Extraction of peppermint leaves with hot water

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.

Pure mono sodium glutamate from Taiwan

A recent article (found via Harold McGee’s News for curious cooks) featuring Heston Blumenthal as a co-author emphasizes the huge difference in glutamic acid contents between the flesh and pulp of tomatoes. Glutamic acid and it’s sodium salt (mono sodium glutamate or MSG) are responsible for the characteristic umami taste. On average the flesh contains 1.26 g/kg glutamic acid whereas the pulp on average contains 4.56 g/kg glutamic acid. Similar differences are found for several nucleotides which posess similar taste qualities. These differences can explain the perceived difference in umami taste between the flesh and pulp of tomatoes - and is worthwhile considering when cooking.

Those concerned about food with added MSG should read the chapter about MSG in John Emsley’s excellent book “Was it something you ate?”. First thing to note is that you can’t be allergic to MSG because our body needs glutamic acid to function properly. Emsley retraces the history of the Chinese restaurant syndrome (CRS) back to it’s roots in 1968 when a letter was published (R.H.M. Kwok, New Engl. J. Med. 1968, 278, 796) describing a series of symptoms experienced after having eaten at a Chinese restaurant. To make a long story short, in 1993 Tarasoff and Kelly reviewed previous studies and conducted a double blind test which led to the following conclusion:

… ‘Chinese Restaurant Syndrome’ is an anecdote applied to a variety of postprandial illnesses; rigorous and realistic scientific evidence linking the syndrome to MSG could not be found.

Following the publication, a critical reply was published by Adrianne Samuels, to which the authors have replied.

Anyway, it was in John Emsley’s book that I first read about the record levels of glutamic acid found in parmesan cheese: 12 g/kg! That’s nearly three times the amount found in tomato pulp. In some cheeses there is so much that it crystallises out in small white crystals visible to the naked eye. Think about this when you sprinkle your food with parmesan. And if you ever wondered why Italian food tastes so nice, now you know that MSG is one reason (but of course not the only one …).

For TGRWT #2 I made banana marshmallows with parsley. The texture came out nice, but the initially fresh parsley flavour had become grassy/hay-like over night. The litterature I referred to last time suggested that the off-flavour is produced by oxidation of unsaturated fatty acids or polyenes. There are several strategies to avoid this. The first would be not to mince the parsley as finely as I did last time to avoid exposure to the air’s oxygen. If the oxidation is enzymatic, blanching would be helpful. And it would also be worthwhile to see if addition of lemon juice (vitamin C and citric acid, are both antioxidants) would have any effect (however, on second thought this would be strange since parsley already has a lot of vitamin C!). Mirko Junge commented last time that freeze dried parsley would possibly retain more of the freshness and he most generously provided me with several samples of freeze dried parsley. I decided to proceed with the following six types of parsley for my marshmallows:

1. fresh parsley leaves, chopped to pieces of about 2-3 mm (picture above, left)
2. parsley leaves, blanched for 30 sec, chopped to pieces of about 2-3 mm
3. parsley leaves, sprinkled with lemon jucie, chopped to pieces of about 2-3 mm
4. parsley leaves, blached for 30 sec, sprinkled with lemon juice, chopped to pieces of about 2-3 mm
5. freeze dried parsley from Goutess (picture above, right)
6. plain, dried parsley from my local store (picture above, front)

I used the same recipe as last time, but split the whipped sugar-gelatin-banana mixture into six different bowls before mixing with the parsley. I used approximately 0.6-0.8 g of fresh parsley for each of the entries 1-4. I tried to estimate the amount of dried parsley to use by eye, comparing with the amount of fresh leaves. The amount of dried parsley used was less than 0.1 g, so my balance was not of much help. The picture below might give you an idea.

Six different types of parsley were prepared immediately prior to mixing with the marshmallow base to minimize oxidation.

If the term ‘parallel cooking’ has not been invented yet, this might be good time to introduce it.

I let the marhsmallows set between two sheets of greased parchment paper.

Blind tasting of banana parsley marshmallows.

My wife helped me do a blind tasting to avoid any bias. The six marshmallow samples were each associated with a three digit code and presented on a plate to the taster. We both did two rounds each (A1/A2 and B1/B2) and the results are summarised in the table below. The scoring only describes the parsley flavour unless otherwise noted.

