Toxic Sous Vide scare
In the General Sous Vide Questions Forum
I did a beef roast - 48 hours at 125 degrees F and when I pulled it out the bag was swollen like a balloon and the thing had a terrible smell when I cut the bag open. We did not taste the meat at all- too scary.
I don't understand what might have happened. I've done sous vide dozens of times and never had a problem. Here are the particulars:
- a tied, rolled beef rump roast.
- had been frozen for over 30 days. Never thawed prior to cooking.
- vacuum packed by the butcher - seal was good so I didn't open it.
- part of 1/2 cow we bought from the butcher. No problems with any of the other beef.
- no swelling at 24 hours. (a little. very small air bubble- 1/2 oz.)
- massive swelling at 48 hours.
- horrible smell upon opening
- incredible soft roast-beef texture.
- beautiful rare roast beef look (cut it open to look before tossing)
It's pretty clear there was some contamination, but I'm really troubled trying to figure out what happened and how to prevent it. I mean- the contamination was probably present at 24 hours, but no accumulated gasses. What if we had eaten it at 24 hours?
I never opened the package and it was sealed quite well, so I know that I didn't contaminate it.
Please- I'd very much appreciate some help explaining this one.
24 Replies So Far
That's really strange about your sous vide beef, I've never had anything like that happen. It definitely sounds like there was something going on in the bag that wasn't killed.
I wonder if it was caused by cooking it at 125F for so long. I never cook sous vide under 130F for more than 2 hours since the safety of that lower end is a little hazy for me, plus I prefer medium rare. If that's the case though it makes sense that the swelling would happen suddenly since the bacteria increases exponentially.
That's my best guess, though I'd be curious to hear from some other people that cook for long periods below 130F.
Via Twitter, @Sousvidemagic
agrees that the low temperature might be an issue:
At 125F & sous vide 4 more than 2.30 hrs, U R in fact incubating bacteria growth. The bath may B off a degree or 2 too low!
Usually 125F if the meat is not contaminated & seared, it would be OK. But sous vide at borderline U need prof. SV equip.
Have you cooked other items at 125F for that long before?
Come to think of it, I haven't. Usually I do at least 131F for "long" sous vide because usually I'm doing something with a lot of connective tissue, like a shoulder roast. I use 125F for steaks- a couple of hours- and then gril them.
I guess I was being greedy- wanting a very rare, very tender roast of beef.
And I think I'm in trouble, because I'm going to keep trying this combo to see if I can make it work. That beef was so tender and so beautiful, and it was a pretty cheap and flavorful cut. I'll probably brown the meat on the outside and see if that works. If it doesn't, I'll start browning on the outside and raising the temperature a bit.
But, other than the fact that I knew it was poison, that beef was mesmerizing. I'm going back to that well a few times before I decide that it can't work.
If my recollection is correct, the minimum pasteurization temp is 128F. 131F is usually recommended because of a safety margin. I had great results on a 24 hour roast at 129F, but I wouldn't go lower. The exception would be a short cook, say 2 hours at a lower temp for a truly rare result, but for a long cook, don't go below about 130F, as bacteria, including botulism, can grow.
I think the main problem is how the piece of meat is prepared before vacuum packing. Deboned and/or rolled meats will always get contaminated "internally" do to folding back/rolling the exposed meat. This will result in an end product with internal contamination before starting the sous vide cooking. Such pieces also tend to be thicker resulting in even longer exposure times at (sub)optimal microbial growth inside the folded/rolled meat (especially with the relatively low temp used here I can imagine these microbes thriving well for the first couple of hours and an remaining batch that will survive and divide throughout the whole process -> you've smelled that feast). Intact pieces of meat that are quickly seared before cooking would be a better choice here I think.
I'm new to this so I won't offer advice. I love beef tenderloin and usually buy whole untrimmed in cryvac. When I open the bag there is so much liquid that even if I wasn't going to trim I would still repackage before sous vied.
Keep us posted on any future efforts
When cooking below 130F, you basically need to keep the cooking time as short as is necessary to get the food up to temp. It can be held a little bit longer (as long as you keep it within the safe limits for food in the hot zone) but you don't want long cook times. (All items that cook for a long time are done so at temps that are outside of the danger zone).
A few hours at under 120F is dangerous rather than overkill. At 113F to 130 F (especially under 120F), your bath is an incubator -- the pathogens will multiply much faster at these temps than at room temp.
So, take a look at Nathan M's tables up-thread and base your cooking times on the time to get the food up to temp.
Also, find Nathan's posts where he discusses the safe time that food can be in the 'hot zone'. He lays out valuable little understood information very well. [Maybe a FAQ or thread that contains just that information could be started? Everyone should really have that info on hand.]
Scott, This was copied From another site. No credit to me
Scott writes that his roast was professionally vacuum-packed, meaning that there was essentially no air in the bag. The roast was almost certainly contaminated with [i]clostridium perfringens[/i], also known as [i]c. welchii[/i], a gas-forming anaerobic bacillus that is known to be a common cause of food-borne illness, and is also the cause of gas gangrene. The roast was, well, in the process of decomposing, and the anaerobic bacilli inflated the bag with foul-smelling gas
I had the same experience when cooking beef at 125 degrees (or lower), but at other times, no gas formed, with similar cuts of beef. The difference probably lies in the handling of the meat, at the slaughterhouse, the wholesaler, the retail butcher, or in your own kitchen.
