The first thing to note is that although ageing does tenderise meat, not all tenderised beef necessarily tastes that great, especially if tenderisation is achieved by quick ageing tricks (or by pounding or mincing the meat as noted earlier).
Aged beef given a quick turn in the pan. Photos: Chris Chan
After several experiments at home, I can confirm that the best tasting beef actually requires more than just tenderising – the flavours which make beef stand out can be absent if tenderisation is stimulated too quickly.
Also, the breed of cattle also has a very significant taste impact. So although the texture can be smooth and soft, without the correct balance of flavour compounds, beef which is tenderised quickly does not necessarily make a sensational dish, and may need help from a good gravy, for example.
Proteolysis, or why enzymes matter
The best beef for eating is undeniably dry-aged beef – that is, beef hung on a hook in a cool room for several weeks to dry. Alternatively, slabs of meat are cut and placed on racks in special coolers – sometimes the racks are made of salt to help extract moisture while dry-ageing.
This loss of moisture apparently concentrates flavours and the long wait while drying allows more time for the natural enzymes in beef to tenderise the meat by breaking down the muscle fibres gently.
Only the best beef is dry-aged as an even distribution of fat in the meat is required to prevent toughening – over 30% of the original weight of the meat is commonly lost during the drying process.
To promote tenderness, some producers also dust the beef with the spores of a psychrophilic (cold-loving) fungus called thamnidium elegans – the fungus adds further enzymes to the meat, which can further improve flavour.
Prepared external proteases.
The side effect of the fungal and other bacterial action during dry-ageing is that the surface of the meat can turn green. Before sale, this unsightly greenish layer needs to be trimmed off, thereby increasing further the cost of such dry-aged beef.
Beef naturally contains endogenous (internally-present) enzymes which act as proteases to promote proteolysis – two particular families of enzymatic proteases are important for ageing, called calpains (including calpastatins) and cathepsins.
Both enzyme families are fascinating in their own right – apart from tenderising meat, they are also crucial for the survival of mammals!
The way they work is pretty complex (involving calcium activated subsystems, pH levels, temperatures, et cetera) but in summary, one can assume that certain members of the calpain family of enzymes degrade the proteins on the Z-lines of myofilaments (this unlinks the chained-up sarcomeres) while members of the cathepsin family degrade actin-myosin linkages and myosin itself in the thick myofilaments within the sarcomeres.
Adding to the complexity is research which has found that calpastatins within the calpain family can significantly impair proteolysis – it is feasible that enzymatic tenderisation cannot begin until other members of the calpain family can fragment the structure of calpastatins beforehand and this might also explain why certain cuts of meat can never tenderise adequately via proteolysis (due to innate high calpastatin content).
So in theory, if it is possible to stimulate proteolysis via the enzymatic activity of cathepsins and calpains (but not calpastatins), the end result should be tender beef.
This was quite an easy experiment to do at home – all one needs to know are the optimal temperatures for the endogenous protease enzymes. And some quick research established that the optimal temperature range for calpains is around 39-40°C and 49-50°C for cathepsins.
Kiwi tenderised the beef, but gave it a weird flavour – a rich sauce rescued it.
At this point, I should stress that you should not try the following experiments at home, especially if you are living in Asia. You probably do not know this but most consumer beef in Asia actually comes from India, which is the world’s largest exporter of beef, beating Brazil, Australia and the United States in 2015 – in fact, beef is India’s largest agricultural export item in 2016, ahead of basmati rice, followed by spices and other kinds of rice.
India’s beef is derived mainly from the water buffalo, a wholly different breed of ungulate than European bovine stock – and therefore the following results may not apply.
Also, you should never cook raw meat at such low temperatures unless you have sufficient culinary expertise – there are just too many risks with bacterial and fungal contamination, even if you are careful.
Experiment 1: Accelerating proteolysis in fresh meat
The first proteolysis test was done using a simple sous vide (warm water bath) device – and a thick piece of rib-eye steak fresh from the local butcher was selected.
Note that the optimal proteolytic temperatures are also applicable for pathogenic bacteria, and therefore the surfaces of the meat were seared at high temperatures to kill off any surface germs and fungi before sealing in the sous vide bag. This searing was done as quickly as possible to kill the bacteria on the outside without cooking the meat.
