Tongs lowering a sealed bag of meat into boiling water
What It Means When Sous Vide Beef Turns Green
Sous vide home chefs may notice beef turn an unpleasant green color if it's left cooking in the sous vide machine for more than a few hours, which could be due to bacteria.
The consensus on the internet is that there are bacteria on the beef's surface that thrive at sous vide temperatures, but reputable food health sources on the issue are scarce.
Despite looking like the meat was rotten, some who have wound up with green sous vide beef reported that the meat didn't smell as if it had gone bad.
USDA guidelines also don't address the issue specifically, but it does stipulate that a change in color alone does not indicate spoilage.
To remove the greenish tinge, sear the meat on both sides after it is done cooking in the sous vide machine to kill the bacteria and turn the beef a nice, textured brown again.