Sunday, 8 June 2014

Curious Cook: The Alkaline Effect

This is what medium cooked beef looks like. - Photos by CHRIS CHAN

This is what medium cooked beef looks like. - Photos by CHRIS CHAN

Once we know how the Maillard reaction works, we can learn to control it and master the science of deliciousness.

In Part I of the story on the Maillard reaction, we learnt how the browning of food caused by the Maillard reaction plays a big role in building complex flavours in cooked food.

The Maillard reaction is affected by how alkaline the ingredients are. Mild alkalis have a tendency to speed up the Maillard process. This is because they help to “loosen” the protons in the amino acids and the reducing sugars thus have a greater chance to react with the amino acids.

In acidic conditions, amino acids will just hold on to their protons and not react – therefore reducing or completely inhibiting the Maillard process. That is why eggs and onions pickling in acidic vinegar solutions do not turn brown.

A German pretzel. – Filepic

So, as a simple tip, to bake browner cakes, just add a little more baking soda (sodium bicarbonate, an alkali) into the cake mix. Germans have been making pretzels extra brown by adding lye to the dough for centuries. Lye is such a strong alkali that it is often used in drain cleaners – but you can now buy it in baking stores, though you should handle it with great care.

The Chinese have also been sneakily adding baking soda to their marinades and sauces prior to dry cooking – the intention here isn’t necessarily to brown the food but to tenderise the meat; unwittingly, they are also speeding up the Maillard reaction so that more flavours are released.

The tender alkaline

So the Chinese have found out that baking soda is also pretty good at tenderising meat because its alkaline nature helps to loosen the proteins in meat and cause muscles to lose its firm stringy structure. 

However, please don’t use too much (around 1/2 teaspoon for 500g of meat) and also don’t leave meat too long in baking soda as the tenderising effect is quite strong – around 20 to 30 minutes would be enough and one should cut the meat first into the required sizes beforehand or else a block of meat can turn into mush quite easily when coated with baking soda.

No boiling around, please

It is interesting to note that the Maillard reaction cannot occur in boiling water. That’s because of an odd paradox – Maillard reactions normally occur either at temperatures well below the boiling point of water, or substantially higher than 100°C. Maillard reactions below 70°C is enzymatic in nature and above 140°C, it is non-enzymatic (as it then requires high heat to initiate the reaction). 

In boiled foods, the presence of water limits the temperature to around 100°C and this prevents the non-enzymatic reaction. However, all enzymes are also killed off if food is cooked to 70°C. Hence, no such reactions occur in soups, stews and other boiled foods – basically, Maillard reactions have no friends to play with if the cooking temperature is between 70°C and 140°C.

What sugars want

So perhaps you are now curious: what exactly happens during the non-enzymatic Maillard reaction? What happens when we dry-cook (fry, grill or bake) food? Firstly, the sugars in the ingredients are broken down into simpler sugars (called monosaccharides), which are basically super-reactive little sugars, hungry to get hitched with anything with a willing proton, like amino acids.

The amino acids are provided by the plant or animal proteins – under heat, proteins break down into amino acids. Some foods have very little sugars, like meat for example – but under heat, the meat proteins break down into amino acids, then further into their component DNA and release ribose, another good reducing sugar. This then combines with the amino acids in the meat to complete the Maillard reaction. And before you ask where the DNA sugar comes from, DNA strands are held together by a sugar – the sugar is 2-dioxyribose which decomposes into ribose, a monosaccharide.

How flavours come about

The flavours turn up because of the higgledy-piggledy nature of the new chains of molecules created during dry cooking. Most of these molecular chains (which are compounds known as polymers) are actually unstable or volatile – and volatile means they evaporate easily in air. That’s the reason why freshly-cooked food smells much better straight off the pan.

The reason why such a mish-mash of polymers gets formed is because of simple chemistry and mathematics. Basically, a reducing sugar is very keen to seek other compounds to bond with, like amino acids. But this bonding process is rather chaotic as bits of sugars randomly hook up with bits of amino acids forming longer and longer compounds (see footnote).

Under the right temperatures, the number of mathematical combinations of such bonding activity increases – it’s like running around the track faster and faster holding up boards of glue under a confetti shower in a stadium.

What sticks to the boards become the flavour polymers created during the Maillard reaction – for example, diacetyl is a chemical that gives a buttery flavour, furan provides a nutty taste and acetaldehyde has the characteristic of rum.

Of course, uncountable numbers of such new chemicals are created but because of the nature of the underlying sugars and amino acids, the probability is very high that the same aromas and flavours will re-occur every time the same ingredients are cooked, provided they are exactly at the same stage of freshness or ripeness.

