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!

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.

For the food blogging event They Go Really Well Together (TGRWT #1) I decided to used baked garlic. Baking gives garlic a slightly sweet, mellow taste and I figured this might work well with the soft texture of an espuma. Just make sure you get fresh garlic without green sprouts - they will give a bitter taste.

4 cloves of baked garlic (baked whole, 30 min @ 150 °C)
3.5 dL strong coffee
30 g sugar
40 g chocolate (70% cocoa)
ground cardamom
3.4 g gelatin (= 2 sheets)
1.5 dL heavy cream (38% fat)
1 iSi cream charger

Mix garlic cloves and coffee with blender or hand-held mixer. Add chocolate, a pinch of cardamom and heat while dissolving sugar. Stir in pre-soaked gelatin. Cool, add heavy cream, sift through fine mesh to remove remaining pieces of garlic and fill 0.5 L iSi gourmet whipper. Charge with 1 cream charger and leave in fridge over night. Serve with a drizzle of instant coffee.

How it tastes? In the finished espuma served cold, the first aroma noticed is coffee accompanied by a sweet taste on the tongue. This is followed by a faint chocolate aroma which then gives way for an aftertaste dominated by garlic. It’s quite surprising and the aromas blend well together. I used 30 g of chocolate, but I’ve increased it to 40 g in the recipe since the cocolate aroma was a little weak. As for uses, I think it would go well with a steak for instance. If used as a dessert I would perhaps reduce the amount of garlic to 2 or 3 cloves so as not to overwhelm the guests (unless they frequent the restaurant Garlic & shots in Soho, London where even the beer is served with garlic!).

Preparing for a presentation on flavour pairing, Bernard Lahousse at Food for design visited François Benzi at Firmenich, a large supplier of aroma chemicals and perfume ingredients. Bernard plans to launch a website dedicated to flavour pairing soon, and in the mean time he posts about it on his blog, including this interesting expansion of the flavour pairing concept:

…you can also use foodpairing to pair food that doesn’t match. Like chocolate and garlic. The trick then is to search for a third food product that has something in common with chocolate and with garlic. An example is coffee. Coffee has flavour components in common with garlic: Dimethyl disulfide and with chocolate: Methyl pyrazine.

My challenge to you all is to come up with recipes that include garlic, chocolate and coffee. Any suggestions?

Were you told by your mom to chew each mouthful 20 or 32 times before swallowing? Her rationale was perhaps to prevent you from choking. But it turns out there is a link between chewing (or mastication) and release of aroma molecules. A group of French researchers have studied model cheese systems with varying hardness (J. Agric. Food Chem., 2007, 3066, 10.1021/jf0633793). Their key finding was that in hard cheese, more aroma is released, and it happens at a faster rate than in softer cheeses. It is slightly counter intuitive, because one would expect that volatile aroma molecules would have a harder time escaping from a hard surface than from a soft surface. The reason however is that when chewing a hard cheese our chewing pattern automatically adopts and we chew more intensely. Furthermore a hard cheese will break down into several pieces when chewed, resulting in a greater surface area from which the aroma components can escape into the air.

(Photo by kurafire at flickr.com)

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!

Dominique & Cindy Duby, chocolatiers based in Canada, have put together two “scientific chocolate tasting kits” (one, two). Some of the science behind is explained in their “tasting notes” (copy the text into a wordprocessor to read it). For a review of the first kit, check out Rob and Rachel’s blogpost over at Hungry in Hogtown.

The kits illustrate the use of various hydrocolloids to produce foams, gels, dispersions, emulsions and pearls. The principle of flavor pairing is illustrated and binary taste interactions are explored. They also include experiments to explore crunchy vs. soft textures. Each kit comes with four different experiments and enough ingredients to make 8 servings. Furthermore they let you serve every experiment at two different tempereatures. This is neat because is allows you to explore the great influence temperature has on texture and aroma. Each kit sells for $125 - expensive yes, but from the presentation it seems like a good bundle.

Science tasting kit no. 1

The following is illustrated in kit no. 1:

Experiment 1: foaming of pectin and gelatin gels, spherification of a fruit juice/chocolate emulsion (there’s no info on this, but I guess the spherification is alginate based)

Experiment 2: explore how temperature influences sweet and bitter tastes, make a chocolate emulsion (with cream, strawberry juice, wine, cocoa butter and oil) and serve it at two different temperatures

Experiment 3: explore the fact that “taste” is 80% smell, illustrate how salt can suppress bitterness, use a special powder made from an aromatic liquid and maltodextrin which is then dried under vacuum with microwaves (sort of like freeze drying, only this uses microwaves in stead)

Experiment 4: Hervé This’ double dispersion chocolate “cake” made with chocolate and egg white foam which is set in a microwave oven (described in his Angewante Chemie article on molecular gastronomy), short lived crunchy texture, flavor pairing is illustrated by combining cumin and coffe with chocolate

Science tasting kit no. 2

Kit no. 2 starts of by exploring culinary “equations” which are remarkably similar to (yet somewhat less comprehensive than) the CDS formalism described by Hervé This elsewhere. The following is illustrated in the second kit:

Experiment no. 1: a “whisky” is constructed from ethanol lignin, aromatic aldehydes, sugars, acetic acid, oak flavor, vanilin, malt etc.

