmol kg⁻¹) but the lower bulk density (0.80 ± 0.04 Tm⁻³), permanent wilting point (17.62 ± 0.75%), and field capacity (30.57 ± 1.02%).

3.2. Quantification of Volatile Compounds by Gas Chromatography

The results of the determination of volatile compounds in the Habanero pepper are shown in

Table 3. Concentration of volatile compounds in ripe and unripe Habanero pepper of two varieties (Jaguar and Mayapan) cultivated in different soils.

Variety	Grade of Ripeness	Soil	1-Hexanol (µg g−1 FW)	Hexyl-3-Methyl Butanoate (µg g−1 FW)	3,3-Dimethyl-1-Hexanol (µg g−1 FW)	Cis-3-Hexenyl Hexanoate (µg g−1 FW)
Jaguar	Unripe	Red	74.11 ± 3.53 d	43.46 ± 3.24 h	137.86 ± 4.79 g	28.08 ± 2.09 f
		Brown	85.29 ± 6.50 d	499.93 ± 5.78 a	357.55 ± 6.40 d	35.29 ± 1.19 e
		Black	163.08 ± 7.47 c	284.06 ± 4.63 c	256.25 ± 4.98 e	33.89 ± 5.01 e
	Ripe	Red	273.29 ± 41.38 b	280.12 ± 5.73 c	549.02 ± 15.81 c	37.57 ± 1.07 cd
		Brow	243.27 ± 32.58 b	277.89 ± 9.02 c	515.51 ± 9.68 c	39.57 ± 1.66 c
		Black	279.58 ± 5.40 b	287.89 ± 9.02 c	525.51 ± 9.68 c	39.52 ± 1.45 c
Mayapan	Unripe	Red	80.87 ± 3.06 d	115.18 ± 3.79 f	173.07 ± 4.74 f	27.76 ± 1.67 f
		Brow	159.27 ± 22.55 c	83.04 ± 13.61 g	119.62 ± 20.11 g	31.16 ± 1.85 e
		Black	166.53 ± 3.81 c	417.11 ± 2.50 b	521.85 ± 5.78 bc	41.22 ± 2.25 b
	Ripe	Red	274.61 ± 14.34 b	161.06 ± 29.76 e	670.61 ± 177.72 b	35.30 ± 4.27 de
		Brown	279.58 ± 5.40 b	199.49 ± 2.37 d	279.47 ± 111.98 e	38.96 ± 4.84 c
		Black	360.14 ± 8.57 a	415.01 ± 4.68 b	1020.61 ± 51.27 a	49.49 ± 1.55 a

Note: Values are the means ± standard deviation. Results followed by different letters in the same row indicate statistically significant differences using minimum significant differences (MSD) test at p ≤ 0.05. The concentration of volatile compounds is expressed on a fresh weight (FW) basis.

. The compound found in highest concentration was 3,3-dimethyl-1-hexanol (1020.61 ± 51.26 µg g⁻¹ FW) in the Habanero pepper of the Mayapan variety, ripe, and harvested in plants grown in black soil. However, of all the quantified compounds, cis-3-Hexenyl hexanoate was found in the lowest concentration (27.76 to 49.49 µg g⁻¹ FW). The highest concentration of 1-hexanol was obtained in the ripe peppers from the black soil and Mayapan variety (360.14 ± 8.57 µg g⁻¹ FW). In addition, the highest concentration of hexyl-3-methyl butanoate was obtained in unripe peppers from the brown soil and Jaguar variety (499.93 ± 5.78 µg g⁻¹ FW). The chromatograms corresponding to the standards and the samples of Habanero pepper are shown in Figure A1, Figure A2 and Figure A3 of the Appendix A.

3.3. Interaction of Factors Influencing the Composition of Volatiles

Table 4. Effect of factors and their respective interaction (p values) for each of the volatile compounds.

