Organisation: Food
and Agriculture Organization of the United Nations, FAO,
Rome, Italy
Author: Lidia Dorantes, PhD., Lidia Parada, MSc., Alicia Ortiz, PhD.
Edited by AGST/FAO: Danilo Mejía, PhD, FAO (Technical), Emanuela Parrucci
(HTML transfer)
Preface
1 Introduction
1.1. Economic and Social Impact
1.2 World Trade
1.3 Primary Product (fresh)
1.4 Secondary product (processed)
1.5 Elements on quality assurance and export marketing
1.6 Consumer preferences
The importance of post-harvest operations in developing countries relies in the quality control of the fresh fruit that they achieve. Post-harvest operations begin with a selection of the fruit, then a cleaning, packing, proper storing and transporting. All these operations benefit producers because they enable the fruit to reach the market at higher prices, and also create jobs in the packinghouses and orchards for both educated and non-educated labor. The domestic and international consumer benefits with a high-quality fresh fruit, free of diseases and other defects.
Avocado is a fruit with an exquisite taste and aroma, which has been traditionally consumed even before the arrival of Spaniards to the Americas. It is called "aguacate" or "palta" in Latin American countries. Nowadays, as a result of different investigations, it is recognized that besides being a source of energy and vitamins, it also delivers specific nonnutritive physiological benefits that may enhance health.
From this point of view, avocado can be considered as a "functional food", according to the definition of Mazza (1998). Some nutraceutical ingredients that have been found in avocado pulp are antioxidants, such as vitamin E or tocopherols (4.31 UI/100 g) and glutathion (17.7 mg/100g). They both work as antioxidants, neutralizing free radicals that may damage aging cells, the heart, and contribute to the development of some types of cancer, such as mouth and pharynx (O'Toole, 2000, Heber, 2001).
It has also been reported that avocado is a source of lutein (248 mg/100g, considered a high content), a carotenoid that helps to protect the eye from diseases such as cataracts. The amount of b-sitosterol in this fruit is similar to the one found in soy and olives. Animal studies have demonstrated that this compound is related to the inhibition of cancerous tumors (Heber, 2001).
An other nutraceutical component in avocado is a mix of high quality lipids: w3, w6, and w9 fatty acids. When Carranza et al (1997) made clinical studies in patients with high cholesterol levels, they found that an avocado enriched diet produced a significant reduction in low-density lipoproteins ("bad cholesterol") and total cholesterol, while diets enriched with soy and sunflower did not change the total cholesterol concentrations.
Lerman et al in 1994 concluded that in non-insulin dependent diabetic patients it was beneficial to replace carbohydrates for lipids, such as the ones found in avocado. This will favor the reduction of triglycerides in the blood plasma.
For all of the above, it can be concluded that the inclusion of avocado in the everyday diet can bring health benefits to the health of human beings, bearing in mind that no food is 100% complete, and a single food will not provide all required nutrients and nutraceuticals (except for breast milk). The diet shall include several food items from all the different groups in order to deliver a good nutrition.
There are 57 avocado producing countries in the world. The land that is currently destined for the growing of this cultivar totals 348,769 ha, producing 2'583,226 tons a year. The average yield per ha is 7.40 tons. The main producing countries in the world are:
|
Country |
% of world production |
Country |
% of world production |
|
Mexico |
36.8 |
Dominican Rep. |
4.30 |
|
U.S.A |
7.93 |
Chile |
4.26 |
|
Colombia |
5.56 |
Brazil |
3.45 |
|
Indonesia |
5.03 |
Israel |
3.32 |
|
|
|
Other 49 countries |
29.35 |
As it can be seen in Table 1, the main producer in the world is Mexico. Some countries can compete in terms of quality, such as Chile, Spain, Israel, South Africa, and Dominican Republic. However, still no country can compete with Mexico in terms of quantity.
Summarized characteristics and scientific name
Avocado is a dicotyledoneous plant from the Ranales order and the Lauraceae family. It was classified as Persea gratissima by Gaertner , and Persea americana by Miller. P. americana developed subspecies due to geographical isolation, that finally originated different botanical types (Figure 1 Avocados derived from Mexican ecological race), with different kinds of adaptation to climatic conditions.
Three of these botanical types are widely known as subspecies or botanical varieties of the P. americana. In horticultural circles, these varieties are known as ecological races: Mexican, Guatemalan, and Antillean (Figure 2 Avocados variety Hass). They are not different enough to be considered separate species, because they have a very similar genoma, hybridation among them occurs easily, and their hybrids have climatic adaptation advantages and improved agronomic characteristics.
