Confectionary coating using an electrohydrodynamic system

In the chocolate coating industry, cocoa butter is a high value ingredient. Due to high cost, shortage of supply and blooming, hard butters are frequently used as cocoa butter replacers. An electrohydrodynamic system (EHD), which forms fine droplets with a relatively narrow size distribution, may be beneficial in confectionary coating to reduce cost and to increase quality because complete and even coverage can be achieved. The objective of this research is to optimize the use of EHD by altering the resistivity, viscosity and yield stress of different types of confectionery coating using lecithin. Non-EHD and EHD coating systems using confectionary coating made of cocoa butter equivalent, lauric cocoa butter or cocoa butter with different percentages of lecithin were analyzed. Droplet size, thickness of coating and minimum flow rate to produce complete coverage was measured. The voltage supplied for EHD coating system was 25kV. As lecithin increased, resistivity, viscosity and yield stress of samples decreased. Lower resistivity, viscosity and yield stress samples produced smaller droplet size, thinner coating and higher minimum flow rate. EHD coating is more efficient than non-EHD coating because more even and complete coverage can be achieved as fine droplets are produced and distributed during coating. The droplet size was significantly smaller for samples sprayed with EHD compared to non-EHD. The thickness was significantly lower under EHD and the minimum flow rate to get complete coverage with EHD was greater because EHD coating tends to spread over a wider area. Under EHD coating, samples with lower resistivity produced smaller droplet size and lower thickness, which is important to reduce cost and increase quality of coated food products.