Note FRUIT CHARACTERIZATION OF VENEZUELAN AVOCADO VARIETIES OF MEDIUM OIL CONTENT

The objective of the present paper was to characterize some avocado fruit varieties to increase the information pool for this fruit. Twelve avocado varieties of medium oil content (8.09-11.12%) from a Venezuelan orchard: Wilson Popenoe, Figueroa 1, Waldin, Puebla, Schaff, Celia, Araira FM, Adolfo, Esencia de la Vega, Lawhon, Winslowson, and Lujo were characterized for pulp oil and moisture; weight (whole fruit, seed, pulp, and peel); length, width, and fruit shape; peel characteristics (roughness, color and hand peeling); and ripeness time. Differences in oil content, moisture content and fruit weight were found when compared with results reported by other authors. The variety Puebla was the lightest (107 g) and the smallest (7.90 x 4.62 cm), while Wilson Popenoe presented the highest pulp proportion (82%). Most of the varieties were ovate, with rough green peel and easy to hand peel. Peak ripeness of some varieties was at 3-12 days. Potential yields of two varieties were higher that the Venezuelan average.


INTRODUCTION
Avocado (Persea americana Mill.) is a popular fruit in Venezuela being cultivated in this country for the last five centuries (Avilán & Ciurana, 1983).Although Venezuela is in the seventh place among the world producers, there are few specialized orchards.Agronomic studies in Venezuela to select the best varieties began in the 30's (Avilán et al., 1994).This work was designed to complement the agronomic studies in order to make an information pool useful to growers and researchers.
The high oil concentration of avocado, which can reach up to 40% on wet basis, is its main feature, and depends on the variety, orchard location and harvesting time (Pearson, 1975;Olaeta et al., 1986).
Avocado is also rich in three of the most important antioxidants (vitamins E, C and ß-carotene), helps to prevent strokes due to its high potassium and low sodium content, provides exceptional quantities of soluble and insoluble dietary fiber, is a superior first solid food for babies, and its fat consists predominantly of monounsaturated oleic acid (Bergh, 1992).
Selection of varieties must include several approaches, a non-exhaustive list being included below.One approache would be to find a high yield variety, with low susceptibility to diseases (Rouse & Knight Junior, 1991).Another one is quite variable and depends on the climatic and soil conditions as soil drainage (Avilán & Rodríguez, 1992), altitude of the potential orchard (Figueroa, 1982); and consumer requirements, as a minimum oil content according to legal regulations (Lewis, 1978), a specific sort of size, color, peel roughness and shape depending on consumer habits (Storey et al., 1973/ 74); flavor (Lewis et al., 1979), amount of pulp fiber (Rouse & Knight Junior, 1991), pulp tendency to brown (Lizana & Luza, 1979), facility of hand peeling etc.In addition, another characteristics must be considered when production is oriented to the fresh or processed product market as a high pulp yield (Rouse & Knight Junior, 1991) or to oil extraction, as high oil yield (Swisher, 1988).For this reason, to provide information of varietal characteristics, instead of stating a priori recommendations, growers and scientifics should choose the best varieties according to their own possibilities and targets.This was the aim of previous articles (Gómez-López, 1998, 1999) and of this one.

MATERIAL AND METHODS
Samples belong to the collection of Centro Nacional de Investigaciones Agropecuarias, Maracay, Venezuela; whose location and characteristics have been indicated previously (Gómez-López, 1998).In 1993, between 14 and 26 mature fruits of each of the following avocado (P.americana Mill.) varieties from trees older than seven years were harvested: Waldin, Puebla, Schaff and Winslowson (from imported plants); Adolfo, Araira FM, Figueroa 1 and Lujo (Venezuelan varieties) (Avilán y Rodríguez, 1995); and Wilson Popenoe, Celia, Esencia de la Vega, and Lawhon.The samples were brought to Instituto de Ciencia y Tecnología de Alimentos, Caracas, and kept in ambiental conditions until ripe.A single fruit was considered ripe, when its skin was ruptured with a 0,8 cm width cylindrical plunger in an Instrom Universal Testing Machine model 1101, using a penetration speed of 1 cm min -1 ; the plunger penetrated the sample perpendicularly to the equator.Three fruits of each variety were measured in five points located equidistantly (Gómez-López, 1998).When samples were ripe, five fruits of each variety were randomly selected, and analytical determinations were performed.
Pulp moisture and oil contents were measured according to Gómez-López (1998) in a pulp pool from five fruits.
Fruit weight (whole fruit, seed, pulp, and peel); length, width at the widest point, and shape; and the peel characteristics roughness, hand peeling, and color were determined.Peel color results are the average of five readings taken equidistantly at the equator of the fruit, measured by a tristimulus colorimeter (Colormet, Metron Instruments Inc., Hamilton, Ontario, Canada) using the Lab Hunter System (Gómez-López, 1998).In this system, lightness scale goes from 0 (pure black) to 100 (pure white), positive values of "a" mean redness and the negative values greenness, positive values of "b" means yellowness and the negative values blueness (Francis & Clydesdale, 1975).Means of TABLE 2 were compared by Kruskal-Wallis test, using the Statgraphics 6.0 program.Estimated yields were calculated by multiplying the average number of fruits per tree according to Figueroa (1982), fruit weight (TABLE 2) and the recommended number of trees (228) per hectare (Avilán et al., 1994) to obtain kg of fruit ha -1 .This value was then multiplied by the pulp ratio (TABLE 2) to obtain kg of pulp ha -1 ; and this result was multiplied by the pulp oil ratio (TABLE 1) to obtain the kg of oil ha -1 .

