I call it a secret weapon, and it's become a critical step in my post-processing workflow for food photography. In your photo editing software there is an option to correct sharpness using what is called "unsharp mask." This is yet another reason to shoot RAW (or RAW + JPG), as this option only exists with RAW photos.
Regardless of how well-focused your photo is, and regardless of where you select your focal point, I believe "unsharp mask" should be addressed every time you take a photo of food. Why? Most cameras are optimized for portrait and/or landscape photography, where a softer look is usually more appealing. When photographing food, we often want to focus on detail. That sometimes means that we want a sharper photo. (Another way of saying this is that we may want to remove the mask that made the photo less sharp.)
Software usually gives you the ability to change the amount (sharpness), radius (fineness), and threshold. I find that adjusting the amount/sharpness is all I usually need to change. Don't go crazy here, just a little bit is all you need. My software (Canon's DPP) gives me a sharpness slider that can be adjusted from 0 to 10. The default is 3 and provides a nice image:
As you look at these photos, pay attention to the background as well as the blueberries and the cereal to see how the image changes. To achieve the softest photo, I set the unsharp mask sharpness slider to 0:
Notice how the detail in the cereal has disappeared and the background has blurred.
Next, I will sharpen as much as possible with the slider at 10:
Yikes, this is looking a bit harsh. The cereal almost looks stale and the background looks a bit grainy.
My final edit with the slider set at 5 provides just a bit more detail than the original, not too soft, not too harsh, just right:
When photographing food in natural light I nearly always end up with unsharp mask around 5 or 6 (on a scale of 0 to 10). Try it and let me know what you think!