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INTRODUCTION
At present, agricultural production is looking for potential alternatives that involve the production of food of high nutritional value and low cost. Therefore, it is necessary to select native plants that provide food and, at the same time, have characteristics of tolerance to progressive salinity, adaptability to eroded soils, at high temperatures and efficient root systems for water extraction.
Tropical fruits are considered important for the food security of developing countries, from the nutritional point of view, as well as for their contribution to the benefits of exports and income. Ninety percent of tropical fruits produced are consumed within the same producing countries, 5% is marketed as fresh fruits and the rest as processed products (FAO, 2005).
In Mexico there are approximately 712 species of fruit trees, of that total, 32 native species are used commercially, only 14 of them appear in official statistics, while the remaining are found in family gardens as harvest crops (Borys and Leszczñska, 2001).
The Nanche (Byrsonima crassifolia) is one of these native fruit trees, known locally and regionally, but which can be potentially productive and generate significant economic income to the population of the areas where it thrives (Bayuelo et al., 2006).
As a fruit species, nanche is a crop little known worldwide. Due to its characteristics of salinity tolerance, adaptability to eroded soils and high temperatures and with deep and efficient root system, it is usually found in the wild and in some geographical areas in the semi-agricultural modality.
This fruit tree is native to tropical America, whose distribution includes extensions from the Tropic of Cancer to the Tropic of Capricorn, from southern Mexico, through the Pacific side of Central America, Peru and Brazil. It also appears in Trinidad, Barbados, Curacao, St. Martin, Dominica, Guadalupe, Puerto Rico, Haiti, Dominican Republic and throughout Cuba, (Morton, 1987; Ciriaco, 2013).In some of the states of Mexico where it is grown, it has acquired considerable importance, due to its wide use, as food, medicine, ornamental, fuel, coloring, beekeeping, reforestation element and components of agrosilvopastoral (Medina et al., 2004; Love y Spaner, 2005; Martínez et al., 2008).
Despite being a little known crop, it has great socioeconomic importance and medicinal uses for many regions.
The color, shape and flavor of the nanche are attributes that the consumer values when making a purchase. The consumer usually selects the nanches by their external attributes; however, when they are consumed they must meet other requirements, given by the combination of intrinsic properties, such as the titratable acidity and juice pH, for which quality parameters for the direct market and industry should be established. Therefore, it is the importance of generating information about those nanche genotypes that satisfactorily meet the characteristics demanded by the various sectors. In this regard, the chemical characteristics, the soluble solids of the pulp and the acidity of the fruit have been useful parameters, because the flavor depends mainly on the balance between sugars and organic acids (Medina et al., 2004).
From the medicinal point of view, it is known that for some people, the decoction in water of the bark or leaves is traditionally drunk, for the treatment of colds, skin infections and snake bites. It has also been described the use of leaves and bark for the treatment of tooth pain, vaginitis, diarrhea, bronchitis and asthma in different regions of the Yucatan Peninsula (Peraza et al., 2007), as well as for the treatment of inflammatory disorders in Central America (Maldini et al., 2009).
However, there are few quality studies on fruits of nanche that allow taking advantage of this plant genetic resource. Therefore, the objective of this work was to evaluate the physical-chemical and mechanical parameters for optimal postharvest handling of the fruits of nanche (Byrsonima crassifolia) and to determine the quality of the fruits from Miguel Hidalgo Zacalapa Community, Copainalá Municipality, Chiapas and for subsequent studies of their shelf life
METHODS
The present study was carried out between the months of August and September of 2019, in Ribera Miguel Hidalgo Community, Copainala Municipality, Chiapas; which is located in the northwest of the State of Chiapas in an area of mountainous and rugged terrain. Its geographical coordinates are 17 ° 13′16 ″ N 93 ° 21′08 ″ W. The fruits were harvested at an altitude of 950 meters above sea level, where the average annual temperatures are higher than 28 ° C, while the temperature in the coldest month ranges between 15 and 20 ° C and the average annual rainfall does not exceed the township’s average.
The physical properties evaluated were height, weight, and coefficient of friction. Height and weight were determined for fruits and seeds, while friction was evaluated on three surfaces (cardboard, wood and plastic). Likewise, the chemical properties of soluble solids, pH, total acids and maturity index for both yellow and red phenotypes were evaluated.
The sample size was obtained from a pre-experiment with 45 fruits, preventing them from bruising or decomposing portions. The procedures were carried out applying the methodology described by Luyarati (1997),
where:
σ |
- standard or standard deviation; |
ts |
- coefficient that depends on the level of confidence and the number of samples, is determined for a Student's t distribution; |
Δa |
- maximum permissible mean error or random error. |
The equatorial (SD) and polar (DP) diameter of the fruits were determined using a caliper or vernier of 0 to 150 ± 0.05 mm accuracy. The PD was determined from the apical end to the base, while the DE was measured in the middle portion of the fruit. The form was determined by the index obtained from dividing the DP / ED (Alia et al., 2012).