	1-Hexanol	Hexyl-3-Methyl Butanoate	3,3-Dimethyl-1-Hexanol	Cis-3-Hexenyl Hexanoate
A: Variety	0.0001 *	<0.0001 *	0.0141 *	0.0865
B: Grade of ripeness	<0.0001 *	<0.0001 *	<0.0001 *	<0.0001 *
C: Soil	<0.0001 *	<0.0001 *	<0.0001 *	<0.0001 *
A × B	0.1300	0.0001 *	0.0620	0.2161
A × C	0.2089	<0.0001 *	<0.0001 *	0.0009 *
B × C	0.1216	<0.0001 *	0.0014 *	0.3641
A × B × C	0.0217 *	<0.0001 *	0.2299	0.2721

Note: (*) = Significant effect.

shows that all the factors evaluated in the present study (variety of pepper, soil, and degree of ripeness) had a significant effect on the concentration of the main volatile compounds in the Habanero pepper. Only cis-3-hexenyl hexanoate was not influenced by the variety of pepper. Moreover, hexyl-3-methyl butanoate was the only compound that showed significative effect in all evaluated factor interactions. This demonstrates the important role that those factors achieve in the concentration of volatile compounds in Habanero pepper.

Interaction plots (Figure 1) show that the four main volatile compounds exhibit a higher concentration in Habanero peppers harvested from plants planted in black soil. In the case of the degree of ripeness, an increase in the main volatile compound concentration was obtained in ripe Habanero pepper, except for hexyl-3-methyl butanoate which was not significantly influenced by the degree of ripeness.

On the other hand, it is possible to observe in Figure 2 that the Habanero pepper of the Mayapan variety exhibited a higher concentration of 1-hexanol (220.17 ± 10.20 µg g⁻¹ FW) and 3,3-dimethyl-1-hexanol (464.20 ± 34.44 µg g⁻¹ FW). Moreover, only the hexyl-3-methyl butanoate presented a higher concentration in the Jaguar variety (280.47 ± 14.47 µg g⁻¹ FW). In contrast, cis-3-hexenyl hexanoate showed no significant differences between the two varieties. Figure 3 shows the relationship between the degree of ripeness and the variety, highlighting the highest concentration of 1-hexanol (304.78 ± 14.51 µg g⁻¹ FW) and 3,3-dimethyl-1-hexanol (656.90 ± 117.76 µg g⁻¹ FW) in the Jaguar variety of the Habanero pepper.

4. Discussion

The results showed that the variety of Habanero pepper is a factor that significantly influences the concentration of the volatile compounds. One interesting finding is that this same phenomenon was observed by Fellman et al. [24] in apple varieties and by Dimita et al. [25] in different varieties of Chinese basil. A possible explanation for this might be that the genetic differences between varieties will affect the production of different essential oils, prioritizing the synthesis of some volatile compounds over others [26]. These results are consistent with those of Sosa-Moguel et al. [8] who also found differences between the two varieties of Habanero pepper (Jaguar and Mayapan) in the concentration of the volatile compounds. They reported a higher concentration of 1-hexanol and 3,3-dimethyl-1-hexanol in the Mayapan variety [8]. On the other hand, Jaguar variety was characterized to have a higher concentration of hexyl-3-methyl butanoate as in the present work [8]. Otherwise, cis-3-hexenyl hexanoate did not differ between the two varieties. According to these data and the results reported by Sosa-Moguel et al. [8], we can infer that the Habanero pepper of the Mayapan variety promotes the production of the mainly volatile alcohols (1-hexanol, 3,3-dimethyl-1-hexanol), while the Jaguar variety produces the main volatile ester (hexyl-3-methyl butanoate) [8]. However, more research on this topic needs to be undertaken before an association between the varieties and the production of volatile compounds in the Habanero pepper can be better understood.

On the other hand, the degree of ripeness has been shown to influence the synthesis of secondary metabolites in previous studies [12]. The results of this study indicate that this factor also affects the concentration of the volatile compounds in the Habanero pepper. One interesting finding is the high concentration of 1-hexanol, 3,3-dimethyl-1-hexanol, and cis-3-hexenyl hexanoate in ripe Habanero peppers. These results are in agreement with those reported by Cuevas-Glory et al. [6] that also found an increase in the concentration of 1-hexanol and 3,3-dimethyl-1-hexanol when the ripeness of Habanero peppers changed from unripe to ripe. Several factors could explain this observation. Firstly, a possible explanation might be that alcohols are one of the last volatile compounds formed in the fatty acid pathway [27]. Furthermore, the increase observed in cis-3-hexenyl hexanoate could be attributed to the ripeness process, because alcohols are biotransformed in esters, after being produced in the fatty acid pathway [27]. Another possible explanation could be that alcohol acetyl transferase (an enzyme that plays an important role in the transformation of alcohols to esters) could have an increased activity due to the degree of ripeness of the Habanero pepper [28].

