Low Temp (LT) 2 Stage Sous-Vide Cooking- aka Warm-Aging
"Warm-Aging-Meat w/ Sous-Vide was my previous post title, but I think the new one really reflects what it is we are doing.
The technique uses a SOUS-VIDE Circulator to promote the Calpain and Cathepsin Enzymes' activity through the manipulation of temperature. Say What? Exactly!!! Words can't even come close to what I was thinking. I knew I had to explore this technique through experimentation. I am not a scientist; however, I know how food is supposed to taste and look. So here we go!!! See some of my experiments HERE. This is an updated paper… The first one was HERE.
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So What is Warm-Aging?
The story goes like this... By bringing up the temperature of the meat to 103 f (I have read 104 f is also used, and that's what I use) Degrees for X amount of time, you increase the activity of the Calpain and at 120 f (I have also read that the upper range is 122 f) the Cathepsin. These are the same enzymes that are present during traditional Dry-Aging that is done in Refrigerators. Of course, with Warm Aging, the process is hastened. Tender meat is the by-product of the enzymatic process. Ok, so far, this process is really sounding good.
UPDATE-Warm-Aging 3-Stage-Processing VS Warm-Aging 2-Stage-Processing
UPDATE-Warm-Aging 3-Stage-Processing VS Warm-Aging 2-Stage-Processing
So is this really Dry-Aged meat? I can answer that with an emphatic NO!!! It's more like a Faux Dry-Aged Meat. I am OK with Faux as long as it tastes good. Real dry age meat loses moisture, and the flavor becomes more intense. Don't forget, after trimming Dry-Aged (cutting off the mahogany layer), your yield is less too. Heck, I am giving you my opinion on something I haven't even tried yet. Stand by; it's coming.
There is hardly anything written on the subject of Warm Aging. I have come across forums that discuss this in great detail, though. Most of it is above my head or understanding. But for the most part, I grasped the critical stuff. The food science sources are mostly silent on the subject except for the following.
After perusing the forums and combing over the available sources, I am moving forward with my experiment. I have outlined the steps below.
The paper above asserts that the Enzyme Aminopesidases break down the products of calpains and cathepsins into smaller flavorful molecules. Hmmm, food for thought. I guess I will keep the temp down to maximize these enzymes.
Additionally, the 104 f degree temp will avoid overheating the alanyl & arginyl aminopeptidases and aminopeptidase and kick the Calpain into overdrive. And before you ask, I know this is in the danger zone, but it will only be there for a short time...Less than 4 hours. The same enzymes that will transform this steak into something special are heated at the temps that accelerate the growth of pathogens; therefore, I will pasteurize the meat using Baldwin's tables. I chose 90 minutes because the steak is not very thick...only 1 3/8 inches. Had it been a much thicker piece of meat, I would have opted for a longer cook time. Note: some people have decided on a pre-sear or quick dunk in boiling water (in the bag) to kill off the surface pathogens. It's not a bad idea, mind you, but I chose a different path. If I plan on pasteurizing it during the cook and searing it afterward, I found this step unnecessary.
In the end, how much risk are you willing to assume?
Something else to consider. We often talk about the 4-hour window of doom, but do you know it's an accumulated time and way more complicated than we were lead to believe. Depending on the variables, it can be stretched out to 6-hours.
Note: When I increase temp from 104℉ to the desired temp, I will add boiling water to the cooking vessel (not on the bag). This will hasten the climb to the appropriate temp. What could have taken 15-30 minutes can be done in less than 5 minutes.
In the end, it's all about your willingness to assume risks associated with all food preparation.
Note 9/09/2017- I was reading in one of Nathan Myhrvold Egullet forums posts that 113℉ is also an excellent temp to Warm Age. As some of you already know, Nathan has written about this in his books. However, many scientists contributed to this very topic in these forums, and it's a great read. So far, I've come across that 104℉ is a great temp, and now 113℉ is too. I plan on making 4-6 steaks and contrasting those two temps. I will report back. There seems to be a consensus that 120-122 produces off-flavors, so I am not even considering this as an option. I once warm, aged at 104℉, then used 122℉, and the results were good, but... I thought I was going crazy, but there was an off-taste. After doing some research, I realized I wasn't crazy…LOL.
