Extraction of Purple Prickly Pear (Opuntia ficus-indica) Mucilage by Microfiltration, Composition, and Physicochemical Characteristics

Abstract

Mucilages are valuable to the food industry, but the solvents used to extract and concentrate them are detrimental to the environment. Therefore, environmentally friendly technologies that preserve the properties of biopolymers and reduce the use of solvents are being sought. In this work, the mucilage of Opuntia ficus-indica (mesocarp–endocarp) was extracted by two methods: In the first one, the pulp from the mesocarp–endocarp was extracted by ethanol precipitation and centrifugation cycles, then dried at room temperature. For the second, the pulp was processed in a three-step tangential microfiltration process: microfiltration (separation), diafiltration (purification), and concentration. The mucilages obtained differed significantly (p < 0.05) in color, betalains, total sugars, and proteins. The proportions of insoluble and soluble dietary fiber were similar. GC/MS analysis identified seven neutral sugars and a high content of uronic acids (31.3% in the microfiltered mucilage and 47.5% in the ethanol-precipitated mucilage). These show a low degree of esterification, which gives them a polar and hydrophilic character and the possibility of interacting with divalent ions through the carboxylic acid groups, which could form gels stabilized by an egg-box mechanism, with application as a thickening, stabilizing, gelling, or film-forming agent for foods with low sugar content.