UPDATE: See update at the bottom of the post, wherein I call into question my assertions here.

Even many casual cooks know to rest their meat after cooking. After this season's Top Chef, some even know to rest their monkfish. Resting meat, supposedly, redistributes the juices. The theory used to be that when you cook meat from the outside in, the juices all somehow flee the outsides in favor of the inside of the meat, and when you rest, they decide to return to their prior climes. Now we know that the truth is actually slightly different. As meat roasts, its juices are expelled the only place they can go--outward. As the outer layers heat up, which are receiving the direct heat, they expel their juices, becoming desiccated and dry. Resting the meat simply makes the juices that remained in the center (because the center did not get hot enough to expel all its juices) redistribute outward to the more dry outer regions of the meat. See This, H., Molecular Gastronomy, Exploring the Science of Flavor, Ch. 9, p. 47.

Today I read something that reminded me of something that had occurred to me before: why do we rest meat after cooking it sous vide? Chef Ryan Farr, master of chicharrones, whose blog is great, wrote about some sous vide vadouvan short ribs (24 hours @ 61.5C). They look fantastic, and I also love the format of his posts. His posts are often just a series of steps, with an image for each step. It focuses the reader on technique. I'm still waiting for him to post the steps to his chicharrones! But on his latest post, about the short ribs, one of the steps he recommends is to rest the meat after cooking it and taking it out of the bag.

Now, there are other reasons why one might rest the meat. As it cools, it firms up and perhaps makes slicing easier, for instance. He doesn't say why he rests them. But if it's the usual reason for resting, to redistribute the juices, then it's unnecessary when cooking sous vide. I don't mean to make an example of Farr's post. He may have other reasons for resting, and either way, it's easy to carry over good habits from one technique even when they are useless in another technique. But I have seen this same recommendation other places, and have even seen it specifically for the stated purpose of redistributing juices. Don't bother! All you're doing is letting your food get cold.

When something cooks sous vide, it is the same temperature inside as outside. If any juices have been expelled, they've been expelled from the center as well, through the outside, and into the bag. The juices have essentially been redistributing ever since the moment the center of your meat reached the temperature of the water bath. So when you take your product out of the bag, there's no need to rest it. It's had a full night's sleep already. Serve it or sear it or whatever, but don't wait just for old times' sake.

UPDATE: I stumbled across an assertion in a Herve This book that the ideal serving temperature for meat is 120-130F. I looked it up in Harold McGee and he said the meat should ideally be rested until it reaches 120F. Neither author specifically provided a reference for these assertions, but McGee said it in the context of a discussion of muscle fibers contracting as they cool and retaining more of their juices. So it may not be as cut and dried as I write above. Though the juices don't need to redistribute, as when cooking a roast, resting may still help cool the meat to an appropriate temperature for retaining juices.

Posted by Barzelay on 2009/03/23 @ 0:11 | Comments (0) | Meat, Science, Technology