Oca
Encyclopedia
Oxalis tuberosa is an herbaceous perennial plant that overwinters as underground stem tuber
s. These tubers are known as oca, oka, or New Zealand Yam. The plant was brought into cultivation in the central and southern Andes
for its tubers, which are used as a root vegetable
. The plant is not known in the wild, but populations of wild Oxalis species that bear smaller tubers are known from four areas of the central Andean region. Introduced to Europe
in 1830 as a competitor to the potato
and to New Zealand
as early as 1860, it has become popular in that country under the name New Zealand yam and is now a common table vegetable.
The flavour is slightly tangy, and texture ranges from crunchy (like a carrot
) when undercooked, to starchy or mealy when fully cooked. Though the original Andean varieties are widely variable in colour from purple to yellow, the usual New Zealand variety is a fleshy pink.
Oca can be boiled, baked or fried. In the Andes
it is used in stews and soups, served like potatoes or can be served as a sweet. Oca is eaten raw in Mexico
with salt, lemon, and hot pepper.
Oca are fairly high in oxalates, concentrated in the skin, but there is significant variation in oxalate concentration among varieties. The traditional Andean preparation methods are geared towards reducing the oxalate level of the harvested vegetable. This is done by exposure to sunlight which decreases the organic acid content and thereby increases the sweet taste of the oca. The bioavailability of oxalate appears to be similar to spinach. Recent oca cultivars have a lower oxalate content, and have also been selected for more flexibility in day lengths.
due to its easy propagation, and tolerance for poor soil, high altitude and harsh climates.
, and are day length dependent, forming tubers when the day length shortens in autumn. In areas with harsh winter climates, early frosts may cut back the foliage before the tubers have a chance to form. In tropical areas where the days are unchanging in length, oca will not set a crop successfully.
Tuber
Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction...
s. These tubers are known as oca, oka, or New Zealand Yam. The plant was brought into cultivation in the central and southern Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
for its tubers, which are used as a root vegetable
Root vegetable
Root vegetables are plant roots used as vegetables. Here "root" means any underground part of a plant.Root vegetables are generally storage organs, enlarged to store energy in the form of carbohydrates. They differ in the concentration and the balance between sugars, starches, and other types of...
. The plant is not known in the wild, but populations of wild Oxalis species that bear smaller tubers are known from four areas of the central Andean region. Introduced to Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
in 1830 as a competitor to the potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
and to New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
as early as 1860, it has become popular in that country under the name New Zealand yam and is now a common table vegetable.
Edibility
The stem tubers of oca form in the ground in the autumn. These are commonly boiled before eating although they can also be eaten raw. The leaves and young shoots can be eaten as a green vegetable.The flavour is slightly tangy, and texture ranges from crunchy (like a carrot
Carrot
The carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh...
) when undercooked, to starchy or mealy when fully cooked. Though the original Andean varieties are widely variable in colour from purple to yellow, the usual New Zealand variety is a fleshy pink.
Oca can be boiled, baked or fried. In the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
it is used in stews and soups, served like potatoes or can be served as a sweet. Oca is eaten raw in Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
with salt, lemon, and hot pepper.
Oca are fairly high in oxalates, concentrated in the skin, but there is significant variation in oxalate concentration among varieties. The traditional Andean preparation methods are geared towards reducing the oxalate level of the harvested vegetable. This is done by exposure to sunlight which decreases the organic acid content and thereby increases the sweet taste of the oca. The bioavailability of oxalate appears to be similar to spinach. Recent oca cultivars have a lower oxalate content, and have also been selected for more flexibility in day lengths.
Cultivation
Oca is one of the important staple crops of the Andean highlands, second only to the potatoPotato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
due to its easy propagation, and tolerance for poor soil, high altitude and harsh climates.
