Sous vide is a very precise cooking technique when it comes to temperature control. This is especially useful for cooking meat and fish, because proteins react strongly to a difference in temperature. A difference of 2 degrees Celcius or 5 degrees Fahrenheit can clearly be tasted in the final result.
Unlike conventional high heat cooking such as on the stovetop, in the oven, or on a charcoal grill, the time is not at all critical when cooking sous vide. There is a minimum time needed for the meat or fish to be heated to the desired temperature all the way to the core, and there may be an additional time required to then tenderize the meat or pasteurize it, but once that minimum time has been reached, the meat or fish can be left in the sous vide for a longer time and the result will only change slowly. (Please note that this is relative. So if you cook pulled pork for 24 hours at 74C/165F then leaving it in another hour will hardly make a difference. But if you cook salmon for 30 minutes at 46C/115F and you would leave it in for an additional hour, the salmon would be completely different. That should make sense, because relatively speaking, cooking the salmon for 90 minutes instead of 30 minutes, would be the same as cooking the pulled pork for 72 hours instead of 24 hours.)
This is why sous vide temperature recommendations are very precise, but time recommendations are not. To demonstrate this, as well as to find out how much leeway there is, I did an experiment with chicken breast. Chicken breast is tender meat, so for tenderness it would need to be cooked as long as needed to heat it all the way to the core. For a chicken breast of 2.5 centimeters (1 inch) thick, that would take 35 minutes. However, because of the risk of salmonella, chicken breast should be pasteurized. With the sous vide set at 60C/140F, the core of the chicken will be 59C/138F after 35 minutes. It then takes an additional 18 minutes to be pasteurized at 59C/138F. So the minimum time to cook chicken breast of 2.5 centimeter (1 inch) thick is 35 + 18 = 53 minutes. This is usually rounded up to 1 hour. Click here for more information about how to determine the minimum sous vide cooking time for meat. 1 hour at 60C/140F is how I usually cook chicken breast sous vide.
For the experiment I used chicken breast from a single package. The breasts were already halved, and I halved them again lengthwise.
I cooked all of them at 60C/140F, which is my personal preference. Please note that if you prefer to cook chicken breast at another temperature, the results with respect to timing will in all likelihood apply to that temperature as well.
The chicken was lightly salted before vacuum sealing. I cooked each piece for a different time, starting at 1 hour with 1 hour increments to 6 hours. I first put the one that was going to be cooked 6 hours into the water bath, then the next one after an hour, et cetera. This way, after six hours all pieces were ready to be eaten at the same time.
I tasted them, and I also weighed each piece with precision scales before and after cooking, to determine how much liquid was lost during the cooking process.
Before looking at the measurements, I tasted the six pieces of chicken, cooked 1, 2, 3, 4, 5, or 6 hours 60C/140F. My observations were:
- I could taste the clearest distinction between 1 hour and 2 hours. The chicken breast cooked for 1 hour was clearly more juicy then the chicken breast cooked for 2 hours.
- It was difficult to taste the difference between 2 and 3, or between 3 and 4, or between 4 and 5, or between 5 and 6 hours. When comparing 6 hours to 4 hours or 3 hours, it was clearly that each piece was slightly less juicy than the previous piece.
- Although the chicken breast cooked for 6 hours was clearly the driest, it still wasn’t bad. Meat that has been cooked sous vide for too long can become mushy. This was not the case.
- The tenderness of the six pieces was very comparable. The chicken breast cooked for 1 hour had slightly more bite to it, but only slightly, and I thought it was pleasant.
These observations were supported by the measurement of the liquid that was lost during cooking. For 1 hour only 7% of the raw weight was lost by cooking. This jumped to 12% for 2 hours, and then increase slowly to 16% for 6 hours of cooking.
Because there was such a clear difference between 1 hour and 2 hours, I decided to do a further experiment to zoom in on this interval. I cut a single half chicken breast into 4 pieces, and cooked them for 60 minutes, 80 minutes, 100 minutes, and 120 minutes.
The difference between 60 minutes and 80 minutes was small, with 60 minutes being only ever so slightly more juicy than 80 minutes. The difference between 100 and 120 minutes was also small. But the difference between 80 and 100 minutes was clear; 100 minutes was clearly less juicy. And so this demonstrates that there is indeed quite a bit of leeway, relatively speaking, as 80 minutes is 33% longer than 60 minutes, but the difference in result is small.
Although this experiment was for chicken breast, from my experience of cooking sous vide for 10 years I am confident in saying that similar results can be expected for other types of meat. If you increase the cooking time by up to 25% of the intended cooking time, it is unlikely that you will be able to taste the difference. And even if you cook for a lot longer, you can still get a good result. With tough types of meat the result will even get better, as the meat will become more tender with more time. There is such a thing as too tender though, and then meat can become mushy. But as the above experiment which chicken breast showed, in this case even 6 times the original cooking time, did not turn the meat to mush.