The following Table describes the main characteristics of the three ecological races:
| Characteristic | Mexican | Guatemalan | Antillean |
| Fruit weight (average) | 98.8 g | 309.8g | 312.5 g |
| Peel thickness | Thin and very thin | Medium, thick or very thick | Thin, medium or thick |
| Peel texture | Membrane-like | Corky | Leathery |
| Medium annual temperature (°C) for native trees | 13.5 to 20.5 | 21.0 to 28.0 | 24.0 to 27.0 |
| Medium annual temperature (°C) for introduced trees | 20.5 to 25.5 | 18.0 to 28.5 | 19.0 to 20.0 |
| Medium annual precipitation (mm) for native trees | 560 to 2200 | 800 to 3400 | 1100 to 3350 |
| Medium annual precipitation (mm) for introduced trees | 300 to 2250 | 250 to 7000 | 600 to 700 |
| Altitude (m over sea level) | 950 to 2250 | 20 to 1200 | 50 to 800 |
Avocado is a fruit from a tree that has a variable growth and development, reaching a height of 10 to 12 meters in its natural habitat (Figure 3 Avocado trees may grow at different altitudes). Such habitat is classified as subtropical-tropical. The tree has a ligneous trunk that can reach up to 80 cm to 1 m in diameter in trees that are 25 to 30 years old (raceme), that can be axillar or terminal.
Systematic studies have classified more than 500 varieties; however, most of them have been discarded in order to "create" commercial varieties, which adapt to production in commercial scale. From this large number of varieties, most have had productivity problems (production time, amount of fruit), quality (protein and fat content), and commercial handling problems (resistance to transportation, etc.).
Commercial varieties are developed from the selection and improvement of these types, or by hybridation (Figure 4 Production of hybrids in the orchard). For example, from the Antillean type the Pollock, Peterson, and Waldin varieties are obtained; from the Guatemalan, MacArthur, Orotava, Nabal, Anaheim, Hass (Figure 5 Small trees of avocados Hass derived from Guatemalan type), Booth 7, Booth 8; and from the Mexican: Puebla, Mayapán, Zutano, Topa-topa, and Bacon. Some hybrid varieties are: Mexican-Guatemalan: Fuerte, Ettinger, Rincón, Robusto, Lula. Antillean-Guatemalan: Gema, Choquette (Rodríguez-Suppo, 1992)
Origin
Based on the archeological evidence found in Tehuacán, Puebla (Mexico), it is believed that avocado appeared approximately 12,000 years ago. It has been determined that the country of origin of this fruit is the central part of Mexico, passing through Guatemala to Central America. In this region, the natural gene stock can be found, which can be useful to the biotechnological improvement of the species. As an evidence of this theory, primitive avocado trees have been found from the Oriental Sierra Madre in the State of Nuevo León, Mexico, to Costa Rica, in Central America.
From this origin center, avocado dispersed to the southeastern part of the U.S., to the Antilles, to a large part of South America: Colombia, Venezuela, Las Guyanas, Brasil, Ecuador, Perú, Bolivia, and Chile. This broad dispersion in areas of ancient civilizations can be explained by a high appreciation of the fruit in these cultures (Sánchez-Pérez, 1999; Rodríguez Suppo, 1992).
Seasonal production
The life cycle of avocado (longevity and productive period) is a long one. A tree of 1 to 4 years is considered young, from 8 years on is considered adult and fully productive, a period that can extend for more than 20 or 25 years. Some types of avocado in favorable conditions grow indefinitely ( Figure 6 Avocado trees).
Avocado is a very productive tree that delivers fruit all year-round. The two harvest periods are classified as maximum and minimum. The maximum harvest period lasts from October to January, and minimum from February to September.
The yield of fruit per tree varies due to the avocado type, cultivation, and zone. An adult orchard typically stabilizes its production from 80 to 100 kg of fruit per tree and year. The yield is also modified by the age and the tree density within an orchard. Young trees have a lower yield than adults, producing from 10 to 20 kg per tree, and stabilize their production at 10-15 years of age. The maximum production of a tree is usually reached at 15 years of age (SAGAR, 1999, Rodríguez-Suppo, 1992, Ing. José Cortez, personal communication).
Main causes of post-harvest losses and poor quality
From a physiological point of view, particularly during the post-harvest stage, the aesthetic and nutritional qualities of fruits can be affected, which could lead to a decrease in post-harvest life (Zamora, 1991). The quality of avocado is often diminished along the packing and marketing processes, and sometimes it does not reach its destination at its best. The following disorders of avocado have been classified as follows (Swarts, 1984):
The main causes of post-harvest loss are:
Chilling injury. Temperature is the main environmental factor in the control of produce ripening. Thus, in order to obtain successful results, it is important to handle this factor properly, keeping the fruit under low, specific temperatures that should never be below 0ºC. However, some fruits suffer chilling injury at temperatures well over the freezing point. According to Pesis et al (1994), avocado is a subtropical fruit that is sensitive to chill injury when exposed to low temperatures, even if they are over the freezing point (for example, 2 to 4ºC). The main symptoms of chilling injury are black stains in the epidermis and a gray or brown discoloration in the mesocarp. Morris (1982) reported that another symptom is the alteration of internal metabolism, which leads to an increase of the levels of anaerobic respiration and, as a consequence, of abnormal metabolites, resulting in the development of foul taste and odor. However, the effects of chilling injury in avocados is clearly seen only when the fruit is ripe, which in some cases may be too late for marketing effects (Corrales-García, and Tlapa-Rangel, 1999).
