Solvent‐free mechanical extraction of Opuntia ficus‐indica mucilage

Abstract

AbstractThe 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.Practical applicationsAt the present time, several authors focused on obtaining mucilage from Opuntia ficus‐indica for the food and pharmaceutical industries by precipitation with solvents, such as acetone or alcohols, with low yields and high production cost, due to high consumption of the organic solvents and long extraction time. While this kind of mucilage may be suitable for foodstuff processing, it must be demonstrated that do not contain a toxicologically dangerous amount, the process of extraction was under good manufacturing practices as well as it is necessary to verify that this mucilage meets the specific purity criteria provided by the application. This involves conducting quantitative analysis that is usually costly and time‐consuming. Therefore, a study on mechanical extraction process has been performed in order to have a Generally Recognized as Safe (GRAS) cactus mucilage. The process developed is a mechanical extraction of low cost, suitable to obtain mucilage at large‐scale, with high yield, low energy requirements, and no solvents involved. The mucilage obtained is a safe powder useful as additive in food processing such as dispersing agent avoiding sedimentation in vegetable protein suspensions for patients with malnourishment.