Archive for the ‘tips & tricks’ Category

Ten tips for practical molecular gastronomy, part 9

Saturday, May 31st, 2008

9. Keep a written record of what you do!

Wouldn’t it be a pity if you couldn’t recreate that perfect concoction you made last week, simply because you forgot how you did it? Last year I made a vegetable soup to which I added garam masala and pepper. I was cooking ad lib, adding a little of this and that without taking notes… Which is annoying, because it turned out very nice! It had a remarkable aftertaste which gave me a somewhat dry feeling on the back of the tongue and it reminded me of mangoes. Even immediately after the meal I wasn’t able to recall all the ingredients.

As an undergraduate student I took an organic chemistry lab course, and I remember we were told not to use post it notes or small pieces of paper for taking notes. Everything should be recorded in a proper journal or – if necessary – small note books. Having finished my Ph.D. a couple of years later, I can only testify to this. Everything you do – be it in the lab or in the kitchen – should be recorded immediately in a journal. It’s amazing how something that was obvious one day, slips your mind a week or month later.

There is a wonderful Donald Duck story by Volker Reiche entitled “The soul of science” (the original appeared in 1981 in the Dutch Donald Duck magazine). At a point “Professor Duck”, who actually works as a janitor in a lab, utters the words “Careful notes are the soul of science” as he is caught experimenting. This is true also for the kitchen and experimental cooking. A German translation of the story was reprinted in the article “Das Leiden des cand. chem. Donald Duck” (open access) in case you want to read the whole story.


Careful notes are also the soul of kitchen science!

When taking notes it’s essential that you are able to re-cook the dish yourself. But if no one else is, the notes are of limited value. The biggest source of uncertainty in the kitchen is the widespread use of volume for measuring powders. This can best be illustrated by the question: How much does a cup of flour weigh?

I bumped into this when I began baking no-knead bread (recipe). I converted the recipe to metric units using an online calculator, but the no-knead bread wasn’t a huge success. The problem was that there is no simple answer to the question “How much does a cup of flour weigh?”. Cooking conversion online states that a cup of all-purpose flour weighs 99 g. King Arthur Mills claim that all their flours weigh 113 g/cup. USDA states 125 g/cup and Gold Medal 130 g/cup. Some cookbooks have settled at 140 g/cup (apparently because this is about half way between a loosely and densly packed cup) and if the flour is hard packed you can reach 160 g/cup. In other words – when following a recipe you would need to know how the volume of flour was measured in order to use exactly the same amount of flour. Some recipes call for “spoon and level” or “scoop and level”, but many do not include any information about this.

My recommendation is to weigh all dry ingredients (and preferably also the wet ingredients). A normal digital kitchen scale typically has a resolution of 1 g with an accuracy of +/- 5 g and they are quite affordable. Weighing liquids is also far more accurate than the average volume measurement in the kitchen. If the scale has a “tara” function it’s also much faster as you can zero the display after each ingredient you add. It shouldn’t come as a surprise that I’m not the only chemist advocating weight measurements in kitchen. And it’s not difficult finding other sites in favor of weight measurements either.

It therefore puzzles me why recipes that call for the following are still so abundant:

1 pack of instant yeast
1 envelope unflavored gelatin
1 gelatin sheet (see comment #4-5)
1 sachet powdered pectin
1 tablespoon liquid pectin
1 stick of butter
… and the list goes on

The only exception to the general advice on weighing ingredients is when very small quantities are used. This could be spices, food coloring or hydrocolloids. With normal kitchen scales, you’ll be better of using volume measurements for amounts less than 5 g (equal to a teaspoon if measuring water). Otherweise it’s worthwhile mentioning that scales with a 0.1 g and 0.01 g readout are getting cheaper and cheaper.

*

There is a summary of the “10 tips for practical molecular gastronomy” posts. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (people/chefs/blogs, webresources, institutions, articles and audio/video) at khymos.org might also be of interest.

Hydrocolloid recipe collection v.2

Wednesday, May 21st, 2008

Texture – A hydrocolloid recipe collection
It’s a pleasure for me to announce that an updated version of the hydrocolloid recipe collection is available for free download as a pdf file (73 pages, 1.8 Mb).

What’s new?
Several new recipes have been added (now counting more than 220 in total), including recipes with cornstarch, guar gum, gum arabic, konjac and locust bean gum. All in all 14 different hydrocolloids are included (plus lecithin which technically isn’t a hydrocolloid). In each section recipes are now sorted according to the amount of hydrocolloid used. The appendix has been updated with tables for comparison of hydrocolloid properties, hydrocolloid densities and synergies. The perhaps biggest change is that all recipes have been indexed according both to the texture/appearance of the resulting dish and according to the hydrocolloid used. Let’s say you want to make spheres, this index will show you which hydrocolloids can be used (that’s right – there are other possiblities than sodium alginate) and list the example recipes.

