Optimisation des propriétés nutritionnelles et fonctionnelles du jus traditionnel de baobab (Adansonia digitata L.) et évaluation de ses effets Oestrogéniques

Abstract

Regular consumption of fruit is crucial for health. The fruit consuming population prefer common exotic fruits, neglecting local fruits which are equally rich and sometimes richer in nutrients and phytonutrients. Baobab’s fruit is one of the local fruits found in Cameroon, its pulp, although very rich in nutrients, phytonutrients and medicinal properties, is less known and still remains under-exploited. It is traditionally processed into juice under uncontrolled conditions which can affect its nutritional and functional qualities. In order to standardize the process for a quality product, the objective of this work was to define optimal production conditions of baobab juice with enhanced nutritional and functional properties. Surveys were conducted among producers, traders, and consumers of baobab juice. The main traditional preparation methods identified were applied and the vitamin C and phenolic compound content, DPPH antiradical activity and Total Antioxidant Capacity (CAT) were evaluated. A global characterization of the pulp preceded the optimization of the nutritional and functional properties of the juice by the surface response method using a composite plan centered with temperature, pulp/water ratio, sugar content as factors and phenolic compound content, antiradical activity, CAT, iron content and general acceptability as responses. Nutritional, microbiological and sensory characterizations of the optimized baobab juice were performed. Its functional properties (antioxidant in vitro, anti-estrogenic in vivo) were also studied. From the results obtained, it appears that for the juice production, four main methods differing by the production temperature are generally used (aqueous extraction at 25 °C, 40 °C, 100 °C and decoction). The main ingredients for the preparation of the juice were baobab fruit, water, sugar and other inputs consisting mainly of chemical flavours (84.74%) most represented by chemical powders for instant drinks (42.37%) and chemical colourants (30.50%). A significant difference for the different evaluated parameters was noted in the application of these traditional methods, with the last method being the most effective. The characterization of the pulp confirmed the presence of all macronutrients, its richness in vitamin C (494.94 ± 69.99 mg/100 g DM), minerals and phenolic compound, its high antioxidant activity, its acidic pH and the presence of secondary metabolites and volatile compounds. The optimization model used was valid, with a total optimal desirability of 0.95 resulting in the optimal point where baobab juice production conditions were 131.28 g/L, 100 °C and 308.36 g for pulp/water ratio, temperature and sugar content respectively. These conditions resulted in a phenolic compound content of 172.33 mg EGA/100 mL, a percentage of DPPH radical inhibition of 39.45%, a CAT of 3.17 g EAA/100 mL, an iron content of 12.19 μg/ml with a general acceptability of 6.84/9. The optimized juice was accepted by the panelists, had good nutritional qualities and had a microbiological quality that met production standards. This juice was rich in phenolic compound (396.74 ± 6.68 mg EGA /100 mL for extraction with HCl 1%), had high antioxidant activity (FRAP: 1177.49 ±1.57 mg FeSO4/ 100 mL; DPPH: 73.25% inhibition /100 mL; CAT: 3.98 ± 0.28 g EAA /100 mL) in vitro and had anti-estrogenic effect (significant decrease in relative uterine weight at all doses) in vivo on Wistar female rats. The consumption of this baobab juice would contribute to cover the Reference Nutrient Intake (RNI) of several nutrients, to the prevention and management of chronic diseases related to oxidative stress and estrogeno-dependants diseases.