Regular readers have seen posts on sous vide popping up repeatedly on this site. The technique cooks meats precisely and evenly. However, optimal cooking temperatures for meat proteins (around 55-65C) are too low to produce a flavourful crust. This needs to be an added step.
Usually, the protein is seared after cooking in a little oil or butter in a pan, under a grill or by using a powerful blow-torch.
While this is successful, there are two slight drawbacks. During searing, heat will be conducted into the underlying meat tissue and, because this has already been cooked to its target temperature, it will overcook. Second, searing is relatively short in duration and more complex browning flavours do not have time to develop.
Browning flavours are more than browning. The maillard reaction starts in earnest when temperatures exceed about 130C, and begin with reactions between amino acids (from meat proteins) and sugars (from meat carbohydrates). But then, further more complex and flavourful reactions start to occur between these byproducts (and their byproducts), steadily developing the complex savoury (umami) flavours that we are familiar with. So the browning reaction is about temperature and time.
For some meat, particularly beef, a pre-sear addresses both drawbacks. Pre-searing starts the maillard reactions under high heat. While these reactions need high temperature to thrive, there is no exact cut-off, and once initiated they will occur, slowly, at lower temperatures. As sous vide usually involves long slow cooks (an hour at least) this adds a time element and allows savoury flavours to develop.
If pre-searing is carried out with the meat at refrigerator temperature, it will take a while for heat conduction to bring the proteins under the surface to temperatures higher than desired, creating an opportunity to sear without overcooking sub-surface layers. One step further is to first freeze or par-freeze the meat. If a pan-sear is to be used, freeze the meat between flat sheets.
After cooking sous vide, it can be nice to give the meat a post-sear to finish off. Pre-searing will significantly reduce the time needed for the post-sear.
Pre-searing is nothing new. Meats to be cooked in a liquid (and therefore limited in temperature) are typically browned first – braises, stews, stock etc. It is sometimes suggested that this seals the meat also, which is wrong. With sous vide, the searing process needs to be finessed so as not to undo the precision of cooking. Sous vide is about the detail.
Earlier this year I supported a Kickstarter campaign for a searing device (Searzall) which recently turned up in the mail. It is an attachment for a standard blow-torch, designed to convert the intense narrow flame into radiant heat across a larger surface (it will soon be available on Amazon). I have used it for this demonstration, but any searing method is valid. If using a naked blow torch, beware of over browning small regions that will impart an unpleasant taste.
The steak was seared from refrigerator temperature and cut to check heat penetration. The sear is confined mostly to the surface, without signs of significant cooking underneath.
Packaged for cooking sous vide (56C, 90m)
Post sous vide, the steak was seared again and cut to check the cross-section. The second sear was quick because the pre-sear had done most of the job. There was a nice sear with little sign of overcooking directly under the surface. It was not an expensive cut, and tender (click for a closer look). The flesh is uniformly cooked contrasting the thin outer sear. If, as for some, it is the outer sear that is the luxury of a steak, then it should be cooked by a conventional method.
Normally, I would not sear salmon/ocean trout skin. To me, the succulence of the flesh is more important than the crispness of the skin. But as a test, this piece of ocean trout was pre-seared, cooked sous vide (48C, 30m) then post-seared. The searing was intentionally a little overdone to check for sub-surface cooking. There was little sign of this having occurred. This result would be difficult by conventional methods.
The flesh was succulent and flaked easily, including directly under the skin, despite the searing temperatures.
So, if you are using sous vide, consider adding a pre-sear.
I remain uncertain as to the wisdom of pre-searing lamb because of its tendency to oxidise, but give it a go if you like.