Introduction

In the state of Michoacan is more than 80% of the area established with avocado in Mexico. Followers Jalisco, Estado de Mexico, Morelos and Nayarit, the latter with more than 4 350 ha. These states concentrate 95% of the established national area (^{SIAP, 2014}).

The climatic diversity of the avocado producing regions in Mexico is due to the altitudinal gradient, topography, exposure to the sun and prevailing winds; this variability may affect the production and fruit quality of 'Hass' avocado (^{Lobell et al., 2007}). The types of weather and the time of flowering of 'Hass' avocado in Michoacan affected the weight of the different tissues of the fruit, such as skin (exocarp), pulp (mesocarp), testa (endocarp + tegmen) and embryo (cotyledon + embryonic axis) and its nutritional composition (^{Salazar-Garcia et al., 2011}). The terrain, tree phenology (mainly flowering season) and quality management infrastructure also affect fruit production and postharvest behavior of fruit (^{Lopez-López and CajusteBontemps, 1999}; ^{Salazar-García et al., 2005}; ^{Salazar-García et al., 2007a}, ^2007b; ^{Rocha-Arroyo et al., 2011}).

A genetic characteristic of 'Hass' avocado is the fruit can remain attached to the tree for more than three months after reaching their physiological maturity. Then, the decision on when to harvest producer considers environmental factors, availability of labor and especially the price in the market (^{Wang et al., 2012}).

The quality of fruits and vegetables includes sensory properties (appearance, texture, taste and aroma), food quality, mechanical properties, functional properties and defects, and is defined by the consumer, which sets its based on preference criteria and personal expectations (^{Abbott, 1999}). In the case of avocado fruit acceptability it is more correlated with the texture and flavor than the content of oils (^{Canto-Pereira et al., 2014}). However, lipid biosynthesis in avocados 'Fuerte' and 'Hass', can be affected by environmental factors such as light, water stress and soil composition and atmosphere in addition to the physical damage and caused by pathogens (^{Ozdemir and Topuz, 2004}).

In Mexico, the price of 'Hass' avocado varies according to their place of origin. Traders argue that is due to differences in skin roughness, seed size and texture and pulp quality. Meanwhile, some consumers prefer little rough and thin-skinned fruit, with a higher proportion of pulp and it contains high oil content as it will increase its palatability (^{Campos et al., 2011}). However, the absence of a study documenting the alleged differences so that in preparation for future studies, this research was performed in order to detect possible differences in some physical, chemical and organoleptic characteristics of fruits avocado 'Hass' produced in the states of Michoacan, Jalisco and Nayarit.

Materials and methods

Features orchards. Jalisco orchards were located at altitudes between 1800 and 2150 m, with humid temperate climate C(w1) and Chromic Cambisol soil. In Michoacan, the heights of the orchards were between 1 500 and 1 850 m, predominantly semi-warm humid climate (A)C(w1) and soil type Andosol ochric. The height of the orchards Nayarit was between 1000 and 1100 m, with semi-warm humid climate (A)C(w2) and andosol soil (Table 1).

Meteorology of the study regions. Temperature and rainfall was obtained from a daily database manager organized in Microsoft Access 2010. Data stations and orchards characterize the regions included in the study were selected. Jalisco data came from the National Weather Service (Tapalpa station). In Michoacan they were obtained from the Meteorological Information System of APEAM (Uruapan season) and Nayarit State Monitoring Network Agroclimatic INIFAP (Tepic station).

Physical, chemical and sensory evaluation of the fruit. Between 15 and 31 october 2013, in each orchard they were harvested nine fruits (27 fruits per region) totaling 81 fruits. The fruits were originated by normal bloom, which occurred in late winter 2012, weighing between 205 and 300 g (sizes 48 and 40), the dry matter content in the pulp> 22% without physical or pest and disease damage.

