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Sunday June 22, 2014 MYT 9:40:00 AM
Sunday June 22, 2014 MYT 10:08:12 AM
by chris chan
The browning of food caused by the Maillard reaction brings deliciousness, but there is an unsavoury side ...
SO we have been nattering about the Maillard reaction for a while now, dwelling on the positive aspects. And we have seen also how we can layer or combine Maillard reactions in different ingredients to enhance the flavours arising from the dry cooking process.
But, Mummy – why do we like it?
It is curious why we humans like and enjoy the flavours created during this chemical reaction – why do our senses find these new complex flavours desirable and delicious?
The origin may again lie in evolution. Remember those pre-historic folks who ate cooked food and lived longer and better?
Well, there is strong evidence that suggests that our taste buds have simply grown accustomed to the flavours of cooked food.
Humans have already evolved taste buds, of course, but they were originally to prevent people from eating really unhealthy stuff – which is why we tend to dislike very bitter, very sour or very unusual flavours. Generally, such intense tastes indicate that the intended food item is poisonous.
Cooked food has been identified as easily digestible and safe (or at least, safer) and so people have learnt to prefer it.
This preference is passed down from one generation to the next – even if it is not a physical evolutionary step for human palates to like cooked flavours, we impart this preference from the time we start feeding young children at the dinner table.
The big, bad AGE
There is a downside to the Maillard reaction though – nothing is ever totally safe and free. Chemically, the Maillard reaction is called glycation – the actual name of the process when reducing sugars react with amino acids (see Footnote 1). Basically, the end result of glycation is a bunch of Advanced Glycation End products or AGE (or AGEs) for short. The problem is that some of these AGE compounds are unstable and therefore somewhat reactive and they can affect the cells and tissues in our body.
An accumulation of AGEs over time can and will damage our cells, especially the protein cells.
That is why muscles stiffen with age, eyes lose their ability to focus and skin loses its flexibility.
AGEs have also been identified as one of the significant factors behind diabetes, brain damage and heart disease, among other illnesses.
Your body needs to know this
The news gets a bit worse as there is yet a third type of Maillard reaction, which is non-enzymatic and does not involve intense heat – and it happens inside your body (for some reasons why it occurs see Footnote 2).
Fundamentally, one can regard the modern human body as effectively a slow cooker running at 37°C with a 75+ years cooking cycle. And this internal human slow-cooked Maillard reaction is a cellular glycation factory which also produces AGEs.
The body actually has some basic mechanisms to get rid of AGE products – for example, it has some clever enzymes to detoxify AGEs before they get out of control – but this is often not wholly effective due to the body also having Receptors for AGEs (or RAGEs).
Why the body have RAGEs is a little mystery as all they seem to do is cause persistent cellular inflammation when activated with AGEs.
However, generally, once sufficient RAGEs combine with AGEs over a period of time, the damage is done.
This is particularly bad news for diabetics because the elevated blood sugar levels in diabetics causes more AGEs to form, which then react with RAGEs – and this worsen diabetic complications. So in short, it’s recommended that diabetics avoid food with too many AGE products as well as sugar.
A fact of modern life
The digression into AGEs and RAGEs recounts a paradox of modern human life. Cooking destroys bacteria, renders food easily digestible and creates flavours which make our food delicious.
Yet the same cooking process also creates harmful chemicals in our food which causes cell inflammation, diabetes, heart disease, cataracts, accelerated ageing, etc.
Maybe it’s because our bodies are designed for a 28-year life span – for pre-historic man, AGEs and RAGEs probably would not have been an issue as there were so many other more serious dangers to life.
Watch what you cook
Personally, I am not particularly wary of AGEs caused by the Maillard reaction as there is nothing I can do anyway if I want to enjoy eating – but I do watch what I cook though.
For example, cooking foods with fructose generates five times as many AGEs as cooking with glucose, so be careful of frying, grilling or baking stuff using commercial sauces as they tend to contain a lot of High Fructose Corn Syrup (HFCS), which – as it says on the tin – is very heavy in fructose.
