Carotenoids retention and in vitro iron bioavailability of traditional cowpea leaf dishes of rural Tanzania.

Food preparation methods play a role in micronutrient retention and ultimately intake. Analyses for carotenoids retention and in vitro iron bioavailability of five cowpea leaf dishes prepared according to the traditional methods of rural Tanzania were carried out. All the five dishes are commonly eaten as relishes for staple meals of maize or rice. Laboratory analyses were carried out at the Nutrition Laboratory of the World Vegetable Centre in Taiwan. Carotenoids were analysed by high-performance liquid chromatography while iron bioavailability was analysed by an in vitro method. Results showed that traditional cowpea leaf dish consisting of sunflower oil, onion, tomatoes and coconut milk cooked for 30 min had the highest retention of β-carotene (40.83 ± 7.00%) and lutein (34.60 ± 3.30%) compared to other traditional recipes (p < 0.05). The highest iron bioavailability (10.04 ± 0.49%) was observed in the traditional recipe which involved boiling fresh cowpea leaves for 15 min. Although recipe variation can affect carotenoids retention and iron bioavailability, simple practices such as reduced cooking time and avoiding direct sun drying also need to be promoted.