Direct Homogenization of Beverage Emulsions with the Innovative Counterflow Injection Process

Soft drinks often contain beverage emulsions in order to incorporate water insoluble flavours (flavour emulsion), to imitate cloudiness of natural juice (cloud emulsion) or both combined. Despite the widespread use, physical instabilities in beverages like ringing or sedimentation are still an issue.

The production of beverage emulsions usually needs three steps: Pre-emulsification by high shear agitation, followed by deaeration and two or more homogenization steps using a high pressure homogeniser with pressures up to 400 bar (5800 psi).

In our project emulsions, particular beverage emulsions, are directly homogenised with a counterflow injection plant, a process derived from the polyurethane production. The advantages of this process are: complete separation of oil and aqueous phase prior to the mixing head, only one combined emulsification and homogenization step and lower injection pressures compared to high-pressure homogenization. This leads to lower temperature rise during emulsification, less energy dissipation and extremely variable batch sizes from lab trials of 200 mL to industrial scale of 2 t/h with one plant.

The plant mainly consist of two vessels and two high pressure metering pumps, each for the oil phase and for the aqueous phase as well as a mixhead with two injection nozzles. Prior to homogenization or during idle times, oil and aqueous phase recirculate in the specified ratio at the required pressure for injection. A spool valve in the mixhead shifts from recirculation to injection resulting in direct homogenization of both phases by high-pressure impingement on one another.

First results show that it is possible to produce stable beverage emulsions at moderate pressures of 120 bar to 160 bar (1740 – 2320 psi). Emulsions mainly consist of 12 % oil phases (orange oil and weighting agent), water, sodium octenyl succinate starch, as emulsifier and citric acid. All trials were repeated for comparison with a standard GEA NiroSoavi high-pressure homogenizer.

At 160 bar a Sauter mean diameter (SMD, D_3,2) of 520 nm was achieved with the counter flow injection plant. The temperature increase of only 4 K compared to 12 K of the high-pressure homogenization shows the efficiency of this new process. Turbidity loss of the emulsions in ready-to-drink beverages at accelerated storage conditions was at the same low level as the standard emulsions made with the high-pressure homogeniser. Further potential will be investigated within the injection process and the layout of the injection nozzles to exceed present emulsion stability by high-pressure homogenization.