Cryomancy is magic involving the removal of heat from an object by converting thermal energy into magical energy, thereby cooling the object. The conversion to magical energy is not perfect (some small amount of heat is released after removing it from the object or area of effect), however I do not believe this will affect your answers.
Food can be cooled from room temperature to just below freezing (30℉/-1℃).
Food can be magically maintained at the intended temperature indefinitely. This is done by enchanting the area around the food, not the food itself. The maximum area of effect is a radius of 15'/4.5m.
The effects of Cryomancy on food are similar to those produced by flash-freezing. Additionally, if it can be frozen via flash-freezing, it can also be frozen using Cryomancy.
Question: How would Cyromancy affect the eating habits of Medieval peoples?
Magic is unavailable to the average person, forcing the employment of mages (much like the average person today not having direct access to flash-freezing equipment). The majority of mages are of equivalent social status as a blacksmith.
For the purpose of this question, assume we're talking about London during the 1500’s