15D-16

Multiple emulsion method is proposed for the encapsulation of sensitive ingredients since it is carried out in mild conditions and without any toxic compounds. This method has been applied in pharmaceutics and chemical industry, while it is relatively new to flavor and food industry. Research on multiple emulsion, especially O/W/O type is limited because of the practical difficulty in preparing a stable emulsion.

Our objective was to investigate some process factors for preparing stable O/W/O multiple emulsion and characteristics of final microcapsules.

Flavor model system (five flavors:rapeseed oil=1:4) was used as core. Different combination ratios of gum arabic to maltodextrin (0:10-5:5) were prepared. Primary O/W emulsion was prepared by blending core:carbohydrate wall mixture (1:3) with mixer and homogenized using a microfluidizer (34-83 MPa) or a piston-type homogenizer (20 MPa). This O/W emulsion was emulsified in molten hydrogenated palm kernel oil containing 5% emulsifier at 13,500 rpm using Ultra-Turrax^TM. Selected emulsifiers were Span 80, Tween 80, polyglycerin polylysinoleate (PGPR) and glycerin monostearate (ES-95^®). O/W/O multiple emulsion was solidified in ethanol:water (9:1) solution. Solid microcapsules were collected by filtration and freeze-dried. The physical properties and morphology of microspheres were determined.

Microfluidizer (at 70 MPa) produced more stable emulsion, as it produced small uniform droplet. Increasing gum arabic content created highly viscous emulsion, which subsequently resulted in stable O/W emulsion. The stability of O/W/O multiple emulsion was highly affected by the type of emulsifiers and the most stable emulsion was prepared using the blend of Span 80 and PGPR. The total oil retention in O/W, O/W/O emulsion and microcapsule was 83.3, 82.9 and 71.1%, respectively. Microcapsules were 273.5 mm in mean diameter, spherical in shape, and had a porous structure.

This O/W/O multiple emulsion method was found to be a suitable technique to prepare flavor microcapsules with good morphological characteristics and satisfactory production yields.