Biochemical Changes of Cubiu Fruits (<i>Solanum sessiliflorum</i> Dunal, Solanaceae) According to Different Tissue Portions and Ripening Stages

Abstract

Cubiu fruits ( Solanum sessiliflorum Dunal, Solanaceae) are known for their high nutritional value and low caloric content. This work aimed at evaluating biochemical indices of cubiu fruits according to different tissues (peel, pulp and placenta) and ripening stages (green, turning, ripe and fully ripe). The fruits were randomly harvested to investigate sensory aspects (colorimetry, blanching effect, pigments) and biochemical indices (moisture and dry matter, Total Soluble Solids (TSS), pH, Titratable Acidity (TA), TSS/TA ratio, ascorbic acid, Alcohol-Insoluble Solids (AIS), pectinesterase activity and pectin content). The analyses were performed at the laboratory of Instituto Nacional de Pesquisas da Amazonia (INPA), Manaus, Brazil. The blanching process preserved pulp colors at all ripening stages. Chlorophylls were higher in green peels; flavonoids and carotenoids, in fully ripe peels. Anthocyanins were entirely absent. Pulp (turning fruits) showed the highest moisture content (91.05), followed by ripe pulp (90.70) and fully ripe pulp (90.62). Pulp TSS changed little whereas placenta TSS declined and were associated with increased TA and pH reduction (fully ripe fruits). Pulp pH and TA varied little whereas placenta pH was notably low and TA was remarkably high (fully ripe fruits). Pulp TSS/TA ratio showed predominance of TSS while in placenta, there was predominance of organic acids. AIS, precursors of pectin, were stable during ripening. The statistical analysis of dietary fiber content showed one modal value in the AIS. In pulp, pectinesterase activity correlated inversely with pectin content. Cubiu fruits were significant sources of bioactive compounds, e.g. chlorophylls, flavonoids and carotenoids, predominantly in the peel and the pulp; soluble functional fibers, e.g. pectin (g/100 g fresh weight), particularly in the green peel (1.00) and the fully ripe pulp (1.12), and other versatile molecules, e.g. ascorbic acid (mg/100 g fresh weight), especially in the fully ripe peel (32.45) and placenta (24.84) and the turning placenta (21.27). Cubiu fruits are rich in ascorbic acid and should be included in the human diet.