However, refrigeration slows the speed of biological processes in the fruit, delaying ripening and senescence. In the case of avocado, storage under refrigeration should not exceed 30-40 days. In order to guarantee a higher efficiency in the refrigeration treatment, a pre-cooling process is recommended (Téliz, 2000, Morales, 2001).
Fungal damage: Anthracnose (Colletotrichum gloeosporioides) is the cause of a fungal infection that is considered of major importance. Besides the damages it causes in the production of avocado, it also reduces the fruit quality during its transport, storage and marketing, where it causes the largest losses. The damages in a green fruit begin with discolored circular areas. The fungus penetrates the fruit and makes it rot. The lesions are of variable size, and of a dark brown color. In the surface of lesions, cotton-like spots appear. This and other funguses are capable of destroying entire boxes or pallets (Figure 7 Avocados showing fungal damage). It is favored by high relative humidity, damaged fruit and foliage, and when branches touch the ground. The chemical control is made with copper-based fungicides that are also used as a preventive measure on leaves and fruit still on the tree (Téliz, 2000, Ing. Salvador Torres, personal communication).
Mechanical damage
Many defects originate - or increase - because of an inadequate handling of the fruits from harvest to packaging. Friction damage, which is characterized by an oxidation of the tissue that later inclines downward and becomes necrotic, is one of the most frequent problems during harvest, and it has been estimated to be present up to 78% of the fruits.
Mechanical damage accelerates water loss and disrupts the superficial arrangement of the tissue allowing a faster gas exchange. Cuts break completely the protective layer of the fruit and expose the tissue directly to the environment. The cicatrisation and production of anti-fungal substances diminishes as avocado ripens (Zamora, 1991, Morales, 2001).
The damage is more notorious in fruits along the packaging process, mainly due to inadequate handling that affects the number of fruits with export quality.
Zamora-Magdaleno et al (1999) explained friction damage before harvest as a result of fruit friction during growth or as a result of friction with leaves or small branches. Damage proportion at this point may be from 2 to 35%, and increased at the packinghouse from 10 to 62%. Fruit coming immediately from harvest had a longer storage life, compared to the packed fruit. Ethylene production was higher in fruit recollected from the last phases of the packaging process, while their respiration rate was lower due probably to the result of mechanical injury.
The resistance to mechanical damage is given by the composition of the cells of the epidermis and the arrangement of the vascular tissue. A strong, elastic peel will not present any damage as a result of mishandling (Morales, 2001).
During growing, fruit loss can be due to a lack of technical counseling on a good nutrition of the trees, disease prevention and pest control (Figure 8 A well nourished leaf and others showing boron and zinc deficiencies). During harvest, a lack of planning and organization may cause: 1) avocados with improper sizes and dry matter contents (21% in the pulp, minimum) that are cut off the trees; 2) contaminated fruit, that is pulled from the tree or cut inadequately, and falls onto the ground; 3) sunburns due to exposure of the fruit. During transport, dirty boxes and containers during transport are another source of contamination. If trucks and containers are not appropriate, the fruit may reach high temperatures when transported to the packinghouse (De los Santos-Vázquez, M., 2001)
1.1. Economic and Social Impact
The economic and social importance of avocado resides in the benefit that its cultivation gives to producers, marketers, processors, and consumers. The orchards create jobs by demanding labor for farming operations, harvest, packinghouse operations, transportation, and marketing (Téliz, 2000). In Mexico, there are 21,511 producers (10,000 are located in Michoacán), 279 packinghouses and domestic traders, 17 packinghouses/exporters, 14 processing facilities for guacamole, pulp, halves, frozen products, refreshing drinks and non-refined oil. All these generate 47,000 direct jobs, 70,000 seasonal jobs, and 187,000 indirect permanent jobs (APROAM, 2003).
According to Lois Stanford "The varied topography of Michoacán's temperate region produces a wide range of microclimates suitable for avocado production almost year-round". The land tenure system is extremely heterogeneous, with an estimated 75% of the production area in private property, and only 25% in the "ejido" or communal sector. The avocado's industry production profile is equally heterogeneous. Orchard size varies greatly, ranging from small orchards of 1 to 5 hectares (both private and communal) to large commercial operation of 500 ha. Of the estimated 6,000 producers, only a handful of private producers have commercial operations and produce for the export market. Despite their limited numbers relative to large numbers of small producers, large avocado growers have played an important role in shaping the political and economic environment of Michoacán's avocado industry."
