Abstract
SUMMARYResearch backgroundEmulsion technology is a suitable way of encapsulating, protecting and releasing hydrophobic bioactive compounds for application in food industries, but they are thermodynamically unstable systems. Good results have been achieved for emulsions stabilized by protein-polysaccharide complexes subjected to high-pressure homogenization. Improved stabilization of oil-in-water emulsions results from electrostatic complexes formed between proteins and polysaccharides at pH lower than the protein isoelectric point, which adsorb at the oil-water interface. In addition, polysaccharides contribute to emulsion stability by increasing viscosity of the continuous phase. The aim of this work is to investigate the production of carotenoid-rich buriti oil emulsions using soy protein isolate and high-methoxyl pectin as stabilizers.Experimental approachUsing a rotatable central composite experimental design, we assessed the effects of oil content, soy protein isolate/high-methoxyl pectin ratio and homogenization pressure on the stability, droplet size, electrical conductivity, electrical charge, microstructure and rheological behaviour of the emulsions.Results and conclusionsAn optimized emulsion was produced with 28% buriti oil, 55% soy protein isolate, and homogenization pressure of 380·105 Pa. This emulsion was stable for at least seven days, presenting reduced average droplet size, low electrical conductivity and high modulus of negative charges. The mechanical spectra showed that the emulsion behaved as a viscoelastic gel under oscillatory, non-destructive shearing, whereas shear-thinning behaviour took place under steady shear conditions.Novelty and scientific contributionThe optimized buriti oil emulsions stabilized by soy protein isolate and high-methoxyl pectin could be suitable for fat substitution, energy reduction and carotenoid enrichment in food products, such as dairy and bakery products, ice cream, salad sauces and vegetable-based cream.
Highlights
Emulsion technology is suitable for encapsulation, protection and modulation of the release of hydrophobic bioactive compounds for use in food and pharmaceutical industries
The optimized buriti oil emulsions stabilized by soy protein isolate and high-methoxyl pectin could be suitable for fat substitution, energy reduction and carotenoid enrichment in food products, such as dairy and bakery products, ice cream, salad sauces and vegetable-based cream
Emulsions containing the carotenoid-rich buriti oil stabilized by Soy protein isolate (SPI)/high-methoxyl pectin (HMP) could be valuable structured systems applied in foods such as dairy and bakery products, ice cream, salad sauces and vegetable-based cream for fat substitution, energy reduction and carotenoid enrichment
Summary
Emulsion technology is suitable for encapsulation, protection and modulation of the release of hydrophobic bioactive compounds for use in food and pharmaceutical industries. Emulsions are thermodynamically unstable systems and require addition of emulsifiers and/or stabilizers, as well as the use of energy (homogenization process) to attain kinetic stability [1]. Proteins are surface-active molecules that act as surfactants and prevent coalescence of dispersed droplets: they spontaneously migrate from the bulk phase to the oil-water interface, as free energy of proteins at the interface is lower than in the continuous phase [2]. The emulsion stabilizing properties of proteins may be enhanced by their potential electrostatic interactions with charged polysaccharides, which results in complex amphiphilic structures. These complexes or association colloids do not require a special legislation and may improve emulsion stability and textural attributes [3-6]. Soy protein isolate (SPI) and high-methoxyl pectin (HMP) are examples of a protein and anionic polysaccharide that may form electrostatic complexes when pH is lower than the
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