IMO, if the image is to be used to document a food item for informational purposes, a small aperture is appropriate. However, if you're looking for esthetically pleasing images of an artistic nature, a larger aperture does a better job.
The common lenses that are used most digital cameras these days have fairly small maximum apertures, like 3.5 or so. Once I can justify spending the money on one (and we're not really talking all that much money), I plan on buying something like an f/1.4 or f/1.8 for food photography.
This is one of the images from the original post in this thread. Notice that the ends of the pizzarito are out of focus, and the background is very out of focus.