Unsetting a loaded VST patch

Hi there,

i load presets from disk into a VST plugin with the following code:

void loadPresetIntoSynth(const File& file, const int programIndex)
    MemoryBlock mb;
    file.loadFileAsData (mb);
    VSTPluginFormat::loadFromFXBFile (instance, mb.getData(), mb.getSize());

where instance is an AudioPluginInstance object.
Now i also offer a reset function where it should be possible to unset the currently loaded preset at position programIndex in the VST plugin.
I don’t see such a static method in VSTPluginFormat, therefore how can this be done best?

Thank you very much!