RESULTS AND DISCUSSION
A gentle pressure applied by fingers is a common practice to assess avocado ripeness.Since that is not scientifically reproducible, analytical texture determinations were performed.The ripeness point of each avocado
Comparing data on fruit characteristics from different countries is very difficult because different factors can induce variability even in the same orchard and at different harvesting seasons (Salazar et al., 1971), but there is no other way to contrast data from different sources.
Comparing data of oil content of this work (TABLE 1) with previous reports, the oil percentage of Waldin is in agreement with a previously published data (California Avocado Society, 1946), but for Winslowson is higher (Salazar et al., 1971) and for Puebla very much lower (California Avocado Society, 1946).
Oil and moisture percentages are constant cgaracteristics very useful to know oil percentages from moisture determinations according to some reports (El-Zeftawi, 1978;Brown, 1984).In this work, these values were between 87.48 (Waldin) and 93.21 (Schaff) (TABLE 1).
Fruits of the Puebla variety were the smallest (TABLE 2), and also the lightest (p < 0.05) (TABLE 3) in this category and among the 49 ones characterized from the indicated orchard.However, there have been characterized other lighter fruit varieties, like the 75 g weight Caliente (Vogel, 1958).
Puebla, Waldin and Winslowson were lighter than the range of weights reported by California Avocado Society (1946), and Waldin also lighter than the values reported by Fersini (1975), but Winslowson was heavier than the weight registered by Salazar et al. (1971).
According to descriptors employed by Avilán et al. (1994) Schaff, Winslowson, and Adolfo varieties were very heavy; Lujo, Araira FM, and Wilson Popenoe were heavy; Figueroa 1 and Lawhon were medium; Celia and Esencia de la Vega light; and Waldin and Puebla very light.
Wilson Popenoe was the variety with the highest pulp proportion (p < 0.05) in this category (TABLE 2) and among the 49 varieties characterized from the indicated orchard.This maximum is lower than the values reached by varieties from other places, like Valle 5 from Colombia (88%) (Salazar et al., 1971) and Alboyce from Texas (88%) (Rouse & Knight Junior, 1991).It is interesting to point out that the varieties cucumber shaped like Russell (Gómez-López, 1998) and Wilson Popenoe were two of the four varieties with highest pulp percentages among the 49 studied in this project, and Alboyce has also a cucumber shape, so it might be some relationship between this shape and a very high pulp ratio.According to descriptors employed by Avilán et al. (1994) Wilson Popenoe and Schaff had high pulp percentage; Winslowson, Adolfo, and Lawhon medium pulp percentage; and Lujo, Araira FM, Esencia de la Vega, Figueroa 1, Waldin, Puebla, and Celia had low pulp percentage.
Seven varieties were oval, four pyriform and one cucumber shaped (TABLE 4).Schaff had an almost rhomboid shape, and Winslowson was almost round.Five had smooth peel and 7 rough peel.The rough texture is related to the development of extensive corky areas in the external fruit surface (Schroeder, 1950) rather than the irregular surface exemplified by the Hass variety.Two varieties had purple peel (positive chromaticity value a, TABLE 4), which might be due to anthocyanin pigments as was obtained by Prabha et al. (1980)

TABLE 1 -
Race a , Floral Group a , and Pulp Oil and Moisture Percentages of twelve Avocado.Varieties harvestedin Venezuela in 1993.
Avilán & Rodríguez (1995)dríguez (1995).b M: Mexican, G: Guatemalan, WI: West Indian, -: no determined.c Data are averages of two samples of a five avocado pool.d Data are averages of four samples of a five avocado pool.

TABLE 2 -
Fruit Weight and Pulp, Seed and Peel Proportions a of twelve 12 Avocado Varieties harvested in Venezuela in 1993.

TABLE 4 -
External Characteristics of 12 Avocado Varieties a Harvested in Venezuela in 1993.
aColor data are means of five readings taken at the equator of five avocados.b Lightness.c Red/green chromaticity.d Yellow/blue chromaticity.

TABLE 3 -
Size a of twelve Avocado Varieties harvested in Venezuela in 1993.
a Data are means of five avocados.