Foreword
A hydrocolloid can simply be defined as a substance that forms a gel in contact with water. Such substances include both polysaccharides and proteins which are capable of one or more of the following: thickening and gelling aqueous solutions, stabilizing foams, emulsions and dispersions and preventing crystallization of saturated water or sugar solutions.

In the recent years there has been a tremendous interest in molecular gastronomy. Part of this interest has been directed towards the “new” hydrocolloids. The term “new” includes hydrocolloids such as gellan and xanthan which are a result of relatively recent research, but also hydrocolloids such as agar which has been unknown in western cooking, but used in Asia for decades. One fortunate consequence of the increased interest in molecular gastronomy and hydrocolloids is that hydrocolloids that were previously only available to the food industry have become available in small quantities at a reasonable price. A less fortunate consequence however is that many have come to regard molecular gastronomy as synonymous with the use of hydrocolloids to prepare foams and spheres. I should therefore emphasize that molecular gastronomy is not limited to the use of hydrocolloids and that it is not the intention of this collection of recipes to define molecular gastronomy.

Along with the increased interest in hydrocolloids for texture modification there is a growing scepticism to using “chemicals” in the kitchen. Many have come to view hydrocolloids as unnatural and even unhealthy ingredients. It should therefore be stressed that the hydrocolloids described in this collection are all of biological origin. All have been purified, some have been processed, but nevertheless the raw material used is of either marine, plant, animal or microbial origin. Furthermore hydrocolloids can contribute significantly to the public health as they allow the reduction of fat and/or sugar content without loosing the desired mouth feel. The hydrocolloids themselves have a low calorific value and are generally used at very low concentrations.

One major challenge (at least for an amateur cook) is to find recipes and directions to utilize the “new” hydrocolloids. When purchasing hydrocolloids, typically only a few recipes are included. Personally I like to browse several recipes to get an idea of the different possibilities when cooking. Therefore I have collected a number of recipes which utilize hydrocolloids ranging from agar to xanthan. In addition to these some recipes with lecithin (not technically a hydrocolloid) have been included. Recipes for foams that do not call for addition of hydrocolloids have also been included for completeness. Some cornstarch recipes have been included to illustrate it’s properties at different consentrations. Recipes where flour is the only hydrocolloid do not fall within the scope of this collection as these are sufficiently covered by other cook books.

All recipes have been changed to SI units which are the ones preferred by the scientific community (and hopefully soon by the cooks as well). In doing so there is always uncertainty related to the conversion of volume to weight, especially powders. As far as possible, brand names have been replaced by generic names. Almost all recipes have been edited and some have been shortened significantly. To allow easy comparison of recipes the amount of hydrocolloid used is also shown as mass percentages and the recipes are ranked in an ascending order. In some recipes, obvious mistakes have been corrected. But unfortunately, the recipes have not been tested, so there is no guarantee that they actually work as intended and that the directions are complete, accurate and correct. It appears as if some of the recipes are not optimized with regard to proper dispersion and hydration of the hydrocolloids which again will influence the amount of hydrocolloid used. It is therefore advisable to always consult other similar recipes or the table with the hydrocolloid properties. The recipes have been collected from various printed and electronic sources and every attempt has been made to give the source of the recipes.

Since recipes can neither be patented nor copyrighted, every reader should feel free to download, print, use, modify, and further develop the recipes contained in this compilation. The latest version will be available for download from the static Khymos site and will also be announced here. I would like to thank readers for giving me feedback and suggestions on how to improve the collection. Feedback, comments, corrections and new recipes are always welcome at webmaster (a t) khymos ( dot ) org.

10 elements of basic kitchen knowledge

Tuesday, May 13th, 2008


Salt in oil. According to Pierre Gagnaire, this is Hervé This’ main discovery. It allows him to sprinkle salt on dishes without the salt dissolving in water from the dish. Thereby the “crunch” of the salt is retained.

