Larry, the dangers are minimal, if any--as long as one cooks to safe temps.
It seems strange, I know, and you are right to intuit, as your post implies, that with the lengthy time there would be significant pathogen growth. C. perfringens, which one would expect on red meats, is an especially rapid grower but one would see significant growth of Campylobacter, Salmonella (both almost definitely present, especially on poultry), E. coli (rare but possible), and others.
All of these are going to be affected as temps rise into the 130s and above. Once temps are at that level it becomes a time @ temp dynamic; in other words, a temp of
X for a specific number of minutes or more, will produce the same kill level as a higher temp for fewer minutes. Pasteurization occurs in both cases but, at lower temps, significant time is needed--well over an over at temps in the low 130s--compared to the few minutes, seconds or instant needed for pasteurization as temps hit 160 and higher.
Staph. aureus, a definite possibility on anything, is a very poor competitor with other bacteria present, especially spoilage bacteria. It would not like be a problem here. It becomes one on cooked foods. Cooking destroys the competition; food contaminated by S. aureus (as happens when the food is touched or by a misplaced sneeze or cough) after cooking has little to no competition at that point and if given the right conditions (like a too lengthy cool down period, or with cold foods, those that warm while sitting out on the counter then the picnic table for hours), Staph can grow to a point where it produces toxin that is very heat resistant. (Reheating won't affect it.)
Still, I see no benefit to barbecuing at temps this low. The leaner items like the poultries certainly don't need it and the fattier items simply do not cook any better by cooking more slowly than typical low/slow temps. And why sacrifice the flavor that develops at higher cook temps?
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There are two branches of sous-vide, pretty much--one, in which foods are cooked at their serving or desired finish temps (or below) and the the other, where foods are cooked above typical serving/finish temps but still lower than usual.
For the former, one might cook salmon at 104-114, lobster at 131, lamb racks, beef tenderloin or the like at 131, flat chuck roasts at 131; for the latter one might cook duck or pork confit at 180, short ribs at 176-180, chuck at similar temps. Much of this comes down to whether the item is considered a naturally tender item (like most seafoods, fishes, the meat tenderloins) or if higher temps are either necessary or 'necessary', the former can be, like for vegs which need higher temps in order to break down the cellulose structure in the veg, the latter, more of a personal preference thing, where on might want a more braised-like finish. An example of this is both confits that I make; another would be chuck or short ribs. Longer times--much longer times--are needed for less tender meats cooked at lower temps. Chuck is very interesting cooked at 131 for a full day. It looks uncooked but isn't. A finishing sear and then immediate service yields an extremely flavorful beefy finish with a soft texture--but a different soft than what is achieved by cooking at higher temps, in which case you'd likely cook more like 7-10 hours depending on the thickness of the meat. For beef, chuck is a favorite, both at low heat and higher. Another is a thick rib-eye, cooked at low heat.
Cook time is determined by the size of the cut (mostly thickness), whether it is a tender cut or not, desired finish texture and temp, and sufficient time to reduce any pathogens that might be present on the food--a time @ temp thing.
One can use a thermometer and rig a therm point on the bag using weatherstripping then use a needle-point probe. Though this can be useful, especially when learning or when needing a specific temo for safety reasons most combinations of time and temp used for sous-vide have that factor built in. (One tends to use combinations that are tried and true, so to speak.)
It is not hard to maintain a 180 temp in a pot of water on the stove (I partially cover) and that is how I got started. For low temps you need equipment because no fluctuations can be allowed. Sous-vide equipment is very expensive, considering, with prices from $900-100 and up for submersible heater/circulators to much more for large waterbath units. A way around this (which is what I did and many others before me have done) is to hit the online lab equipment resellers and get a used lab unit.
Strict food safety protocols are required for sous-vide, as you'd imagine.
There is a lot of information on
this thread--but be prepared, it's 100+ pages. Read at your leisure but I suggest starting at the beginning. That way you'll see how other people new to sous-vide handled different concerns and you'll see the questions they asked, the answers they got, and the results of their experiments, as you read along. Hope this helps. If you have any questions let me know.
!! I've never heard of anyone cooking that low before (I know cold smoking temps are around that range).