That is why the flavours of certain dishes are different if the ingredients are not fresh – even though the underlying proteins and sugars are pretty much the same, the denaturing of some of the ingredients means that the mathematical distribution of the possible reactions will have changed.

It is as if the sizes of the sticky boards have changed, the track in the stadium has also changed and the boards are now binding with different clouds of confetti as the Maillard reaction runs around the ingredients.

Footnote: A reducing sugar has strands of carbon and oxygen bonded loosely together. Each amino acid has strands of 2 hydrogen atoms bound to a nitrogen atom. The Maillard reaction starts when random strands of carbon in the sugars decide to hook up with random strands of nitrogen in the amino acids and they ditch the hydrogen and oxygen atoms around them (most of which then become H2O or water). As the strands recombine, they are altered from their original composition and form complex compounds (polymers), some of which impart the food flavours we can savour.

And now, a little demo

Maybe you would like to see for yourself some Maillard reactions while creating a nice little dish. You don’t need much – a piece of beef (or lamb or pork or chicken), some roughly sliced garlic, cooking oil (preferably olive oil), some fresh herbs (rosemary or thyme or oregano is fine), a slice of cold butter and some salt. Pepper is optional.

We will actually use three separate Maillard reactions to maximise the flavours in this example. I include some garlic simply because I like the complex flavours arising from cooking it – but you can omit it.

1. Pat dry the beef and sprinkle some salt on top

Remember that the dry-cooking Maillard reaction is inhibited by water (which lowers the cooking temperature) – so it is always best to start with the meat as dry as possible. Salt is denser than water so scattering some salt crystals on top will also draw out more of the water on the surface of the beef. Of course, this also adds some nice salty flavour as well.

2. Roughly slice up some garlic

Slice the garlic a little thickly to maximise the cooking surface area so that the Maillard reaction can start. But don’t mince or slice the garlic too thinly as it will just burn.

3. Cook in olive oil till garlic is slightly brown

In a frying pan under medium heat, cook garlic in some olive oil (keep tossing it around to distribute the heat evenly) and wait for the garlic to start browning – around a minute or less. This is the stage when the Maillard reaction is most active in the garlic. The aroma of fried garlic will also begin to be noticed. Do not let it get too brown as that means that caramelisation will have commenced – if this happens, it will completely change the flavour of the garlic.

4. Place the meat on top of the garlic

In this step we are going to combine two Maillard reactions simply by placing the meat on top of the garlic. The garlic is now at its most aromatic and by starting the meat cooking on top, we are combining the flavours of two parallel Maillard processes as the garlic now cooks together with the beef.

 Don’t worry about the meat not cooking on top – as long as the temperature on the meat surface is above 140°C or more, it will brown. Turn the meat over after a minute or so and do this 3-6 times depending on the size of the piece, to infuse the meat with the garlic flavours. You may also turn the heat up a little initially (just a minute or so) for this step as the pan will lose quite a bit of heat when the meat is added – but turn it down if you smell the garlic burning.

5. When the meat is brown, remove from pan

When the meat is seared and brown on the outside, but not fully cooked, remove from pan. This is done to pause the Maillard reaction on the outside while still letting the inside of the meat continue cooking. Note that the internal cooking of the meat is not the Maillard reaction – it is being cooked by a wholly different process.

6. Drop in a slice of cold butter with some herbs into the pan

Butter is now added as the 3rd Maillard reaction along with any nice herbs you would like to use. Actually, butter has a low smoking point (between 121°C and 149°C) and a lot of water and generally, if left to fry too long, it will lose the water very quickly and burn. This will turn it rancid or bitter in taste — so although we like its unique flavour, we cannot use butter too early.

As soon as the butter has melted and is reacting with the heat and herbs, put the meat back on top of the butter. This third Maillard reaction will now add the buttery and herb flavours to the meat.

7. Flip the meat a few more times in butter and remove

The dish is almost ready. Flip the meat over just a few times in the hot butter to get the butter flavours into the meat. To check how done beef is, press the flesh slightly with your finger. If it feels spongy, it’s still rare. A little springy is medium and springy is well done. The principle is roughly the same for other meats though I would not advise eating pork or chicken rare.

8. Serve as quickly as possible

The flavours from the Maillard reaction tend to be volatile and dissipate quickly. So serve as soon as possible. Here it is served very simply with avocado – because I like a buttery salad vegetable with a buttery-tasting meat. But you can serve it with anything you like.

Meat cooked perfectly.

9. What medium-cooked beef looks like

The outside layer of the meat modified by the Maillard reaction is very thin, less than 1mm. But this is enough to create and drive the flavours well into the rest of the meat.

Tags / Keywords: Lifestyle , curious cook , maillard reaction


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