The production of avocado in Mexico started in the 50's. During these years the first cultivars were developed in the state of Michoacán, and during the 60's this activity expanded within the state, up to 15,000 ha. More and more cultivars appeared, and the year of 1975 recorded that 23,000 ha of land were destined to avocado production. During the first 15 years of production, the Mexican government considered the fruit as "highly profitable", and did not support avocado producers with scientific research or credits.
In the 70's, small landholders (from 0.5 to 10 ha) and communal landholders ("comuneros" or "ejidos") began cultivating avocado. As a consequence, in the 80's the avocado crops occupied 43,200 ha with 5 million trees, and employed 15,000 labor workers. The scientific and technological support during these years allowed the increase of the fruit production in 20%, along six years (Figure 9 Agronomic engineer and avocado nutrition adviser in an orchard).
During the first 15 years of avocado cultivation in Michoacán, no relevant social changes in the region were accounted for. The wages paid to labor workers were below the minimal range established by the government, and only few farmers offered benefits such as overtime payments, loans, vacations, etc. However, the whole local population benefited form the cultivation of avocado due to investments, the growth of the transportation network and service industry, as well as banking activities. At the beginning of the 80's, new industries developed alongside the cultivation of avocado: packinghouses, industrialization, and avocado exporters. As mentioned before, jobs have been created for a large number of specialized professionals, administrative and labor workers (Figure 10 Labor workers at avocado orchard), whose wages are over the minimal and enjoy benefits.
During the 80's and 90's, the government established changes in tax and labor laws, which force the farmers to pay taxes and offer higher salaries and benefits to the workers. In the long run, these changes proved to be beneficial to the local population. Because the profit margins were set in 20-80%, the wages are at least 50% higher than the minimum, and the tax payments supported the construction of roads, schools and hospitals (Morales, 2000).
The presence of avocado in the world market has been growing steadily in the past two decades, and it is no longer considered an exotic fruit but part of the everyday diet of many countries. This tendency has been reinforced by the consumer tendency to look for natural products. Avocado has a large market as a fresh fruit, besides its use in the oil, cosmetic, soap, and shampoo industry; as well as processed foods derived from it, such as guacamole, frozen products and avocado paste (Téliz, 2000).
The NAFTA (North American Free Trade Agreement), has opened new markets for the Mexican producer, and at the same time, creates the necessity of offering fruits with an excellent quality in order to captivate foreign markets. Otherwise, fruit exports will be a cause for economic sanctions and, in the long run, it could mean the closure of these new opportunities (Zamora-Magdaleno et al., 1999).
Nowadays, many Mexican producers have explored the possibility of exporting avocado, since the domestic price of the fruit is only 20% of its value in other countries, such as Europe, U.S., Canada, and Japan. Even though the demand for avocado exists in the developed world, the quality requirements are usually higher than the domestic ones (Figure 11 Standard for the international market). The producer has to take the responsibility of a better operation of his cultivation in order to obtain a product of the desired quality that is able to compete in the international markets. At this point, the volume of fruit that has enough quality to be exported is only a small percentage of the total production (Morales, 2000).
Generally speaking, the consumption of avocado in the world from 1990 to 1999 increased from 376 to 381 g per habitant, per year, meaning that the total volume rose from 2 to 2.3 million ton/year (Giacinti, 2002).
Importer countries
The main avocado importer country is France, which takes 39% of the total imported volume. Other importers are U.S.A. (10%), United Kingdom and Belgium (6.5% each). The leaders of international commerce are South Africa, Israel and Spain, countries that have been the main exporters since 1993. The world trade of avocado has increased significantly from 1980, and in the case of Mexico it has been limited to the U.S.A. and Europe. Japan has begun to import large volumes of the fruit, being the main importer in Asia. Japan imports have increased 73% since 1990, Mexican avocados are received from September to December, and avocados from the U.S.A. from February to September. The Mexican avocados get lower prices than the American. (Téliz 2000; El Aguacatero, 2001).
In the European Union (E. U.), familiarization with avocado has motivated an increase in its consumption for the past two decades. The per capita consumption in the E.U. is shown in the table 3:
| Country | Kg/habitant/year | Country | kg/habitant/year |
| Austria | 0.160 | Ireland | 0.194 |
| Bel-Lux | 0.899 | Italy | 0.033 |
| Denmark | 0.580 | Netherlands | 1.128 |
| Finland | 0.150 | Portugal | 0.035 |
| France | 1.420 | Spain | 0.596 |
| Germany | 0.157 | Sweden | 0.610 |
| Greece | 0.228 | United Kingdom | 0.315 |
The Netherlands and France re-export an important percentage of their avocado imports to other countries in the Union, therefore the consumption data should be consider partial.
