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Wageningen University (2010)

Baobab (Adansonia digitata L.) foods from Benin : composition, processing and quality

Chadare Flora Josiane

Titre : Baobab (Adansonia digitata L.) foods from Benin : composition, processing and quality

Auteur : Chadare Flora Josiane

Université de soutenance : Wageningen University

Grade : PhD thesis 2010

Résumé
In 2007, more than 923 million people did not have enough to eat (FAO, 2008), especially in developing countries. Simultaneously, several forest foods are available but under-utilized. Among them, the baobab tree (Adansonia digitata L.) is a key economic tree, a multipurpose, widely-used species, rich in nutrients in its leaves and fruits, used daily by local populations in several African countries for food, medicines and other purposes. The tree contributes significantly to nutrient supply in those areas where it grows. So far, few studies have been undertaken on the valorization of the species and on its contribution to food security in Africa. The present work focused on indigenous knowledge and nutritional aspects concerning baobab foods, necessary for further valorisation and improvement of local food processing practices. The objectives of the study were to (i) review the nutritional value of baobab parts, (ii) document ethno-food knowledge related to baobab food products in rural areas in Benin, (iii) assess the effect of traditional processing on in vitro digestibility and bioavailability of minerals and carotenoids in sauce made of baobab leaves, (iv) characterise the microbiological flora of baobab fermented food products, and (v) build quantitative information on degradation of baobab pulp quality during storage. The review on baobab foods showed that pulp from baobab fruits is particularly rich in vitamin C (150 to 360 mg/100 g dw). The leaves are particularly rich in calcium (307 to 2640 mg/100 g dw). The whole seeds and the kernels have a relatively high lipid content, viz. 12 to 33 g/100 g dw and 19 to 35 g/100 g dw, respectively. The pulp and leaves exhibit antioxidant properties with a higher activity in the pulp than in the leaves. Two hundred and fifty-three processors of baobab food products were surveyed in Benin, to investigate the ethno-food knowledge related to baobab and the variation among socio-cultural groups. Local populations reported up to 35 baobab food products processed from the leaves, the pulp, the seeds and the kernels, most of which have never been characterized. Multivariate analysis showed that the types of foods processed from baobab differed among socio-cultural groups. The survey revealed that seed decortication is considered to be the most laborious processing operation and that the preservation of pulp and kernels is difficult in local conditions. The effect of processing on the quality of traditionally processed baobab leaves was evaluated. Assessment of in vitro digestibility and bioavailability of Ca, Fe, and Zn in non processed and processed baobab leaves showed that 10-30% of total Ca was available and that lutein and beta-carotene are the most important carotenoids. Moreover, “bitter leaves” are richer than “sweet leaves”, though the latter are the preferred ones. However, the experiments on Fe and Zn in vitro digestibility require further attention because of experimental difficulties caused by the sliminess of the leaves. The fermented baobab products recorded during the survey have been characterised and results show that two of them, namely Tayohounta (fermented kernels) and Dikouanyouri (fermented seeds), are flavouring agents and the third one, Mutchayan (sorghum paste with baobab pulp), is used as a drink and a main dish. Fermentation of Dikouanyouri and Tayohounta appeared to be induced mainly by Bacillus spp. (8.5 and 9.5 Log cfu/g, respectively) and that of Mutchayan mainly by lactic acid bacteria (8.1 Log cfu/g) and yeasts (7.2 Log cfu/g). Detailed microbiological studies on Tayohounta showed that the microbiota responsible for the fermentation were sporeforming bacteria, mainly Bacillus subtilis and other Bacillus spp. One preservation problem reported during the survey, namely quality degradation of baobab pulp during storage has been investigated. The results show that as storage time increases, pulp colour looses its lightness with decreasing L* values and becomes more brownish with increasing a* value (reddish) and b* value (yellowish) ; vitamin C degraded following roughly a first order kinetic reaction. Reaction rate is faster at higher temperatures and water activity. More data are necessary to build prediction models of quality degradation of baobab pulp during storage. The work presented here shows the potential of baobab for food and nutrition in rural Benin, and may open up research on other forest foods.

Mots clés : adansonia digitata / ethnic foods / nutritive value / ethnography / food processing / fermentation / fermented foods / benin

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Page publiée le 14 novembre 2011, mise à jour le 30 mai 2022