Microencapsulação de ácido ascórbico com pectina extraída do albedo de maracujá (Passiflora edulis)

Abstract

Pectin is a polysaccharide widely used in microencapsulation processes due to its ability to form gels through the ionic gelation technique. In this work, pectin was extracted from the albedo of yellow passion fruit (Passiflora edulis) by acid hydrolysis with HNO₃ (50 mmol·L⁻¹), followed by drying, grinding, and particle size standardization (250 μm). The use of albedo as a raw material presents high technical and environmental viability, since this byproduct comprises about 50% of the total mass of the fruit and is usually discarded by the juice and pulp industry. In addition to reducing the volume of organic waste, its reuse adds value to the production chain, transforming an abundant residue into an accessible source of quality pectin, with yields comparable to those of industrial processes. The extraction was conducted for 30 and 60 minutes, resulting in yields of 13.30% to 18.98%, consistent with conventional processes. The degree of esterification (DE) ranged from 80.65% to 86.78%, classifying the samples as high DE pectins. Subsequently, an alkaline de-esterification process was performed to obtain low DE pectin. Structural characterization by infrared spectroscopy confirmed the presence of the characteristic functional groups of pectin and the reduction of methyl esters after de-esterification, demonstrating the effectiveness of the process. Microcapsules were produced using the ionic gelation technique, employing three types of pectin: de-esterified extracted pectin (PD), commercial pectin (PC), and high DE extracted pectin (PA), combined with sodium alginate. Three different concentrations of ascorbic acid were incorporated into each formulation. Macroscopic and scanning electron microscopy morphological characterization revealed marked structural differences between the samples: PD microcapsules presented a more uniform surface; PC microcapsules exhibited an intermediate morphology; and PA microcapsules showed an irregular structure, attributed to the high viscosity of the polymer solution and the lower availability of carboxyl groups for crosslinking with Ca²⁺. The release kinetics were evaluated in an acidic medium (pH 1.5) to simulate the physiological conditions of the stomach. PD microcapsules presented the most controlled and stable profile, reaching concentrations close to 60 μg·L⁻¹. PC microcapsules showed lower crosslinking density, while microcapsules exhibited continuous release and high final concentrations, although accompanied by less structural uniformity and the occurrence of ascorbic acid oxidation.