Overview of Blue Agave
The Blue Agave, A. tequilana, is a domestic species of agave that is descended from Agave angustifolia (Gentry 1982). Blue agave is culturally and economically significant because it is the only species of agave that can be used to produce tequila which is certified by the Mexican government (NOM-006-SCFI-2012). Its sap is the main and defining ingredient of all forms of the alcoholic beverage and, “By federal law in Mexico, A. tequilana Web var. azul is the only variety of agave permitted for the production of any tequila (Gil Vega et al. 2001).”
Many botanists acknowledge that the separation of Blue Agave as its own species is nominal (Lopez et al. 2003; Valensuela Zapata & Nabhan 2003; Franck 2012; Garcia-Mendoza & Chiang 2003; Gentry 1982). However, Gentry and others have been reluctant to synonymize it with the wild species A. angustifolia because the tradition of maintaining separation is important to the tequila industry (Valensuela Zapata & Nabhan 2003). The tequila industry relies on the species classification of A. tequilana to provide commercial distinction between tequila and other mezcals and does not allow any other varieties besides agave tequilana var. azul for pure tequila (NOM-006-SCFI-2012; Valensuela Zapata & Nabhan 2003).
The sap of Agave tequilana is sweet and edible. It has been used since Pre-Columbian times, along with other agave species, to make alcoholic beverages and traditional medicines (Vargas-Ponce et al. 2009; Mohr 1999). Various indigenous Mesoamerican cultures have considered agaves to be sacred plants because they supplied many products necessary to everyday life and there (Bye 1993). In part because of this, there is an agave goddess in the Aztec pantheon named Mayahuel that is particularly associated with the traditional alcoholic beverage pulque, which blue agaves and their species of origin were likely used to produce (Vargas-Ponce et al. 2009; Bye 1993).
Today, the market for pulque has shrunk considerably and most Blue Agave is grown for tequila production (Mohr 1999). The tequila industry has grown substantially in the last 15 years, featuring a 19.82% yearly increase between 1995 and 2008 (Valenzuela 2011).The industry has seen as switch to intensive cultivation of Blue Agave in monoculture plantations since the beverage gained worldwide popularity in the 1980s (Dalton 2005). In the past 10 years especially, this has resulted in environmental impact in the form of soil erosion as well as soil, air and water pollution as well as the displacement of traditional food crops and Agave landraces in the zone designated Appellation of Origin for Tequila (Zizumbo-Villarreal et al. 2013).
Gloves should be worn when handling Blue Agave. All tissues of A. tequilana have calcium oxalate crystals, which are sharp at both ends and cause irritation and persistent rashes when they come in contact with the skin. In tequila distilleries 5/6 of workers that handle the stems and 1/3 of workers who harvest agave experience irritation characteristic of contact dermatitis (Salinas et al. 2001).
Environmental Impact of Intensive Cultivation of Blue Agave
Intensive Cultivation by the Tequila Industry
In 1999 there were over 90,000 acres of Blue Agave under cultivation in Guadalajaa Mexico and the Tequila industry has grown substantially since then (Valenzuela 2011; Mohr 1999). Growth has been especially strong in the last 15 years, leading to a 19.82% annual increase in the industry between 1995 and 2008 (Valenzuela 2011). As a result, cultivation has been intensified and industrialized leading to the danger of erosion in germplasm diversity among agave plants used for the production of mescals in west-central Mexico. While traditional non-industrial growers in southern Jalisco cultivate up to 20 varieties of agave, the only variety that can be cultivated to produce Tequila legally recognized by the Mexican government is Agave tequilana Weber. var. azul, Blue Agave (NOM-006-SCFI-2012; Valenzuela 2011; Colunga-GarcíaMarín & Villarreal 2007).
Trends in Cultivation and Biodiversity Concerns
Because of the industry's efforts to meet growing demand, mono-crop plantations are replacing small traditional farmers with increasing speed. In 1950, nearly 50% of total Tequila produced was made from Blue Agave grown in mono-crop plantations while the rest was produced by farmers in river canyons using agaves from different species and varieties grown in milpa plots or collected from wild populations (Zizumbo-Villarreal et al. 2013). When Tequila acquired international protection under the 1978 Appellation of Origin the name “Tequila” became restricted to agave spirits (mescal) which were made with Agave tequilana Weber var. azul in 5 Mexican states: Nayarit, Jalisco, Michoacan, Tamaulipas & Guanajuanto (NOM-006-SCFI-2012; Valensuela Zapata & Nabhan 2003). The industry then pressured the government into supporting growth of Blue Agave by financing small producers(Zizumbo-Villarreal et al. 2013).
This led to a raw material surge that resulted in a market crash which made growing agave unappealing to many small growers who then abandoned cultivating the crop. This boom and bust cycle plays out every 8-10 years alongside the plant’s life cycle(Valensuela Zapata & Nabhan 2003). During short falls the industry has often resorted to using other species of agave including wild populations which has resulted in some wild populations being severely depleted by this activity, and an overall decrease in biodiversity (Valenzuela 2011).
