Introduction Processing of Nopalitos Harvest Storage
Minimally Processed Nopalitos Industrial Techniques Nopalitos as Products In Brine Pickled
Sauces, Marmalades, Jams, Candies, and Juices Mucilage
Dietary Fiber from Cladodes Use of Cladodes in Medicine Cochineal
Pre-Colonial and Colonial History Decline and Resurgence Importance and Uses Carminic Acid Biology of Cochineal Origin and Diversity Morphology and Life Cycle Host
Environmental Factors and Natural Enemies D. coccus versus Wild Cochineal Marketing of Cochineal Production and Prices Supply and Demand Conclusions and Future Prospects Literature Cited
A common use of cactus stems is nopalitos —tender young cladodes—a traditional vegetable eaten fresh or cooked in various dishes. Mexicans are the principal consumers. Nopalitos are generally obtained from Opuntia ficus-indica, O. robusta, or Nopalea spp. The number of spines and the color are quality factors evaluated by consumers. Several new consumable products are being developed from the stems (e.g., marmalades, blends for breakfasts, and pickles), and the cladodes have medical and cosmetic uses.
Another important use of Opuntia stems is the production of carminic acid, a natural colorant developed by the precolonial indigenous people of Mexico. Carminic acid is produced by an insect known as cochineal, or cochinilla del nopal, a parasite that infests several species of cacti belonging to two closely related genera, Opuntia and Nopalea. Identified by the scientific name, Dactylopius, the genus has been recognized worldwide since the 16th century as the source of a valuable red pigment, whose main component is carminic acid. Native to the Americas, cochineal was known in colonial times as nocheztli or grana in New Spain, and as macno or magno in the Andean region of South America.
The chemical composition of cladodes determines their use as a raw material in the food industry. Cactus stems, as other vegetables, have low protein and fat contents (Table 13.1). The crude fiber is higher than in most other vegetables and is an important consideration for human health. The nitrogen-free extract content is high and includes soluble dietary fiber, insoluble dietary fiber, and some sugars. The ash depends on the soil composition, but the main components are calcium and potassium; sodium and phosphorus are present in lesser amounts. Calcium oxalate crystals, which are insoluble in water, increase with age and can constitute 85% of the ash of old cladodes (Pimienta Barrios 1990; Granados and Castañeda 1991; Sáenz et al. 1997). The crude fiber also increases with cladode age (Table 13.1). This is significant, because young nopalitos can be used as a fresh vegetable in salads, whereas old nopalitos, whose high fiber content makes them difficult to chew, are useful for other purposes. Cladodes have high concentrations of phenylalanine, leucine, and vitamins (retinol and ascorbic acid; Zambrano et al. 1998
Nopalitos have formed part of the diet of Mexican people since pre-Hispanic times; nowadays, they are also a specialty vegetable in the United States. Production in Mexico is about 600,000 tons fresh weight per year; under intensive management involving close planting in irrigated and fertilized beds that are often covered with plastic, productivity can be 250 tons ha-1 year-1 (Flores 1997; Nobel 1998). In Mexico, people prefer to buy thin and turgid cladodes with a fresh appearance and a brilliant green color. They are cooked at home as an ingredient in various recipes for stews, dishes and desserts. Outside Mexico, people of Mexican origin can purchase processed nopalitos. Young cladodes are in a rapid growth phase and have high metabolic activity and high transpiration rates (Cantwell 1991). However, once they are harvested as nopalitos, they have moderate respiration rates (25 microliter CO2 g-1 hour-1 at 2o°C) and a low ethylene production (0.2 nanoliter g-1 hour-1 at 2o°C; Cantwell et al. 1992). Nopalitos are highly perishable after harvest; the deterioration processes lead to wilting, browning, and microbial contamination by Alternaria sp., Penicillium sp., and other fungi (Ramayo-Ramirez et al. 1978a), especially when they have been despined and diced.
Cladodes for nopalitos are harvested by hand, gripping the bottom of a pad and twisting more than 90° until it snaps off the mother plant. The lower tissues can be torn if this action is not carried out with care, so detached cactus stems and the mother plants can easily be infected by microorganisms. For this reason, cutting a pad at its base with a knife is better than simply twisting it off. In any case, harvested nopalitos must be protected from the sun to lessen metabolism, transpiration, and infection (Corrales 1992a). After harvest, intact nopalitos (with spines) are directly taken to local markets; for distant markets, nopalitos are packed in a shady area.
The form in which nopalitos are transported depends on where the sale takes place and on the distance to the market. The following modalities occur: (1) transportation of intact or despined nopalitos over short distances in vans for sale by bulk in local markets; (2) intact or despined nopalitos, packed in baskets called colotes containing approximately 200 pads; (3) 500 to 550 intact nopalitos packed in sacks for the large markets of Mexico City; (4) intact or despined nopalitos packed in cardboard boxes or wooden crates of 10 to 15 kg capacity, when the market is in California or in Mexico near the U.S. border; and (5) intact nopalitos packed in a cylindrical packing unit (paca), which is the main mode used for the large markets of Mexico City and other cities in central Mexico (Nobel 1998). The latter packing unit is 1.6 to 1.7 m in height and 0.7 to 0.8 m in diameter, containing 2,500 to 3,000 pads (Corrales 1992a). For a paca, nopalitos are placed horizontally on cloth as a layer inside a metal mold; following its
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