Among the factors that increased the acceptances of tropical fruits, such as avocado, in the European Union are:
Exporter countries
During 1996-2001, 305,383 tons of avocados were exported, with a value of 292.3 million dollars. A growth rate of 5.03% was registered in the same period. It is noteworthy that the 1993-2001 periods had a growth rate of 16%. The main exporter countries are shown in Table 4:
| Country | % of total exports | Country | % of total exports |
| Mexico | 22.09 | South Africa | 9.07 |
| Chile | 17.78 | France | 5.38 |
| Israel | 12.65 | Netherlands | 4.95 |
| Spain | 12.23 | U.S.A. | 2.89 |
| Others | 18.34 |
Mexican exports of avocado in 2003 were of 71,621 tons, which that represented 22.09% of the world exportations. This amount increased fourfold in the last four years. The main destinations of Mexican exportations are: U.S., Central America, France, Canada, Japan, United Kingdom, Netherlands, Germany, and Belgium-Luxemburg.
The 7.5% of Mexican production of avocado is exported as fresh fruit. The exportations of Mexico during the period 1996-2001 are valued in 350.3 million dollars. Only 3.4% of the avocados produced in Mexico are exported as a processed product, non-refined oil, and beverages, equivalent to 18,875 ton or 18.1 million dollars in 2001. The main destinations of the products derived from avocado are: U.S.A., Germany, France, Spain, New Zealand, Japan, Canada, and Australia.
The exportations for the period 1998-2004 are expected to increase 40% for the fresh fruit and 47% for processed avocado (Source: APROAM, 2003).
Exporter countries operate with different free on board (FOB) prices per kg of avocado that may be seen at table 5:
| Country | FOB Price in US$ | Country | FOB Price in US$ |
| Philippines | 2,61 | Israel | 1,14 |
| Morocco | 2,06 | Mexico | 1,06 |
| Peru | 1,76 | Dom. Republic | 0,65 |
| Belgium-Luxemburg | 1,64 | Indonesia | 0,62 |
| Germany | 1,53 | Brazil | 0,57 |
| United Stated | 1,22 | South Africa | 0,44 |
| Chile | 1,16 | Venezuela | 0,33 |
Consumer countries: The main avocado consumer countries may be observed in Table 6.
| Ranking | Volume (ton) | Country |
| 1 | 815,749 | Mexico |
| 2 | 228,310 | United States |
| 3 | 128,447 | Indonesia |
| 4 | 127,697 | Colombia |
| 5 | 85,598 | Brazil |
| 6 | 79,298 | Dominican Republic |
| 7 | 79,020 | France |
| 8 | 76,355 | Peru |
| 9 | 63,667 | China |
| 10 | 49,000 | Cameroon |
| 11 | 45,000 | Haiti |
| 12 | 39,145 | Venezuela |
| 13 | 32,662 | Chile |
| 14 | 32,446 | Israel |
| 15 | 32,079 | South Africa |
| 83.7% | 1'914,503 | Partial Sum |
| 100% | 2'288,208 | World Total |
Avocado is mainly consumed as a fresh fruit (Figure 12 Commercialization and consumption of avocados is mainly fresh). The nutritional content for some varieties cultivated in Mexico is described in the Table 7.
| Variety | Energy | kJ/kcal | Moisture (g) | Ash (g) | Fat
(g) | Protein (g) | Carbohy-drates (g) | Total fiber (g) |
| Pellejoa | 519/124 | 77.40 | 1.10 | 1.37 | 1.37 | 1.37 | 3.70 | 3.73 |
| Grandea | 176/42 | 88.60 | 0.50 | 1.37 | 1.37 | 1.37 | 4.82 | 2.25 |
| Verdea | 757/181 | 72.40 | 1.10 | 1.81 | 1.81 | 1.81 | 5.89 | 0.40 |
| Hassb | 715/171c | 77.30 | 1.30 | 1.60 | 1.60 | 1.60 | 5.60 | ---- |
| a INNSZ, 1996 b Ortiz, A., 2003 c this value was estimated from the nutrient contents. |
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Some recipes for fresh avocado are presented in the Annex (pag76), with the aim of illustrating some ways of consumption of the fresh fruit. (Verti and Villanueva 2001, APROAM 2000). Additionally, some examples of traditional recipes are presented. An example is presented in Figure 13 showing guacamole and main ingredients. The authors of the present work, encourage the reader to make its own recipes; combining a good source of high quality lipids and vitamins (avocado), with ingredients that contain proteins (meat, fish, egg white, soybean, cheese, nuts), carbohydrate sources such as bread or tortillas, and dietary fiber (lettuce, fruits, asparagus, etc.) . Add your favorite spices and enjoy your meals with avocado!
