You can tell that the days were packed during my visits to Belgium (The Flemish Primitives) and Denmark (Molecular gastronomy seminar) in March by the fact that I still blog about it in June. After the sous vide masterclass I attended a master class on taste technologies hosted by Quico Sosa (the man behind the Sosa company) and chef Dave De Belder. Many may frown upon flavors and their use in high end gastronomy, but anyone who considers using flavors as a shortcut to better cooking should rethink this as both successes and disasters are amplified (interestingly, Bruno Goussault said exactly the same about sous vide in the preceeding masterclass).

In haute cuisine, technology must be at the service of flavour and not otherwise. We must escape from the myth that everything was better in the past and also, that everything new is better. (“The technology of flavours”, Sosa ingredients)

From his presentations, advocating flavors and essences, one could easily think Quico Sosa was a chemist or a food technologist because of his very pragmatic approach to flavors and flavorings (in fact he studied philosophy). His motto could easily be summed up as: Use natural whenever possible, but understand when technology can give nature a boost! -If something is not beautiful it does not exist, says Quico Sosa. A fruit without flavour does not exist. We should of course use fresh fruit whenever possible, but we should not be afraid of using flavors.

Mackerel with carrot is a classic pairing, but the challenge for any chef is to capture the freshness of the carrot. The piece of mackerel served with carrot powder was a very good example of this. I think I’ve never tasted such a concentrated yet fresh carrot!

-We don’t know the flavor of a fresh product any more because we can’t buy it, he says and continues: If you go to a restaurant and it’s not tasty, you should complain. Today chefs have no excuse! Another example mentioned was mousse of lychees. It’s difficult to make because the flavor is so dilute, especially if it is also combined with other, stronger flavors. -In this case you need a bit of technical help, says Quico.

Quico Sosa composes flavors as were they perfumes. He always tries to use natural extracts, but adds pure compounds as required to achieve the desired flavors.

The essence of pea skins (left) gives the creamed peas an incredible freshness. The pea cream was served on a thin disk of white chocolate with royal Beluga caviar and freeze dried whole peas (top right). Anu Hopia, professor at University of Turku and fellow food blogger (molekyyligastronomia.fi, google translation) is ready to taste (bottom right).

After the session I asked Quico about how he perceives the natural/artificial debate, and his reply could just as well have come from a chemist: -The most dangerous thing we sell is natural nutmeg essence, says Quico. (due to myristicin in case you wondered!)

Yoghurt foam flavored with bergamot and sprinkled with liquorice powder (left). Liquorice extract is quite yummy just by itself (right).

A handout on the technology of flavors was provided during the session. Apart from repeating the common misconception of the tongue map of tastes it is well worth reading, in particular the second part on “New flavour technologies” which covers the different functions the flavor products may have as well as the different techniques used in their preparation (freeze drying, grinding/conching, concentration at low temperature/pressure, cold confit/candization, extractions). In a restaurant setting the use of flavor products and aroma extracts is quite different from the typical industrial setting. Examples include:

• provide variation in textures
• separate flavors from their texture/color
• enhance flavors that fade during cooking or are particularily unstable/weak
• use of aromas to scent the dining room
• experiments with flavor pairing

As a chemist I guess I’m quite open minded with regards to the use of flavors. But how do chefs see this? Is it OK to use flavors or is it regarded as cheating in high end restaurants?

The master class session with Quico Sosa included countless samples for tasting

Peter Barham’s presentation at the MG seminar in Copenhagen focused on how food can be used to make students interested in physics and chemistry (not a bad thing, especially since 2011 is the International Year of Chemistry) -Most people think science is boring and difficult, he said. But demos can help bring science to life, and believe it or not – experiments are much better when they go wrong. Using balloons, champagne, potatoes and liquid nitrogen Peter Barham proved his point. As an example he asked the audience how much air weighs. He first filled a balloon with a few milliliters of water, then squeezed out all the air, tied a knot and heated the water in the microwave until all had evaporated. The first balloon exploded since he used to much water (this shows that water expands when boiled and that balloons are not infinitely stretchable!). Using a little less water for the second balloon, everything worked fine. Assuming that steam has approximately the same density as air, the size of the balloon can be measured and from this the weight of air be calculated. One finds that the volume of the water increases by a factor of approximately 800x.

