Preparation and characterization of buriti (Mauritia flexuosa) oil emulsions and microcapsules using soy protein isolate and high-methoxyl pectin as stabilizers

Author(s)

Mírian Luisa Faria Freitas

• Document type: Doctoral Thesis
• Press: São José do Rio Preto. 2018-04-19.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências Letras e Ciências Exatas. São José do Rio Preto
• Defense date: 2018-03-23
• Advisor: Vânia Regina Nicoletti; Ana Paula Badan Ribeiro; Yrjö Henrik Roos

Abstract

The aim of this study was the preparation and characterization of buriti oil emulsions and microcapsules using soy protein isolate and high-methoxyl pectin as stabilizers. The biopolymers were characterized individually by analysis of solubilization, charge, turbidity and optical miscrocopy. The soy protein isolate-high-methoxyl pectin complexes were characterized by turbidity and optical microscopy analyses. Characterization of the buriti oil was performed by analyses of physicochemical and thermophysical properties, unsaponifiable matter, fatty acid composition, acylglycerol classes, triacylglycerol composition, triacylglycerol classes, and thermal behavior. The buriti oil emulsions were characterized by analyses of stability, particle size, electric conductivity, zeta potencial, optical microscopy, confocal laser scanning microscopy, and scanning electron microscopy. The rheological behavior of the emulsions was analyzed by constant shear and oscillatory shear tests. The buriti oil microcapsules were produced by spray drying of the optimized conditions for elaborating buriti oil emulsion added with maltodextrin as a drying aid. The microcapsules, in turn, were evaluated by analyses of colour, moisture content, encapsulation yield, particle size distribution, encapsulation efficiency and retention of carotenoids, encapsulation efficiency and retention of oil, water sorption, water plasticization and mechanical relaxation. The microcapsules morphology was analysed by optical and scanning electron microscopy. Through the biopolymer characterization, it could be noted that the highmethoxyl pectin showed high solubilization, independent of the pH, and the negative charges increased with increasing pH until stabilization. The soy protein isolate had low solubilization near the isoelectric point and it increased with increasing pH in alkaline solutions, up to reach 100% at pH 11. This biopolymer presented positive charges in pH below the isoelectric point and negative charges at pH above the isoelectric point. At pH lower than the isoelectric point there was attractive interaction between soy protein isolate and high-methoxyl pectin, leading to definition of the pH 3.5 for preparation of the emulsions. The characterization of buriti oil confirmed its high quality, showing high levels of carotenes, tocols and monounsaturated fatty acids. The CCRD experimental design was adequate for the study of buriti oil emulsions, leading to definition of an optimized conditions for producing emulsion rich in oil, stable for at least 7 days, with reduced droplet size, low electric conductivity and high modulus of negative charges. This material was characterized as pseudoplastic and showed viscoelastic behavior with storage modulus greater than the loss modulus. Moreover, through microscopic analysis it was possible to observe the interaction of soy protein isolate with buriti oil forming oil droplets and the interaction of high-methoxyl pectin with soy protein isolate forming the double layer of the emulsion. The excess pectin was observed dispersed in the continuous phase, contributing to system stability. The different samples of microcapsules presented significant differences (p ≤ 0.05) with respect to color parameters, encapsulation yield, encapsulation efficiency and retention of carotenoid, and encapsulation efficiency and retention of buriti oil. The sample with the highest maltodextrin content presented less intense coloration, in contrast, presented the highest encapsulation yield, encapsulation efficiency and retention of bioactive compounds. The glass transition and relaxation temperatures of the microcapsules were dependent on the ambient relative humidity, and the higher the relative humidity, the lower the glass transition temperature and the relaxation temperature. (AU)

• FAPESP's process: 14/08520-6 - Preparation and characterization of emulsions and microcapsules of buriti oil (Mauritia flexuosa) using isolated soy protein and high-methoxy pectin as stabilizer
• Grantee: Mírian Luisa Faria Freitas
• Support Opportunities: Scholarships in Brazil - Doctorate