Changes in the chemical composition of the fruits of Grewia coriacea Mast. during development and ripening.

Abstract

Introduction. Grewia coriacea is a widespread plant species that occurs spontaneously in tropical forests of Central Africa. It is one of the most important commercial spontaneous fruit crops in the Republic of Congo (Brazzaville), where it is harvested, sold and consumed on a rather large scale. However, similar to many other spontaneous products of the tropical rain forest in Africa, G. coriacea remains poorly studied and its nutritional potential is unknown. Because the fruit of G. coriacea is an important food for indigenous people in a large portion of the Congo River Basin, we studied the evolution of some compounds of this fruit starting from its fruit setting until its maturation. Materials and methods. The contents of various pigments (chlorophyll a and b, and carotenoids), and concentrations of soluble sugars, ascorbic acid and soluble proteins of the fruit pulp of G. coriacea were analyzed in the laboratory and they were followed during maturation. Results and discussion. The curves of evolution of the studied parameters followed some anticipated trends: increasing, decreasing or relative stability. Increasing applied to the carotenoids (3,0 mg·g^–1 at the beginning of the fruit development up to 8.2 mg·g^–1 at the end of its maturation), soluble sugars (9,9 µg·g^–1 up to 75,4 µg·g^–1), ascorbic acid (25 mg·100 g^–1 up to 230 mg·100 g^–1) and soluble proteins (7 µg·g^–1 up to 40 µg·g^–1). In contrast, the two chlorophyll pigments (chlorophyll a and b) showed an overall decreasing trend. Finally, the concentration of soluble proteins remained rather constant in the later stages, despite an initial increase in the early stage of development. Conclusion. To our knowledge, these results are the first data published concerning the temporal changes in physico-chemical parameters of G. coriacea fruits in tropical Africa. The study shows that the studied fruits have high nutritional potentials, and that their ability to accumulate rather high levels of ascorbic acid could make them a potential source of vitamin C.