Retherm, or not retherm – that is the question.

From T.M., 8 November 2011, cooking sous vide: a question about reheating.

Q: I’ve just read your piece on sous vide and have my kit arriving today.

You mentioned, as a way of getting ahead, that meat can be cooked on monday, then refrigerated, and rethermed for serving on sunday.

But does retherming in the water bath not take just as long as cooking in the first place?

Also, can you advise how to best use sous vide when wanting meats and vegetables? I guess it’s best to cook veg first at the higher temp, then cook meat, and then pan warm the veg before serving??

A: Thanks for your question. It’s actually a really great question (two questions, I mean).

I mentioned in an earlier piece that sous vide technology makes it possible to cook proteins in advance, chill down, and then retherm them at serving time before drying off and searing in a hot pan. This process, termed “cook-chill,” nearly always saves time, but is not always worth the effort. The example I gave in my earlier piece referred to preparing a dozen pork chops in advance, chilling down, and then retherming at serving time. Why does this save time?

Well, it doesn’t always. If you live alone or with just one or two other people, and eat mostly lean, tender proteins, it probably doesn’t make a whole lot of sense to use cook-chill. Generally speaking, for any food 1″ thick or less, about 30-45 minutes back in the circulator is enough time to bring previously cooked/chilled foods back to the serving temperature (you will need to add time for thicker items). But lean protein like chicken breast, turkey breast, loin/tenderloin cuts of pork and beef, and most fish will cook completely within 30-40 minutes (depending on thickness), and sometimes much less (as in the case of fish), because the protein is palatably cooked once it reaches the serving temperature. So if you’re looking to eat a boneless pork loin chop on Friday, there’s not a lot of point to cooking/chilling it on Monday and then throwing it back in the circulator. You might as well just wait until Friday, because it’s going to take about the same time to retherm as it is to cook. Your only time savings are the effort of bagging and sealing the meat on Friday.

Here’s where cook-chill will save you time:

* If you are cooking a protein that, by definition, must be cooked for a long time at the optimal temperature to achieve collagen breakdown, such as duck legs, pork shoulder or belly, or beef short rib or brisket, among others.

* If you are cooking a thicker cut of protein that needs to remain at a particular temperature to achieve pasteurization, as different proteins have different densities and water contents.

Here’s where cook-chill might save you time:

* If you’re cooking numerous portions.
* If you are anxious about precision and are unsure how long to cook your product; you can cook longer up front to be sure about doneness and just retherm at serving time.
* If you have more time for preparation on certain days of the week than others; you can bag and seal your product, cook it, chill it down, and at a later date, you can just retherm it without worrying about the other preparation aspects of cooking.

One additional caution about cook-chill. To be safe, you need to take the “chill” part of cook-chill very seriously. In a restaurant setting, you might put your cooked food into a blast chiller to bring down its temperature in a matter of minutes. In the home setting, though, it is harder to bring down the temperature of food so quickly, especially for cuts that are more than 2″ thick. I recommend preparing a water bath with ice and immediately placing your cook-chill product in the bath for about 15 minutes, draining water and adding ice as necessary, until the product is cold. Then you can refrigerate. Unless your product is 1/4″ thick or less, I don’t recommend just throwing it into the refrigerator because it probably won’t cool quickly enough.

Regarding vegetable cookery – this is where advance preparation really can come in handy. I have several immersion circulators, so I can prepare different-temp items simultaneously, but vegetables are well-suited to cook-chill. Since vegetables need to be cooked at a higher temperature than most proteins to cook properly (usually around 183-185C for non-green vegetables, and boiling or higher for green vegetables), once cooked, you can retherm them in the bag alongside your proteins. Say, for example, that you cooked baby peas with butter in the bag in a pot of boiling water, and then chilled them down immediately. You can retherm them along with your lamb loin at 133F until warmed through. Vegetables are higher in water content and usually do not take as long to retherm as do proteins.

You also usually can finish vegetables from cold in a hot pan. Say, for example, that you cooked baby turnips sous vide at 183F for 50 minutes. You can chill them down and then, in a day or two, take them from the refrigerator, drain and pat dry, and then throw into a hot pan with some duck fat for a nice golden crust. The cooking takes only a minute or two, since you already have cooked the vegetables and dried their surfaces.

If you intend to use your vegetables in a purée, soup, or sauce, you can cook them sous vide, purée them down immediately after with stock or water or cream (or whatever else), and refrigerate or freeze until you’re ready to use them. This is a great way to prepare purées and soups. Don’t add butter or cream until you’re reheating for service.