In order to increase commercialization on a large scale and give avocado an added value, it is important to develop food products derived from this fruit with a shelf life long enough their transportation and distribution to consumers (Figure 14 Avocado products guacamole).
This would also promote the creation of processing plants, which in turn would generate new jobs, and increase the profit of the farmers.
The main problems that a food processor faces when developing and preserving avocado products are:
The microbial contamination that is present in the fruit peel, due to lousy agricultural practices (particularly in developing countries). This contamination is hard to eliminate because of the rough texture of the peel, especially in the Hass variety.
Minimally processed avocado products meet the consumer demand of having fresh-like products; however, the shelf life of these products is relatively short, from one to several weeks. Usually, the preservation factors are a combination of additives and refrigeration. Welti-Chanes et al., in 1998, recommended a firmness range of 800 to 1500 g for avocados to be minimally processed.
Table 8 presents some studies on avocado processing. The foundations of each method are different (second column). The temperature decrease in processes such as refrigeration and freezing has been extensively used in the development of guacamole-type products. Nowadays, methods are combined with the addition of additives to improve the sensory quality and avoid syneresis. Frozen avocado products have a shelf life of one to two years.
| Method | Foundations | Remarks | References |
| Freezing | Decreases enzymatic and microbial activities. | Avocado mixture can be preserved for 9 months when packed with nitrogen (inert gas). Nowadays, shelf life of frozen guacamole is of 1 to 2 years. | Stephens, T.S., Lime, B.J., and F.P. Griffiths. 1957. J Rio Grande Valley Hort. Soc. 11, 82-89 |
| Conventional thermal treatments | Decreases or eliminates microbial population, inactivates enzymes. | Off-flavors are generated, depending on the processing time and temperatures. | García, R. Et al. 1975. J Food Sci, 40:200 |
| Freeze-dry | Decrease of water activity to avoid microbial growth and enzymatic activity. | Good results in samples with a <2.5% moisture content. It is considered expensive. Shelf life is up to 9 months. | Gomez, R.F., and R.P. Bates. 1970. J Food Sci, 35(4) |
| Additives plus refrigeration (minimal processing) | Compounds that inhibit polyphenoloxidase activity, at controlled pH and water activity to inhibit microbial growth. | Avocado slices treated with cystein and sodium pyrophosphate, at pH=5.5 lasted for 8 days in refrigeration. | Dorantes, L. 1998. Food Science and Technology International, 4, 107-113. |
| High hydrostatic pressure | Pressure between 300 and 600 MPa can inactivate food spoilage and pathogenic microorganisms. | When combining high pressure and lowering pH, it was possible to obtain a good refrigerated product. | López-Malo et al. 1998. Food Research International, 31, 549-556. |
| Microwave, combined methods | A thermal microwave treatment, microwaves, pH lowering, and formation of complexes chlorophyll-zinc are combined. | Color is less deteriorated by the formation of stable complexes. Flavor is better preserved than in conventional processes. | Guzmán, R.I. et al. 2002. Innovative Food Science and Emerging Technologies 3, 47-53. |
The combination of reducing substances, organic acids, and sequestering agents in refrigerated products has shown to be effective in delaying guacamole and avocado paste browning (Sánchez et al., 1991, Dorantes-Alvarez et al., 1998). Some type of bacteriostatic substance is added as well.
The decay of freeze-dried guacamole and avocado purée was studied by Gomez and Bates in 1970. Their freeze-dry method has been useful in samples with a moisture content <2.5%, because its efficiency is based on lowering water activity at a level that interferes with enzymatic activity and microbial growth. It is considered a relatively expensive method since it requires freezing and vacuuming (<5 mmHg), in order to sublimate the water present in the samples. The product that was packed with an inert gas such as nitrogen may last for 9 months, maintaining a high quality.
The application of novel technologies in the development of guacamole-type products presents some alternatives that eventually generate commercial products, as the high hydrostatic pressure process. This process damages the microbial cellular structures (mainly their membranes), inactivating them, and resulting in a safe product (López-Malo, 1998). The commercialization of this type of product is carried out mainly in developed countries, since the consumption of the fruit in developing countries is mainly as a fresh produce.
Other application of novel technologies in the development of avocado products is the microwave thermal treatment, combined with a decrease in pH and the formation of complexes chlorophyll-zinc (Guzmán et al., 2002). Microwave heating can be considered as a high temperature-short time treatment (HTST), which decreases the generation of off-flavors and loss of texture. The addition of a zinc salt prevents the loss of green color by forming a complex chlorophyll a-zinc during the thermal process. Also, Ortiz et al (2003) reported that preheating with microwaves may lead to obtain a good quality and yield of avocado oil, free of trans fatty acids.