To obtain the weight of the fruits, a digital scale with an accuracy of 0.001 g was used, BLC-220 Boeco model. In order to obtain greater precision in weighing, each nanche fruit was weighed individually, according to the sample number calculated in the pre-experiment. For the classification of the fruit size, the following scale was used: 1) small <4.9 g, 2) medium 5-6.7 g, and 3) large> 7 g as proposed by Medina et al. (2004)
The angle of friction between the material of the fruits and the surfaces described above was determined in an inclined plane, placing the fruits on each of the surfaces and moving the ramp from the horizontal position (0º) until obtaining the angle at which the fruits begin to slide. It was measured with an angle conveyor that is in the inclined plane and the rolling of the fruits was avoided by joining them in groups of three with adhesive tape. This operation was performed the number of times it was calculated in the pre-experiment
The following expression was used to calculate the static friction coefficient (Cd):
Content of total soluble solids (SST) of the fruits of nanche. A drop of the pulp of these was placed on the prism of the surface of a calibrated refractometer of brand CIVEQ CVQ-4013, with characteristics of measurement range: 0 a 90% Brix, accuracy: 0.5%. Size (mm) 27x40x160, weight 175 g and the measurement was recorded in ºBrix, as described in NMX-F-103-1982 (1982).
For the pH analysis a potentiometer or pH meter (pH 600, pH Meter) was used with an electrode previously calibrated with buffer at pH 7 and pH 4. Twenty milliliters of the pulp were taken, the electrode was introduced in the center of the sample with constant agitation and the reading was recorded.
For the subsequent classification of the flavor of the fruit, the scale proposed by Medina et al. (2004),based on the ° Brix / AC ratio, was used, such as: acids (5.1-8.1), bittersweet (8.1 -10.1) and sweets (> 10.1).
In the case of titratable acidity the measurement was performed for citric acid; 30 g of pulp were weighed and diluted in 200 ml with distilled water, a 20 ml aliquot was taken and titrated with 0.1 N NaOH, to the pH of 8.3 which is the turning point of the phenolphthalein indicator, the reading of consumption was recorded, as described in NMX-F-102-NORMEX-2010 (2010).
The results obtained were tabulated and evaluated for which descriptive analysis was performed. In order to verify the significant differences of these variables between the two phenotypes, means tests were performed by the Tukey method (0.05) to compare the differences between groups. These analyses were performed with the Statgraphics Centurion XV.II statistical package (StatPoint Technologies Inc., Warrenton, VA, E.U).
RESULTS AND DISCUSSION
Dimensions and Shape of the Fruits of Nanche
The statistical summary of the equatorial and polar diameters variable is presented in Table 1. It includes measures of central tendency, variability and shape. Of particular interest here is the standardized bias and kurtosis, which determine that the sample comes from a normal distribution, since its values are within the range of (-2 to +2) which do not invalidate the statistical procedures that apply to this data.
When analyzing in Table 1, it is observed that the polar or longitudinal diameter of the fruits evaluated ranged between 1.41 and 1.75 cm, results that contrast with those obtained by several authors such as Martínez et al., (2006) who cited intervals from 1.82 to 2.63 cm and Medina et al. (2004) who found, in the evaluated selections, fruits of nanche that vary in their longitudinal diameters from 1.62 to 2.29 cm. That difference that could be given because the harvested fruits come from a wild plantation.
Table 1 Descriptive statistics of the dimensions of the fruits.
| Green Fruits | Red Fruits | |||
|---|---|---|---|---|
| Polar diam | Equat. diam | Polar diam | Equat. diam | |
| (cm) | (cm) | (cm) | (cm) | |
| Count | 3,50 | 3,50 | 3,50 | 3,50 |
| Average | 1,56 | 2,05 | 1,61 | 1,72 |
| Stand. dev. | 0,72 | 0,76 | 0,80 | 0,84 |
| Coeff. Var. | 0,05 | 0,04 | 0,05 | 0,05 |
| Minimum | 1,42 | 1,82 | 1,41 | 1,46 |
| Maxim | 1,75 | 2,15 | 1,74 | 1,89 |
| Est. bias | 1,51 | -0,55 | -1,44 | -1,47 |
| Kurtosis. Est. | 0,95 | 0,05 | 0,11 | 1,92 |
In the case of the equatorial diameter, these varied from 1.82 to 2.15 cm. These results are also lower than those cited by Medina et al. (2004) from 1.68 to 2.48 cm. as well as those obtained by Martínez et al., (2006), who reported ranges from 1.75 to 2.55 cm.
Likewise, it can be seen in the previous table that the green fruits, between the two phenotypes, have larger dimensions with an average polar and equatorial diameter of 2.05 and 1.71 cm, respectively. This characteristic affects the quality of the fruits for acceptance by consumers.