So do try to make your own sauces from fresh ingredients and avoid using tinned or bottled sauces if you can.
By the way, HFCS isn’t made from sweet corn kernels like you would think – it’s actually made from corn stalks, which is why it is so cheap and used so much by industrial food manufacturers.
I find the stuff rather icky – and the very high and unnatural fructose composition of HFCS is also really very bad for your liver.
Clarification about caramelisation
At this point, one should note that many people confuse caramelisation with the Maillard reaction, primarily because the end result is a brown colour.
For the purpose of cooking, this does not really matter as caramelisation can also add lovely aromas and flavours to food as well. If you’re really interested, caramelisation is the darkening caused when sugar is heated.
No proteins or amino acids are involved, which is why it is not a Maillard reaction.
Some tips and hints
Louis-Camille Maillard himself never worked with food – there is no evidence that he had ever cooked a dinner or baked a cake. Fortunately though, from his discovery, many people are now engaged professionally in using the Maillard reaction to improve the appearance, taste and flavour of food.
So at this point, here’s a little advice on how to manage the Maillard reaction at home. Please note that the Maillard reaction is only one aspect of flavour and aroma creation – there are other methods of rendering delicious flavours into food and they will be covered in later articles.
1 If you like it brown
When roasting chicken or turkey, you can make the skin browner by brushing a light solution of baking soda on the skin before roasting. Use half a teaspoon of baking soda to 100ml of water. For baking, you can make bread more crusty or cake more brown by adding in half a teaspoon of baking soda per 150g of flour. Do not overdo the baking soda as it has a nasty taste if overused.
2 Not too hot, please
The dry-heat Maillard process works best at temperatures between 140°C to 180°C. However, most foods contain water so it makes sense to cook at temperatures above the optimum range to compensate for the water. Despite containing water, the surface of most food items will still undergo the Maillard reaction when its temperature reaches above 140°C. It’s inevitable.
Above temperatures of 180°C (which you sometimes see used when roasting or deep frying, for example), the part of the food exposed to the heat will either caramelise or burn and the cooler food layer underneath will undergo a Maillard reaction. Caramelisation adds flavour to food so it is often a desirable effect but burning seldom is.
However, if one leaves food cooking too long at any temperature (especially 140°C or higher), the food will lose all its water, dehydrate and burn. Any Maillard reactions will stop, having used up all the available sugars and amino acids, the volatile compounds will have dissipated and all that will be left are the gunky non-volatile compounds which you have to scrape off.
So watch what you are doing and don’t leave food to overcook.
3 Don’t flip it!
Generally, the advice for frying steaks is not to flip it over too often. This is so that the maximum amount of flavours can be developed on the cooking side of the meat. Keep the pan hot so that the meat surface is always cooking at around 150°C. However, for fish, especially for fish steaks, one should not flip it over more than once.
The reason is that the fish tends to disintegrate when cooked due to its high water content, so one should cook fish steaks skin side down until the skin has hardened and then flip it over one time to cook on the other side.
4 Using recipes with your nose
Not all food ingredients cook at exactly the same temperature or time given in the recipes. That’s partly because everyone’s kitchen is different and the ingredients are seldom wholly identical. So use your nose and be sensible.
Popping spices in hot oil to fry is a classic example. Depending on the heat, it will release its flavours very quickly – but leave it a few seconds too long, and all you will get are little lumps of charcoal.
So when you sniff that the cooked ingredients are at their peak in terms of flavour creation, then it is time to go on to the next stage in the recipe, regardless of timings given.
To kill any Maillard reactions dead, just pour in some water and take it off the heat. To hold Maillard flavours created, add a little good vinegar.
5 It’s a bit like chewing gum
When chopping up vegetables, don’t chop them too finely. The cooking heat will deplete flavours very quickly from small pieces of ingredients and even make them burn. It is like chewing small pieces of chewing gum – the gum taste disappear much quicker with a small piece of gum.
