Concrete will stain if it is not maintained and spillages are not cleaned off and left.
That said all is not lost and stains can be removed and repaired.
Assuming that the concrete has not been waxed and the underlying sealer has at partially failed, often saturating an area that has suffered a stain will dilute the offending mark. This may take a few goes but will normally do the trick.
At this point once the concrete has dried it would be wise to re-wax the concrete as though the concrete was new, to build up a layer of protection.
Here is a link to our food-safe concrete wax.
If the stain does not dilute the next option is to remove the top layer of concrete by sanding. Our sealer is penetrative and saturates quite deeply in to the top layer of concrete so the stain will not penetrate too far.
Using an orbital sander on a slow speed with a 180 grit sanding pad will remove the top layer. Once the stain has been removed the sealer in this location will need to be reapplied.
Depending on the condition of the remainder of the concrete you may decide at this point that it is worthwhile resealing the whole top. Depending on the condition also you may be able to apply only one or two coats of sealer instead of four as per our sealer instructions.
Here is a link to our concrete sealer.