Rheological properties and microstructure of monodispersed O/W emulsion agar gel

Abstract

This chapter describes the effect of oil droplet on the rheological properties and microstructure of monodispersed OAV emulsion agar gel prepared by membrane emulsification technique is investigated by mechanical measurements and SEM observation. An emulsion gel containing oil droplets is a good food model. Oil droplet size and oil volume fraction have important effects on the texture and rheological properties of the emulsion gel. This chapter investigates the effects of oil droplet size and volume fraction on the rheological properties and to observe microstructure of emulsion agar gel by mechanical measurements and SEM observation. Agar powder (1%) is dispersed in the emulsions containing 0.1,0.2 and 0.3 volume fractions of oil, after which these agar emulsion dispersions were stirred gently for 60 min at 20°C, heated for 30 min at 70°C and then heated again for 30 min at 9 0°C during swelling. After being degassed, these sols are poured into cylindrical glass containers (inside diameter 24 mm, height 38 mm). These glass containers are held for one hour at room temperature and then held in a water bath for 24 hours at 25°C before measurements. In each gel, the uniformity of dispersibility of emulsion droplets is confirmed by determining droplet number and diameter at top, center and bottom of emulsion gel. The compressive gel strength of emulsion gel decreases with an increase in oil droplet size, while that of emulsion gel determined by puncture test shows almost no change. It also includes Cryo-SEM observation reveals that oil droplets aggregated in the emulsion gel and that the gel had some void spaces between gel network and the oil droplet aggregate.