A well-designed medium temperature refrigeration system will maintain both a proper case temperature and relative humidity (rh).
The preservation of food depends not only on the temperature, but also on the relative humidity within a case. When rh is too high (above 95 percent), mold and slime conditions may occur, particularly on stored meats. When the rh in the refrigerated case is too low, excessive dehydration will occur. Proper case rh is maintained by achieving the correct evaporator temperature difference.