Caractérisation du fruit du baobab et étude de sa transformation en nectar

Résumé

Introduction. The baobab tree (Adansonia digitata L.) grows wild in Senegal where the fruit is consumed in various forms. Although the plant ecology and botany have been well studied, works relating to the fruit processing or the impact of processing on the quality of the final products are rare. In order to evaluate the technological potential of these fruits, as a precondition to the development of their processed products on the local, regional and international markets, we attempted to characterize the raw material better (biochemical composition and nutritional quality), and we studied the processing of the product into nectar. Materials and methods. Our study related to twelve without-shell fruit samples of A. digitata collected between 2004 and 2006 in various zones of Senegal. Proportions of the various components of the fruit (pulp, seeds, fibers) were assessed, then various physico-chemical characteristics of the pulp and seed were analyzed. The microbial flora present in traditionally prepared drinks was studied. Pasteurization techniques and crossflow microfiltration of nectars were applied. Various uses and traditional fruit processing were evaluated starting from a survey carried out with a sample of 93 people questioned in Dakar and Saly. Results and discussion. The pulp was characterized by a low water content (6-15%), a strong acidity (68- 201 mEq·100 g-1) and high contents of sugars (20-32%), ascorbic acid (125-312 mg·100 g-1), minerals (6%) and starch (41-47%). The chromatograms obtained by GC/MS on the fruit pulp identified 10 aroma compounds, especially isopropyl myristate, an unidentified phenolic compound and nonanal. Without special precaution, the pulp composition evolved during storage and its quality was quickly degraded. The survey carried out showed that the fruit pulp of the baobab tree is mainly used for the development of drinks of nectar type with a [fruit / water] mass ratio of [1 / 3]. Stabilization of nectar can be obtained by pasteurization (80 °C /10 min). Nevertheless, heat treatment damaged the product quality. When cold stabilization by crossflow microfiltration was carried out on nectars with [fruit / water] mass ratios of [1 / 3] and [1 / 5], the permeate flux was between [(23 and 77) L·h-1·m-2] for a volumetric reduction ratio ranging between 1 and 2. These low permeate fluxes compromise the potential of crossflow microfiltration for the stabilization of the nectar. Conclusion. In the future, from the point of view of a local production of nectar from the baobab tree fruit, research will have to be focused on the thermal stabilization of drinks.