WINNER IS 113 ℉
From Baldwin Himself….
Enzymes
Recall that enzymes make up a significant portion of the sarcoplasmic proteins. The sarcoplasmic calpains and lysosomal cathepsins are especially important in aging or conditioning. These enzymes catalyze the hydrolysis of one or more of the proteins — calpains the Z line proteins and cathepsin the myosin, actin, troponin, and collagen proteins. Dry aging is usually done at 1–3.3◦C/34–38◦F with about 70% humidity for 14 to 45 days. Higher temperature aging is also possible, see (Lawrie, 1998, pp 239– 40); Myhrvold et al. (2011) found that even 4 hours at 45◦C/113◦F can significantly improve tenderness. (Lawrie (1998) notes that at 49◦C/120◦F, that tenderness is particularly increased but that it has a somewhat undesirable flavor.) At sous vide cooking 6
temperatures between 55◦C/130◦F and 60◦C/140◦F, many of the enzymes have been denatured, but some of the collagenases are active and can significantly increase tenderness after about 6 hours (Tornberg, 2005).
Warm Age process and why I do it.
I found that the whole reason for warm aging is the reduction of purge hence more moist meat. With Trip-Tip- if I warm age at 113f for 3 hours and finish at 133 f for 7 hours, I get the same results had I SV at 133 f for 10-12 hours with less purge and much more moisture retention.
Note- below and taken directly from egullet forums. Douglas Baldwin's comments below.
You're absolutely right that there many things that affect how tender cooked meat is. I certainly didn't mean to imply that the conversion of collagen into gelatin by thermal or enzymatic processes was the whole story: I was just trying to briefly clarify Pedro's post.
I'd be very interested to know which recent articles you've found that illuminate this fascinating topic. You're certainly right that most the studies -- even recent ones -- use absurdly high temperatures and this limits their applicability to sous vide cooking.
So everyone can follow the discussion, let's step back a moment and discuss the main ideas.
Heat and Proteins
Meat is roughly 75% water, 20% protein, and 5% fat and other substances. When we cook, we're using heat to change (or denature) these proteins. Which proteins and how much we denature them mainly depends on temperature and to a lesser extent on time. I like to divide the proteins into three groups: myofibrillar (50--55%), sarcoplasmic (30--34%), and connective tissue (10--15%).
Myofibrillar proteins: While there are about 20 different myofibrillar proteins, 65--70% are myosin or actin. Myosin molecules form the thick filaments and actin the thin filaments of the muscle fibers. The muscle fibers start to shrink at 95--105°F (35--40°C) and the shrinkage increases almost linearly up to 175°F (80°C). The water-holding capacity of whole muscle meat is governed by the shrinking and swelling of myofibrils. Around 80% of the water in muscle meat is held within the myofibrils between the thick (myosin) and thin (actin) filaments. Between 105°F and 140°F (40°C and 60°C), the muscle fibers shrink transversely and widen the gap between fibers. Then, above 140°F--150°F (60°C--65°C) the muscle fibers shrink longitudinally and cause substantial water loss and the extent of this contraction increases with temperature.
Sarcoplasmic proteins: Sarcoplasmic or soluble proteins are made up of about 50 components, but mostly enzymes and myoglobin. Unlike the myofibrillar proteins and connective tissue, sarcoplasmic proteins expand when heated. The aggregation and gelation of sarcoplasmic proteins begins around 105°F (40°C) and finishs around 140°F (60°C). As Nathan mentioned, before these enzymes are denatured they can significantly increase the tenderness of the meat. The ratio of myoglobin (Mb), oxymyoglobin (MbO2), and metmyoglobin (MMb+) also determines the color of the meat; see Belitz et al. (2004) pages 576--579 or Charley (1982) pages 395--398 for more details on meat color.
