Does dry ice freeze the product? At the point of contact, yes: a source at -78.5 °C is at least 60 degrees colder than the target of any cold chain product. The job of a coolant is to hold the product within its target range, and dry ice touching the product drags that spot far below it.
In fresh produce this is freezing injury. The USDA storage handbook describes produce with ice crystals in its tissue turning water-soaked and mushy on thawing; apricots, avocados, bananas, cucumbers, lettuce and peaches are hurt by even one light freeze. In frozen goods the contact surface over-chills and plastic packaging turns brittle.
The burning part applies to people, not the product: dry ice causes frostbite on skin. The carbon dioxide it gives off is heavier than air and collects in enclosed spaces, which is why a box carrying dry ice is never airtight.
How eutectic plates differ
A eutectic plate melts at a set temperature and stays there while it melts; GEBHARDT plates come in -3, -14, -18 and -21 °C versions, chosen to match the product's target. If dry ice is used, an insulating layer goes between it and the product, the ice is spread through the load, and the logger sits beside the product closest to the dry ice.
