If you work in studio (in a setup environment), with tripod, flashes and all calm, as I suppose you do with food, then I would suggest you buy a tilting-shifting bellow and a bellow-specific lens. I don't know if somebody make those for the Sony-Konika-Minolta bayonet mount, but you should certainly find something on eBay for the Pentax K-mount.
When shooting macro and food you probably want a very high degree of planarity of field and you probably would like very much to be able to move your focal plane (I mean not the focal plane on film, but the focal plane in front of the lens) to adapt it to your subject.
The tilting-shifting bellow will not be immediate to use (and probably it will not have auto-diaphragm) but you will see the difference in the final result, with the steak in focus and the potatoes, too.
Bellow-specific lenses always give better macro performances than macro lenses or than normal lenses on bellows, because bellow-specific lenses are designed to work on near subjects and to have a field of focus as planar as possible, also they are corrected for constance of center-edge definition.
Cheers
Fabrizio