The fruits were transported to the laboratory in a thermos and analysis was conducted in two phases: 1) harvest, consisting of four fruits that were tested on arrival at the laboratory; and 2) consumption maturity at room temperature, using five fruits kept at room temperature (21 ± 1 °C) and analyzed to reach maturity consumption, four of them for physical and chemical characteristics and one for sensory evaluation.

Washing fruits became water with sodium hypochlorite (200 mg L^-1) and weighed on a precision balance (Ohaus model P2001, Florham, NJ, USA.). The length and diameter were obtained with a digital vernier (MTC500196, Mitutoyo Co., Japan). Firmness was determined in the front equatorial section of the fruit pulp, after removal of a section of skin, with a penetrometer (Chatillon DFE-051 model, Largo, FL, USA; punch 10 mm). The fruit was split longitudinally and separated into two parts. In the section between the stalk and the seed cavity, the height of the fruit Ecuador, the thickness of the pulp and skin on both sides was measured. The fruits were separated in skin, flesh, seed coat and embryo for the fresh and dry weight each. The yield of pulp, physiological weight loss and the dry matter content was calculated from the data of the physical characterization of each fruit.

The roughness was determined in a fraction of the skin removed during evaluation of fruit firmness evaluated "harvest". In a stereoscopic microscope (Zeiss Stemi 2000-C model, Barrington, NJ, USA) with a digital camera (Canon Power Shot G11 model, NY, USA) an image of 2 x 2 cm (3 648 x 2 736 pixels) was obtained for each of the 36 fruits (four fruits per garden). Each image was incorporated into the geographic information in ArcView version 3.2 and was treated as a satellite image of the Earth's relief. With the "Spatial Analyst" module surface with a slope greater than 20% (value various trials was considered the more faithfully representing the roughness of the skin) was quantified. Values were converted to surface roughness value percentage to the total area of the image analyzed.

The oil content in the pulp was measured with ether extract technique (^{AOAC, 1990}), in a sample of two fruits per each including orchards.

For an untrained sensory evaluation of 12 members who evaluated the characteristics of smell, texture and flavor with a hedonic scale structured panel it was formed three levels. The characteristics evaluated were: odor intensity (low, medium, high); texture 1 (dry, oily, very oily), with her wet or greasy feel of the sample was evaluated; texture 2 (soft, firm and very firm) needed to compress the sample between the tongue and palate force is assessed; Flavor intensity (low, medium, high) (^{Espinosa-Manfugas, 2007}).

Statistic analysis. The experimental design was completely randomized, with three replications (orchards) by producing region. Data on the chemical and physical characterization and analysis of variance test (Tukey, p≤ 0.05) with Minitab statistical package were subjected (^{Minitab, 2010}). For the evaluation "A harvest" and "maturity consumption at room temperature" a principal component analysis in SAS (^{SAS Institute, 2002}) program was conducted.

Results

Weather study areas

The weather conditions that prevailed during the fruit development of 'Hass' from anthesis to harvest corresponded to the typical climate expression of each producing region (Table 2).

Table 2 Summary of meteorology occurred during fruit development of ‘Hass’ (Dic. 2012-Oct. 2013. 

Región	Temperatura media 1(°C)			Precipitación acumulada (mm)
	Del periodo	Máxima	Mínima
Jalisco	16.3	25.4	7.3	971
Michoacán	182	24 3	12.1	1,632
Nayarit	21 8	28 5	15 1	921

Michoacan had higher precipitation (1 632 mm), Jalisco and Nayarit (less than 1 000 mm). Regarding temperature, Nayarit scored the highest records in the average maximum and minimum as well as the average for the period. The lowest average period of minimum temperature (7.3 °C) and a half of the period (16.3 °C) occurred in Jalisco.