There will be more foam when champagne is poured into a dirty glass due to more nucleation sites providing the dissolved carbon dioxide with more escape routes.

Ever heard about how a spoon in the neck of an opened champagne bottle can keep the champagne fizzy? Well unfortunately this is a kitchen myth. The only thing that helps is keeping the bottle cold. The spoon has no effect whatsoever. And the balloon once cooled can help illustrate this. When all the steam had condensed there was a significant amount of gas left in the balloon (remember that all the air was squeezed out to start with). This illustrates that gases are soluble in water at low temperature, but not at higher temperature. When water is boiled the gas escapes. Gas (and in particular carbon dioxide) is more soluble at lower temperatures, and that is the explanation why champagne may retain quite a lot of the fizz if stored cold. The spoon is only there to confuse you!

How long does it take to boil a potato?

Next question was: How long does it take to boil potatoes? Since the visual appearance of a potato changes around 60 °C it is possible to monitor heat transfer by simply slicing a potato in two. If boiled in water a nice ring with a slightly darker color indicates how the heat travels uniformely towards the center. If you plot the width of the ring against the square root of the time you get a nice straigth line. However, if heated in a microwave a different pattern emerges. The wavelength of microwaves is on the order of several centimeters and as a consequence the distance between hot and cold areas are about 2 cm. Slicing a microwaved potato shows how only one side has been heated. This is the simple reason why food heated in a microwave oven must be left to stand for a while to allow the heat to diffuse.

When heated in boiling water the heat travels uniformly towards the center of the potato as evidenced by the “ring” that occurs once the temperature reaches 60 °C.

When heated in a microwave there will be hot and cold areas as illustrated with this potato.

Peter Barham also mentioned the experiment that demonstrates the difference between taste and aroma. If you close your eyes, hold your nose and have a friend give you either a piece of apple or pear, you’ll have a difficult task saying which is which. But the second you let go of your nose you recognize what you have in your mouth. The experiment can also be conducted with lemon and lime or other fruit pairs with similar textures. The reason for this is that when you hold your nose, hardly any air from the mouth will enter your nose through the retronasal passage. As a result you will not be able to “smell” what’s in your mouth. But the second you let go of your nose, air can pass freely and you immediately smell what’s in your mouth. This is also the reason why the aroma of food is subdued if you have a cold and a runny nose.

Close your eyes, hold your nose and experience the difference between taste and smell! Apples and pears taste remarkably similar when the aroma is blocked out by holding your nose.

Peter’s last demonstration was liquid nitrogen ice cream and an attempt to break the current world record of 10.34 seconds. More on that in the next post

Oils and fats are long molecules which are mainly non-polar and hence the opposite of water which is a polar molecule. Ethanol which has both a polar and a non-polar end falls in between oil and water. I’ve covered extractions using water and ethanol previously. That water and oil are opposites is easily observed by the fact that they don’t mix, and because of it’s lower density oil floats on top of water. This property allows us to easily separate water and oil.

Volatile molecules – the molecules that we detect by their smell – are mainly non-polar and therefore soluble in oil. This is one reason why foods with fat often have a different and often better flavor compared with their fat-free counterparts (fat of course also influences mouth feel etc.). Everytime you cook with oil it will actually help extract aroma (or smell flavorants) from the food ingredients and deliver these to your nose.

There are several oil extracts used in the kitchen, and the nice thing about them is that the oil extracts aromas and then protects them from the air. This is good as it prevents oxidation of the aroma molecules, but in some extreme cases bad because the anaerobic conditions may promote growth of botulinum spores – more on that in the last paragraph. When the flavored oil is added to a dish you get can immediately perceive the aroma. If the oil is tasted pure it serves as a carrier for the aroma giving a small explosion in the mouth (or nose to be more precise…). Some examples I can think of where the oil plays an important role in extracting and delivering aromas are: pesto, tapenade, mayonaise, aioli, curry paste (and all other spice pastes), chili oil and truffle oil to mention a few. Notice that in most of these the source of the aromas is still present in the oil.

