Roots & Tubers
Cassava is an edible root that provides an important source of carbohydrates for an estimated 500 million people in Africa, Asia and the Americas. World production was 230 million tonnes in 2008, with Nigeria as the largest producer followed by Brazil, Thailand and Indonesia (FAOSTAT). Key post-harvest considerations include the rapid deterioration of roots two to three days after harvesting and the presence of cyanides, which need to be detoxified during processing to make the root safe for consumption.
Edible aroids are root crops grown widely in tropical and sub-tropical countries. Taro also known as cocoyam and tannia are the more common species. World taro production in 2008 was over 11 million tonnes principally in Cameroon, China, Ghana and Nigeria, with smaller production in other areas of Africa, Asia and South Pacific (FAOSTAT). The corms provide a useful carbohydrate source but must be cooked prior to consumption to detoxify the calcium oxalate crystals present. The growing season ranges from 6 to 12 months depending on the species. The short storage life of aroids at ambient temperatures of only 2 to 6 weeks is a limiting factor in their use.
Potato is an important staple food world-wide, claiming fourth place after maize, rice and wheat. It is a good carbohydrate source in addition to other nutritional benefits. Potatoes are cooked before consumption which reduces the presence of the toxic alkaloid solanine. Developing countries now produce approximately one third of world production, which was 314 million tonnes in 2008 (FAOSTAT). Though commonly consumed in its fresh form, the tuber is versatile and may also be used frozen, fried or dehydrated. Potatoes store for many months in optimum cold store conditions but losses increase dramatically under ambient conditions.
Yams are second to cassava as the most important tropical root crop and are a staple food in many parts of Africa, Southeast Asia and the South Pacific. Seventy percent of the 50 million tonne world output of 2008 was grown in Nigeria (FAOSTAT).The starchy tuber, with a rough brown skin, is produced by a herbaceous vine and takes from 8 to 11 months to mature after planting. Yams are mainly grown for direct human consumption and are marketed as fresh produce in all the growing regions. The tubers can be stored for up to six months without refrigeration.