Bioaccessibility of Vitamins and Minerals in Processed Tubers and Leaves of Manihot esculenta Crantz Varieties

Manihot esculenta Crantz (cassava) is an important food crop in developing nations, with its tubers and leaves being a source of ascorbic acid, thiamin, riboflavin, and niacin (vitamins) and calcium, iron, potassium, and zinc (minerals). Malnutrition prevalence in some Kenyan Counties that relied on cassava-based diets has partly been attributed to processing methods and/or nutrient bioaccessibility. The study area Kilifi County grows Kibandameno and Tajirika cassava varieties and is on record for high prevalence of undernutrition. The levels of vitamins and minerals, and their bioaccessibility in raw, boiled, and deep-fried tubers, and pounded then boiled leaves of Kibandameno and Tajirika cassava varieties were studied. Digestion was done using static gastrointestinal digestion prior to the determination of vitamins (by HPLC) and minerals (by AAS and AES). Bioaccessibility of both vitamins and minerals was significantly higher (P < 0.001) in boiled followed by deep-fried and lowest in raw tubers. Bioaccessibility ranged between 27% (Fe)–85% (vitamin C) in boiled, 20% (Fe)–79% (vitamin B₁) in deep-fried, and 15% (Fe)–(72% (K) in raw tubers. Bioaccessibility in processed leaves was significantly higher (P < 0.001) than in raw. This ranged between 11% (Fe)–81% (vitamin B₁) in processed and between 8% (Fe)–67% (K) in raw leaves. Processing therefore significantly reduced levels of ascorbic acid, thiamin, riboflavin, niacin, calcium, iron, potassium, and zinc in raw tubers and leaves of Kibandameno and Tajirika Manihot esculenta Crantz varieties. Their bioaccessibility however significantly increased, being higher in tubers than in leaves.