One significant addition to the aroma molecules is capsaicin which gives chiles their pungency. Capsaicin is not particularily volatile so it never reaches your nose, but it certainly does burn your tongue! The funny thing is that the receptor being attacked by capsaicin is a protein which is also sensitive to temperature. So when talking about “hot” food it’s true in a double sense. There is an overlap in how our brain perceives food which has a high temperature and food which is spicy.

The fact that water and oil are non-miscible can be utilized in the kitchen. Oil can be used to extract non-polar compounds from a water phase, and oppositely water can be used to extract polar compounds from an oil phase. In the organic chemistry lab water and oil would be separated with a separatory funnel, but in the kitchen a normal plastic bag will work fine. Check out the pictures and description of how a plastic bag is used to clarify butter over at Cooking for Engineers.

Although most of the aroma molecules will be present in the oil, a tiny amount will remain in the water. It is possible to measure how molecules partition between oil and water, and instead of cooking oil one uses octanol. You can read more about the partition coefficient K_{octanol/water} over at Cumbrian food lab.

To start experimenting with this in the kitchen I suggest you start with some colored foods. Flavor compounds are normally colorless so it’s hard to see where they end up. One can put up a very general list of compunds responsible for the color of foods:

We can start with blueberries. For the experiment I used a blueberry syrup and mixed it vigorously with oil using an immersion blender. However, when the phases separated the oil was colorless and the waterphase was still blue. The reason for this is that anthocyanins which give blueberries their nice color are water soluble. No matter how much you blend the blueberries with oil the blue color will remain in the water phase.

I should have waited longer to allow the phases to separate properly, but notice the oil clinging to the glass wall in the right picture – it’s totally clear without any traces of blue/purple color.

For our next experiment we will use carrots or carrot juice. Add some oil and mix with an immersion blender to extract the carotene. What you observe now is that the oil phase turns orange/yellow. The reason for this is that the carotenes are oil soluble. If desired one can separate the two phases with a plastic bag as mentioned above.

Extraction of carotene from carrots. Pictures: 1) I finely grated carrots, 2) Blended them with water and filtered of the remains – the water phase was then layered with plain cooking oil 3) Water and oil were mixed with an immersion blender and the phases left to separate, 4) A plastic bag serves as a separatory funnel – cut a small hole to let out the liquid. The water phase turned grey, probably because I left it at room temperature to allow the phases to separate (1-2 days).

Now that the effect has been demonstrated with food colors it’s time to move on to tastes and aromas. The four basic tastes are all soluble in water, whereas the pungency found in chiles for instance is soluble in oil. Aromas or smell flavorants however are primarily soluble in oil. To test this one can take some clear meat stock, add oil and taste the water and the oil phases separately. The water phase will be salty, and also have a little meaty flavor (our nose detects the tiny amounts of oil which remain in the water water phase, even if no oil droplets can be seen – and of course there are also umami flavorants in the water phase). The oil phase will not be salt at all and have a strong meaty aroma.

Even though you seldom will go to the extremes of separating oil and water phases, it can be good to think about where your aromas goes when you cook. And so you won’t forget I rewrote the first few lines of the Shoop Shoop song:

/ D7 – C7 – / D7 – - – /
Can you tell me where the aroma goes
and how it enters into my nose?

/ Am7 D7 Am7 D7 / / G Em7 Am7 D7 / G C D – /
It’s through the oily phase – Oh yeah, into the nose
In the water phase? – Oh, no, that’s just the salts
If you wanna know where the aroma goes
It’s in the grease, that’s where it is

(aroma should be pronounced more like ‘roma when singing)

–

Somes words about safety: When infusing spices, herbs or garlic – think about the fact that you create anaerobic conditions. If pH is above 4.6, the oil is kept at room temperature, and Clostridium botulinum spores are present you might be bad off (botulinum toxin causes botulism). There are sites that cover this in greater detail. Perhaps the easiest way of preventing the growth of botulimum spores is by adjusting the pH with an acid such as phosphoric or citric acid (that would be the pH of any water phase present as they are not soluble in the oil).

Ethanol is a molecule with both a polar and a non-polar end, so it’s properties are somewhat in between those of water and oil (which will be the topic of the next post in this series about extraction). This is easily illustrated by the fact that both water and oil are soluble in pure ethanol (albeit not at the same time – adding water to ethanol reduces the solubility of oil). Many taste molecules are polar whereas most aroma molecules are non-polar, and the good thing is that ethanol can be used to extract both groups of compounds.

I belive the most widespread use of ethanol for extractions in the kitchen is for sweet liqueurs where fruits or berries are extracted with ethanol and the extract is sweetened with sugar. The word liqueur comes from the Latin word liquifacere which means “to dissolve”, and this is essentially what happens – the ethanol and water extract and dissolve flavor and color from the fruit.

Some also make their own spirits by infusing spices and herbs. One example is aquavit which is based on carraway combined with a number of other spices for complexity such as dill, coriander, anis, fennel, liquorice, cardamom and lemon. Commercial aquavits are distilled, but at home it’s suffices to filter of the spices and herbs. As a result home made aquavits are always amber colored (such as the one pictured in a previous post).

For extractions like these, one always uses diluted ethanol, typically 30-60% ethanol in water would be used, and most often somewhere around 40-50%. One reason for this is that higher concentrations of ethanol would extract to many bitter and astringent compounds. Another reason is that in some (most?) countries it is illegal to posess, buy and/or sell ethanol at higher concentrations for consumption (pure ethanol for technical use is denatured if sold in normal stores and requires special permissions if used in laboratories).

Apart from the steping herbs and spices in ethanol to make liqueurs, the only other example of relevance for the kitchen I can think of is for extraction of vanilla beans to make pure vanilla extract. This is quite surprising actually, and although I really don’t know if ethanol is used for extraction in professional kitchens, it is my impression that ethanol extractions are underutilized in the kitchen.

There are several benefits with ethanolic spice and herb extracts:

• fast – no need to wait for the spices to be extracted since they have been “pre extracted”, you can taste the dish immediately and add more spice extract if necessary
• no residues – seeds, leaves or bark are filtered off before use
• convenient – spice extracts are an excellent way of adding clean, concentrated aromas
• stable – spice extracts keep very well (although the storage may also change the flavor profile somewhat and “mature” the flavor)
• new flavors – some spices and in particular herbs will change upon extraction and storage and this can open up new possibilities (this needs quite some experimentation though – some herb flavors change to the worse…)

What are your experiences with ethanol extractions in the kitchen?

Water is a polar molecule, meaning that one end has a small negative charge and the other a small positive charge. Because of this water is a very good solvent for other polar molecules and ions. For instance water is the solvent of choice for substances that provide taste, be it salt, sour, sweet or bitter as these are normally quite polar molecules.

A general rule is that the solubility of molecules and ions increases with the temperature of the water. Extractions are therefore faster if the water is boiling. This is the reason why we use hot water to extract tea leaves or ground coffee beans, even if we want to prepare ice tea or ice coffee. But by lowering the temperature and extending the extraction time we can change the relative proportion of what we extract. It therefore makes perfectly sense that different temperatures are recommended for different types of tea. Using different temperatures for the same kind of tea will of course also influence the flavor profile.

Polar molecules are more easily extracted than non-polar molecules. This is evident if we leave a tea bag for a long time in hot water. The bitter taste is due to the slow extraction of large polyphenol molecules which are less soluble in water. If tea is brewed at a lower temperature, less of the bitter tasting substances will be extracted.

Although water is polar, less polar and even non-polar substances can be extracted with water, especially if the water is boiling hot. You do this every day when prepare coffee. If you take a close look at cup of freshly brewed coffee you can notice small pools of oily substances floating on top of the coffee. The more severe conditions used when extracting coffee to make an espresso ensure that even more oily substances are extracted. Other examples of extraction using water in the kitchen include preparation of stock, soups and gravies.

The principle of extraction is simple, but a number of questions remain largely unexplored with regard to flavor: How do ions affect extraction? What role does pH play? How does temperature influence flavor? There is surprisingly little research on this that includes a sensory evalution.

When invited over to friends for dinner, even before eating, you judge the food by it’s aroma, handing out compliments such as “It really smells nice”! Thankfully, nature is on the cook’s side, because when we prepare food and heat it, volatile aroma compounds are released which trigger very sensitive receptors in our noses. It is generally said that 80% of “taste” is perceived by our nose (what we refer to as aroma), whereas only 20% is perceived by our tongue. How important smell is becomes clear if you catch a cold – suddenly all food tastes the same. Too illustrate the importance of smell, prepare equally sized pieces of apple and pear. Close your eyes, hold your nose and let a friend give you the pieces without telling which is which. Notice how difficult it is to tell them apart. In fact, with a good nose clip you wouldn’t even be able to tell the difference between an apple and an onion! Then, with a piece of either in your mouth, let go of your nose. Within a second you can tell whether it’s apple or pear!

Taste
Our tongue has approximately 10.000 taste buds and they are replaced every 1 to 3 weeks. Their sensitivity increases roughly in the following order: sweet < salt < sour < bitter. In addition to the four basic tastes there is umami, the savory, fifth taste. This taste is produced by monosodium glutamate (MSG), disodium 5’-inosine monophosphate (IMP) and disodium 5’-guanosine monophosphate (GMP). Pure MSG doesn’t taste of much, but can enhance the taste of other foods. There are also some claims of a sixth taste.

A number of taste synergies/enhancements exist. I’ve also included three examples of how flavours can influence taste:

The only general, over-all trend which can be found is that binary tastes enhance each other at low concentrations and suppress each other at higher concentrations (but there are several exceptions!). Do check out “An overview of binary taste–taste interactions” (DOI:10.1016/S0950-3293(02)00110-6) if you’re interested in more details on binary taste interactions. I’ve tried to visualize taste enhancements (green) and suppresions (red) in the following figure using arrows to indicate the direction. For example, salt suppresses sweetnes at high concentrations.

In addition to taste, our tongue also percieves texture, temperature and astringency. An interesting thing about the temperature receptors is that they can be triggered not only by temperature, but also by certain foods. The cold receptor is triggered by mint, spearmint, menthol and camphor. There is even a patented compound, monomenthyl succinate, that triggers the cold receptor, but without the taste of menthol. It’s marketed under the name Physcool by the flavour company Mane.

Substances such as ethanol and capsaicin trigger the trigeminal nerve, causing a burning sensation. Capsaicin also triggers the high temperature receptors of the tongue, hence the term “hot food” which can refer both to spicy food and food which is very warm. For a general article about taste, check out “Taste Perception: Cracking the Code” (DOI:10.1371/journal.pbio.0020064, free download).

Flavour
Our nose has about 5-10 million receptors capable of detecting volatile compounds. There are about 1000 different smell receptors and they allow us to distinguish more than 10.000 different smells – perhaps as many as 100.000! In order for us to smell something, the molecule needs to enter our nose at a concentration sufficient for us to detect. Aroma compounds are typically small, non-polar molecules. The fact that they are small means they will have low boiling points – they are volatile and spread rapidly throughout a room. They are often referred to as essential oils and are very soluble in fat, oil and alcohol. These aroma compounds generally not soluble in water, but there are also water soluble aroma compounds; just think of a well prepared stock – no fat but lots of taste and aroma!

A challenge with aroma molecules is that they should remain intact during storage and not be released until cooking (or even better, until consumption). A example would be to install a Liebieg condenser over your pot. Dylan Stiles has explored this in his column Bench Monkey by placing a bag of ice on top of the lid. He claims that his roommates prefereed the curry which has been cooked under “reflux conditions”. The study was performed in a double blind manner (which I will come back to in part 8 of this series).

Because aroma compounds are volatile, spices should be obtained whole and stored in tight containers away from light. If possible, fresh herbs should be used. The flavour of herbs and spices can be extracted by chopping or grinding to increase the surface area. To speed up grinding in a mortar you can add a pinch of salt or sugar.

Heat can help extract flavour (just think of how we brew tea or coffee), but will also evaporate volatile compounds, so a general advice would be to add spices at the start and herbs towards the end of the cooking time. Some herbs can even be sprinkeled over the food just before serving. In Southeast Asia (and especially India) it is quite common heat spices in a dry pan or in oil. This matures flavours and allows reactions to occur (possibly Maillard reactions). Coarse spices should be added earlier than finely ground spices.

In addition to adding flavour using spices, herbs and other foods, we can also use heat to create new flavours. When sugar is heated, caramel is formed. And if a reducing sugar is heated in the presence of an amino acid, they react and form a host of new flavour compounds in what is known as the Maillard reaction. Caramelisation and the Maillard reaction are known as non-enzymatic browning. Enzymatic browning on the other hand is detrimental to many fruits (such as apples and bananas), but there are a few exceptions. Enzymatic browning is essential in the production of tea (black, green, oolong), coffe, cocoa and vanilla, although this is rarely attempted in kitchen.

Another source of flavour is fermentation. It refers to a process were sugar is converted to alcohol and carbon dioxide by the action of a yeast. In the process a number of flavour compounds are formed as well which is why this is of great interest also from a molecular gastronomy viewpoint. Some examples of fermented products include wine, beer, cider and bread. Fermentation also refers to the process where some bacteria produce lactic acid. Some examples of foods resulting from lactic acid fermentation are yoghurt, kimchi and pickled cucumbers.

Flavour pairing
Cookbooks and recipes throughout the world are the result of billions of experiments. As a result, some very good combinations of herbs and spices have been discovered. Some of these mixtures have even been given names of their own and it is fascinating how easily one can forget that curry for instance is a mixture of spices. Wikipedia has a wonderful overview of herb and spice mixtures from all over the world. I must admit I only new a fraction of these:

Adjika | Advieh | Berbere | Bouquet garni | Buknu | Cajun King | Chaat masala | Chaunk | Chermoula | Chili powder | Curry powder | Djahe | Fines herbes | Five-spice powder | Garam masala | Garlic salt | Harissa | Herbes de Provence | Khmeli suneli | Lawry’s and Adolph’s | Masala | Masuman | Mixed spice | Niter kibbeh | Old Bay Seasoning | Panch phoron | Quatre épices | Ras el hanout | Recado rojo | Shake ‘N’ Bake | Sharena sol | Shichimi | Spice mix | Tajín | Tandoori masala | Tony Chachere’s | Za’atar

A book which I’ve found to be very useful when combining flavours is “Culinary artistry” by Andrew Dornenburg and Karen Page. It is the most comprehensive book about flavour pairing that I’m aware of, and I would say it is indispensible for someone who likes to cook without a cookbook. It has lists of basic flavors contributed by various foods. For example a sweet taste is contributed by foods such as bananas, beets, carrots, coriander, corn, dates, figs, fruits, grapes, onions, poppy seeds, sesame and vanilla (plus sugars and syrups of course). It has lists of “flavor pals”, a term attributed to Jean-Georges Vongerichten. For example, the flavour pals of ginger are allspice, chiles, chives, cinnamon, cloves ,coriander, cumin, curry, fennel, garlic, mace, nutmeg, black pepper and saffron. By far the most extensive part of the book are listings of food matchings. An illustrative example is pork which combines well with (classic/widely used combinations in bold):

apples, apricots, bay leaves, black beans, beer, brandy, cabbage, Calvados, dried sour cherries, clams, Cognac, coriander, cream, cumin, fennel, fruit, garlic, ginger, hoisin sauce, honey, juniper berries, lemon, lime, marsala, molasses, mustard, onions, orange, parsley, black pepper, pineapple, Chinese plum sauce, plums, prunes, quinces, rosemary, sage, sauerkraut, soy sauce, star anise, tarragon, thyme, vinegar, walnuts, whiskey, white wine

Despite the abundance of combinations, I dare say that little is understood about the science behind these flavour pairings. Why do these combinations of herbs and spices go particularily well together? Is it all about getting used to the combinations, so that we learn to like them? What influence does the complexity of the flavour play? These are easy questions that probably have rather complex answers.

Very recently a different approach to flavour pairing has emerged. If two foods share one or more key odorants, chances are that they will go well together. The first step towards finding new pairings would be to identify key odorants. More info on key odorants can be found in the article “Evaluation of the Key Odorants of Foods by Dilution Experiments, Aroma Models and Omission” (DOI: 10.1093/chemse/26.5.533, free download). I’ve initiated the food blogging event “They go really well together” (TGRWT) to explore new flavour pairings and develop new recipes. There are also several blogposts with interesting comments on about flavour pairing.

*

Check out my previous blogpost for an overview of the tips for practical molecular gastronomy. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

As shown in the figure, the radical reacts with sulfur containing proteins, thereby forming a thiol called 3-methylbut-2-ene-1-thiol or just MBT for short. The amazing thing about this compound is that we can smell it at concentrations as low as a few parts per billion (ppb). The perhaps not-so-amazing thing is that this compound gives beer a “skunky” aroma. Obviously one would want to avoid this, and that’s why beer is sold in dark brown glass bottles that act as the beer’s own sunglasses. Canned beer of course will not go skunky (well not until it’s poured into a glass and served outside in bright sunlight – that will turn any beer skunky within minutes).

Unfortunately however, not all beer is sold in dark bottles! One well known brand is shown in the picture below…

And yes – as you might have figured out, 3-methylbut-2-ene-1-thiol is present in Corona beer (and other brands sold in clear bottles, to a lesser extent MBT is also found in green bottled beer). For some references to “skunky” off flavours in beer check out these links: here, here and here. The ubiquitious slice of lime served with Corona beer is nothing but clever marketing since it helps camouflage the smelly thiol formed! (but how well does lime actually camouflage the thiol aroma?)

The take home message is: keep your olive oil, milk, butter and beer away from sunlight!

1. Use good and fresh raw materials of the best quality available.

2. Know what temperature you’re cooking at. A dip probe thermometer with a digital read out is a cheap way to bring science into your kitchen.

3. Get a basic understanding of heat transfer, heat capacity and heat conductance. “Heat” in this context des not imply high temperature since it also applies to the understanding of freezing/thawing.

4. Learn how to control the texture of food. Some key points: temperature induced changes (freezing, heating), emulsifiers, thickeners, gelling agents, moisture content, pressure/vacuum, osmosis.

5. Learn how to control taste and flavor. Some key points: flavor pairings, spice synergies/antagonies, influence of temperature (Maillard reaction, caramelization, temperature stability, volatility), taste enhancers, taste suppresants, solubility of flavour compounds in fat/water, extraction.

6. Remember that prolonged exposure to a flavor causes desenzitation, meaning that your brain thinks the food smells less even though it’s still present in the same amount. Therefore, let different flavours enhance each other. Similarly, variation in taste, texture, temperature and color can open up new dimensions in a dish. This is referred to as “increased sensing by contrast amplification”.

7. Be critial to recipes and question authority – they do not necessarily represent “the truth”. Nevertheless, you can certainly learn a lot from the experts.

8. Dare to experiment and try new ingredients and procedures. Do control experiments so you can compare results. When evaluating the outcome, be aware that your own opinions will be biased. Have a friend help you perform a blind test, or even better a triangle test to evaluate the outcome of your experiments.

9. Keep a written record of what you do! It would be a pity if you couldn’t recreate that perfect concoction you made last week, simply because you forgot how you did it.

10. Have fun!

Heat causes many changes in food, but few appreciate how important it is to know at what temperature they are cooking and at what temperature the desired change occurs.

These tips for molecular gastronomy relate to the technical and scientific aspects of food preparation and eating, and I plan to elaborate on each of the points in separate blog posts. However, according to Hervé This’ definition of molecular gastronomy, one should also investigate the social and artistic components of cooking. A good example of this is the “Five Aspects Meal Model” developed at Grythyttan in Sweden (Gustafsson, I.B. et al. Journal of Food Service, 2006, 84.). Although intended for a restaurant setting, the general idea can also be applied for home cooking.

The meal takes place in a room (room), where the consumer meets waiters and other consumers (meeting), and where dishes and drinks (products) are served. Backstage there are several rules, laws and economic and management resources (management control system) that are needed to make the meal possible and make the experience an entirety as a meal (entirety – expressing an atmosphere).

Or to put it differently: average food eaten together with good friends while you’re sitting on a terrace with the sun setting in the ocean will taste superior to excellent food served on plastic plates and eaten alone in a room with mess all over the place.

One last thing: once you’re finished in the kitchen with your culinary alchemy, your gastro physics, your cutting edge science cuisine, your molecular cooking, your hypermodern emotional cooking, your science food or whatever fancy name you attach to it – remember the social and artistic components when you serve the food. Just so people won’t refer to you as a techno chef, a mad scientist or a modern day Willy Wonka. After all, molecular gastronomy is about the science of deliciousness, not technical wizardry.

Questions and topics for future blog posts are welcome at webmaster [a] khymos.org (substitute @ for [a]) or as a comment below.