Flavor emulsions are oil and water emulsions which are normally prepared as a concentrate and can be diluted to form a final product.
There are two types of flavor emulsion which are used in the food industry. One is a high concentration oil emulsion which is essentially essential oil stabilized with emulsifiers stabilizers and other additives, the other is a flavored oil emulsion with added vegetable oil which is formulated to give a cloudy appearance. The emulsions must be stable over time (both in their concentrated and diluted forms). Sedimentation of flocculated material at the bottom of the container, or creaming of oil to the top of the container are both undesirable. The system is often stabilized by the addition of hydrocolloids such as xanthan gum, gum Arabic, alginates and carageenans. These will absorb to the oil water interface and can impart both electrostatic and steric (electrosteric) stability to the emulsion. The optimal particle size is often considered to be < 3 microns (especially if caramel color is used as an emulsifier). The concentrate also will consist of sugar and preservatives. By monitoring the change in particle size upon storage or upon dilution, laser diffraction can be used to screen new formulations so that unstable formulations can be rejected.
Problems can also occur with the crystallization of sugar within flavor emulsions which can lead to batch to batch problems. Figure 9 shows two different flavor emulsions of similar sizes, one of which had a stability problem. There is a peak of large particles (could be coalesced oil droplets or sugar crystals) in the 10 – 100 um region seen on the particle size distribution of the unstable formulation.

Laser diffraction used to detect outsize particles in flavor emulsions
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