Experiment no. 2: ice cream is made without churning using foamed egg whites to incorporate air (is this what Italians refer to as a frozen parfait?)

Experiment no. 3: Hervé This’ chocolate chantilly

Experiment no. 4: meringues floating on a pool of custard sauce drizzled with caramel

If you’d rather reverse engineer the dishes, my list of hydrocolloid suppliers might come handy. The “tasting notes” also gives you some hints if you want to have a go on your own.

A group of Japanese researchers (J. Agri. Food Chem. 2007, 231) has recently shown that the ranking of Japanese green tea can be predicted by careful analysis of several compounds. In the resulting model used for the predictions it turned out that sucrose and glucose contents were most important in predicting the quality of green tea, followed by quinic acid, fructose and caffeine.

(Photo by entso at flickr.com)

Based on this it is tempting to speculate whether the addition of small amounts of sucrose and glucose could improve green tea of lesser quality? Certainly this will not improve the volatiles of the tea, but perhaps it could still improve the overall impression? The amount of sugar should be very small - we are talking about milligrams, not grams.

My first guess would be: no, this will not improve the tea. But with peppermint tea I have noticed that a little sugar greatly improves the aroma. Could the same be the case for green japanese tea?

Some years ago, a group of researches studied the formation of lightstruck flavor in beer (Chem. Eur. J. 2001, 4554). They found that isohumulones, compounds contributing to the bitter taste of beer, decomposed when exposed to ultraviolet light. In a recent blogpost, Harold McGee elaborates on this and it turns out that the way this happens is even more complex than first anticipated. The researchers (J. Agric. Food Chem, 2006, 6123) found that riboflavin (vitamin B2) acts as a photosensitizer in beer (and in olive oil, milk and butter) which catalyzes the conversion of oxgyen to a more reactive type of oxygen (singlet oxygen). This oxygen then “destroys” isohumulone and in the process radicals are formed.

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.

No amount of cooking and preparation - be it traditional, modern or molecular - can fully disguise ingredients of poor quality. No one will probably disagree with this and it’s elementary knowledge for every cook, yet I include it because after all molecular gastronomy is also about the raw materials you use. Do not always reach for the cheapest products. Eat better, but less - it won’t cost you more, because you’ll just get less calories for the same price!

I will also encourage you to support local producers. This will probably make me sound like a slow food practitioner which is fine, because molecular gastronomy is not in any opposition to slow food or traditional cooking, it’s more about understanding the chemical and physical principles underlying all handling and preparation of food. Part of my motivation when writing about molecular gastronomy is actually to bring it a little more down to earth.

When talking about freshness it’s important to consider how food deteriorates. Assuming that safety and toxicological issues are taken care of, from a molecular gastronomy viewpoint it is interesting to discuss flavor. The most important pathways to flavor deterioration include exposure to air (particularly oxygen), light, moisture, high temperature, bacteria and fungi.

The flavor of foods stems largely from the presence of volatile organic compounds. Because of the low boiling point, these compounds easily escape from the food. And at higher temperatures evaporation of aroma compounds is even faster. Also, many of the compounds can react with oxygen in air. A typical example is the oxidation of fats which gives a rancid flavor. Generally, fats and oils should be stored in the refridgerator to slow down this oxidation, but it turns out there’s an exception for olive oil.

To retain as much of the volatile compounds as possible it is advisable to store spices in tight containers kept in a dark and cool place. If you for some reason need to store spices for a long time, put them in the freezer. Since the loss of aroma comounds is proportional to the surface area of the spice, it’s also a good idea to buy whole spices and grind them yourself immediatly prior to use. I would also recommend the use of spice pastes (such as curry pastes for instance) since the oil helps extract aroma compounds. Such pastes should preferably be stored in the fridge.

Like me, you probably have many different spices in your pantry. Some of them have probably been sitting around there for years which is far from optimal. Therefore, as a reminder to myself, I have started to mark each spice with the date of opening (or purchase) using a water proof pen.

With fresh fruit and vegetables, finding the right storage conditions can sometimes be difficult, but this pdf from UC Davis provides a quick overview of recommended storage conditions (ie. what should be stored in the fridge and what should be stored on the countertop).

One last example of the importance of correct storage conditions is the staling of bread. Contrary to popular belief, staling of bread is not caused by evaporation of water from the crumb. This is easily demonstrated when you heat a slice of bread in a toaster or a microwave oven. What happens upon storage is that starch and water crystallize. As a consequence the crumb loses its elasticity and goes stale. The aging process proceeds fastest at 14 °C. Because of this, bread should be stored at room temperature - never in a fridge. When freezing bread, rapid cooling is important because the staling is halted below -5 °C.

*

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.

