The Use of Mucilage Obtained from Vegetable Oil Sources in the Preparation of O/W Emulsions

Abstract

One of the factors that markedly affects the characteristics and stability of oil-in-water (O/W) emulsions is the presence of polysaccharides in the aqueous phase. Polysaccharides act mainly as stabilizing agents, granting physical stability of the emulsion for a long period of time by immobilizing the droplets of the dispersed phase, increasing the viscosity of the aqueous phase. However, some polysaccharides also present an emulsifying effect associated with the presence of a proteic component related to its structure. In the present work, the potential use of mucilages obtained from vegetable oil sources in the formulation of O/W emulsions was analyzed. Chia (Salvia hispanica L.) is an annual plant native to Central America. Recently, the possible exploitation of this seed has been reappraised given its content and quality of oil (33%), proteins, dietary fiber and bioactive compounds. It also contains mucilage (a complex polysaccharide of high molecular weight), which is secreted by the seed when it becomes wet, forming high-viscosity solutions. O/W emulsions (20:80 wt/wt) prepared with refined corn oil and dispersions with ≥0.75% mucilage (6.8 and 18.8% protein content) and 0.1% Tween 80 presented very good stability during storage at 4±1ºC for 120 days (QuickScan, backscattering value 78%). The emulsions prepared with mucilage with lower protein (6.8%) and lipid content (0.9%) were more stable. Locust bean, flax (Linum usitatissimum) and fenugreek (Trigonella foenum-graecum) seeds with 25.0, 42.0 and 7.24% oil, respectively, presented important levels of mucilage in their structure (26.7-33.2, 6.5-8 and 22%). The stability of O/W emulsions (40:60 wt/wt) prepared with canola oil and dispersions of mucilage from locust bean and flax seeds was higher when the mucilage concentration was increased from 0.5 to 1.5% in the aqueous phase, whereas emulsions formulated with mucilage from fenugreek seeds exhibited high stability (100%) during all the storage time (90 days, 25±1ºC) for all the mucilage concentrations tested (0.5-1.5%). The stability of the O/W emulsions against creaming can be improved by adding flax mucilage and soybean protein isolates due to the interactions between these compounds. It was also found that flax mucilage reduces the creaming phase in carrot juices, and helps to stabilize meat products by its interactions with the meat proteins. In general, polysaccharide dispersions increase the viscosity of the aqueous phase of the emulsions, limiting the mobility of the oil droplets in the dispersed phase to migrate, and therefore to flocculate or coalesce. Thus, the physical stability of O/W emulsions against gravitational phase separation can be improved with the addition of chia mucilage, given its role as a thickening agent.