Connective tissue: Connective tissue (or insoluble proteins) holds the muscle fibers, bones, and fat in place: it surrounds individual muscle fibers (endomysium) and bundles of these fibers (perimysium) and bundles of these bundles (epimysium). Connective tissue consists of collagen and elastin fibers embedded in an amorphous intercellular substances (mostly mucopolysaccharides). Collagen fibers are long chains of tropocollagen (which consist of three polypeptides wound about each other like a three-ply thread). Collagen fibers start shrinking around 140°F (60°C) but contract more intensely over 150°F (65°C). Shrinking mostly destroys this triple-stranded helix structure and is transformed into random coils that are soluble in water and are called gelatin. Elastin fibers, on the other hand, don't denature with heating and have rubber-like properties; luckily, there is much less elastin than collagen -- except in the muscles involved in pulling the legs backward. As Nathan reiterated, there isn't one temperature above which the collagen is denatured but that it increases exponentially with higher temperatures; for safety reasons, we usually use 130°F (55°C) as the lowest practical temperature for denaturing collagen.
Tenderness: When chewing, you deform and fracture the meat. The mechanical forces include shear, compressive, and tensile forces; most studies use a Warner--Bratzler shear test perpendicular to the muscle fibers, and this seems to correlate well with taste tests. Typically, W-B shear decreases from 120°F (50°C) to 150°F (65°C) and then increases up to 175°F (80°C). While this increase in tenderness used to be attributed to a weakening of connective tissue, most now believe it's caused by the change from a viscoelastic to an elastic material: raw meat is tougher because of the viscous flow in the fluid-filled channels between the fibers and fiber bundles; heating up to 150°F (65°C) increases tenderness because the sarcoplasmic proteins aggregate and gel and makes it easier to fracture the meat with your teeth; over 150°F (65°C) and up to 175°F (80°C), the meat is tougher because the elastic modulus increases and requires larger tensile stress to extend fractures (Tornberg, 2005).
Both the intramuscular connective tissue and the myofibrillar component contribute to toughness. In many cuts, connective tissue is the major source of toughness, but the myofibrillar component is sometimes dominant and referred to as actomyosin toughness.
- Connective tissue toughness: Both the collagen content and its solubility are important. Muscles that are well worked have connective tissue that makes them tougher than muscles that were exercised comparatively little or that are from young animals. The more soluble the collagen, the more tender the meat is, and collagen from younger animals tend to be more soluble and soluble at lower temperatures.
- Actomyosin toughness: Actomyosin toughness can be a major contributor to toughness in young animals and in relatively little-used muscles. Immediately after slaughter, the warm flesh is soft and pliable. In a few hours, the meat goes into rigor and becomes rigid and inelastic. Cross-links form between the myosin and actin filaments where they overlap -- where the muscles are allowed to contract or shorten -- and are locked in place during rigor. After rigor has passed, the meat again becomes soft and elastic. (If pre-rigor meat is chilled to below 60°F (15°C), then cold-shortening of the muscles may occur and significantly increase toughness.)
Enzymes
Recall that enzymes make up a significant portion of the sarcoplasmic proteins. The sarcoplasmic calpains and lysosomal cathepsins enzymes are especially important in aging (which is also called conditioning). These enzymes catalyze the hydrolysis of one or more of the proteins -- calpains the Z line proteins and cathepsin the myosin, actin, troponin, and collagen proteins. Dry aging is usually done at 34--38°F (1--3.3°C) with about 70% humidity for 14 to 45 days. Higher temperature aging is also possible; see Lawrie (1998) page 239--40 or some of mine, Pedro, and Nathan's posts in the previous thread. As Nathan just discussed, this higher temperature aging at 113°F (45°C) for even 4 hours can significantly improve tenderness. (Lawrie notes that at 120°F (49°C) that tenderness is particularly increased but that it has a somewhat undesirable flavor.) At our sous vide cooking temperatures between 130 and 140°F (55 and 60°C), many of the enzymes have been denatured, but some of the collagenases are active and can significantly increase tenderness.
