Encapsulation of flaxseed oil using plant proteins

• Other Authors: Nickerson, Michael T.
• Language: English
• Published: 2014
• Subjects: flaxseed oil; microencapsulation; plant protein; emulsion
• Online Access: http://hdl.handle.net/10388/ETD-2012-10-740

The overall goal of this research was to develop a plant protein-based microcapsule capable of carrying, protecting and delivering flaxseed oil within the food and gastrointestinal environment. Specifically, the research aimed to: a) screen a variety of plant proteins and pre-treatment conditions based on their emulsifying properties for use as a wall material; b) develop and optimize encapsulation protocols for entrapping flaxseed oil; and c) study the oxidative stability and delivery of entrapped oils from capsules under different environmental and simulated gastrointestinal conditions. In Chapter 3 and 4, the emulsifying and physicochemical properties of legume and oilseed protein isolates, respectively produced from isoelectric precipitation and salt extraction were investigated. Findings in Chapter 3 indicated that both the legume source and method of production showed significant effects on the emulsifying and physicochemical properties of chickpea (ChPI), faba bean (FbPI), lentil (LPI), pea (PPI), and soy (SPI) protein isolates. The emulsion capacity (EC) values ranged between 476-542 g oil/g protein with LPI showing the highest capacity. Isoelectric-precipitated ChPI and LPI displayed higher emulsion activity index (EAI) (~46.2 m2/g), (emulsion stability index) ESI (~84.9 min) and (creaming stability) CS (98.6%), which were comparable to those of SPI. In Chapter 4, findings indicated that both protein source and method of production had significant effects on the physicochemical and emulsifying properties of canola (CaPI) and flaxseed protein isolates (FlPI). CaPI showed significantly higher EC (~515.6 g oil/g protein) than FlPI (~498.9 g oil/g protein). EAI for FlPI was found to be higher (~40.1 m2/g) than CaPI (~25.1 m2/g) however, ESI values of CaPI and FlPI were similar. Creaming stability of emulsions stabilized by CaPI and FlPI ranged between 86.1 and 96.6%. CaPI and FlPI were shown to have emulsion forming properties; however their stability was low. In Chapter 5, ChPI and LPI-stabilized emulsions were optimized based on pH, protein concentration and oil content for their ability to form and stabilize oil-in-water emulsions using response surface methodology. Droplet charge was shown to be only affected by pH, while droplet size and creaming index were affected by protein concentration, oil content and pH. Optimum conditions for minimal creaming (no serum separation after 24 h), small droplet size (<2 μm), and high net droplet charge (absolute zeta potential (ZP) value >40 mV) were identified as: 4.1% protein, 40.0% oil, and pH 3.0 or 8.0, regardless of the plant protein used for emulsion preparation. Flaxseed oil was microencapsulated by freeze (Chapter 6) or spray (Chapter 7) drying employing ChPI or LPI and maltodextrin. Effects of emulsion formulation (oil, protein and maltodextrin levels) and protein source (ChPI vs. LPI) on the physicochemical characteristics, oxidative stability, and release properties of the resulting capsules were investigated. Optimized capsule designs were found to have high encapsulation efficiencies, low surface oil, and afforded protection against oxidation over a 25 d room temperature storage study relative to free oil. Microcapsules were also able to deliver 84.2% of the encapsulated oil in the simulated gastrointestinal environments.