Maximum connection of devices to a single socket
You need to assure that your refrigerator's metal chassis is firmly connected to the electrical supply's safety ground pin.
Then, you need to assure that your house's wiring is tip-top as far as the safety ground.  The receptacle's ground is connected properly to the panel's metal chassis, AND, the panel's chassis is properly connected to grounding rods, an Ufer ground cast into a concrete foundation, or a metal water main not interrupted by a plastic meter.
Further, things like gas pipes and metal water pipes interrupted by a plastic meter also need to be bonded to the abovementioned grounding rods.
Then this check needs to be done for all other electrical circuits and devices in the kitchen.  It could be that the refrigerator is grounded properly but something else you are touching is leaking current.
If that is correct and complete, it should arrest any shocks.
It may also be appropriate to think about an RCD for the house.  That is a ground fault detector, which looks at current coming in and going out, and assures they are equal.  If they are equal, all current is accounted for and it's not likely to be traveling through weird routes such as through a human.