The puddle under the cold display
Melt water is where the salad bar goes wrong
Ice starts at zero and warms as it melts. The water it becomes has been in contact with everything above it.
A cold well packed with ice looks controlled at the start of service. By the second hour, the pan is a third water, the salad bowls are sitting in it, and the surface temperature of the food has drifted well above where it started.
Two problems in one pan
Temperature: an ice bed is at its coldest for the first hour and warms steadily as it melts. Hygiene: the melt water has been in contact with the ice, the pan, every bowl base and every drip from the serving spoons, and it pools where the food sits.
What inspectors see
Water in the pan, food below the surface line, no record of when the ice was last changed.
A dry display
A cold cell holds −10 °C for eight hours with nothing to melt. The tray under the food is as dry at the end as at the start, and the food stayed at the cold end of the safe range for the whole service.