How to cook the perfect steak, with science

How to cook the perfect steak, with science

The recipe for cooking a perfect steak isn’t complicated: take the right cut of meat, add salt and a very hot pan, cook it for precisely the right amount of time on both sides, and rest.

But it’s a recipe most of us mess up. Even top restaurants struggle to get it right, a fact revelled in by those dining companions who are only too willing to lean in and whisper that they only ever order their steak slightly rarer than they prefer.

The chemistry for success is more complex than the recipe but it does explain how an expensive Wagyu ribeye can transform into tough old shoe leather within minutes on the barbecue.

It starts with the beast

Meat – otherwise known as skeletal muscle – consists mainly of a combination of water, proteins, and fat.

Muscle is made of connective fibres called mybrofils, a collection of filaments created by actin and myosin proteins which bind water within the meat, and held together by collagen. Muscle is about 20% protein and 75% water, depending on the species of animal, and it’s the water that’s critically important later when it comes to adding salt and heat.

Turning these fibres into a tender steak starts with an animal: older animals and those fed hormones will be tougher, said Murdoch University’s Professor David Pethick in a 2020 statement.

That’s because the collagen fibres that glue protein fibres together become brittle in older animals and also become thicker and tougher. Hormones cause more muscle growth while also dampening the amount of a nifty little enzyme which appears after death, calpain, which helps to break down the muscle.

Muscle is about 20% protein and 75% water, depending on the species of animal.

And finally, there’s the fat.

The hardest core of vegetarians and vegans may still be unaware of the wonders of Kobe and Wagyu beef from Japan, but for the rest of us it’s difficult to avoid the extolled virtues of those fatty cattle. They are at the extreme of the idealised steak, with seams of fat that create a marbling effect throughout the meat and a texture that, sometimes, does feel like it’s melting in your mouth because there are fewer muscle fibres.

Not only does it add flavour, but more fat actually prevents water loss during cooking and lubricates muscle fibres as water escapes, thus making for a juicier steak.

“As the intramuscular fat (IMF) increases from 6.6% to 21.5%, the moisture content declines from 73.7% to 60.9%,” wrote two South Korean researchers alongside CSIRO meat expert Damian Frank in 2017. “A higher fat content in beef also results in higher initial, and sustained, juiciness scores given by consumers and trained panellists.”

Add time

Patience is a virtue for steak aficionados because time is essential for a good steak. But the longest part of the process is completed before the ravening hordes descend on the dinner table: ageing.

“In ageing, it’s a process whereby you loosen the connective tissue [through] a chemical process where the tissues release the proteases… enzymes that break down proteins,” says University of Melbourne food chemist Ken Ng. “When these proteases act on the collagen they break it down and loosen the connections.”

It takes 14 days for those enzymes to do their job, and another 21 days for complex flavours to emerge as fats oxidise and aerobic bacteria – the same kind as fromagiers encourage on a blue cheese – embark on a kind of contained decomposition, breaking down collagen and muscle fibres.

It is possible to do this at home, but only if you’re prepared to buy most of the cow and have a specific cool room or shed. Individual steaks won’t age in the fridge.

It takes 14 days for those enzymes to do their job, and another 21 days for complex flavours to emerge.

Marinades have the same effect by using proteolytic enzymes, or acids, but need a day to work their magic.

“If the purpose is to tenderise meat, then the marinade has to have a process chemically to break down the muscle fibre arrangement in the meat, as that is the sole cause of meat toughness,” Ng says.

Papaya, pineapple juice and kiwifruit both have proteases that break down proteins and are so effective that, if left too long, can even turn meat “mushy”, he says.

“Because the muscle fibres of proteins degrade into smaller fragments and if you leave it too long and [they] become too small, the whole structure starts to disentangle too much and it falls apart within one day.”

Vinegar, on the other hand, unravels the proteins but doesn’t break them down.

Salt draws water out of meat by osmosis.

And what of salt? Seasoned barbecuers may say to salt seconds before it goes on the barbie, or to salt hours – possibly even a day for large cuts – beforehand.

Both are correct. Just don’t try to cook your steak between five and 60 minutes after salting.

Salt draws water out of meat by osmosis. For those who’ve left high school chemistry far behind, water molecules are attracted to salt molecules which means initially the salt sucks the moisture from the meat. But the bonds holding water molecules together are stronger than those holding the salt molecules together, meaning the salt dissolves in the water it’s just extracted.

The end result is the newly salty water is reabsorbed – given enough time – into the meat.

Water, as we’ll find out, is the critical element in making your steak juicy and tender – or leaving it merely edible.

Those meat juices are gold

It’s taken weeks since that steak was a living animal, but it’s finally arrived at the barbecue and it’s time for the biggest question of them all: do you flip often or flip once? And if you’re a one-time-only flipper, when is the right time?

It depends.

Both theories come down to the interaction between heat and water and the Maillard reaction.

Heat causes a breakdown in fatty acids which provide steak’s beefy flavour.

And it also causes the Maillard reaction, a chemical reaction between sugars and amino acids that’s kicked off when the temperature hits 150°C. It’s that point with meat when you get the sear – or browning – and the reaction gives off volatile chemical compounds such as furans and pyrazines which deliver steak’s meaty flavours. The hotter and longer the cook, the more flavours – until the sear starts to burn and creates bitter flavours.

This reaction helps create a seal on the cooked side of the steak, which lessens the amount of water loss from that side.

The best time to flip is one third through the cooking time.

But heat, especially high heat, causes collagen fibrils to shrink, which squeezes fluids out of the meat and away from the heat – that’s the liquid you can see pooling on top of the steak on a hot plate.

The flip-once protagonists say turning the meat loses those juices, and the more times you flip, the more juice you lose. Indeed, Texas A&M University meat scientist Chris Kerth found the best time to flip is one third through the cooking time, reducing the volume of juices on the uncooked side, which cool the hot plate on flipping and so cause the meat to take longer to sear.

Kerth also found that thinner steaks benefit from a slightly longer cooking time to enable more fatty acid breakdown, so cooks need to keep the hot plate temperature up high, but to make sure there’s lots of fresh air moving around the top of the steak. For thicker steaks, the Maillard reaction moves too quickly to the char stage so a more moderate grill with the barbecue lid down gets better results – alternatively, you can sear the steak and then pop it in the oven to finish.

The multi-flip brigade relies on the sear to keep more water in the piece of meat, saying more flips more often can reduce the amount of time it takes to get that impermeable layer of browned meat because there is less water on the uncooked side to cool the hot plate.

Can we eat yet?

The last stage is resting.

Ng says resting allows meat to re-absorb lost moisture, as well as giving the meat a little more time to finish cooking. The resting rule of thumb is one minute per 100 grams of meat.

But even resting meat is a controversial idea: a cold dinner, soggy crispy bits, and the meat becoming overcooked are all accusations thrown at the resting protagonists.

That’s the steak story from paddock to plate. Now, for the remainder of the southern hemisphere summer, you’ve no excuse for producing tough, boring steaks.

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