New Zealand Yams, Papa Roja, Truffette Acide
Oxalis tuberosa F. Oxalidaceae
Herb Book Commendations
Compact, perennial, tuberous herb to 30cm high, with succulent stems carrying clusters of 2-5cm wide, trifoliate, heart-shaped leaflets, giving the plant an attractive appearance, resembling clover. As days shorten in autumn, the stolon roots form rhizomes. The rhizomes develop into oval-shaped tubers, 3-15cm long, with indented line markings and eyes at the centre of each indent. The skin is bright pink, purple or red. There are over a dozen cultivars. Inside texture is firm, crisp, and creamy-white in colour. Yellow/orange or red flowers are tristylous in form, with seed-set being very rare. Each plant, given optimum conditions, may produce from 30-50 tubers.
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Nutritional value of tubers is considered similar to potatoes. On average, they contain 70-80% moisture, 11-22% carbohydrate, 1% fat, and 9% protein with a balance of essential amino acids (valine and tryptophan are the limiting ones). The carbohydrate is usually rich in sugar and is easy to digest. Some cultivars have been found to contain much lower levels of oxalic acid than potatoes. It is recorded that all levels of oxalic acid found in oca, are far below those of spinach and several other widely-eaten, green vegetables.
calcium, iron, phosphorus
Oca is used in numerous ways and highly prized as a vegetable. In South America, some types are eaten raw, sprinkled with salt, lemon and hot pepper. Mostly, they are cooked, by steaming, boiling, roasting, frying, added to soups, stews, stirfries, pickles and made into chips. Cooked tubers have a flavour similar to parsnip and sweet potato. After steaming oca is served with a little butter, or served with a white sauce. Leaves and stems are eaten raw or cooked, and have a similar taste to shamrock. They have a mild, sour taste, so a leaf at the beginning of a meal is useful to stimulate the digestive juices in the mouth. Leaves are used as a garnish. Large amounts should not be eaten on a daily basis, due to the oxalic acid content, as this substance can hinder calcium availability in the body.