Cut vegetable ingredients around 1cm or bigger in size and this will hold a reservoir of flavour as you cook. The internal moisture will also help prevent early burning.
For stir-frying meats, there are no fixed rules though the Chinese tend to cut the meat into strips, to maximise the pan contact, and they then cook the meat very quickly under high heat.
6 The other bad stuff
Should one eat the brown compounds (AGEs) that result from the Maillard reaction? The suggestion is simple: be a little careful. Food that is burnt and crispy will have far more AGEs because the extended or high cooking heat will have caused more chemicals to react.
So it’s not such a great idea to eat burnt toast or the black bits around a hunk of char siew or the charred bits on sticks of satay. The brown parts of fried potatoes contain acrylamide, which is a known carcinogen.
Therefore, avoid too many crispy chips and packet crisps if you can.
Don’t use fructose when dry-cooking (or any form of cooking).
Fructose creates far more AGEs than other sugars so avoid using commercial sauces with High Fructose Corn Syrup if possible. Not everybody labels the use of HFCS – often it is disguised as “sugar” or “sugars” or sweetener or syrup.
Ma, we’re all chemists now!
Now that you know about the flavours from the Maillard reactions, one might be tempted to dry-cook lots of stuff all together in search of deliciousness.
Actually, I wouldn’t recommend that – it can end up like a woman using a perfume that is too heavy. One can get too many things going at the same time which counteract each other and end up with something tasting too busy or weird.
So try not to overdo the flavours – and stick to trusted recipes (or formulas) that you like. Experiment often of course, as it’s great fun - but experiment gently.
This story concludes our series on the Maillard reaction. You can read the other stories in the series online. at www.thestar.com.my/Lifestyle/Food
Part 1: The Maillard reaction
Part 2: The Alkaline effect
Glycation happens in three stages. The first stage involves the formation of Schiff bases – this is the step when carbon atoms in the sugars bounce across to embrace nitrogen atoms in the amino acids. Hugo Schiff was a German chemist who discovered these products in the 19th century – as an aside, there’s no evidence that he liked fine dining as he was also a rabid socialist who hated the bourgeois.
The second stage is called an Amadori rearrangement, named after Mario Amadori who figured this process out in the early 20th century. This is pretty technical so let’s just say that the Amadori rearrangement is just an intense shuffling of the Schiff bases with some hydrogen and oxygen atoms getting involved to glue together new molecules along the way.
The last stage is the formation of polymers known as Advanced Glycation End products (AGE or AGEs). This stage combines the resultant molecules from the Amadori rearrangement to create the very complex polymers that form aromas and flavours. Unfortunately, as they are somewhat unstable and reactive, some AGEs can affect the biology of cells (by messing with the cell structures), or screw up the action of hormones, or introduce free radicals into the body, among other things.
Certain AGEs are bad for body tissues and the existence of these compounds is one of the primary reasons why Raw Food groups came about. AGEs are present in abundance when food is over-cooked or burnt (pyrolysis) – and they can be volatile (ie. you can smell the food burning) and non-volatile (ie. you have to scrape them off the bottom of your pot or pan).
AGEs can also react with oxygen to produce whole new types of AGEs (via glyoxidation), so AGE formation is a bunch of seriously complex chemical equations, not all of which have been documented or even discovered.
Cellular glycation can happen in the human body in several ways. Stress in cells can cause oxidation reactions with free radicals in the body, or it may be due to random and erratic interactions between damaged cells – which allows carbon and nitrogen molecules to react (such as a carbonyl-amine reaction). The eye lens and muscle tissues eventually lose their elasticity because they are long proteins which accumulate AGEs over time. It is also highly probable that skin ageing is also affected by AGEs. It doesn’t matter if we ingested the AGEs or if they were manufactured by our own bodies – the effect is cumulative and progressive. AGEs have also been implicated in cancers as several AGEs detected in dry-cooked food are known carcinogens.
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