The Water Chestnut: Culinary Uses and Nutrition
Water chestnuts are the bulbs of an aquatic plant that grow in shallow rivers and marshes. The plant originates from southern China where it has been a traditional crop since ancient times. The crop is seasonally rotated with rice in paddy fields. Water chestnuts are popular in the cuisines of Thailand, Vietnam and Japan, as well as China, were they are also prized in Chinese traditional medicine. Fresh water chestnuts have a superior sweet taste and crunchy texture as compared with the slightly bland taste of canned water chestnuts. In the past only canned and not fresh water chestnuts were available in the west. These days fresh water chestnuts can be found in Chinese supermarkets during the winter months.
There are two main varieties of water chestnut. The water caltrop, (Trapa natans) also known as the horned chestnut because it has a pair of horns protruding from both sides. The water caltrop grows wild in Europe and also North America, where it is considered an invasive species. And the common water chestnut or Chinese water chestnut (Eleocharis dulcis). The main differences between the two is that the common water chestnut has a dark mahogany colored skin and can be eaten raw. The caltrop, which comes from a different botanical family, known as Trapaceae, contains toxins and must be thoroughly cooked before eating. Water caltrop is also grown in India, in particular Kashmir, where it is used as food and also for its shell, which is made into rosaries. In fact another name for water caltrop is Jesuits-nut.
Culinary Uses: Water chestnuts have a unique flavor similar to Jerusalem artichoke only fragrant with an apple like sweetness. After washing them thoroughly to remove dirt, this vegetable can be peeled before or after cooking with a sharp paring knife. The water chestnut has a whitish flesh which tends to darken during cooking. Adding lemon juice to the water will help prevent this. Water chestnuts cook quickly. Boil or steam them for about five minutes. In southeast Asia this bulb vegetable is often stir fried with ingredients like bamboo shoots, ginger and sesame oil. It is also combined with rice, pasta and rich meats such as duck or beef. In Thailand water chestnut is the main ingredient in the dessert tabtim krob and it is also served along with palm fruits. In western cooking water chestnuts wrapped in bacon is a classic hors d’oeuvres.
Nutritional Content: Water chestnuts are a good source of vitamin C, and also vitamin B6. They are an excellent source potassium, magnesium, riboflavin and phosphorus. One hundred grams of raw water chestnuts contains approximately 107 calories and the same amount of canned contains 50 calories. The reason being is that fresh raw water chestnuts contain slightly more fat than the canned variety.
Antioxidants: A 2007 study by the Chinese Academy of Sciences identified a number of phenolic compounds that have high antioxidant and free radical scavenging activity in water chestnuts. The antioxidant compounds are from the subgroup of flavonoids, known as catechins, specifically epicatechin. Other foods that contain catechins are dark chocolate, red wine and green tea.
Water chestnuts have a high nutritional value and as such have traditionally been used to make healing tonics. In traditional aboriginal medicine, medicine men harnessed the antimicrobial effects of Eleocharis dulcis by crushing the bulb and using it to heal wounds. Water chestnut was also used by aboriginals and early settlers as a source of ‘bush tucker’ or food.
If eaten uncooked water chestnut can transmit faciolopsiasis, an infection caused by an intestinal fluke found on many aquatic plants.