‘Yams’ is a collective name for some plant species of the genus Dioscorea that possess edible tubers. They are cylindrical in shape, blackish-brown to light pink in colour, have bark-like skin and have white, reddish or purple flesh. Yams are native to Africa and Asia and a majority of the production, approximately 95% happens in Africa. They are monocots which are related to lilies and grasses.
Nearly 870 species of yams are known to date and they can be as small as the size of a potato to as heavy as 60 kg. A tuber can grow up to 4.9 ft deep into the soil and 7.6 to 15.2 cm high. The plant disperses by seed. It has a rough skin which is difficult to peel so it is heated to make it soft and the inner mass is known as ‘meat’ which is the edible part of the tuber.
Yam crop seeds are planted into mounds at the beginning of the rainy season and the crop yield depends on how well the sets are planted, on inter-plant spacing and the sizes of the mounds. Their dormant and growth phases correspond to the dry and wet seasons respectively. The yams require a humid tropical atmosphere with an annual rainfall of above 1500 mm which should be distributed uniformly throughout the season, for best results and maximum yield. Despite the high requirements of labour and cost of production, high consumer demand makes its cultivation quite profitable for farmers.
Difference between yams and sweet potatoes
Yam is often mistaken as sweet potato. Depending on the species, the colour of the flesh of sweet potatoes also varies from white to orange and even purple, therefore it is very difficult to differentiate between a sweet potato and a yam. When compared to a sweet potato, yam is starchier and drier. Also, sweet potatoes have a smooth skin unlike yams and are tapered. Read more about the difference between them on https://foodfacts.mercola.com/yam.html
Yams are a nutrient-rich vegetable that is beneficial for the human health. Studies have shown that eating plant foods such as yam helps in promoting a healthy body as well as preventing many lifestyle diseases like diabetes, obesity etc. Read about the health benefits of yams in detail in the subsequent sections.
Yams are available all year around but are mainly harvested in the month of August.
Selection- Select a yam that are firm and without soft spots or bruises.
Storage- As yams are tubers, they respire when stored which results in the oxidation of starch and converts it into water. Considering this, yams should not be stored at low temperatures, not below 12 degree Celsius (it will damage cells through chilling), as it reduces the respiration rates.
Researchers have concluded that roasting yam is a better option than boiling them because that can lead to some loss of nutrition.
|See the table below for in depth analysis of nutrients:
Yam (Dioscorea spp.), raw, Nutrition value per 100 g. (Source: USDA National Nutrient data base)
|Principle||Nutrient Value||Percentage of RDA|
|Total Fat||0.17 g||0.5%|
|Dietary Fiber||4.1 g||11%|
|Pantothenic acid||0.314 mg||7%|
|Vitamin C||17.1 mg||28.5%|
|Vitamin A||138 IU||5%|
|Vitamin E||0.35 mg||2%|
|Vitamin K||2.3 µg||2%|
- It helps in curing skin diseases like boils, ulcers etc. when applied to the skin.
- It is known to relieve cough, irritation in the respiratory tract and other respiratory problems too.
- As it is a good source of Vitamin B6, it helps in breaking down homocysteine that damages the walls of the blood vessels, therefore, lowers the risk of cardiovascular diseases.
- Yam contains an enzyme that is a natural alternative to hormonal replacement in women who have reached menopause. It also supports women’s endocrine system. Vitamin B6 is a vital supplement for Premenstrual Syndrome.
- Antioxidants like beta-carotene and Vitamin C helps to get rid of cancer-friendly free radicals, which can damage the body in reaction with DNA.
- Yam is a low glycemic index food, therefore, one can eat without worrying about the rise in blood sugar levels.
- The dietary fibre present in yam decreases bad cholesterol as it binds to it, preventing the body to absorb it and also reduces constipation.
- Copper present in yam helps in the production of red blood cells and improves blood flow in the body.
- As yams grow under the ground, they are naturally prone to diseases and infestation of pathogens and pests.
- They contain alkaloids which are toxic when ingested.
- They contain oxalates which crystalize in the body when in excess amount, therefore an individual with impaired kidney or bladder should not add it to their diet.
- Phytic acid in yams prevents absorption of minerals like iron and zinc as it binds to them while digestion.
You can make tasty dishes with yams, the links to the recipes of which are below: