How to unearth the secrets of your plate
Ever wondered how your taste buds work? Why you like something that others detest? Maybe you’re an amateur chef, interested in improving your favourite recipe or simply interested in the science behind what you eat. In a world of ever growing knowledge, where we seek the answers to all life’s puzzles – be they big or small – you can now find out. Scientists from all different areas are studying the secrets of gastronomy, whether directly or not. Spanning biochemistry, neuroscience, psychology and genetics, discoveries and innovation have led to a better understanding of what we eat. And to better cooking? Well we shall see!
The science now known as molecular gastronomy is the study of the physical and chemical processes that occur during cooking. It was the first discipline in its field. The term “molecular and physical gastronomy” was coined in 1992 by Hungarian physicist Nicholas Kurti and French physical chemist Herve This. The idea came from cooking teacher Elizabeth Cawdry Thomas who had an interest in the science behind cooking. At a conference in Italy, she initiated talk about the topic, ultimately leading to Kurti and This, alongside famous science writer Harold McGee, to set up official workshops. The first was held in 1992 in Erice, Italy with the mission of connecting professional cooks and scientists. These workshops have been held every few years since 1992 – the most recent in 2004. Every conference has a specific topic like sauces, food flavours or interactions of food and liquids. Some of the seminars held have included: chemical reactions in cooking, heat conduction and stability and flavour.
The scientists and chefs originally worked on 5 objectives:
– investigating culinary and gastronomical proverbs
– exploring existing recipes
– introducing new tools, ingredients and methods in the kitchen
– inventing new dishes
– helping public understanding of the contribution of science to societySome of these objectives have become somewhat obsolete and outdated. The three components of the current objectives are more succinct: social, artistic and technical.
So what has happened to those who set this all up? Nichola Kurti, who famously was one of the first TV chefs with his show “The Physicist in the Kitchen” in 1969, passed away in 1998. But not before organising the main events at the Italy conference for several important years. Hervé This still lives in France where he heads a research lab dedicated to investigating molecular gastronomy everyday. He is the author of many books on the subject and several blogs covering his work. Harold McGee is still very much part of the affair currently teaching classes and writing a column for the New York Times – The Curious Cook. And the teacher who started it all? Elizabeth Cawdry Thomas sadly passed away in 2007, not without leaving behind her a series of recipes and a new foody craze!
Many restaurants and famous chefs are very taken by the topic. In the UK, you have probably heard of Heston Blumenthal or watched one of his wacky cooking sessions on TV. Although he dislikes the term, deeming it too complicated, he is an avid molecular gastronomer, researching and putting into action various aspects of the science. His restaurant The Fat Duck is where the proof is. Other well-known adepts are French chef Pierre Gagnaire, Spanish owner of elBulli, Ferran Adrià and American restaurateur Grant Achatz.
So what can the study of food, its cooking and our eating of it help us understand? Over the next few issues, we shall discuss all aspects of this innovative field. What can it teach us of our everyday eating habits? Let us take a more personal point of view. How do taste buds work? What composes different aromas and how does our brain translate them? We shall decode some worldwide cooking myths. Which old wives tales are worth the story? We will then take a more biochemical view point: how and why does food change colour and texture when cooked? Finally, with the rise of GM foods and the recent development of synthetic bacteria, are we far off from eating synthetic produce? And if so what are the real facts?
Nicholas Kurti is famously quoted to have stated: “I think it is a sad reflection on our civilization that while we can and do measure the temperature in the atmosphere of Venus we do not know what goes on inside our soufflés”. Let’s find out if we have! Taste buds and cooking myths
In this second portion on the science behind what we eat, we shall cover two main topics of Molecular Gastronomy research. If you missed Part 1, molecular gastronomy aims to study different aspects of food and cooking, from a scientific point of view. From cooking techniques to molecular components through to food psychology, scientists all over the world are demystifying our everyday eating habits. Now that we have been through the history of how this new subject came to be, let us concentrate on a specific field of research: neuroscience!
One question is on the tip of everyone’s tongue: what are taste buds and how do they work? Taste buds cover our tongues, allowing us to receive the taste sensation and transmit it to our brains. The buds can be found in taste pores – small opening on the tongue’s surface – and are usually flask shaped with a broad base and small neck-like opening onto the skin. There are around 100 cells of two different kinds in taste buds : supporting cells and gustatory cells. The supporting cells are thought to simply be a source of basic sensation while the gustatory cells (also known as chemoreceptors) are where it all happens. They usually sit at the centre of the bud and are spindle shaped. They have gustatory hairs at the top of them near the tongue’s surface and are innervated by the seventh, ninth and tenth cranial nerve. It is these nerves that will pass the information from your mouths to our brains.
But how does do these receptors, and then the brain, differentiate between the difference tastes we subject them to? The five different “taste sensations” have been defined as: sweet, bitter, savoury (sometimes referred to as unami), salty and sour. Although the myth goes that there is a map of the tongue, with different areas controlling different tastes; it is now thought that the taste qualities are spread all over the tongue, even if some regions may be more sensitive than more. With between 2,000 to 8,000 taste buds by tongue, how does the brain differentiate?
Now for some basic neuroscience. Different receptors in the taste bud cells are thought to be responsible for differentiating tastes. As most of us probably know, signals are transmitted to the brain via an electrical current coursing through nerves. There are many different ways of activating this current, most of which involve the transport of ions through a communication channel between cells and neurons. These channels are embedded in the membranes of cells and neurons and often link them together. The idea here is that different channels could “code” for different tastes. Salt and sour are supposedly measured by a flow of cations (positively charges molecules) through these channels. Sweet, bitter and unami and through to use a group of more elaborate receptors called GPCRs (G Protein Coupled Receptor) which are activated by the presence of particular proteins. Research into which specific receptors are responsible for which taste is still underway. For example, A taste receptor named TAS2Rs has been shown to be responsible for the ability to taste bitter substances.
Part of the reason for these receptors, like most things in our body, is the ultimate goal of keeping us alive. Our ability to “like or dislike” certain tastes were initially set up to protect us from eating poisonous foods and push us to consume those our bodies need to function. For example, we have a basic dislike of things that are sour, like some berries. This is probably because many berries are highly poisonous! And why do we like sweet things? Our bodies need glucose to maintain a level of activity, thus it pushes us to seek foods containing it. Although these rules may not apply in the modern whole we now live in, our taste buds had originally evolved to guide us to the right foods.
A little side note: why has unami (savory) only just been recognised in the West when it has always existed in Japan? Unami is meant to describe the taste of meat, cheese and mushrooms. The main substance we are detecting is called carboxylate anion of glutamic acid, an amino acid present in meats (particularly bacon). It can be used as a flavour enhancer, particularly its salt components. You might have heard of it being often used in Asian cooking – it’s called MSG. The reason we have only just started taking it into account, is that the separate receptors for unami were only discovered in 1996 at the University of Miami. Before that, it was only considered as a sensation mix of the other tastes.
The interesting thing about taste buds is that we can trick them. This is where psychology comes into play. It’s just a case of mind over matter. Many experiments have proven this in the past. Take for example, a group of wine buffs. They can supposedly separate various tastes in the wine they are drinking, from oak to cherries. They often comment on the texture and weight of the wine. A lot of this they can tell not only by smelling and tasting the wine but by looking at it. Thus a white wine will often be perceived as light and crisp with fresh fruit or citrus tastes. Red wine is heavier and dustier, maybe with the taste of berries. But what happens if you switch the wine colours? Experiments have been performed of transforming red wine to a white colour and vice-versa. The wine tasters where completely duped, analysing completely wrong associations in the wine simply due to the colour it showed. Other similar experiments have been made showing how our perceptions can alter our taste. Taste some ice cream. It takes… well ice creamy! Now taste it whilst thouching some velvet cloth: the ice cream will seem creamier. Taste some whilst touching some sand paper: the ice cream will feel gritty. How do we fool ourselves? These are some of the things scientists and chefs are trying to investigate within molecular gastronomy.
Although these concerns are of a more serious scientific nature, one particular aspect of their research might be very useful to your everyday meals. In a field where good cooking practice is all word of mouth and grandmothers hidden recipes, the molecular gastronomers are taking it into their own hands to rectify some basic cooking myths. For all you kitchen lovers, these have probably been drilled into your head (as they had mine), but have no scientific basis whatsoever. Myth number1: always add salt to water when cooking green vegetable. This one has an array of reasons: to keep the vegetables green, salting the water or heightening the boiling point. All untrue. The pigment in vegetables is not affected by salt but mainly by the acidity of the water (usually the calcium content). Adding salt to water does in theory increase the boiling point, but by a fraction of a degree. This is less than the difference between boiling the water at the top of a block of flats or at the bottom. Myth number 2: the cooking time for a roast is dependent on its weight. Now, any mathematician can probably work this one out. The point of timing a roast is to get it to a stage where the inside is as cooked (or uncooked depending on your tolerance for rare meat) as needed. The time it takes for the heat to diffuse to the centre of your roast is not dependent on its weight but on its diameter. Imagine chopping your roast into two segments along the width. The diameter would still be the same, thus the time it takes for the heat to reach the centre will not have changed. According to tradition, roast baking time would have been halved. And the best for last. Myth number 3: when making a meringue, if there is a spot of egg yolk in the egg white mix it will not rise. Every tried making a meringue? It takes some effort! Foody author Peter Barham rumanged through his cooking books and found a recipe for a different cake which also demands the whisking of eggs to stiff peaks. The recipe calls for egg yolks and whites. And it works. So don’t panic next time you get some yolk in your egg whites, it’s all a myth!
Food colours and engineered fare
As we have seen, Molecular Gastronomy is a new innovative field researching the science behind food and cooking. From perfecting the ultimate recipe to understanding how our taste buds work, it encompasses many different areas of science. So there’s something for everyone. We have seen how the field was started and by whom, what it can teach us about our eating behaviour. We have debunked some cooking myths and described how we taste and the implications on our cooking habits. In the final section of this piece, a more biochemical view point shall be taken.
|Myoglobin heme ring
Ever wondered what makes food change colour when it is cooked? Why the texture can be so different? It all comes down to basic chemistry. Everything around us is made up of atoms, combined into specific shapes – molecules. All molecules code for different things and the shape of a molecule can code for the colour or texture of the body storing it. The atoms in molecules are held together by bonds. These bonds can be disrupted many different ways, inside or outside the body, ultimately leading to the molecule changing shape or loosing some of its atoms. It will then code for something different, or in our case a different colour or texture. Let’s clarify with some example. Raw red meat is, by definition, red. Meat is mainly composed of muscle cells which contains myoglobin, a protein which can bind to iron and oxygen. Combined with oxygen, myoglobin forms a molecule called oxymyoglobin which is red. The interesting component of myoglobin is the heme ring on its surface. As meat is cooked, the heme ring in myoglobin changes shape. An iron molecule becomes oxidated, leading to the formation of metmyoglobin, which is brown. Think of it as iron rusting after a prolonged exposure to oxygen.
Eggs are a noteworthy double example. When cooked not only do they change colour (the egg white in fact turns white) but its consistency transforms from a liquid to a solid. The change in texture in due to the proteins contained in the egg white. Proteins are made up of long chains of amino acids. In their raw form, these chains are folded into specific shapes, with a certain number of interactions and bonds. When an egg is cooked, a process called denaturation occurs – the bonds holding the proteins together break. The amino acids of a protein are now free not only to bond with each other with also with the amino acids of other proteins. It is this increase in bonds which causes the texture to change from fluid to firm. This same process is responsible for the colour change. When the proteins all bind together, they form a tight weave. In this structure, they are capable of deflecting rays of light that would normally pass through the slack net of a raw egg white.
A controversial topic encompassing food and science is GM (Genetically Modified) foods. Whether you are for or against, it seems there is insufficient data to prove whether they are a danger to our eco-system or a solution to world hunger. So what is all the fuss about?
GM foods are foods that have had their DNA tampered with by genetic engineering techniques to allow them to grow more efficiently. Transgenic plants have been the main focus of this work. The inspiration is to create plants which are resistant to the bugs, viruses or pesticides which lead to crop failure. There is also the idea of increasing these plants’s content in vitamins and such to provide better nutrition.
Here’s a for instance (from my Molecular Genetics course in 3rd year!). Plants are often attacked by insects, which depletes the crop substantially. It is possible to engineer plants which contain a biopesticide – often a bacterium which would kill the insect eating the plant. After a while, the insects stop trying to eat the plant. A bacterium called Bacillus thuringiensis (or Bt) can be used to attach the insects. It produces a protein (in the form of a protoxin) which can attach itself to the cell lining of an insect’s stomach, creating holes in it which leads to the insect’s death. Obviously it’s not quite this simple, genetic engineering is very complex and there is always the issue of the insect builing up resistance to the bacterium but thats’s the main idea.
|Bt toxic mechanism of action
This year saw the creation of the first synthetic life-form. A bacterium that lives in the intestine’s of goats and cows, Mycoplasma mycoides was successfully copied and Mycoplasma mycoides JCVI-syn1.0 was born. After sequencing the whole genome of this organism, the feat of molecular genetics was achieved by creating over 100 cassettes composed of 5,000-7,000 base pairs of nucleotides (the founding parts of DNA – see my article on the genetic code) and assembling them to create the 580,000 long sequence of the Mycoplasma mycoides genome. This discovery has also been the subject of controversy. With a media craze denouncing the researchers as “playing God”, the understanding of the science behind the discovery and its purposes is minute. But what has this got to do with food and molecular gastronomy? One of the notions born of this research is that scientist will start to produce synthetic foods. While this might sound scary, it can also be hopeful. Here might be another way of resolving world hunger. It could also mean bridging the gap between meat eaters and vegetarians; if meat could be created without the killing of live animals. Although the idea and theoretical knowledge to do so is there, we are far from achieving this kind of futuristic science. It is also very important to understand the technology used, what the risks are and perform extensive research in the field. This goes for both the scientist getting too excited about his newfound discovery and the media which often fails to properly explain things to the public. And as far as ethics are concerned, we can be sure that, like with GM foods, ethics procedures as well as risk assessments will be top of the list of priorities.
|Mycoplasma mycoides JCVI-sync1.0
And some we come to the end of your gastronomic journey. What have we learnt? With the help of molecular gastronomy, we can better understand what we eat, how we taste it, how we cook it, why we like it and how we can engineer it. From fun facts demystifying old wives tales to hard molecular genetics through information to make us all better cooks, this new field is definitely one to watch!