In-pack radio frequency heating of liquid whole egg: Effect of agitation on heating rate and uniformity

In-pack radio frequency (RF) heating of liquid whole egg (LWE) was performed using a 27.12 MHz parallel-plate radio frequency (RF) system. To do this, 600 mL of LWE was subjected to RF heating in a RF-transparent plastic bag (140 mmx180 mm). Experiments were conducted at two different electrode gap settings (98 and 103 mm) with and without orbital movement in the horizontal plane. The effect of agitation on heating rate and uniformity was investigated for varying rpm's (120 and 140 rpm) for a constant orbit diameter (35 mm). An orbital shaker was specially designed and coupled with the RF system for this purpose. Fiber optic probes were used to continuously measure the temperature of LWE at four different internal locations. Temperature uniformity index (TUI) was calculated to evaluate the uniformity of heating. Coagulation of LWE around the headspace was inevitable when the package was stationary during the treatment. Agitation brought about by orbital movement prevented the coagulation. Drastic improvement in heating rate and uniformity was observed upon orbital movement of LWE at all conditions.