Extração de pectina do albedo do maracujá com líquidos iônicos

Abstract

Brazil is the world's largest producer and exporter of passion fruit, generating a lot of peel and seed waste, which is generally discarded. However, this waste can be utilized in various ways, one of which is to produce flour and extract pectin. Pectin is a fiber found in various fruits and has been used to make jellies since the 18th century. The method used to extract it can be physical, chemical or enzymatic, which influences its chemical structure and functional properties. The most common extraction method is in hot acid media, which is harmful to the environment and to the structure of the pectin. An alternative is the use of ionic liquids (ILs), which are less polluting than acids, have a similar extraction capacity, and do not damage the structure of the pectin. The ionic liquid synthesized in this work and used in the extractions was pyridinium hydrogensulphate. Initially, conventional extractions of pectin from passion fruit albedo and orange peel were carried out with nitric acid for comparison purposes. After the LI syntheses, triplicate extractions were carried out with various concentrations of pyridinium hydrogen sulphate in a water bath at 85 °C for 30 minutes. The pectin extracted in each of the methods was precipitated with ethanol, dehydrated and crushed before analysis. The highest yield obtained was 14.6 % with ionic liquid at a concentration of 0.6 % and the highest degree of esterification was 83.7 % with ionic liquid at a concentration of 0.06 %. The amount of pectin extracted, and the degree of esterification were similar to the results of conventional extraction, with a yield of 13.2 % at the acid concentration of 5 % and a degree of esterification of 79.5 %, but with a higher viscosity at almost all LI concentrations. The viscosity obtained in the nitric acid extraction was 1.31 mm2/s and, in the ionic liquid extraction, the values obtained were 1.34 mm2/s, 1.47 mm2/s, 1.28 mm2/s, 1.52 mm2/s, 1.58 mm2/s, indirectly indicating a higher molar mass of the pectin obtained with this solvent, which is industrially more advantageous. These results showed that it is possible to replace the acids generally used in pectin extraction with ionic liquids.