From december to march (period of fruit growth), Jalisco had the lowest minimum temperature values throughout the period from december to april and was below 5 °C, while from may to october was less than 12 °C The maximum ranged from 22 to 29.1 °C and may was the warmest month. Michoacan reaching a maximum between 22 and 27.3 °C, while the minimum was maintained below 15 °C and february was the coldest with 9.4 °C. Highs in Nayarit occurred between 25 and 31 °C, may being the hottest month, while the minimum was kept below 15 °C until may, followed by an increase to 19 °C from june to september. In Jalisco 80% of the annual rainfall was recorded in the period from june to september, 83.5% in Michoacan, Nayarit and 95.5%. September was the wettest month for Jalisco and Michoacan, nayarit while they were in july and august (67.9% of the rain period). In all three regions the rainy season began in june; however, his term was variable since in Jalisco and Nayarit ended in september, while for Michoacán was in october (Figure 1).

Figure 1 Mean monthly minimum and maximum air temperatures in the three producing regions of ‘Hass’. Period December 2012-October 2013. 

Physical and chemical characteristics of fruits

The origin of the fruit determined some of their physical and chemical characteristics. The assessment "at harvest", the fresh weight of the fruits of Michoacan was lower than those of Jalisco, while the fruits of Nayarit were not different from those of Jalisco and Michoacan. The differences were detected for the skin (thickness and proportion in relation to the fresh and dry weight), the testa and the embryo (proportion of fresh and dry weight), and the fruits of Nayarit were those with higher values. In the case of pulp, the highest proportion in fresh and dry weight corresponded to Michoacan and Jalisco. The content of dry matter and oil did not differ between Michoacan and Nayarit, Jalisco but with lower values of occurrence (Table 3).

Table 3 Some physical and chemical characteristics of fruits of ‘Hass’ avocado from three producing regions characteristics. 

Tejido	Característica	A la cosecha			Madurez de consumo a temperatura ambiente
		Jalisco	Michoacán	Nayarit	Jalisco	Michoacán	Nayarit
Fruto completo	Peso fresco (g)	266.54 az	241.39b	255.22 ab	260.43 a	223.96 b	250.95 a
	Relación largo/diámetro	1.45 a	1.38a	1.46 a	1.43 a	1.42 a	1.47 a
	Pérdida fisiológica de peso (%)	-	-	-	13.07a	12.58 a	11.94a
Piel	Espesor (mm)	1.39b	1.53b	1.82a	1.19 a	1.74 a	1.58a
	Porcentaje en peso fresco (%)	13.38b	15.10a	16.51a	12.37b	12.95 ab	14.08 a
	Porcentaje en peso seco (%)	11 64b	13.16 ab	15 35 a	1032b	11.46 b	14 lia
Pulpa	Firmeza (kgf)	33.37a	33.18a	32.79 a	7.62 b	10.70 ab	14.03 a
	Espesor (mm)	15.70 a	14.96 a	14.50 a	13.02a	11.95a	12.08 a
	Porcentaje en peso fresco (%)	69.83 a	67.53 a	64.65 b	60.30 a	59.21a	58.67a
	Porcentaje en peso seco (%)	67 53 a	67 66 a	58 88b	65.85 a	65.50a	61 23 a
	Contenido de materia seca (%)	24.86 b	27.95 a	25.49 ab	25.85 a	28.65 a	25.85 a
	Contenido de aceite (% base húmeda)	14.69 b	17.48 a	14.87 ab	16.50a	19.35 a	16.37a
Testa	Porcentaje en peso fresco (%)	0.53 b	0.53 b	0.87a	0.42 a	0.45 a	0.43 a
	Porcentaje en peso seco (%)	0.23 b	0.32 b	0.86a	0.26 b	0.34 b	0.58 a
Embrión	Porcentaje en peso fresco (%)	12.28 b	13.84 ab	16.16a	15.72a	16.64 a	16.54a
	Porcentaje en peso seco (%)	20.60 b	18.87b	24.91a	23.56a	22.71a	24.09 a

^zMedias con la misma letra para cada característica y dentro de cada fecha de evaluación, no presentan diferencias significativas, de acuerdo con la prueba de Tukey, p≤ 0.05.