Legend:
5 fresh parsley, strong
4 fresh parsley, weak
2 grassy/hay-like parsley, weak
1 grassy/hay-like parsley, strong
0 neither fresh nor grassy, weak overall
- disagreeable
* banana dominates

I was quite surprised once I had decoded the score sheets. Fresh parsley cut into relatively large pieces gave a parsley flavour without any hints of grassy or hay-like off flavours! Blanching or treatment with lemon juice were both detrimental to the parsley flavour, and even more so when combined. The variation observed for could be a result of an uneven distribution of the parsley in the marshmallow (increased parsley flavour if you happen to chew a leaf). The freeze dried parsley didn’t do very well compared with fresh parsley, but outperformed the dried parsley from my local store which didn’t have much flavour at all. Both samples of dried parsley however were dominated by a grassy/hay-like flavour. I should add that the grassy/hay-like flavour in itself is not especially disagreeable, but it does not go very well together with the banana.

The result is interesting and perhaps a little counter intuitive. Generally one would say that a larger surface area (= finely chopped) would enhance the flavour release. This experiment however shows that this is not universally true, especially if the flavours can be oxidized. So next time you make banana parsley marshmallows remember that less chopping gives better parsley flavour.

A while back I saw Evelin’s post on how to make marshmallows for Valentine’s day, and I knew immediately that I would like to give it a try. With TGRWT #2 coming up (that’s the second round of the food blogging event “they go really well together”), I thought I’d make marshmallows with a banana parsley twist. I figured that the banana flavour should fit very well with the soft and airy, yet elastic texture of marshmallows. And I was very curious to find out how the parsley would fit in!

Marshmallows were originally made using egg whites and the sap of the root of the marshmallow plant which were cooked with sugar and whipped into a foam. Today the marshmallow sap and egg white have been replaced by gelatin which is a protein produced from collagen in the connective tissue of animals. Proteins are good at stabilising foams (see previous post on how to make a Vauqelin). Addition of sugar increases the viscosity which stabilizes the foam even more. In marshmallows this is taken to an extreme. A large amount of gelatin is added to a concentrated solution of sugar (and corn syrup). This mixture is whipped for about 10 minutes to incorporate air and to break up larger air bubbles into smaller ones.

The first challenge was to find a suitable recipe. There are recipes that call for sugar only whereas others call for sugar and corn syrup (this recipe also gives a hint on how to substitute fruit purree for water). Corn syrup is added to prevent crystallization. Also some recipes use egg whites which are said to give a lighter texture. I decided to go for a simple recipe and used only sugar. I would also need to substitute mashed bananas for some of the water. Addition of parsley shouldn’t need any special adjustments of the recipe. I ended up with a recipe which is more or less a mixture of all these.

If you’re unsure about the process of how to make marshmallows, Cooking for Engineers has a detailed step-by-step description with pictures. The pictures at the end of this post should also give you an idea of what the texture is like. If you’re still lost, check out this video (the first in a series of six) on how to make mango marshmallows.

Banana marshmallows with parsley
65 g water
200 g sugar
10 g gelatin, bloomed in plenty of water
65 g banana, mashed
parsley (see comment below on why it shouldn’t be finely chopped)

Bring water and sugar to boil while stirring. Remove from heat when temperature reaches 110-115 °C (230-240 F). Add bloomed gelatin sheets and mashed bananas. Whip for 10 minutes (much longer than you think!). Add parsley to taste. Grease a pan, sprinkle with powdered sugar and spread mixture in pan. When set, invert pan on a surface dusted with plenty of powdered sugar and starch. Cut up in desired pieces and coat every cut surface with powdered sugar and starch.

What about the taste? I tasted the mixture before it set and was surprised by how well the banana and parsley blended together. To be honest, it tasted really nice! The next day however, after I had cut the marshmallows into squares, they tasted quite different. The parsley aroma had changed significantly and was more reminiscent of hay, so I was quite disappointed. The banana flavour was still intact, but I felt it was somewhat weaker than in the fresh mixture. Nevertheless, some guests I served it to reached out for both a second and a third piece of my banana marshmallows with parsley, so they couldn’t have been that bad after all. Perhaps it had to do with the texture which was really, really nice!

It turns out that the hay like off flavour of parsley is well known and described in the litterature! See for instance “Hay-like off-flavour of dry parsley” or “Evaluation of the effect of drying on aroma of parsley by free choice profiling”. The molecule responsible for the hay-like off flavour is 3-methyl-2,4-nonanedione. And apparently vacuum-microwave drying of parsley gives less hay flavour.