The development of hurdle and novel technologies will result in the generation of new processes and products based on avocado that will hopefully benefit developing countries.
Recently in the region of Michoacán, technical efforts have been made in order to improve the quality of avocados, with the aim of entering foreign markets, especially the US. These technical efforts have been further strengthened by legislation, specifically the publication of NOM-066-FITO-2002 on August 1996. This is a Mexican federal order that establishes the legal requirements and phytosanitary specifications for commercializing avocado in both national and international markets. This order also establishes the legal base for a regional system of phytosanitary control that requires that every avocado grower must enter the state pest control program and obtain certificates for their orchards if they intend to market their fruit at regional packinghouses.
The regulations established the procedures that growers must follow in the orchard maintenance, harvesting techniques, initial transport to the packinghouse, and registration of their orchards with the Agricultural Ministry (Stanford, 2002).
The federal order NMX FF-016-SCFI-2002 establishes quality specifications for fresh Hass avocados, excluding the fruit that is destined to industrial processing (Figure 15 Poster of the Union of Avocado Packers from Michoacán, México, showing the avocado standards of quality and damages).
This is done with the aim of creating a reference frame for producers, packers, brokers, traders, and consumers. Avocados shall be:
Every box destined to the market shall contain, at least, the following data:
Every package used in avocado transportation shall follow the next:
Federal order NMX-FF-008-1982 establishes the fruit calibers for commercialization (Figure 16 Fruit calibers for commercialization of avocados in México), as follows:
There is also a federal order that establishes the requirements and specifications of the observation and certification of good agricultural practices in the production of fresh fruits and vegetables, NOM--034-FITO-1995. The main objective of this is to prevent food-borne illnesses due to contamination with fecal matter (human or animal), infectious diseases transmitted by workers in contact with the fruit, as well as lack of training in proper handling practices. These facts are decisive for delivering safe products to the consumer, which in turn influences their confidence to Mexican products (Morales, 2001).
On the other hand, Food and Drug Administration and the United States Department of Agriculture published in October 1998 the "Final guide: Guide to minimize microbial food safety hazards for fresh fruits and vegetables". Both "Final Guide" and NOM-034-FITO-1995 point out good handling and agricultural practices such as washing, selection, and packaging done with sanitary practices.
According to its authors, the guide is consistent with the commercial rights and obligations of the USA and does not try to impose barriers or unnecessary restrictions to foreign producers and exporters.
These regulations should also help to improve the safety and quality of fruits and vegetables of third world countries that export to the USA. A synthesis of the main points to consider when exporting produce to the USA is presented as follows:
Water quality
Water for agricultural practices: it can be temporally contaminated as a result of sewage discharges.
Water for processing: it is in high contact with the product.
Water for washing: washing can help to reduce microbial content in the surface of fruits and vegetables (Figure 17 Avocados submerged in chlorinated water).
Water for cooling: water and ice deposits might be contaminated by products carrying pathogens.
Some preventive measures to prevent water contamination are: the identification of the origin of the water and to keep it in good condition, identification of potential contamination sources, protection of deposits from wild or farm animals, periodical analyses of the water quality, disinfection of deposits and water.
Manure and bio solids from sewage If used as soil fertilizers and handled inappropriately, constitute a source of hazardous microorganisms.
Treatments to reduce pathogen levels: such as pasteurization, heath drying, aerobic and anaerobic digestion, sterilization, etc.
The following practices are recommended to reduce the risks: place manure as far as possible from the fresh produce and inside containers, minimize leakages, minimize the potential of cross-contamination by birds or rodents, and obtain the manure specifications from the supplier.
Non-treated manure should not be applied to the soil during seeding and cultivation, the time between the application and the harvest should be maximized, and if not possible, non-treated manure should not be used at all.
Animal feces: domestic animals should be excluded from the fields and their waste removed.
Workers hygiene: the workers must understand and apply basic hygiene principles to avoid being a hazard (Figure 18 Workers with proper dressing in a packing house).
Recommendations: It is important to assure that every person that comes close or in contact with the product will follow the hygiene rules. A training program should be established, including demonstrations, for example, of how to wash the hands. Operators should be able to recognize signs of infectious diseases and lesions of workers, who must be protected. All visitors must follow the hygiene rules too.
Lavatories: should be accessible to workers at every time; should be placed far from water deposits; well supplied with soap, paper towels and bins; keep facilities clean, and have an emergency plan in case of leakages.
Cultivars: clean all the storage facilities before use; be sure that all washed product is not re-contaminated.
Packinghouse: remove mud and soil (as much as possible) from the fruit before it leaves the field, dispose of all damaged packaging material that cannot be cleaned; clean all containers; protect the unused containers from contamination; clean all the machinery and equipments, as well as packing areas, at the end of the day.
Pest control: establish a supervision program for the affected areas; maintain the fields free of leaves, grass and rubbish; keep a list of all the actions taken to combat pests.