| fresh | dried | |
| Energy Energy In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems... (J) |
255 | 1360 |
| Water Water Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a... (g) |
84.1 | 15.3 |
| Protein Protein Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of... (g) |
1.0 | 4.3 |
| Carbohydrates (g) | 13.3 | 75.4 |
| Ash Ash (analytical chemistry) In analytical chemistry, ashing is the process of mineralization for preconcentration of trace substances prior to chemical analysis. Ash is the name given to all non-aqueous residue that remains after a sample is burned, and consist mostly of metal oxides.... (g) |
1.0 | 3.9 |
| Calcium Calcium Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust... (mg) |
2 | 52 |
| Phosphorus Phosphorus Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks... (mg) |
36 | 171 |
| Iron Iron Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust... (mg) |
1.6 | 9.9 |
| Retinol Retinol Retinol is one of the animal forms of vitamin A. It is a diterpenoid and an alcohol. It is convertible to other forms of vitamin A, and the retinyl ester derivative of the alcohol serves as the storage form of the vitamin in animals.... (µg) |
1 | 0 |
| Riboflavin Riboflavin Riboflavin, also known as vitamin B2 or additive E101, is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a... (mg) |
0.13 | 0.08 |
| Niacin Niacin "Niacin" redirects here. For the neo-fusion band, see Niacin .Niacin is an organic compound with the formula and, depending on the definition used, one of the forty to eighty essential human nutrients.Niacin is one of five vitamins associated with a pandemic deficiency disease: niacin deficiency... (mg) |
0.43 | 0.85 |
| Vitamin C Vitamin C Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress... (mg) |
38.4 | 2.4 |
Distribution
Outside of the Andean region Oxalis tuberosa is cultivated commercially in Mexico and New Zealand.Propagation
Oca is usually propagated vegetatively by planting whole tubers. Propagation by seed is possible but is rarely used in practice.Climate requirements
Oca need a long growing seasonGrowing season
In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....
, and are day length dependent, forming tubers when the day length shortens in autumn. In areas with harsh winter climates, early frosts may cut back the foliage before the tubers have a chance to form. In tropical areas where the days are unchanging in length, oca will not set a crop successfully.
Soil requirements
The crop grows with very low production inputs and in generall on plots of marginal soil quality and tolerates acidities between about pH 5.3 and 7.8.Cropping factors
The cultural practice is similar to potatoes. Planting is done in rows or hills 80–100 cm apart with plants, spaced 40–60 cm apart in the rows.). Monoculture predominates, but interplanting of several tuber species in one field is common in Andean production. In many instances Andean farmers will allow a mixture containing two or three tuber crops to be planted in one field. Often this mixture consists of several different clones of each species. Such mixed fields may later be sorted into tuber types during harvest or before cooking. Mixed planting with legumes or grain crops is occasionally practiced.Pest and Diseases
Crops in the Andes are usually infected with viruses, causing chronic yield depression. Adequate techniques to remove viruses have to be applied before the varieties can be used outside the Andean region. Cultivation is also constrained by the oca weevil (Ariodistus tuberculatus), Andean potato weevil (Premnotrypes spp) and the ulluco weevil (Cylydrorhinus spp), beetles often destroying entire crops. Further notable pests are nematodes.Yields
Yields vary with the cultural method. Annals from Andean countries report about 7-10 tons per hectare for Oxalis tuberosa production. But with adequate inputs and virus free propagation material, oca production can range from 35 to 55 tons per hectare.Limitations
As already mentioned, viruses, day length restrictions and the precence of oxalates can be considered as limiting factors. Scientists work with specific breeding, selection and virus cleaning programs on these purposes.Agricultural potential
Potential distribution to other suitable ecogeographical zones of for example Asia and Africa is possible. The cultivation and use of Oxalis tuberosa in New Zealand already indicates a wider utilization and agricultural interest than has been previously recognized.Alternative names
- Apilla in BoliviaBoliviaBolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
- Apiña in BoliviaBoliviaBolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
and PeruPeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean.... - Hibia in ColombiaColombiaColombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
- Yam in many other places, such as PolynesiaPolynesiaPolynesia is a subregion of Oceania, made up of over 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are termed Polynesians and they share many similar traits including language, culture and beliefs...
and New ZealandNew ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, where the DioscoreaDioscoreaDioscorea is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending into temperate climates...
vegetables known elsewhere as yamYam (vegetable)Yam is the common name for some species in the genus Dioscorea . These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania...
s are generally very uncommon.
Further reading
- Davidson, Alan. Oxford Companion to Food (1999). "Oca", p. 547 ISBN 0-19-211579-0
External links
- Oca in Lost Crops of the Incas
- NewCROP page on oca
- Genetic Resource Conservation of oca and other Andean tubers at International Potato Center
- Oca, ulluco, and mashua at the International Potato Center
- Oxalis tuberosa at Plants for a Future