It probably would not damage the probe, but it is not intended to be used directly in the mash. The cable and epoxy used to seal the probe are not tested or intended to be food safe. I am not saying that they are definitely unsafe to use with food, just that they are not tested to be. To be on the safe side, I would recommend using some food grade heatshrink. Adafruit sells some for this exact purpose:
You would just put this over the cable and the top of the stainless tip of the probe, leaving the bottom exposed. Then it should be fine to use directly in the mash.