For evaluation in "consumer maturity at room temperature" the fruits of Jalisco and Nayarit were heavier than those of Michoacan. The difference between producing regions for different parts of the fruit was observed in the skin, where the fruits of Nayarit had higher values in the ratio of the weight of it, both fresh and dry. Regarding the firmness of flesh, the fruits showed the strongest Nayarit and Jalisco lowest. The head of the fruits of Nayarit had a ratio of 0.58% by dry weight, being higher than those of Jalisco and Michoacan. The rest of the physical and chemical determinations analyzed showed no differences between the regions studied (Table 3).

The principal component analysis (ACP) showed that the assessment "harvest" were two components explained 62.16% of the variability of the fruit. The first principal component (45.60%), was determined by the proportion of the fruit pulp and skin, including roughness, while the second component (16.56%) it was the dry matter content and oil content in the pulp (Figure 2A).

The number represents the fruit analyzed and the literal to the region of origin of the fruit (J= Jalisco; M= Michoacan; N= Nayarit).

Figure 2 Principal component analysis for assessing A) harvest; and B) eating ripeness at room temperature. 

The ACP evaluation "eating ripeness at room temperature", showed that 67.40% of the variability of the fruits was explained for two components. The first component (47.21%) corresponded to the proportion in cool, dry skin weight. The second component (20.19%) as determined by the total weight of the fresh fruit and pulp firmness (Figure 2B).

Rugosity

With a scale roughness data generated four levels: low, medium, high and very high (Figure 3). The lower level is characterized by a lower surface coverage to 10%. The average level occurred between 10 and 19.9% of rough surface with pronounced bumps. The upper class occurred between 20 and 39.9% of rough surface, with its characteristic presence of numerous bumps that fail to join. In the case of very high rougher it showed a 40%, whose characteristic bumps were continuous they came to be pronounced bumps.

Figure 3 Scale skin roughness for ‘Hass’ avocado. 

By using the scale of roughness in Figure 3, the fruits of Jalisco were equally distributed in the lower and middle levels, while most of the fruits of Michoacan (66.7%) had low levels of skin roughness. The fruits of Nayarit presented the highest roughness since 25% of them were in the high level and the other at very high (Figure 4).

Figure 4 Distribution (%) of the fruits of ‘Hass’ avocado from three producing regions, according to the roughness of the skin and according to the scale of Figure 3. 

The roughness of the skin of the fruit showed differences between production regions. The fruits of Jalisco and Michoacan had similar roughness, 10.3 and 8.17% of the surface of the fruits, respectively, presented outstanding ≥ 20%, while the fruits of Nayarit were more roughness, since these slopes occurred in 49.3% of skin surface. (Figure 5).

Literal equals are not significantly different (Tukey, p= 0.05).

Figure 5 Roughness of the skin (to be ≥20%) of fruits of ‘Hass’ avocado. Average results of each producing region. 

The analysis of the air temperature and some physical and chemical characteristics of the fruit showed a positive correlation with roughness and thickness of the skin and skin ratio, testa and pulp relative to the fresh weight. Regarding the ratio by dry weight of skin and pulp oil content correlation was negative. Values showed highest correlation with the average temperature, except for the roughness of the skin, where the maximum temperature had the highest correlation (Table 5). Rainfall and diurnal temperature range showed no significant correlations with the physical and chemical characteristics evaluated.

Table 5 Correlation between mean air temperature (December 2012-October 2013) and some physical and chemical characteristics of the fruit of ‘Hass’ avocado. 

Característica	T. mínima	T. Media	T. máxima
Rugosidad de la piel (%)	0.72*	0.88**	0.94**
Espesor de piel (mm)	076*	0 81**	0 70**
Proporción de piel en peso fresco (%)	0.76*	0.77**	0.54ns
Proporción de piel en peso seco (%)	-0 78*	-0.79*	-0.61ns
Proporcióndetestaenpeso fresco (%)	0.82**	0.93**	0.88**
Proporción de pulpaenpeso seco (%)	0.79*	0 82**	0.47ns
Contenido de aceite en pulpa (% base húmeda)	-0.57ns	-0.68*	-0.71*

^ns= correlación no significativa; ^*=p≤ 0.05; ^**= p≤ 0.01.