To combat short falls the industry changed its strategy begining in 2000 (Zizumbo-Villarreal et al. 2013). It began renting land from small producers to increase crop density and intensify cultivation itself, applying agrochemicals (herbicides, fungicides, pesticides and fertilizers) and expanding cultivation to areas outside its optimum climate, topography and soil range (Valenzuela 2011). This has resulted in the displacement of traditional food crops and Agave landraces in the designated Appellation of Origin zone for Tequila as well as soil erosion and soil, air and water pollution (Zizumbo-Villarreal et al. 2013; Valensuela Zapata & Nabhan 2003).
Traditional, non-industrial farmers tend to maintain high levels of agro-biodiversity which is helpful to biodiversity conservation. In Mexico’s central western region near the south of the state Jalisco (where mescal originated) multiple landraces of Agave angustifolia Haw. are still cultivated for mescal production (Vargas-Ponce et al. 2009). Traditional cultivation practices, which include in situ management of wild populations, are being replaced as commercial Blue Agave monoculture plantations expand (Vargas-Ponce et al. 2009). Loss of landraces threatens biodiversity because A. angustifolia's traditional landraces have genetic diversity similar to wild populations (Valenzuela 2011; Vargas-Ponce et al. 2009).
Most botanists agree that Blue Agave is among the most economically important species of the Rigidae section of the genus Agave. According to Gentry’s 1982 comparative analysis of floral morphology, the Blue Agave is derived from one species of highly adaptable Agave called Agave angustofolia (Valenzuela Zapata & Nabhan 2003). It has been acknowledged by many botanists, including Gentry, that the separation of Blue Agave as its own species is nominal (Gentry 1982). However, he and others have been reluctant to synonymize it with the wild species A. angustifolia because the tradition of maintaining separation is important to the Tequila industry (Valensuela Zapata & Nabhan 2003). The Tequila industry relies on the species classification of A. tequilana to provide commercial distinction between Tequila and other mezcals (Valensuela Zapata & Nabhan 2003).
The low genetic diversity of this nominal species has made it especially vulnerable to disease, climate shifts and pests (including the bacterium Erwina carotovora and the fungus Fusarium oxysporum) which has led to years when entire fields have been lost to blights (Simpson et al. 2011; Dalton 2005; Valensuela Zapata & Nabhan 2003). Recent research demonstrates there may be more genetic diversity within the Blue Agave species than first thought and that it could be exploited to promote stability and health of the crop, however this process would likely require that the zone of Appellation of Origin be expanded (Simpson et al. 2011; Vargas-Ponce et al. 2009; Colunnga-GarcíaMarín et al. 2007).
Relevance to Humans and Ecosystems
Products of the Blue Agave
Tequila is a variety of mescal liquor that was originally produced in the town of Tequila in Jalisco, Mexico. It is a Spanish modification of a fermented beverage called pulque that was made by the Aztecs for religious and medical purposes (Mohr 1999; Miller & Taube 1993). Tequila is obtained from the distillation of the fermented juice of the agave plant. Plants require 7 to 12 years to mature before they can be tapped for sap. The productions process consists of cooking to hydrolyze the inulin polysaccharides into fructose, milling to extract the sugars, fermentation with a strain of Saccharomyces cerevisiae to convert sugars into ethanol and organoleptic compounds, and finally distilling it in a two-step process (Cedeño 1995). A key distinguishing feature between pulque and Tequila is that pulque can be made from many different species of agave and is not distilled, while Tequila is distilled and must be made from Agave tequilana var. azul to legally qualify as Tequila (NOM-006-SCFI-2012; Mata Pizón & Zolla 1994b).
Agave tequilana, or Blue Agave, is the only species of agave that can be used to produce Tequila certified by the Mexican government. According to the Tequila Regulatory Council of Mexico, a distilled alcoholic spirit must be made from at least 51% Blue Agave to be recognized as Tequila under the Norma Oficial Mexicana (NOM-006-SCFI-2012). Pure Tequila must be made from 100% Blue Agave (NOM-006-SCFI-2012).
Because Blue Agave yields an internationally popular product, it has also indirectly created tourism that benefits its zone of production. The town of Tequila became a mescal center in the 1780s and later enlarged its market when railroads were built in the region (Walton 1977). The reputation of Tequila’s mescal spread until eventually it came to be called Tequila. In 1978 tequila acquired international Appellation of Origin protection, meaning Tequila production has been restricted to 5 states in Mexico: Nayarit, Jalisco, Michoacan, Tamaulipas & Guanajuanto (NOM-006-SCFI-2012; Valensuela Zapata & Nabhan 2003). The increase in world-wide popularity of the drink since the 1980’s has made it a major export of Jalisco, and the Appellation of Origin has also contributed to making the town of Tequila a tourist destination promoted by the Mexican government (Dalton 2005).
It has been suggested that biomass (such as leaves which are usually left in the field) could be co-harvested during the course of Tequila production so that biofuel could be produced without additional land demands. Furthermore, if this were put into practice, abandoned agave farms in Mexico and Africa that had produced raw materials for the natural fiber market could be converted to bioenergy cropland (Valensuela Zapata & Nabhan 2003).
