With increase in age, chewing ability and intake functionality decrease. This can induce aspiration pneumonia, which is one of the major causes of death. Therefore, appropriate food texture is needed for easy swallowing by the elderly to prevent aspiration. Unsaturated fat, which is an important food ingredient that is converted to various bioactive compounds in the human body. However, use of unsaturated fat in food for the elderly is limited due to its strong lipophilicity and low oxidative stability. An oil-in-water (O/W) emulsion is useful as a utility form of lipid. The emulsion is a thermodynamically metastable dispersed system, and it leads to phase separation after creaming, flocculation, and coalescence due to high interfacial tension between the aqueous and oil phases. Thus, stably concentrated emulsion is required for the production of food with functional lipid for the elderly. In this study, the effect of oil droplet size on the stability of concentrated O/W emulsion with unsaturated fat was examined.<br/>A 90-mL aqueous solution containing pectin (6%–8%, w/v) and decaglycerol monolaurate (1%, w/v) was prepared and was added to 10 mL of soybean, olive, or fish oil. The mixture was emulsified using a rotor/stator homogenizer for 15 min at 15,000 rpm in a tube immersed in ice water. The prepared emulsion was stored at 37°C in a dark container. Particle size distribution of oil droplets in the emulsion was measured using a laser diffraction particle size analyzer. Furthermore, to evaluate the oxidative stability of the emulsion, peroxide values of the emulsion were periodically measured.<br/>The concentration of the pectin was directly related to the viscosity of the emulsion. At any concentration of pectin, the viscosity gradually decreased with the length of the storage. The initial median diameter of oil droplets in the emulsion decreased with increasing pectin concentration, indicating the emulsifying ability of pectin. However, similar tendency was observed for the emulsion, whose pectin concentration was 6% (w/v), with different initial median diameter and particle size distribution. This indicates that particle size in the emulsion affects the viscosity of the emulsion. The oxidative stability of the emulsion was low at high pectin concentration and low initial median diameter. This cause remains unclear but heat generated during homogenization may destabilize the emulsion for lipid oxidation.

Effect of oil droplet size on stability of concentrated oil-in-water emulsion with unsaturated fat

255th National Meeting (2018)

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