Discussion

The fruits of 'Hass' avocado analyzed in this investigation met the quality requirements to be marketed fresh, according to international standard Codex Stan 197-1995 (^{FAO, 2014}).

In Nayarit fruits showed higher values in the proportions in cool, dry skin, coat and embryo weight, the fruits of Jalisco and Michoacan, which is similar observed values to those reported by ^{Salazar-Garcia et al. (2011)}, for these characteristics. The fruits of Nayarit had thicker skin than those of Jalisco and Michoacan. In the latter two regions skin 'Hass' presented a thickness similar to that mentioned for this cultivar produced in Colombia (^{Forero et al., 2007}).

The proportion of fruit pulp of the three producing regions was greater than the minimum quality indicated by ^{Forero et al. (2007)}. However, the proportion of fruit pulp of Nayarit (fresh and dry weight), was lower than the fruits of Jalisco and Michoacan, where the pulp fraction coincided with the findings of ^{Salazar-Garcia et al. (2011)}. The oil content in the fruits of the three regions (14.5-19.5% wet basis) was similar to that reported by ^{Villa-Rodriguez et al. (2011)}, for fruits of 'Hass' produced in Michoacan. A higher proportion of pulp and total oil content, lower proportion of embryo and seed coat are desirable characteristics by consumers, hence this could be the reason why the fruits of Michoacan and Jalisco are best quoted by traders.

In this study, organoleptic characterization showed no difference in the properties evaluated in the fruits of 'Hass' produced in the three regions. Texture "dry-fat" with which were rated most fruit producing regions coincided with the preferred by a group of panelists tasted avocado 'Hass' occurred in several countries (^{Obenland et al., 2012}).

The average monthly temperature and precipitation differed among the three producing regions of 'Hass'. In Nayarit highest (maximum, minimum and average) average temperature was recorded during the period of fruit growth and lower rainfall accumulated with a concentrated distribution in fewer months. These differences did not affect the organoleptic characteristics assessed in the fruits; however, if they were affected some physical and chemical characteristics, particularly a greater roughness in the skin of the fruits of Nayarit, from those of Jalisco and Michoacan. This coincided with ^{Barrientos-Priego et al. (1996)}, who suggested that the roughness of the skin of 'Hass' was greater in warm climates than in fresh. A higher mean maximum air temperature was increased skin roughness (r= 0.94; p≤ 0.01) and lower pulp oil content (r= -0.71; p≤ 0.05), both characteristics mentioned by ^{Hass (1935)} as distinguishing of 'Hass' and that he referred will vary depending on weather, topographic, orographic and orchard management conditions.

Similarly, the increase in average temperature was associated with an increased skin thickness (r= 0.81; p ≤ 0.01) and a higher proportion of head fresh weight (r= 0.93; p≤ 0.01) and pulp weight dry (r= 0.82; p≤ 0.01), this last quality very desirable for merchants and consumers. Although preliminary, this research for the first time documented the influence of the environment on chemical and physical properties of the fruit of 'Hass', especially skin roughness properties. Future research should include a larger number of orchards to verify this finding. Another important contribution of this work is the scale of roughness for quantitative evaluation of skin roughness type 'Hass' fruit, which will be useful for future work on eco-physiology of the roughness of the skin of this important growing avocado.

Conclusions

The fruits of 'Hass' avocado orchards produced in some of Michoacan, Jalisco and Nayarit differed only in their physical and chemical characteristics, which no demeritaron its organoleptic quality. The fruits of Jalisco and Michoacan had a higher proportion of pulp and a lower proportion of embryo and testa, compared with those of Nayarit. The total oil content was higher in the fruits of Michoacan. The organoleptic characteristics evaluated were not affected by the region where the fruit was produced. The average air temperature was the meteorological variable most associated with the physical and chemical differences of the fruit and that best correlated with the thickness and roughness of the skin.