Acid extraction and physicochemical characterization of pectin from cubiu (Solanum sessiliflorum D.) fruit peel

Cubiu (Solanum sessiliflorum Dunal) is a fruit from the Amazon region. Pectins were extracted from cubiu fruit peels using boling mineral acid (HNO3) or organic acid (citric acid) at pH 2 for 1h. The highest uronic acid content was obtained using HNO3. Extractions were then carried out with HNO3 at pH 1.0, 1.5 or 2.0 for 2 or 4 h. Among the pectins with the highest yields, the one extracted using HNO3 at pH 1.5 for 2h (14.2% yield) had the highest uronic acid content (75.0%). The pectin obtained under these conditions was characterized by chromatographic, spectroscopic and spectrophotometric methods. The polymer was mainly composed of a high methyl-esterified homogalacturonan (degree of methyl esterification of 62%) with low acetyl content (5%). It formed gels in acidic medium (pH 2.5-1.5) with 60% sucrose and the gel strength increased with decreased pH, suggesting possible applications as an additive in acidic products with high soluble solids content.