Physicochemical, microstructural and functional characterization of dietary fibers extracted from lemon, orange and grapefruit seeds press meals

The aim of this study was to characterize dietary fibers extracted from defatted press meals of lemon, orange and grapefruit seeds. After an ultrasound-assisted aqueous extraction, the fibers were investigated for proximate composition, soluble/insoluble fiber contents, color, viscosity, degradation temperature and enthalpy, near infrared (NIR)spectra, X-ray diffraction patterns, scanning electron microscopy (SEM)images, and functional (water and oil holding capacity, swelling capacity)properties. The fibers contain 2.0-3.45 mg/g phytate, 1.36-2.26 percent ash, 4.95-7.95 percent soluble fiber, 75.95-82.24 percent insoluble fiber. NIR spectra showed the presence of cellulose and lignin as main components with corresponding bands. Major peak at 22-23 Å X-ray diffraction also indicated presence of cellulose crystals. Crystallinity values of 33-80 percent were measured. SEM images showed the microfibrillar structures present in the samples. Water and oil holding capacities (4.79-7.76 g/g and 3.44-4.19 g/g), and swelling capacities (22.44-24.55 mL/g)proved that the fibers are functional, and especially good for oil containing foods. The utilization of these new fiber sources would be important in terms of by-product valorisation. The data presented in this study may provoke further studies and/or applications of these new dietary fibers.