Obtenção de óleo de abacate por diferentes processos: avaliação da qualidade, perfil de biocompostos e incorporação em fibras ultrafinas de zeína

Abstract

The avocado (Persea americana Mill), belonging to the family Lauraceae, is a subtropical fruit that has great economic importance due to the nutritive quality of its fruits and its oil extracted from the pulp, which has great similarity of composition of fatty acids with the olive oil. Thus, the objective of this work was to obtain oil from the avocado pulp through different processes and to use the oil for inclusion in ultrafine zein fibers by means of the electrospinning technique. In order to extract the avocado oils, the pulp was submitted to drying in an oven under ventilation (40 ºC and 60 ºC) or in a vacuum oven (60 ºC), and the oil extraction was performed by mechanical pressing or by Sohxlet using solvent. The avocados of the Breda variety are largesized fruits containing about 72% of pulp in relation to the total weight of the fruit, being distinguished by the expressive content of moisture, proteins and high antioxidant activity. The oil content obtained in function of the different processes was in the range between 25 to 43% with the mechanical pressing and, between 43 to 55% with the solvent extraction. After evaluating the quality indexes, bioactive compounds and the fatty acid profile, it was verified that the bioactive compounds were superior when the avocado pulp was dried at 60 ° C (oven under ventilation or vacuum) and the oil extracted by mechanical pressing. In order to develop ultrafine zein fibers by the electrospinning technique, the avocado oil with the highest content of bioactive compounds, among which, carotenoids, that was obtained by the vacuum drying process of the pulp followed by mechanical pressing, it was incorporated in the concentrations of 15 and 30% (w / w) in 20, 25 and 30% (w / v) zein polymer solutions. Analyzes of the polymer solutions indicated an increase in the apparent viscosity with the increase of the zein concentration, but the same did not occur with the electrical conductivity. Among the different concentrations of zein and avocado oil incorporated in the fibers, encapsulation efficiency was higher than 77% for most of the fibers, with the concentrations of 30% zein independent of the oil concentration used, presented to ideal concentration for the formation of continuous ultrafine fibers without the occurrence of fragmentation and formation of beads and with smooth surfaces with a diameter distribution ranging from 357 to 971 nm. The Fourier Transform Infrared Spectroscopy technique evidenced the encapsulation of the oil in zein fibers. The X-ray diffraction showed the amorphous structure of the fibers. Regarding the release of carotenoids at different conditions, it was verified that at pHs close to neutrality (6 and 8), temperatures of 60 and 90 ºC and shaking at 18 rpm for up to 1 min, reduced the carotenoid release of the composite fiber of 30% zein and 30% oil. The same fiber composition presented an ideal profile of carotenoid release in simulated gastrointestinal conditions.