The sous vide bag of beef was then immersed in water pre-heated to 39°C and left at that temperature for 60 minutes – this promotes proteolysis via calpains (and as it was rib-eye, there was not much calpastatin content in the meat). Then the temperature was raised to 49°C and then left for another hour to stimulate the action of cathepsins.
Finally, the temperature was raised to 54°C and the meat left to cook to medium rare for another 90 minutes. At the end, the meat was seasoned with more salt and pepper and seared quickly again in hot butter till a thin brown crust developed all around the steak.
Beef aged for seven days.
This is not just to improve taste but also to kill off any surface bacteria missed during the start of the experiment.
The resulting meat was indeed very tender – but to be quite honest, it still lacked the flavour of really good aged beef and I had to whip up some accompanying girolle gravy to compensate for the lack of flavour depth, so it still eventually ended up as a tasty experiment for the family.
The obvious conclusion reached is that highly-accelerated proteolysis is not the solution to achieve the flavour of good aged beef although it can accomplish the target of tenderness.
As an aside, the official scale used to measure the tenderness of meat is the Warner-Braztler shear force method – as I do not have the equipment, objective results of this test are not available.
However, for comparison purposes, I had also cut a slice off from the original steak and fried it as a control texture sample. Everyone agreed that the untreated meat was significantly tougher in the mouth – so accelerated proteolysis via enzymatic processes does have a significant impact on texture, at least subjectively.
Since we may now have established a way to achieve tenderness in beef, flavour is now the major consideration, and so the next stop might appear to be lipolysis – the breakdown of fats (rather than proteins) via other endogenous enzymes (such as lipases) plus bacterial action. And perhaps also oxidation as well – both lipolysis by bacterial action and oxidation require time to take effect.
However, the optimal temperature of lipases appears to be between 37°C and 50°C, so the earlier sous vide experiment with protease stimulation would have also stimulated lipolysis via endogenous enzymes.
Therefore the difference in taste between quick proteolysis/lipolysis and proper ageing might appear to be mainly due to additional bacterial action and/or oxidation.
Regarding these factors, I was not very keen on promoting unknown bacterial growth in meats in an uncontrolled environment such as a refrigerator which is opened and closed many times a day (thereby exposing internal contents to external bacteria and fungi) – so this issue became a little problematic.
Also, lipolysis was already promoted in the first experiment and it had not helped the flavour much.
Experiments 2 & 3: External enzymatic proteases
At this point, my chemist daughter came to the rescue – her last birthday present to me was a comprehensive multi-part tome called Modernist Cuisine, which I love reading, and in there was a suggestion of how to age beef within a few days by the judicious use of fish sauce.
This provided an alternative route to lipolysis – as the introduction of external enzymes may be significant in the development of flavour (as seen by the use of thamnidium elegans mould during commercial beef ageing). And fortunately, I had brought over some fish sauce from London several months ago.
Fish sauce is particularly interesting because proteases are very widely used in the making of fish products – for example, fish is often commercially descaled these days using enzymes and fish meal is also derived from enzymes acting on waste fish products.
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| Fish sauce-tenderised meat, after three days; darker fish sauce works better. |
There is an interesting history about how fish sauce came about – and it seems that it was probably by accident when someone observed a fish caught in a rock pool … which had started digesting itself over time.
The first fish sauce in Europe was probably garum, which was allegedly derived from a fish called garos by the Greeks; garum was used as a cooking ingredient probably before the 7th century BC. The Romans loved using garum in their food as it was affordable and easily transportable, despite the rather strong odour.
Garum and other fish sauces were traditionally made by fermenting fish proteins in salty water using endogenous fish enzymes such as trypsin, chymotrypsin and cathepsins – a slow process which can take around three years.
As such, modern fish sauces are now made by applying exogenous (external) enzymes such as bromelain, ficin, papain or other commercially-produced enzyme concoctions such as Protamex, Protex 51FP and Neutrase – these enzymes can fully hydrolyse (ferment in water) fish sauce within a few short weeks.
It is therefore an interesting, very plausible idea to use these same enzymes to speed up ageing in beef. As another parallel side experiment, I decided to also tenderise and age beef using a more conventional proteolytic enzyme – and I have chosen actinidin from the kiwi fruit, mainly because there are no papayas (papain) or pineapples (bromelain) easily available here in rural France.