The analysis of the DP / DE form or relationship showed an index between 0.77-0.81, so it can be argued that the polar diameter of the fruits is smaller than the equatorial and. therefore, its form is oblate. Similar results (0.84 to 1.0) were obtained by Medina et al. (2004) and Maldonado et al. (2016), who classified their oblate-shaped nanche fruits. These results demonstrate the variability in nanche fruits, regardless of their phenotype and genotypes, in different regions of Mexico. These characteristics affect the quality of the fruits and could be given by their origin (wild or domesticated).
Weight of Fruits and Endocarps of Nanche
In the box and mustache diagram of Figure 1, it can be seen that for the total data there is a significant difference between the medians of the green and red fruits. In addition, it is observed that the fruits of greater weight are the green ones, with values that ranged from 3.65 to 4.6 g and on average 4.03 g. These values are relatively higher than those reported by Bayuelo et al. (2006) of 3.8 g in studies conducted on harvested fruits in Michoacán
Taking into account the results obtained and according to the classification proposed by Medina et al. (2015),it can be inferred that the fruits of nanche harvested in Miguel Hidalgo Community are small, since the average of their weights is between 3, 27 and 4.03 g, variable that affects its quality for fresh trade, however, not for tanning processing.
Static Friction Coefficient of Nanche Fruits on Cardboard, Wood and Plastic Sheets
In Figure 2, the average values of static friction coefficients are presented. It is observed that the surface with homogeneous and lower friction coefficient values was the plastic, with means between 0.66 and 0.64, considering this surface the one that less damage could cause the fruit during transportation and postharvest handling.
Based on the previous results, a comparison was made between the coefficient of friction values of fruits on plastics. Figure 3 shows that there are no statistically significant differences between the means of the coefficients of friction of the fruits evaluated, with a level of 95.0% confidence, according to the method of highly significant difference (HSD) of Tukey, procedure used to discriminate among the means.
Total Soluble Solids Content (TSS)
The average TSS values of the fruits evaluated are presented in Figure 4. It can be seen that the highest concentration of ºBrix occurred in green fruits with an average of 10.35 ºBrix, these results differ from those reported by Medinas et al., (2015) of an interval between 8.93 and 15.99 ° Brix and are greater than the range of 3.2 to 7.9 ° Brix reported by Martínez et al. (2008).
The results obtained could corroborate what was stated by Kays (1991), that the values of the total sugars in the fruits of nanche can vary according to the time of the year, the precipitation or the degradation and biosynthesis processes of the polysaccharides.
In Figure 5, the pH values obtained as a result of the statistical analysis are shown. It can be seen that the average acid values ranged from 3.83 to 4.43, which were higher than those published by Medina et al. (2004) and Martínez et al. (2008), from 2,6 to 4 and from 3,50 to 4,38, respectively. However, Villachica (1996) and Muñoz de Chávez et al. (2002), suggest that on average, in 100 g of nanche pulp, the pH can be 2.8. Taking into account this, it can be deduced that the values obtained are within the permissible range.
On the other hand, in Figure 5, it can be seen that for the case under study, the pulp with averages of a greater degree of acid (3.83) was in red fruits. These data corroborate the data obtained in the concentration of SST in red fruits, in which, coincidentally on average, the percentage of ºBrix was lower with 10.03.
Titratable Acidity in Nanche Fruits
As a result of the determination of titratable acids (percentage of citric acid), it was obtained that the red fruits presented a higher percentage, followed by the green ones with 1.75% and 1.49%, respectively. These values are lower than those obtained by Villachica (1996) and by Muñoz de Chávez et al. (2002) of 2.45%. Taking into account the results obtained for the percentage of citric acid of the fruits studied, it is possible to classify them in bittersweet because they are in the range between 0.6 and 1.9%, according to the classification of Medina et al. (2004).
Considering the above-mentioned and taking into account the scale proposed by Medina et al. (2004), in relation to the classification of fruits according to the taste index, it can be argued that red and green fruits are acidic. These results corroborate what was stated by Landanilla (2008) and Maciel et al. (2010), who state that organic acids are responsible for the acidity and the particular aroma of the fruits and that acidity is a useful feature to know the ripening state of the fruits.
CONCLUSIONS
The physical properties of the fruits under study showed that nanche is a species of great variability. The polar and equatorial diameters of the fruits ranged from 1.56 to 1.61 cm and from 2.05 to 1.72 cm, respectively, being the green fruits, those of greater diameters. The weight ranged from 3.27 to 4.03 g on average and that is why they are considered small and low quality fruits from their morphology.
The best values of TSS were recorded in green fruits with an average of 10.35 º Brix. The same occurred in the pH with a value of 4.43 on average, while red fruits had a higher percentage of citric acid with 1.75%.
The material that could cause less damage to the fruits during transportation and post-harvest handling is plastic, since it has a relatively low coefficient of friction of 0.66 and 0.64.
