For larger openings often sliding doors are used.
Various types of sliding doors are available; 
Mainly chill- and freezer doors. 
Coating and finish to your requirements; frames are made from aluminium, coated steel or a stainless steel.
Doorleaf finish can be fibreglass, coated steel of stainless. 
Various kinds of hardware or extras can be applied; windows, foot plates, locks, door closers or automatic opener/closer and door protection bollards.