In the case of the soil, the results of this study indicate that it has significative effects on the concentration of the four main volatile compounds. In accordance with the present results, studies have reported that soil affects the production of metabolites in Habanero pepper, for example capsaicinoids and polyphenols [10,11]. This is mainly related to the physico-chemical characteristics of the soil, because these affect the synthesis of some metabolites, prioritizing the development of certain compounds over others [29]. Interestingly, the results shown in Figure 1 indicate that the highest concentration of the four volatile compounds occurred in peppers from plants grown in the black soil. This soil had the highest cation exchange capacity (38.50 ± 0.50 cmol kg⁻¹) of the three soils evaluated, suggesting the higher cation exchange capacity, the more main volatile compounds developed. These results are consistent with those of Bononi et al. [30] who evaluated the volatile compounds of Artemisia absinthium L. in different soils of the Camonica Valley (Italy) [30]. They also reported a higher concentration of the main volatile compounds in those plants from soils with higher cation exchange capacity [30]. According to these data, we can infer that in black soils, the minerals for the plants are more available. This is because the cation exchange capacity contributes to the retention of minerals to support plant growth. These minerals play a critical role in plants due to their function as cofactor of the enzymes involved in the synthesis of metabolites [31]. In addition, in a prior study Oney-Montalvo et al. [11] have noted that black soil is also characterized by a higher nitrogen concentration (52.01 ± 7.05 mg kg⁻¹) in comparison with red and brown soil. As nitrogen is essential to the biosynthesis of nucleotides, co-enzymes, and secondary metabolites, this nutrient could also contribute to the production of volatile compounds [32]. The black soil is also characterized by having a higher percentage of organic matter (10.93 ± 0.23%), which is considered a valuable component that helps both the growth and development of plants [32].

On the other hand, the lower value of bulk density (0.80 ± 0.04 Tm⁻³), permanent wilting point (17.62 ± 0.75%), and field capacity (30.57 ± 1.02%) in the black soil could be related to its higher organic matter in comparison with the other two soils [11]. The low bulk density is also associated with less compaction, allowing a better flow of nutrients present in the soil when irrigated [33]. The field capacity indicates the highest filtering capacity, possibly because black soil was the least compacted (as indicated by the apparent density values).

There are still many unanswered questions about how these factors could affect the acceptance of the Habanero pepper by consumers. For this reason, it is important to evaluate the contribution of the main volatile compounds in the aroma profile of the Habanero pepper. According to Cuevas-Glory et al. [34], the volatile compounds cis-3-hexenyl hexanoate and 3,3-dimethyl-1-hexanol are considered the most important due to the fact they contribute to the characteristic aroma of the Habanero pepper [34] and bring the characteristic smells of sweet and chili to the pepper, respectively. On the other hand, hexyl-3-methyl butanoate is also considered an odor-active molecule that is characterized by a fruity smell [35]; however, its contribution to the aromatic characteristics of the Habanero pepper is smaller compared with cis-3-hexenyl hexanoate and 3,3-dimethyl-1-hexanol [34]. In addition, the 1-hexanol is a compound associated with green odors [36], but its contribution to the aromatic profile is also slight compared with the two molecules mentioned above. Further research should be undertaken to investigate if the concentration of volatile compounds changes with the kind of soil and if it could affect the perception of the aroma.

5. Conclusions

The results showed that the concentration of the four main volatile compounds in Habanero peppers was affected by the soil and the degree of ripeness, while the variety of the pepper had a significant effect only on 1-hexanol, hexyl-3-methyl butanoate, and 3,3-dimethyl-1-hexanol. Habanero peppers that were harvested from plants planted in black soil (Box lu’um) presented the higher concentration of 1-hexanol, 3,3-dimethyl-1-hexanol, hexyl-3-methyl butanoate, and cis-3-hexenyl hexanoate. These results could be associated with the higher cation exchange capacity of the black soil in comparison with the other soils evaluated (red and brown soil). These results suggest that of the three soils evaluated of Yucatan Mexico, the black soil favors the production of volatile compounds (1-hexanol, 3,3-dimethyl-1-hexanol, hexyl-3-methyl butanoate, and cis-3-hexenyl hexanoate) in the Habanero pepper, and it is recommended to be used by farmers of the Yucatan Peninsula whose aim is to develop Habanero peppers that stand out for aromatic characteristics. Those actions will establish practices for farmers that will make peppers more attractive to the consumer and will open the possibility of making products with different and desirable aromatic profiles from Habanero pepper fresh weight basis.