It is suggested that the hay like off flavour is formed by oxidation of unsaturated fatty acids or polyenes. As a consequence, I would suggest not to chop the parsley (or at least leave large pieces intact) to limit the exposure to oxygen. After parsley has been added, the mixture should be mixed carefully to keep the leaves intact. I used finely chopped parsley when I made the marshmallows in order to increase the release of volatile compounds from the parsley, and I think this is the main reason why I got the hay like off flavour.

Whip until you get a thick, creamy texture.

Spread in a pan greased with butter/fat and sprinkled with powdered sugar.

It’s time to sum up the contributions to the food blogging event They go really well together (TGRWT). There were five seven contributions plus a number of suggestions in the comments to the announcement post and I would like to thank you all very much indeed for taking time to experiment in your kitchens! Here are the results (in no particular order):

Lamiacucina: Candied, chocolate coated Garlic. Garlic cloves were heated in a strong sugar-coffee solution. Cloves were then dried and coated with chocolate. Succession of taste and aroma: strong, unpleasant character of garlic. Bloggers verdict: disappointing!

Blog & White: Chocolate-Coffee Mayonnaise with Garlic. Adapted from Hervé This’ chocolate mayonnaise with added coffee and garlic. Succession of taste and aroma: chocolate aroma is followed by taste of garlic and sweetness of chocolate, coffee aftertaste. Bloggers verdict: Interesting (but wife hates it!).

Should you eat that: Mocha Tofu Mousse with Garlic. Roasted garlic cloves were added to an adapted version of Scharfenberger’s mocha tofu mousse. Succession of taste and aroma: coffee followed by chocolate, then a subtle, sweet, roasted garlic aftertaste. Bloggers verdict: I would definately make it again!

M’s blog: Mocca garlic creme brulee. As the name suggests a creme brulee with espresso, chocolate and a garlic clove. Bloggers verdict: Tasted like mocca creme brulee.

Khymos: Coffee espuma with garlic and chocolate. Coffee and cream espuma with added chocolate and roasted garlic. Succession of taste and aroma: coffee with sweet taste, then a faint chocolate aroma followed by a garlicky aftertaste. My verdict: Aromas blend well together. Would use less garlic for dessert version.

Entries added after first posting:

GrapeThinking: Roasted garlic dipped in melted chocolate with coffee beans. Succession of taste and aroma: Roast garlic doesn’t have much of a smell. Chocolate and coffee always smell good. Bloggers verdict: Good aroma. Taste was good in the beginning; slightly funky aftertaste. Texture of garlic was good.

Kompottsurfer: Espresso-risotto with bitter chocolate, tomatoe and mozzarella (posting in German). Bloggers verdict: Color was a disaster, and difficult to get relative proportions right. But aroma worked out prette nice.

From the different comments it seems that garlic is a difficult beast to tame, especially when used raw. A major challenge is finding the right balance between the aromas. Garlic was either too strong or almost absent. Chocolate and coffee however seem to go very well together (and my preliminary search for odor activity values confirm this - more on this soon!).

I also find it interesting that ratios of chocolate, coffee and garlic used influence the succession of aroma and taste (”>” meaning “followed by”):

Is it a coincidence that coffee is the first aroma noticed in the two “foamy” preparations or is this simply a result of the different ratios used?

I should mention that I also tried to make a chicken mole using the three ingredients. Based on a couple of recipes from the net and some tinkering I ended up with a chicken mole that had a little too much chocolate… It tasted … eh … strange, so I decided to add balsamic vinegar which helped a lot! The coffee blended in very well however, so this is how I would make it the next time using less chocolate:

Chocolate coffee chicken mole
800 g canned, crushed tomatoes
750 g chicken breast,
1 red chili, chopped
2 t chili paste
2 onions, chopped
6 cloves of garlic, chopped
3 dL coffee
150 g pistacchio nuts, chopped
1 t ground cumin
30-50 g dark chocolate
2 T sugar
1-2 T balsamico vinegar

Brown onions. Add the rest and simmer. Season to taste with chocolate, balsamico vinegar and sugar. Serve with rice. Sprinkle with coriander/cilantro or ruccola/rocket salad.

There were also a number of recipe suggestions in the comments to the three posts on the coffee/chocolate/garlic theme.

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!).

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?

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.

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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