To prevent this problem for long cooks, I suggest that vacuum pack then immerse in boiling water for 60 seconds. This doesn't cook anything, BUT it will kill the surface bacteria (inside intact meat is sterile).
Usually do this for cooks over 6 hours.
We also choose to cook tough meats (i.e. those cooking for more than 4 hrs) at a minimium of 131 degrees so it pasteurizes the bag.
Sounds to me like the problem was basically that you did not thaw the meat prior to cooking. A roast has a lot of mass, so while the water bath may have been maintained at 125F, the surface of the meat was cooled, for the duration of the thaw, by the internal frozen mass to a temperature low enough for bacteria to thrive. For large mass items, I think it's important to raise the internal temperature to whatever your refrigerator is set at before attempting sous vide cooking. This is the same reason an ice bath is recommended if you're not going to eat your sous vide-cooked food right away - it takes the food down to a safe temperature quickly enough. Apparently, just tossing it back in the refrigerator is a risky business.
I've had this happen to me once with ox tail cooked for 100 hrs, though this had nothing to do with vacuum or water temp but because the bag had come loose and some part of it was above the water surface.
Whilst most of the points above are valid, there's a risk that there's some confusion, for instance the advice to dunk in boiling water for a short time is good but only applicable to solid muscles and not necessarily useful for minced, rolled or otherwise processed meat.
Thirty-six hours ago I sealed 3 bags of veal osso bucco and one lamb shank in the standard onion, celery, carrot and chicken stock cooking liquid. The plan was to cook all 4 bags at 142 degrees for 48 hours. When I took a look at my water oven at 36 hours, the lid was pushed up and the bag with the lamb shank was swollen almost to the burst point. I could see bubbles forming along the top of the liquid in the bag. It looks like I had some fermentation occurring. I opened the bag expecting a rotten smell, but the lamb smelled fine. I still threw it out. None of the bags were swollen at 24 hours. The veal seams fine. All 4 preparations were very similar with the exception of a few more herbs on the lamb and I did tie the shank with kitchen string to keep it together. All pieces of veal and the lamb were browned before placing them in the cooking liquid. I thought that cooking for 24 hours at 142 degrees was supposed to pasteurize the meat and liquid. I can understand how some pathogens can grow along the top of the liquid in the lamb bag after the bag started floating as this layer was not in contact with the surrounding water bath. What I can’t understand is why the bacteria survived 24 hours at 142 degrees.
Cary, the problem is that once the bag is floating the temp of the exposed bit of the bag is going to be less than the water temp, even in a fully insulated container.
The other thing is that although smell is a good indicator as apparently not all harmful bacteria produce foul smelling gas compounds. If in doubt I always bin it.
TonyB, thank you for the quick reply. I'm now at 44 hours and just lost another bag due to gas pressure. The recipe calls for 48 to 72 hours at 142 degrees. The liquid I'm cooking the osso bucco in was reduced wine and chicken stock. I know about cooking with wine and made sure that all of the alcohol was evaporated. I've lost around $60 (US) in veal and lamb that I've thrown out as the bags inflate. I checked the water oven temperature with a digital probe to make sure that the temperature was correct and the digital thermometer actually shows that the water temperature is 146 degrees rather than the set 142. What microbes can be growing at this temperature? I'm not new to sous vide cooking, but usually seal individual cuts of meat/fish dry or slightly seasoned without a cooking stock. Has anyone heard of this type of problem cooking veal or lamb in a tomato, wine and stock for 48 hours?
Cary, sorry you are having problems. Provided the bags have been fully submersed and the temp is as you've checked, I think it the problem is likely to be something else other than bacteria.
I hadn't noticed you'd included alcohol in the sauce. I'm sure I've seen it somewhere authoritative, maybe MC or MC@H, that despite popular belief, you have to cook a sauce for several hours, rather than minutes, to get rid of all the alcohol.
Thinking on the hoof as it were, one possible way to check might be to cool one of the pouches that has blown up, if you still have one, if the swelling is due to alcohol or water vapour it will probably deflate pretty much entirely whereas if its CO2 or other waste gas from bacteria it will still be swollen somewhat, and will continue to swell.
I'm not sure what else it could be.
