importance of the vacuum seal cooking sous vide?

In the General Sous Vide Questions Forum
How important is it to have a tight vacuum seal when cooking sous vide?
I read where a commercial grade vacuum sealer (as opposed to a Food Saver type home machine) creates a "tighter" vacuum seal that holds in juices better when cooking meats. Is this true? I usually cook in Ziploc Vacuum bags & yes, there is substantial juice (purge) in the bags after long periods of slow cooking. I always assumed this was normal for all types of sous vide preparations. Am I getting a lesser quality product by not using a commercial vacuum sealer?
Thanks!
By Jerry on Wednesday, January 11, 2012 at 08:11 PM


4 Replies So Far

Hi Jerry, my understanding is that a tighter vacuum won't keep the juices in any more, but I could be wrong there. Most of what I've heard and experienced is that unless you are doing compression or something of that nature then the vacuum isn't nearly as important as the temperature control. Leading some places, like the French Culinary Institute to push to call it "low temperature cooking" instead of sous vide because of how little the true vacuum actually matters.
By Jason Logsdon on Wednesday, January 11, 2012 at 08:19 PM
I think that's right, as I understand it.

Plus, air is a much poorer conductor of heat than the surrounding water.
The less air in the bag, the better the heat conduction into it, and therefore the food.
By weedy on Thursday, January 12, 2012 at 06:11 AM
I agree with Jason and Weedy in that the main purpose of the 'vacuum' is to improve cooking efficiency and effectiveness, it also prevents the bag from floating. Additionally, some water in the food will evaporate during the cooking so the high(?) vacuum isn't maintained and the bag will expand a little in any case. Also high vacuum can damage some fragile food such as some seafood.
By TonyB on Thursday, January 12, 2012 at 10:59 AM
Thanks all!

That's good news. I didn't want to start shopping for a commercial grade
vacuum machine. They are tres expensive.
By Jerry on Thursday, January 12, 2012 at 05:00 PM


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