Vegetables cook at at temps over 180 degrees. Years ago it was pretty much settled that raw garlic in a pouch, as well as fresh herbs would result in off tastes with proteins cooked at temps less than 180. now I see recipes from profession sites that call for these raw items with steaks etc. What gives?
Not everyone accepts science. It’s not just in the cooking world. 
@Ember do you happen to have some insightful, go-to resources to share on (not) cooking with garlic? It seems the internet has a ton of a conflicting information on this. 
As @Stulevy says, vegetable matter doesn’t start to break down until we get into the higher end of the temperature ranges used for sous vide, while we cook meats at the lower end of the scale. There’s almost 20-30C difference in the targets, which you must admit is a significant amount. The herbs will impart a little topical flavour to the outside of the meat product and to the purge, because they have a small amount of volatiles that are active at low temperatures, but herbs generally require heat processing to extract their essential oils.
The big argument for not adding fresh herbs or anything other than the basic salt to the meat for cooking is that it simply won’t penetrate beyond the surface of the meat. Anything other than salt becomes nothing more than a surface treatment.
Here’s a good article that explains it:
http://amazingribs.com/recipes/rubs_pastes_marinades_and_brines/zen_of_marinades.html?hc_location=ufi
Now, the article is specifically about marinades, but if a marinating liquid won’t penetrate very far it is even less likely that the oils from a stick of raw rosemary will penetrate.
It’s worth noting that this doesn’t only apply to sous vide. Adding herbs to the outside of a roast that goes into the oven will still only flavour the surface layer, but in these instances there will be more interaction with the surface layer due to the temperatures involved.
Of course, there is no harm done by adding the greenery to the bag. It looks pretty in photos. Garlic will impart some flavour to the meat where it contacts. Raw onions will too. The onion and garlic both have flavour compounds that are active at low temperatures. These are the ones that give the raw alliums their heat. These volatiles depart with cooking allowing the other subtler (more desirable?) flavinoids to come to the fore.
I know there’s a lot of stuff flying around about raw garlic being a contamination risk for botulism, but that same risk exists in raw onions and other things that grow in the soil.
3 Likes
Thanks so much for sharing this! Reading now. @Ember
1 Like