The experiments for producing aged beef at home then continued. Even though it was suggested in the Modernist Cuisine to use 3g of fish sauce to each 100g of rib-eye beef, an earlier experiment proved that this was too much with Limousin beef.
So I used 2ml of fish sauce plus 1ml of water for each 100g of beef, coating the mixture evenly over the meat and sealing it in a food bag. I also found that it works best with darker fish sauces (for unknown reasons).
Another bag was prepared using a blitzed-up peeled kiwi fruit, glazing another rib-eye steak with the kiwi paste before sealing it in another food bag. Both bags were left in the fridge for at least three days to allow the enzymes to work in a cool environment and also introduce an element of slow lipolytic ageing (hopefully).
The initial results were genuinely interesting – after extracting the fish sauce-treated meat from its bag, the steak was patted dry on kitchen paper, and seasoned with salt and pepper. The surfaces were then quickly seared over a hot pan to kill off any surface bacteria and the steak placed in a glass dish to cook slowly in an oven set at 100°C – the meat was monitored until the internal temperature reached 54°C.
This gave a chance for a final burst of proteolysis from both the internal and external enzymes. Another little fry in hot butter afterwards (just to add in some more Maillard reaction flavours) completed the experiment. There is no doubt that the fish sauce-treated steak was tenderised very nicely, despite only three days of treatment and it also tasted significantly better than the fresh meat cooked purely using endogenous enzymes via the sous vide method earlier.
However, due to having an extremely sensitive nose, I was also aware of an indistinct and very faint fishy odour – this was not noticed at all by anyone else, so it is probably just me.
Regardless, it was still definitely an improvement.
Next was the steak treated with kiwi fruit actinidin – which was washed, dried and then cooked exactly the same way as for the fish sauce-treated meat. The result was also very tender beef but it was unfortunately infused with a rather weird flavour, probably from other compounds in the kiwi fruit. So this method would appear to work only if the intent is to cook tender beef in strong-flavoured sauces – by itself, the meat tasted too weird for me.
Experiment 4: Home dry-ageing
Notwithstanding my earlier comment about the risks of bacterial growth while attempting to dry age beef in a home refrigerator, curiosity meant that I could not resist one last experiment to see if internal bacterial activity and oxidation were significant in the development of aged beef flavour.
So I sprinkled lots of salt on all sides of a rib-eye steak and left it exposed on a tray in the refrigerator for a week – the salt was meant to curtail bacterial activity on the surfaces of the meat so bacterial action would be confined only to the inside of the meat.
After seven days, the meat was taken out and prepared in exactly the same way as the first sous vide test – except that this beef was left to dry-age by itself for a week beforehand.
The tenderness of the extra dry-aged meat from this final test was again significantly improved although the meat flavour was only marginally better than the first experiment with fresh beef – apart from the fattiest parts of the steak, which seemed to have more improvement in taste.
A hunk of fresh rib eye.
But overall, my subjective view is that it was not worth the effort (or the risk) to dry-age meat in such a way in the refrigerator – so if you have been thinking of specially making room to age beef in your fridge, then perhaps you now do not need to bother.
Summary of speed-ageing results (subjective observations)
All the experiments confirm that both endogenous and exogenous enzyme proteases do undoubtedly tenderise beef and the actions of the enzymes can also be significantly speeded up. However, accelerated meat flavour improvement appears to be a more complex matter and it may even be impossible with the meat of certain breeds of cattle due to genetics.
Overall, my subjective opinion is that the best result (with Limousin beef) was derived from using exogenous proteases from fish sauce to age the meat faster (while introducing new meaty flavours via external enzymes) – my daughter also said it compared well to aged beef from good London steak houses.
All the other experiments also worked well in terms of tenderising beef, although the use of kiwi fruit actinidin was the least successful due to the unwanted flavours introduced by other kiwi fruit compounds.
Regardless, all the experiments ended up with tender, enjoyable steaks – and they were considerably improved on the dinner plate by some homemade French forest mushroom gravy. If you need the recipe for the gravy, please let me know.
http://www.star2.com/food/food-news/2017/08/27/tender-moment-part-2/
