Posts Tagged ‘aroma’

TFP2011: Flavor master class with Quico Sosa (part 4)

Sunday, June 5th, 2011

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)


Wonders of extraction: Oil

Friday, October 24th, 2008

Brazilian chiles in oil (very nice with Moqueca!)

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.

Wonders of extraction: Ethanol

Sunday, June 8th, 2008

Extraction of cherries with ~45% ethanol in water

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?

Practical molecular gastronomy, part 5

Tuesday, May 1st, 2007

5. Learn how to control taste and flavor.


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!

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:

  • MSG, IMP and GMP enhance each other
  • IMP and GMP enhance sweetness
  • MSG, IMP and GMP generally enhance saltiness and vice versa
  • Salt enhances MSG, so foods with a natural high level of MSG (tomatoes) taste more if a pinch of salt is added
  • Salt and acid at low/medium concentrations enhance each other
  • Salt at low concentrations enhances sweet taste
  • Black pepper reduces sweet taste
  • Vanilla enhances sweet taste
  • Cinnamon enhances sweet 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).

    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 might also be of interest.

    DJ for your nose: Aroma jockey Odo7

    Friday, March 30th, 2007


    Erich Berghammer, also known as Odo7 [homepage, myspace] is an aroma jockey or AJ for short. He blows scents over his audience with huge fans and has stocked up a pantry with exotic spices, roots, leafs, oils, extracts and herbs. The smells are vaporized using hot water. This video from Roskilde gives you an idea of the set up (but no smells unfortunately).

    From what I can see from his webpage Odo7 has been AJ’ing at clubs, parties, concerts, fashion shows, movie theaters and product presentations. But why hasn’t Odo7 been invited to a restaurant yet? Considering the fact that taste (as used in everyday terms) is 20% taste and 80% smell I could imagine some very interesting eating experiences with an AJ present. Think of it as a way of adding aroma to your food!

    I wonder what smells you would use with the different dishes? Perhaps recreate the smell of sea for the starters (seafood). Then the smell of pine, moss and wood for the main dish (wild boar, elk or reindeer) and finish up with orange blossom for the dessert (strawberries).

    The two last pairings are based on something I recall from the last International workshop on molecular gastronomy in Erice in 2004. Hervé This mentioned that strawberries combined with orange blossom extract, lemon and sugar are reminiscent of wild strawberries! At the same meeting Jack Lang suggested that branches of pine or juniper be placed around the rim of a large serving plate in front of each person. To speed up aroma extraction and vaporization one would pour hot water over the branches and then serve the food (dark meat/wild game) on a smaller plate placed between the branches. This brings us right back to the flavour pairing principle discussed earlier. But now – instead of combining two foods – we can combine a food ingredient or a dish with the appropriate aromas.

    Perhaps at a restaurant experience in the not to distant future you could expect not only a waiter and a sommelier to come to your table, but also an aroma jockey!

    I should also mention that the idea of using essential oils in cooking explored in great detail in the book “Aroma: The Magic of Essential Oils in Foods and Fragrance”. I justed received a copy and haven’t had much time to look at it. The fact that recipes for food and bath foam can be found on the same page might be disturbing for some, but I like the whole concept – simply because it takes the science of taste, eh.. aroma, seriously!

    Ten tips for practical molecular gastronomy

    Saturday, January 27th, 2007

    In a recent survey 72% of chefs say they may want to experiment with molecular gastronomy in 2007. That’s an impressive number and considering the attention molecular gastronomy gets in media I bet many home cooks would want to experiment in the kitchen as well. Here’s a list of things to consider if you want to make a scientific approach towards cooking:

    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] (substitute @ for [a]) or as a comment below.

    Odor recognition by shape or vibration?

    Thursday, December 28th, 2006

    Over Christmas I have been reading Luca Turin’s book “The Science of Scent”. This became a real eye-opener for me with regards to my understanding of how the sense of smell works. (BTW, Luca Turin was also featured in Chandler Burr’s book “The Emperor of Scent” which I haven’t read yet).

    secret of scent cover

    The first part of the book includes a lot of basic chemistry (which can be skipped if you’re familiar with chemistry) plus descriptions of many perfumes and perfume ingredients which made we wish the book came with it’s own smelling strips. But then comes the interesting part. I have always thought of smell to be a result of molecular recognition – a typical interaction between a drug and a receptor or and enzyme and a substrate. The reason I guess is that this seems very intuitive – just like a shape sorter toy for children! I had also read a review article on “Structure-Odor Relationships” (Rossiter, K. J. Chem. Rev. 1996, 3201). Now the interesting thing is that this might be wrong (or at least not the whole truth – and scientific controversy is always exciting)!

    shape sorter

    Luca Turin suggests that it is the molecular vibrations of a molecule that we recognize as it’s smell. In an easy accesible article on this (at least for chemists), Turin puts up pro’s and con’s for both theories, including the following:

  • isosteric molecules smell different (ie. similar shape, different smell)
  • most enantiomeric pairs smell the same, or similar (this is contrasted by medical drugs where enantiomeric purity is often crucial)
  • we smell functional groups (for example alcohols (OH) never smell like thiols (SH), regardless of molecular shape and concentration, this supports the idea that we smell vibrations rather then shape)
  • deuterated molecules (probably) smell different from their protio analogues (experiments here are not trivial to perform, as purity is a major issue here)
  • A very recent review entitled “The Nose as a Stereochemist. Enantiomers and Odor” (Bentley, R. Chem. Rev. 2006, 4099.) mentions Turins work, but with a short dismisal:

    … a theory by L. Turin proposes inelastic electron tunneling to account for the biological transduction of molecular vibrations.[35][36] Recent experiments to test predictions of the theory found no evidence to support it [37]

    Reference 35 and 36 can be downloaded from – the latter needs to be saved/renamed as a pdf before opening. The contents of 37 is described here. It’s surprising however that Bentley uses ref 37 to disprove the vibration theory, because the authors refer to their own work as “… a paper of solely negative results”. What they did was to perform experiments, partly outlined in Turin’s book, that suggest that molecular vibrations alone cannot explain all aspects of smell. Despite the controversy, Luca Turin and his company Flexitral have been quite succesful in designing new odorants, especially stable odorants which imitate other, less stable molecules. The development of these new odorants is based on designing stable molecules with vibrations similar of the molecule it’s supposed to imitate.

    But the story doesn’t end here: Very recently, physicists at University College London reported that they have discovered a physical mechanism that would allow a receptor to distinguish different molecular vibrations (read press release, preprint and SciAm news report). Put simple, the researchers have shown that when a molecule with the correct vibration binds to a receptor, a switch closes allowing electrons to flow. This means that there is experimental theoretical evidence that supports the vibration theory!

    Now what does all this have to do with molecular gastronomy and food? When we talk about taste, it’s actually 80% aroma and 20% taste (more on this page). And with aroma, we’re talking about the smell of volatile molecules. Luca Turin touches upon this on the very last pages of the book were he writes that “An area which, in my opinion, is ripe for revolution is that of flavours”. Perhaps it will be possible one day to “synthesize” any desired odor (or aroma!) with a set of molecules (or condiments) with different molecular vibrations?