Effect of Cooking Methods on the Vitamin C and Beta-Carotene Content of Selected Nigerian Vegetables

Micronutrient retention in vegetables during household cooking is a critical nutritional concern in Nigeria, where vitamin A and C deficiencies remain prevalent, particularly among children under five and women of reproductive age. This study evaluates the effect of boiling, frying, and steaming on the vitamin C and beta-carotene content of three commonly consumed Nigerian vegetables: ugwu (Telfairia occidentalis), efo riro (Celosia argentea), and garden egg leaves. Fresh vegetables were obtained from Bodija market in Ibadan, Oyo State, and subjected to standardized cooking procedures at defined time intervals of five, ten, and fifteen minutes. Raw and cooked samples were analysed for vitamin C content by the 2,6-dichlorophenolindophenol titrimetric method and for beta-carotene by high-performance liquid chromatography with UV detection. All three cooking methods resulted in significant losses of both nutrients compared to raw values, with boiling causing the greatest degradation. Vitamin C losses after fifteen minutes of boiling ranged from 62 to 78 percent across vegetable types, while beta-carotene losses ranged from 34 to 55 percent. Steaming for five minutes produced the least micronutrient degradation, preserving 74 to 86 percent of initial vitamin C content. Frying caused intermediate losses but introduced additional fat content. Cooking duration was identified as a more critical determinant of micronutrient loss than cooking method alone for beta-carotene. The study recommends promoting shorter cooking times and steaming methods in public nutrition education programmes. Keywords: vitamin C, beta-carotene, cooking methods, Nigerian vegetables, micronutrient retention.