Solvent-free mechanical extraction of Opuntia ficus-indica mucilage

The performance of solvent-free extraction methods used for obtaining mucilage powder from Opuntia ficus-indica has been evaluated in terms of yield, energy-drawn, and the rheological parameters as well as its rheological properties and content of polysaccharides. Three different methods based on mechanical extraction were investigated, namely the simple filtering method (SFM), the filtering-clarifying-concentrating method (FCCM), and the filtering-concentrating method (FCM). The SFM method consisted of obtaining the mucilage powder by spray-drying the filtered cactus juice. For the second method (FCCM), the mucilage powder was obtained by drying the filtered, clarified, and concentrated (evaporation by boiling for the elimination of part of the water) cactus juices, while for the FCM method the filtered juice was concentrated and dried. The highest mucilage yield was obtained with the SFM method, while the highest consistency, in terms of viscosity combined with the lowest energy requirement was obtained when using the FCM method. The polysaccharide spectrum characterization was carried out by Nuclear Magnetic Resonance (NMR) Spectroscopy. Spectra obtained from the different extraction processes indicate the presence of mixtures of polysaccharides such as unesterified rhamnose, xylose, mannose, and galacturonic acid. Remarkably, rhamnose is the most abundant in two of the three extracts, although almost 50% of the concentration of galacturonic acid present in the three extracts is unesterified.