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

As a followup to the previous posts on chocolate pairings (chocolate sauerkraut cake and chocolate + caraway and other pairings), here’s a picture of an exotic chocolate I got for Christmas. It’s from Schloss Bückeburg in Germany, but a label on the back says it’s made in Austria (possibly by Johannes Bachhalm, one of Austria’s most famous chocolatiers).

Sprinkled on top the chocolate you see green and pink peppercorns! Furthermore it’s flavoured with vanilla, rosemary, juniper and cured red deer meat. What it tastes like? The pepper certainly goes well with the chocolate. Rosemary and juniper add some freshness. The taste of cured meat was more difficult to identify, but I guess it did add som saltiness. All in all very tasty!

One important aspect of molecular gastronomy is the application of scientific principles to food preparation in a normal kitchen. This can very well be illustrated by discussing the preparation of a steak. The surface of the meat needs to be heated to > 120 °C (250 F) for the Maillard reaction to take place at a reasonable rate. This gives meat much of it’s characteristic aroma. The interior of the meat however should not be heated to more than 50-65 °C (120-150 F) for a rare or a medium rare appearance. If the heat is provided by a frying pan with a temperature typically in the range 120-160 °C (250-320 F), the different temperature required for the interior and the surface of the meat can actually be quite difficult to achieve. Bringing the meat to room temperature before cooking by taking it out of the fridge 1-2 hours in advance helps. Also, half way through the cooking it’s advisable to let the meat rest on a plate to allow the heat to diffuse into the interior and to let the surface cool down a little.

There is however an easier way to make a perfect steak! In restaurants the method has been around since the 70’s and is known under the name sous vide (fr. under vacuum, more info on history of sous vide in this NY Times article). The meat is packed in plastic bags, vacuumed and put into thermostated water baths. This equipment is not (yet?) found in the average kitchen. So here is a simple DIY procedure. You just use a normal plastic bag, leave the meat in the water bath for 30 min (or longer) and then quickly fry both sides to generate the products of the Maillard reaction. You do need a thermometer though to control the temperature of the water bath, preferably one with a dip in probe.

1. Put the meat (I used a rib eye steak for this experiment) in a thick plastic bag. Only put one or two pieces of meat in each plastic bag - this ensures a greater contact surface with the water.

2. Add any spices you like (salt and pepper always works well - for the experiment shown I used curry paste, soy sauce and chili sauce in stead), press (or suck) out the air and close the plastic bag tightly by tying a knot (or use a zip-lock bag). You don’t want any water to enter the bag!

3. Heat a pot of water to the desired temperature (or use hot tap water) and place the plastic bag with meat in the water. Cover with a lid (not shown in the picture) to reduce heat loss. If you use a large pot of water it’s easier to keep the temperature constant. Also, it’s easier to control the temperature with an induction or gas stove top than with an electric plate since there is no additional heating once you turn them off. Regarding the temperature, start with 60 °C (140 F) and experiment from there (or check this table at Wikipedia for doneness temperatures of meat). You should leave the meat in the water for at least 30 minutes - more for a thicker cut. But the good thing is you can leave it for much longer (several hours) provided the temperature does not come above 60 °C (or whatever temperature you decided on). A convenient way to keep the temperature constant for a long time is to put the pan with water into the oven and use the thermostat of the oven.

4. Heat a frying pan, add a fat of you choice, remove meat from plastic bag and brown both sides of the meat. Since you take the meat directly from the water bath it’s already at about 60 °C. Therefore the browning is very fast.

5. A temperature of 60 °C (140 F) gives the meat a pink interior. It’s succulent and juicy. The short frying gives it a nice browned crust and the chewing resistance is perfect. All in all a wonderful combination of taste, aroma, texture and mouth feel!

Update: Click for more practical tips on molecular gastronomy

I have been pondering on the chocolate sauerkraut cake I wrote about, and considering the fact that caraway is a spice used in sauerkraut I did some googling… And voilá - I found a page on different chocolate and cognac pairings! In October 2006 a tasting sessions was held for sommeliers - it was hosted by John Campbell (author of “Formulas for flavour”) and sponsored by Hennesy. Here are the chocolate and cognac pairings that were offered:

“Another interesting flavour to arise was the peanut and Merlot vinegar chocolates. Whilst trialing the combination of a merlot vinegar flavoured chocolate and the Hennessy Paradis Extra Cognac we noticed an unexpected third flavour element, present only when the two were combined: peanut. We underscored this unusual taste discovery by adding salted and roasted peanuts. The result is amazing”

“The long tradition of savouring cognac together with a suitably matched, high-quality cigar led us to the logical conclusion that both of these products must contain taste elements that matched or complemented each other. Once we blended various tobaccos and oak it resulted in a smooth underscore of the tobacco taste that is present when smoking a fine cigar. This coupled with Richard Hennessey makes the experience unique. On further experimentation the Ganache itself delivers the aromas slowly, you therefore savour the chocolate as you would a fine cigar.”

Any cooks out there who can come up with recipe suggestions for the different chocolate dishes? I have added theses pairings to the list of other known pairings.

Caraway seeds (photo by Joyous! at flickr)

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).

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)!

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:

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 www.flexitral.com - 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?