Transportation: make sure that trucks are clean before loading the product; keep the right storage temperature during transportation, minimize damage when loading and unloading.
Trace back: a trace back system will help identify the origin of a food borne disease and help eliminate the hazardous processes. An effective documentation system should include the harvest date, farm identification, and a list of people that worked in the batch. Technologies should be developed to identify the origin of the fruit.
As it can be seen in this short summary, the application of the recommendations given in the "Guide" implies that the farmer should make big great efforts and investments in order to assure the quality of fruits and vegetables. It also creates the necessity of a system that verifies, certifies and informs the consumers about the new quality assurance procedures. All this is done with the aim of placing the product in national and international markets at higher prices.
From a technical point of view, and based on current scientific evidence, avocado has minimal risks of microbial contamination. Nevertheless, sanitary aspects have been (and continue to be) a technical barrier to the commercialization of avocado in the U.S. In consequence, the general recommendation made to avocado producers is to comply with the Guide in order to avoid hurdles when entering this important market (Salazar-Arriaga and González Sánchez, 1999).
Quarantine pests in the United States
Nowadays, the only potentially importer country that limits the buying of avocado due to sanitary quarantines is the United States. The U.S. Department of Agriculture published a list with 21 species of fruit fly, classified in 10 genres, detected since 1905 and 1918. This information was verified in 1942-1965, and since then and 1979, weevils are mentioned (4 species). Except for the weevils, the rest of the species are not important as pests, and there are not published studies on their detection and control. Furthermore, they are not known by the farmers and do not appear in technical reports. However, in the case of fruit flies, international quarantines still apply to prevent their spread into free zones. Twelve weevil species are mentioned: 6 of Conotrachelus, 2 of Helipus, 2 of Stenoma, and 2 of Copturus.
In Mexico, avocado is mainly consumed as a fresh fruit, and it is considered a traditional food (Figure 19 The consumption per capita is 10.0 kg, the largest market in the world). It has no substitute products, and the domestic demand is fulfilled. However, it is believed that the demand for avocado will increase once it is recognized as a functional food. As years go by, the domestic market has had a positive response to the increase of the offer, by increasing the demand and maintaining an equilibrium in the prices that is enough to keep and promote the growth of the cultivars in the region.
This status has been maintained without any marketing campaign aimed to raise avocado consumption or suggest other uses for the fruit. No overproduction has been generated, so its industrialization has not been carried out in large volumes, as it is done in other countries. The Mexican market is not characterized by the demand of high-quality avocado; the consumers tend to focus on low prices. The marketing categories for avocado, according to the Mexican federal order NMX FF-016-SCFI-2002 are:
The whole process required to supply the fruit to the domestic market lasts from 4 to 10 days. Under the current handling conditions, the medium shelf life of the fruit is 12 to 14 days, which gives an appropriate time frame for the fruit to reach the consumer. In Mexico, consumers prefer fruit that is already dark in the peel and soft to the touch, this condition covers up some lesions originated in the field, such as anthracnose, avocado blight, or slight mechanical damage.
The consumer preferences in non-producer countries that import avocado may vary. However, the general aspects that the consumers of these countries look for are:
(Morales et al., 2000)
Recently, a big interest on organic foods has developed in many countries, particularly about organic fruits and vegetables. In the United States, sales of organic products have grown approx. 20% annually since 1991. According to Katherine DiMatteo, from the Organic Commerce Association in the U.S.A, the highest growth within this market is expected for frozen and prepared organic foods. This can influence the market of avocado products such as dip and frozen guacamole.
In 1995, the first organic cultivar in Mexico was certified. By 1997, eight orchards were certified, which produced 10,000 tons of fruit by the year 1998. Organic avocado is becoming an important part of the national marketing strategy, because of the increasing number of consumers and producers that are concerned about the environment. The industries of developing countries can benefit from the production of oil, cosmetics, and guacamoles elaborated from organic avocado, while consumers can benefit from clean and free of residue fruit (Quintero-Sánchez, 2001).
On the other hand, people around the world have contributed to diversify the uses of avocado, for example: in Brazil, it is added to ice creams and sorbets, in Japan it is eaten in sushi rolls, in Cuba the pulp is mixed with capers, green olives, lemon juice and olive oil to make a sauce that is served with steamed fish, in Nicaragua is stuffed with cheese, fried and baked.
In other countries like Taiwan, it is eaten with milk and sugar, in Korea is mixed with milk and used as a facial cream and body lotion, in Indonesia is mixed with coffee, rum and milk to make a refreshing beverage, in the Caribbean mixed with salt, garlic, and coconut and served as an entry, in the Philippines the avocado purée is mixed with sugar and milk, to make a beverage that is served as dessert (Ayala, 2001)