Characterization of tropical fruits: Rheology, stability and phenolic compounds

Abstract

This study assessed the rheological behaviour, physical stability, and the phenolic compounds of Eugenia pyriformis Cambess. (uvaia) and Eugenia uniflora L. (pitanga) fruits. The effect of temperature on the rheological behaviour of the fruit was evaluated (10–60 °C) by means of non-oscillatory rheological analysis in a rheometer. The whole samples (purée) exhibited shear-thinning behaviour (n<1), whereas the centrifuged samples exhibited Newtonian behaviour (n=1). The Arrhenius equation accurately described the effect of temperature on the apparent viscosity of the fruit. The stability study was performed by means of sedimentation and turbidity testing. The stabilisation of purées occurred on the second (Eugenia pyriformis Cambess.) and on the third (Eugenia uniflora L.) day of storage. The results demonstrated that turbidity increased with an increase in homogenization velocity. The phenolic compounds of the fruit were identified and quantified by reverse-phase high-performance liquid chromatography (RP-HPLC). The samples presented significant differences in the concentration of phenolic compounds. Among the phenolic acids identified, gallic acid was the one with higher concentration in both fruit assayed. Comparing the fruits, it was observed that Eugenia pyriformis presented higher content of flavonoids (5-fold) and Eugenia uniflora presented higher content of phenolic acids (8.5-fold), especially gallic acid. Myricetin and quercetin were the main flavonoids determined in Eugenia pyriformis.