The aperture definition in digital photography
The aperture is the unit of measurement that defines the size of the opening in the lens. The size of this hole will regulate the image sensor’s degree of exposure to the light.
Every lens has its own aperture ratio. The smaller number on the lens (F/1.2 or F/2) the better it behaves in a low light situations. However, if you only shoot with studio lights you may be fine with the larger numbers on your lenses such as F/5. As we talking about food photography here where the nice bokeh is an advantage, you may like to purchase lenses with bigger aperture diameter (F/1.2 or F/2). And for sure read some reviews before buying.