Radiofrequency energy is applied to a container having an outer housing and an inner housing disposed at least partially within the outer housing. At least a portion of the inner housing is transparent to RF radiation. At least one antenna is configured to apply RF energy to an energy application zone within the inner housing. A processor is configured to control the application of RF energy to the energy application zone by selecting a set of modulation space elements (MSEs), and cause RF energy application at the modulation space elements of the selected set.