References
H.-D. Belitz, W. Grosch, and P. Schieberle. Food Chemistry. Springer, 3rd edition, 2004.
Helen Charley. Food Science. John Wiley and Sons, second edition, 1982.
R. A. Lawrie. Lawrie’s Meat Science. CRC, 6th edition, 1998.
E. Tornberg. Effect of heat on meat proteins—implications on structure and quality of meat products. Meat Science, 70:493–-508, 2005.
By Nathan Myhrvold
The issue with meat tenderizing is much more complicated than you are suggesting. It is not just collagenases that are present; there are also various enzymes - calpains and cathepsins - that degrade proteins other than collagen, as well as some that act on collagen. Meat toughness is largely about collagen, but not exclusively.
It is a very complicated system, and most explanations of it are highly simplified. In part, this is because it has not been figured out yet. A lot of recent meat science research has been about using molecular biology tools to study things that were oversimplified in research done in the 1970s.
The key thing is that the rates of enzymatic reactions are greatest above the animal's original body temperature (37C/100F). The higher the temperature, the faster the reaction (dramatically faster, they are exponential in temperature), until you get to a point where the enzyme itself is destroyed by the heat. Between 40C and likely about 50C there are some important enzymes active that cause tenderization. They quit at various temperatures depending on the enzyme.
Conversely, at low temperatures, some of these reactions do occur and likely are the cause of tenderization by meat aging. However, instead of taking hours they take weeks (21 - 45 days are typical meat aging times).
The trouble with directly interpreting the Laakonen et al result is that their heating ramp, coupled with the thermal gradient in the meat (which depends on the thickness of the meat) means that different parts of the meat would be at different temperatures. So, while they report that tenderization occurred between 50C and 60C, the question is what part of the meat was at those temperatures?
Besides enzymes, there is also thermal conversion of collagen into gelatin. Note that "gelatinization" or variations on that word are not really the correct term. It is generally called denaturing, or hydrolysis, but there is no single accepted term.
This likely starts at 37C (studies differ on this), but at such a slow rate that it is hard to measure. Various scientific studies, particularly those from the years back, say that this process "starts" at various temperatures, but that is almost surely wrong. This is particularly true of meat science studies done long ago, which used ridiculously high temperatures, and in general oversimplified things.
Empirically, the fact is that by 52C, the conversion to gelatin is certainly occurring, and for food safety reasons most long-time sous vide occurs at 55C/130F, where it is happening. The rate is much slower at those temperatures than higher (again, exponential in temperature), which is why you typically have very long cooking times.
Bottom line is this:
- Holding meat at 40C-50C (specifically we find pretty good results at 45C/113F) for up to 4 hours is within food safety guidelines, and has a significant tenderizing effect.
- Cooking meat at 55C/130F for at least 8 hours (and often 24, 48, or even up to 100 hours, depending on the cut) also has a significant tenderizing effect.
For really tough meat, you can do both. This works best if you have two water baths and switch the meat from one to the other, or if you have a programmable water bath and set a timer to change the temperature.
From Serious Eats Article while discussing Reverse Searing.
"This one is not quite as obvious, but it can still make a detectable difference: enzymatic tenderization. Meat naturally contains enzymes called cathepsins, which will break down tough muscle protein. Their activity is responsible for the tenderness of dry-aged meat (see our complete guide to dry-aging here).
At fridge temperatures, cathepsins operate very, very slowly—dry-aged meat is typically aged for at least four weeks—but, as the meat heats up, their activity increases more and more rapidly, until it drops off sharply at around 122°F (50°C). By slowly heating your steak, you are, in effect, rapidly "aging" it, so that it comes out more tender. Steaks cooked via traditional means pass quickly through that window, reaching the 122°F cutoff point too rapidly for this activity to have any real effect."
Mcgee touches on this subject at bit too... 200-202
Mcgee touches on this subject at bit too... 200-202
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