Characterization of pectins extracted from different varieties of pink/red and white grapefruits [citrus paradisi (macf.)] by thermal treatment and thermosonication

Abstract

The physical and chemical properties of pectin extracts obtained from different white and pink/red varieties of grapefruit [Citrus paradisi (Macf.)], using both conventional heating (CHE) and thermosonication (TS), were investigated. The content of galacturonic acid (GalA), degree of esterification (%DM), color and antioxidant capacity were analyzed. Fourier-Transform Infrared Spectroscopy (FTIR) associated with multivariate analysis enabled a structural comparison among the pectin extracts, and differential scanning calorimetry (DSC) completed a full landscape of the investigated extracts. Pectin extracts obtained by CHE showed mostly higherGalA than those obtained by TS. All the extracts had a high antioxidant capacity, as determined by 2,2 diphenyl 1-picrylhydrazyl (DPPH∗) and 2,2-Azino-bis(3-ethylbenzothiazoline- 6-sulfonic acid) diammonium salt (ABTS∗+) assays, and a high correlation with the GalA content. The main differences observed in the FTIR spectra occurred in the 1200 to 900 cm−1 region (differences in GalA). The glass transition temperatures (Tgs) of all extracts were above 85 °C, making them interesting as stabilizing agents for the food industry.