Before talking about herbs or no herbs, I would like to compliment SousVide Supreme for their excellent customer service.
After six years of faithful service, my SousVide Supreme water oven had burnt out. I e-mailed customer support about this, and they offered to replace my faulty unit with a refurbished one. I only had to pay for shipping my unit to them (which cost me 10 euros), and upon receipt of my faulty unit they immediately dispatched the refurbished unit. After six years, a lot longer than the 1-year warranty, that is very good service indeed!
There is a Facebook group on sous-vide cooking called Exploring Sous Vide that is well worth joining if you cook sous-vide, because it has an active community to ask questions or share your successes (and failures). I am one of the more active of the more than 5,000 members. Some members make the craziest assertions that I know for a fact are untrue after more than six years of intensive experimenting with sous-vide cooking, but sometimes I am not completely sure either and it prompts me to do another side-by-side experiment.
One of these questions is whether or not it makes sense to include herbs in the bag when you cook meat sous-vide. There was some debate about this and one member stated that because there are juices in the bag at the end of the cooking, that means that flavor only goes out of the meat and does not go in. That didn’t make any sense to me, but to make sure I decided to do a side-by-side experiment.
I started with a nice piece of leg of lamb, that I cut into two pieces. Then I seasoned both pieces with salt and freshly ground black pepper, and vacuum sealed one of them with a generous amount of fresh rosemary. The other piece was vacuum sealed without rosemary.
The lamb was then cooked sous-vide for 2.5 hours at 55C/131F. (This is slightly lower than the core temperature of 57C/135F I prefer for lamb, as I wanted to make sure that the searing would not overcook it.)
After those 2.5 hours the lamb looked a bit grey, as is usual with sous-vide cooking.
Then I browned it in olive oil over high heat…
…on both sides.
The result: both pieces of lamb were delicious, tender and juicy. A clear hint, but not more than a hint, of rosemary was detectable in the piece that had been cooked with rosemary. The hint was clear enough that I could distinguish between the two in a blind experiment conducted with the assistance of Kees. So the result of the experiment is: yes, it does make sense to include herbs in the bag, but don’t expect a strong flavor if the cooking time is short.
A couple of remarks: for a more pronounced rosemary flavor, it may help to put some olive oil in the bag (as the essential oil of rosemary dissolves more easily into oil than into water). The rosemary flavor will be stronger if the meat is cooked with the rosemary for a longer time, or if it is allowed to marinate before or after cooking.