I can't figure out the faux smoke ring caused by marinating, but I get them too. A marinade is more of a surface treatment (verses a brine), so do you suppose the 'ring' is an indication of the depth of penetration? For example... on the short side of the marinade timetable and cooking time, this is a 3/4" thick sirloin steak that was marinated in some beef injection for several hours, seasoned with Montreal steak seasoning and SV'd at 130° for 75 to 90 minutes, then seared for less than 2 minutes. I don't put any additional marinade in the bag, yet all my sirloin steaks have a 'ring'.