It has also been found that Blue Agave sap has the potential to yield a diabetic friendly sweetener since its fructans are not of the inulin polysaccharide group (Lopez et al. 2003). Additionally, because the sap has an iron content of 2.15mg/100g and 1.41 mg/100g zinc content, it has the potential to be used as a food supplement to correct mineral deficiencies (Lopez et al. 2003).
Agave tequilana, commonly called blue agave, tequila agave, mezcal or maguey is an agave plant that is an important economic product of Jalisco, Mexico, due to its role as the base ingredient of tequila, a popular distilled spirit. The high production of sugars—mostly in the form of fructose—in the core of this plant is the most important characteristic of the plant making it suitable for the preparation of alcoholic beverages.
The tequila agave is a native of Jalisco, Mexico. The tequila agave favors high altitudes of more than 1,500 meters and grows in rich and sandy soils. While commercial and wild agaves have different life cycles, both grow into large succulents, with spiky fleshy leaves, that can reach over two meters in height. Wild agaves, however, sprout a shoot when about five years old that can grow an additional five meters and are topped with yellow flowers.
The flowers are pollinated by a native bat (Leptonycteris nivalis) and produce several thousand seeds per plant. The plant then dies. The shoots are removed when about a year old from commercial plants to allow the heart to grow larger. The plants are then reproduced by planting these shoots; this has led to a considerable loss of genetic diversity in cultivated blue agave.
It is rare for one kept as a houseplant to flower; nevertheless, a 50-year old blue agave in Boston grew a 10 m (30 ft) stalk requiring a hole in the greenhouse roof and flowered in the summer of 2006.
Tequila is produced by removing the heart of the plant in its twelfth year. Normally weighing between 35–90 kg (77–198 lb). This heart is stripped of its leaves and heated to remove the sap, which is fermented and distilled. Other beverages like mezcal and pulque are also produced from blue and other agaves by different methods (though still using the sap) and are regarded as more traditional.
Researchers from Mexico's University of Guadalajara believe blue agave contains compounds that may be useful in carrying drugs to the intestines to treat diseases, such as Crohn's disease and colitis.
As agave production has moved to an industrial scale since the end of 1980s, diseases and pests, collectively referred to as TMA (tristeza y muerte de agave, "wilting and death of agave"), have hit the crops. Through the 1990s, diseases spread, particularly Fusarium fungi and Erwinia bacteria, exacerbated by the low genetic diversity of the agave plants. Other problems include the agave weevil, Scyphophorus acupunctatus, and a fungus, Thielaviopsis paradoxa.
- ^ Johnson, Carolyn Y. (July 11, 2006). "What's really up on Beacon Hill: 50-year-old plant starts its blooming finale". The Boston Globe. http://www.boston.com/news/local/massachusetts/articles/2006/07/11/whats_really_up_on_beacon_hill/. Retrieved 2006-07-11.
- ^ "See the 50-year-old agave blooming video from YouTube". http://www.youtube.com/watch?v=6idrlI9erV0.
- ^ Reference, Chicago Sun-Times Sun April 1, 2007 p. 6A, or announcement made at ACS's annual meeting March 2007 in Chicago.
- ^ Dalton, Rex (2005-12-22). "Alcohol and science: Saving the agave". Nature 438 (7071): 1070–1071. doi:10.1038/4381070a. ISSN 0028-0836. PMID 16371973.
- ^ Altuzar, A.; E. A. Malo, H. Gonzalez-Hernandez, J. C. Rojas (2007). "Electrophysiological and behavioural responses of Scyphophorus acupunctatus (Col., Curculionidae) to Agave tequilana volatiles". Journal of Applied Entomology 131 (2): 121–127. doi:10.1111/j.1439-0418.2006.01135.x.
- ^ Martinez-Ramirez, J.; P. Posos-Ponce, J. Robles-Gomez, K. Beas-Ruvalcaba, L. Fucikovsky-Zak. "Base leaf spot and a black rot of agave caused by Thielaviopsis paradoxa". Phytopathology. 96. 2006 American Phytopathological Society Annual Meeting. Quebec City, Canada. pp. S74. doi:10.1094/PHYTO.2006.96.6.S1. http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO.2006.96.6.S1.
- ^ Jimenez-Hidalgo, I., Virgen, G., Martinez, D., Vandemark, G.J., Alejo, J., Olalde, V. (March 2004). "Identification and characterization of soft rot bacteria of agave tequilana weber var.azul". European Journal of Plant Pathology 110: 317–331. doi:10.1023/B:EJPP.0000019791.81935.6d. http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=142278.
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Caution (when Handling)
All tissues of A. tequilana have calcium oxalate crystals, which are sharp at both ends and cause irritation and persistent rashes when they come in contact with the skin. In tequila distilleries 5/6 of workers that handle the stems and 1/3 of workers who harvest agave experience irritation characteristic of contact dermatitis (Salinas et al 2011).
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