Traditional vegetable preparation methods in rural Tanzania and carotenoids retention and in-vitro iron bioavailability in vegetable dishes
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Date
2007
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Sokoine University of Agriculture
Abstract
Vitamin A and iron deficiency problems affect a huge proportion of population in
Sub-Sahara Africa including Tanzania and vegetables are potential rich and
sustainable sources of these nutrients. This study was designed to investigate
feasible food preparation methods to increase carotenoids retention and iron
bioavailability of leafy vegetable dishes traditionally prepared by Tanzanian
households. The first part of the study used structured questionnaire to interview
156 women in Arumeru, Singida, and Kongwa districts to identify the traditional
methods of preparing indigenous vegetables. The second phase assessed lutein
and P-carotene retention and in-vitro iron bioavailability in sweet potato leaf
dishes. The most consumed vegetables identified by the survey were amaranth
(81.4%), jute mallow (75%) and sweet potato leaves (64.7%), most commonly
cooked by boiling in Singida and Kongwa and by stir-fiying in Arumeru districts.
In the laboratory, fresh and dried sweet potato leaves were prepared by traditional
modified methods. Traditional methods involved cooking with sunflower oil and
without oil. Modified methods involved the use of oil, tomato, lemon and
soybean. In-vitro iron bioavailability was done by simulating gastrointestinal
digestion system. Carotenoids were analysed by High Performance Liquid
Chromatography method. Traditional methods retained carotenoids in the range
of 17 - 72%, while modified methods retained carotenoids in the range of 60 -
116%. Iron bioavailability was improved by 1.52 - 3.30% in modified dishes.
The highest levels of P-carotene and lutein retention and iron bioavailability were
obtained in dishes cooked with oil + tomato. The study concludes that modifiediii
preparation methods with appropriate ingredients have potential for retaining
lutein and 0-carotene; and improve in-vitro iron bioavailability. Furthermore,
dishes with higher retention of lutein and 0-carotene also showed higher iron
bioavailability, suggesting a relationship between the two. Hence there is a need
for further studies to explain this relationship.
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Keywords
Carotenoids retention, Vitro iron, Traditional vegetable, Vegetable dishes