Six years ago I blogged for the first time about a technique that I called “warm aging”. Aging is a technique that is used to improve the texture of meat and sometimes also to give it more flavor by the activity of enzymes that are naturally present in the meat. You have probably heard of “dry aged” beef. This means that the beef has been aged for a long time (3 to 6 weeks or even longer) and allowed to gently dry. Dry aged beef is expensive because drying means losing weight, and because the outer edges have to be trimmed. Dry aging makes the meat more tender and, if aged for along enough, develops the flavor. An alternative is wet aging, which is to vacuum seal the meat and then store it at refrigerator temperature for 3 weeks or so. This has the same tenderizing effect as dry aging but without the weight loss (and without the flavor component).
The enzymes that do the tenderizing act very slowly at typical refigerator temperatures of 4C/39F. At higher temperatures they work more quickly, and so the effect of weeks of aging can be achieved in hours. In Modernist Cuisine it is suggested to ‘cook’ beef first at the temperature at which calpains are the most active (39C/103F) and then at the temperature at which cathepsins are most active (49C/120F), without becoming very specific of how to go about this. There is food safety to consider, so you shouldn’t do this for longer than 4 hours. I tried it for 2 hours and was impressed by the result, and have used this technique often ever since. I am pleased to see that many have picked up on it, and that the term “warm aging” that I came up with seems to have stuck. (I think that is more appropriate than calling this ‘cooking’, since at such low temperatures the meat stays quite raw.) There have been some that claim that the side-by-side experiment that I performed was inaccurate, because I compared beef that was first warm aged for 2 hours and then cooked for 2 hours at 55C/131F with beef that was just cooked for 2 hours at 55C/131F. It was argued that the warm aged meat was more tender because it had been cooked for a longer time, and so I should have compared 4 hours at 55C/131F with 2 hours of warm aging and 2 hours at 55C/131F.
Although I believe that both cases are not fully comparable, there is some merit in the fact that if you have 4 hours to cook beef, it makes the most sense to find out what will give the better result: all 4 hours at 55C/131F, or half at warm aging and half at cooking. But still I thought the difference between cooking at 55C/131F for 2 or 4 hours would be too large (because in my opinion no actual cooking occurs at warm aging temperatures), and so I came up with an alternative experiment and that is to use flat iron steak/blade steak.
This is a cut of beef that, provided it is butchered in such a way that the tough sinew that runs through the center is removed, can even be just pan fried. Personally I prefer it with 8 to 12 hours of sous vide cooking at 55C/131F, as otherwise I think can be too tough. (This does depend on the source of the meat, for example grain-fed can be more tender than grass-fed.) Due to the longer cooking time I could come up with an experiment that had less of a difference in cooking time, but with the same overall time in the sous-vide.
I took the nice piece of blade steak above, and cut it in two pieces. Do you notice the nice marbling?
They were both seasoned with salt and freshly ground black pepper, and vacuum sealed.
To avoid food safety issues, I scalded both pieces in boiling water for 20 seconds after vacuum sealing. (In the experiment six years ago I seared the beef before vacuum sealing, but since then I have developed the scaling technique that is a lot safer.) Especially 39C/103F is a temperature that pathogens thrive at, so it this is a good precaution.
Even though this step wasn’t really necessary for food safety reasons for the piece to be cooked at 55C/131F, I scalded both pieces to keep the experiment on equal footing.
Then I conducted the experiment as follows:
- One piece was first warm aged for 2 hours at 39C/103F, then warm aged for 1 hour at 49C/120F, and then cooked for 5 hours at 55C/131F.
- The other piece was cooked for 8 hours at 55C/131F.
My thinking was as follows: because of the scalding step I was confident enough to warm age for 3 hours. As both types of enzymes are active at 39C/103F and only the cathepsins are still active at 49C/120F (and more active than at 39C/103F), I thought it made sense to use a longer time at 39C/103F to get the best of my 3 hours. I suppose I could do further experiments to optimize this further.
After this process I patted both pieces dry with paper towels…
…and seared them quickly over high heat in clarified butter.
The warm aged piece is on the left, the other on the right. The difference was clearly visible and even more clear to taste. I knew which was which, but my guinea pig Kees did not. He thought (and I agreed) that the piece that I later revealed to him as the warm aged piece was more juicy and had a better texture. The other piece was softer, but a bit too soft. The tenderizing that happens at 55C/131F is a different type of tenderizing than what happens by the enzymes at lower temperatures. The warm aged piece was not more tender than the piece without warm aging, but the texture was definitely better.
If you still don’t believe me, try it for yourself. You will be glad that you did!