COMPARATIVE ASSESSMENT OF THE NUTRITIONAL VALUE OF COMMERCIALLY AVAILABLE COCOYAM AND POTATO TUBERS IN SOUTH AFRICA

Potato (Solanum tuberosum) is a popular staple food in South Africa, whereas cocoyam (Colocasia esculenta) remains unpopular and not well known outside KwaZulu-Natal Province, where it is cultivated mainly for subsistence. A comparative study of the nutritional compositions of commercially available tubers of both crops in South Africa was carried out. The results showed that the tubers of the two crops were high in carbohydrate and energy but low in lipid contents. Although potato was significantly higher in moisture and ash than the tubers of cocoyam, carbohydrate, caloric and crude protein contents were not significantly different (P < 0.05) in both tubers. Whereas boiling improved the availability of crude protein, fiber and lipid contents for both species, boiling reduced the ash contents in the tubers of both crops. Manganese levels were not detectable, whereas iron contents were appreciably high, but magnesium and copper contents were in the average range in both tubers. Whereas cooking reduced iron level in potato (11.20-9.95 mg/100 g DM), a significant increase in iron was observed for cocoyam (9.08-13.87 mg/100 g DM). Cooking significantly lowered magnesium, potassium and copper contents in both crops. Oxalates and phytate contents were significantly higher in cocoyam when compared with potato. Cooking remarkably reduced the anti-nutrient contents of both tubers. PRACTICAL APPLICATIONS This study provides evidence that commercially available cocoyam (Colocasia esculenta) and potato (Solanum tuberosum) in South Africa have very close nutritional values. Cocoyam compared favorably with potato and even excelled in some nutrients. Thus, cocoyam consumption could be encouraged and popularized as an additional tuber crop.