Development of a Multilayer Emulsion System for the Protection of Polyunsaturated Fatty Acids in Flaxseed Oil

Abstract

Among the various components of food, fats are considered as an offender for cardiovascular problems in human beings. However, many polyunsaturated fatty acids are identified as being beneficial to health. Fats are an integral component of many food system and is difficult to eliminate its presence completely. There is an increased interest in substituting the harmful fats with health promoting polyunsaturated fatty acids including ω-3 fatty acids. All PUFAs are characterized with unsaturated chemical bonds that render them unstable due to oxidative degradation. The susceptibility of ω-3 fatty acids to lipid oxidation has hindered the incorporation of these heart healthy polyunsaturated fatty acids into healthful foods and beverages. The contributing factors to oxidation include metal pro-oxidants, heat and light. Therefore, emulsions are devised as a means of protecting the ω-3 fatty acids in oil.
An attempt is made to encapsulate the advantageous flaxseed oil with the aid of multilayer oil-in-water emulsion. This is achieved in a conventional primary emulsion when oil/water interface morphology is modified using a multitude of surface active biopolymers. It is desired that the biopolymers interact constructively and form an emulsion that is resistant to flocculation and aggregation with increasing storage time, salt concentration and temperature. The aim of this research is to create a novel tertiary and secondary emulsion and test its suitability for protecting the oil phase from stress factors (temperature and salt variation) and chemical (oxidative) breakdown.
In this study, plant based flaxseed oil rich in ω-3 fatty acids were dispersed into primary, secondary and tertiary emulsion system. A primary emulsion (1% flaxseed oil, 0.4 % sodium caseinate) containing sodium caseinate stabilized cationic droplets were prepared by homogenizing flaxseed oil as oil phase and sodium caseinate solution as aqueous phase in an ultrasonicator. A secondary emulsion (1% flaxseed oil, 0.4% sodium caseinate + 0.25% sodium alginate) comprising of sodium caseinate- sodium alginate anionic droplets were produced by diluting appropriate primary emulsion with alginate solution. Further, tertiary emulsion (1% flaxseed oil, 0.4% sodium caseinate + 0.25% sodium alginate + 0.25 % chitosan) composed of sodium caseinate- sodium alginate-chitosan coated cationic droplets were produced by diluting suitable secondary emulsion with chitosan solution. The resistance of primary, secondary and tertiary emulsions with the same lipid concentration to destabilization by thermal treatment (30−90 °C for 30 min), high sodium chloride concentration (≤ 70 mM NaCl) and oxidative degradation (hydroperoxide concentration and TBARS) were determined. The results showed that secondary emulsions could resist variation in environmental stresses of salt and heat as well as protect the oil phase from decomposition better than primary and tertiary emulsions. Interfacial engineering could be used to design emulsion system with desirable characteristics.