Well, my wife and I just dined on the last 2 bags of the sous vide cooked osso bucco. I started with 3 vacuumed bags of veal osso bucco and 1 bag of the lamb shank and threw out 2 of the bags as they inflated over the 48 hours of the recommended cooking time at 142 degrees F. I have a degree in biology so I'm not a complete layman in this area. I'm fairly convinced that the inflated bags were due to bacterial growth, especially when I saw bubbles being produced near the top of the liquid in the bags that inflated (an indication to me that this was biological rather than a break down in the polyethylene bag). So, in summary, given that my opinion is based upon my observations without culturing the solutions in the bags that inflated, I think that the cooking temperature of 142 degrees was TOO CLOSE to the upper limit of the safe temperature for a lot of food-borne pathogens to be safe. It took an expensive error on my part to learn that prolonged cooking times should err on the side of higher temperatures rather than just barely above the safe limits. Again, I’ve never encountered this problem with simply sealing beef, pork, chicken or fish in bags and cooking for less time at lower temperatures (normally cooking most meat at a medium-rare temperature). Even cooking beef round roast or pork roast for 24 hours at 130 degrees never created the inflated bag problem. This is the first time I have cooked sous vide for over 24 hours and also the first time I have used a liquid marinate. Thank you for the advice to throw out anything that doesn’t seem right.
I think I have figured out what went wrong. My theory that cooking at 142 degrees F wasn’t adequate to pasteurize the veal and lamb after 24 hours was at odds with all of the sous vide literature, so I thought some more about my method. When I first started sous vide I was cooking pieces of meat and fish without any liquid using zip-lock bags. I had developed a habit of clipping the top of the bags to the wire rack that separates the bags inside the oven to ensure that no water leaked into the cooking bags. Even though I now use a vacuum chamber to remove air and seal the bags, I still clip them to the top of wire rack that protrudes about 1 inch above the top of the water bath. When I placed the veal and lamb into the sealed bags with the marinate and then clipped them to the wire rack, the liquid was pulled up above the water level by capillary action (you can see this easily in bags that are sealed tightly as you lower them into the water oven). The thin layer of liquid above the water level would not have been heated directly by the 142 degree water, thus creating a temperature “danger zone” area within the bag. This could easily account for why I did not see any gas build up at 24 hours as the few bacteria that survived the initial cooking process prior to vacuum sealing had just started to multiply. After 36 hours the bacteria had produced enough gas to start floating the bag with the lamb shank. As gas build up increased, the bag started floating, moving even more surface area just to the top of the water level and subsequently creating a larger danger zone. The second bag took a little longer to inflate (40 hours), probably due to fewer surviving bacteria to start the process. Bottom line is that ALL liquid inside sous vide bags should always be kept below the level of the water bath to ensure that everything inside the bag gets cooked to a pasteurization point.
It's a surprise to how many responders didn't quickly observe that 125 degrees is too cool to prevent the growth of bacteria, etc., over time. Your meat rotted because it needs to be cooked at above 130.4 degrees F unless the cooking time is very limited. Typically, fish is the only food cooked at or below 125 degrees F, and cooking times are typically kept under 20 minutes if the temperature is that cool. Rare beef can be prepared at 125 F for about a half hour (but most sous vide cooks go with 131 F or above.
HI all, and thanks for a great discussion. I just had a very similar experience with a butterflied leg of lamb. The meat was like paste and smelled putrid. We had a dry marinade in there, and who knows whether the bacteria came from the bag, the meat, the marinade or the equipment. My target temperature was 55c (131f) but suspect I took a long time to get to this temperature. Am I right in assuming that the net view of this forum is that I should consider going a little hotter earlier, and staying a little hotter (giving up my dream of a perfect rare lamb)?
I have just had a very similar disaster; 2.6kg of pichana rump, defrosted in the fridge, seasoned & vacuumed packed.
After reading a section from Modernist Cuisine by Nathan Myhrvold (39c for calpains and 49c for cathepsins enzyme activity to tenderize) I went completely over the top at tired 12 hours at 39c and a further 12 hours at 49c.
Following the overnight 49c stint I awoke to find the vacuum bag had ballooned, although still appeared to be sealed; it smelt pretty bad when opened.
Devastated, but I guess its too risky.
Sorry to hear you had a bad cook Doug. Which book/page are you referring to from Modernist Cuisine? (so I can look it up)
You really can't cook beef (or any meat) at much less than 54c for more than a few hours. Doing the rump at 39c for 12 hours is basically the equivalent of letting it sit in your car in the sun for the whole day. For tender cuts, you can cook it at a low temperature for a few hours, but any cook over 2 to 3 hours needs to be above the danger zone.
Yes, very poorly interpreted knowledge on my half, lesson learnt. Page 3-78.
Main problem as also noted above by other posters is the uncertain temp control through the supply chain of the meat before it drops into your sous vide. Also the freezing process/duration of the meat before any high temp treatment of same meat is a place where many bacteria thrive well. If you are familiar with e.g. salmonella prevention in eggs before you tenderize them in your sous vide, I strongly suggest you do the same with your meat before entering the meat into hyper low sous vide cooking. So take your meat (fully defrosted) and drop it into boiling water for max 1 minute. will kill all bacteria on the surface of the meat without cooking it really. And most bad bacteria is always on the surface, not inside the meat itself. I do my own roast beefs at 126.5F (52.5C) and never had a problem with bad bacteria/bloated bags. Insist though always to make them from never-frozen meat from my local butcher.
This is a useful thread, especially as someone new to SV cooking. It would be useful to have the dates of these contributions include the year! Are these recent, one year old, or even more?
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