hi There! I have never seen this before. I did a cranberry and savoury marinated duck breast. Cooked it to perfection (132 pulled from oven with a proper resting period) in the main kitchen. Transported them on site and sliced them on site just prior to service (25 minutes). They were gorgeous! I put them in an on site warming oven (180 F) to bring the temp up and checked on them 5 minutes before service and they had developed green patches -some very green! This was for buffet service. I have never done duck breast buffet style, always plate service and sliced them during plate up. I was shocked as you can imagine to see this result and lost about an eighth of my product - almost all of the aiguillettes were affected? I have never done a cranberry marinated duck before - I have glazed with it before but never in the marinade process. What happened here? Any insight would be really appreciated! The only thing that I can think of was that there was an oxidation that occurred because of the citric levels?? Thanks in advance!