Rob Mifsud, perhaps best know for his Hungry in Hogtown blog has interviewed Hervé This. At the end of the interview Hervé lists 10 elements of basic kitchen knowledge. Some may seem obvious, but they are not, according to Hervé. Here’s the list so you can judge by yourselves:

  1. Salt dissolves in water.
  2. Salt does not dissolve in oil.
  3. Oil does not dissolve in water.
  4. Water boils at 100 °C (212 °F).
  5. Generally foods contain mostly water (or another fluid).
  6. Foods without water or fluid are tough.
  7. Some proteins (in eggs, meat, fish) coagulate.
  8. Collagen dissolves in water at temperatures higher than 55 °C (131 °F).
  9. Dishes are dispersed systems (combinations of gas, liquid or solid ingredients transformed by cooking).
  10. Some chemical processes – such as the Maillard Reaction (browning or caramelizing) – generate new flavours.

Ice cubes and air bubbles

Sunday, April 13th, 2008

Ice cubes are used both to cool drinks, but also to significantly impact the flavour of certain drinks. No matter your motivation, you should never use “old” ice cubes which have been sitting in your freezer for a while. Why? Melt some “old” ice cubes and taste the water. You’ll smell why! The reason is that volatile compounds in your freezer slowly find their way into the ice cubes which for some reason mostly are made in trays without a cover. But as I surfed around, researching this post I discovered that oxo and other producers now sell ice cube trays with lids. That’s a small step forward!

Another thing about ice cubes is that they look nice. I admit that air bubbles can sometimes be quite beautiful (and even artistic when pictured with a macro lens as above), but there are times when I whish I could make perfectly clear ice cubes. At room temperature a certain amount of air is dissolved in water. When you cool water, the solubility of air increases (!), but only until the water starts freezing. At this point the water can no longer keep the air dissolved and a bubble is formed. Vice versa – when you boil water the solubility of air decreases and the dissolved gases escape.

When making ice cubes, the bubbles that are formed can easily escape as long as there is no ice blocking their way. This is sort of a catch 22 situation since the air expulsion is directly related to the ice formation. When making ice cubes in a normal freezer, the ice cubes are cooled from the outside, causing the air to get trapped throughout the ice cube.

Many people have thought about smart ways to achieve this (as a quick patent search shows). There are two strategies to obtain clear ice cubes. Let the gas escape while the water freezes or degas and filter the water before freezing. Icicles are a good example that when running water freezes, it normally produces very clear ice. This is utilized in commercial ice cube makers. Here a “cold finger” is exposed to water that moves. This way bubbles are carried away before they can get trapped. These ice cubes typically are ring or cup shaped. The second method is suggested many places on the net. I’ve listed them here together with some thoughts and discussion.

Degassing
Degas the water (i.e. remove the dissolved air). This is easily done by boiling the water for a couple of minutes and letting it cool again. Some webpages suggest that the process should be repeated for best results.

Slow cooling
If the water is cooled too quickly, the ice will not be able to push the impurities ahead of the freezing interface. But if an ice cube freezes from all sides it doesn’t really help as the bubbles get trapped in the middle. A drawback with slow cooling is that the solubility of gas will increase when the water is cooled and so it will allow more gas to dissolve before the water freezes. So slow cooling should probably be combined with some kind of gas tight cover.

Directional cooling
I’ve been pondering about making trays with insulated sides and cover and a metal base, thereby utilizing the fact that metals are superb heat conductors compared to plastic, wood or glass. The metal would then serve to conduct away heat from the water. Bubbles would form on the ice front, but they would probably escape, rather than become encapsuled into the ice. I’ve tried to illustrate it here:

Turns out that someone has actually patented something similar where metal “fingers” are used to conduct away heat from the center, giving ring shaped ice cubes. Does anyone know if these were ever made for sale? Perhaps an ice cube tray in aluminum would work if one insulates the top so that the cubes freeze from the bottom and up, keeping the water on top free flowing so bubbles can escape.

Layer-by-layer method
There might be a simple (but time consuming) way of achieving directional cooling: By building up the ice cubes layer by layer. Once the first layer is frozen this will help freeze the next layer from the bottom up and so on. I guess layers of 1-5 mm would work, but this needs more testing. My experiments so far have not been very promising. Plenty of bubbles, even with a layer of only 2 mm.

Filtering
Particles can act as nucleation sites for air bubbles. To avoid this filter the water and make sure that all the equipment is clean. Also, don’t use a towel to try your equipment as this will probably leave small fibers behind.

Remove salts
Both tap water and bottled water contain trace amounts of salts. When water freezes these minerals are not incorporated into the ice structure. As a consequence the soluble salts will concentrate in the water that’s not yet frozen. In the end there is so little water left that the concentration of the salts becomes sufficiently high so that the freezing point of this remaining water is lower than the temperature in the freezer (meaning that this water won’t freeze). Other salts, especially calcium salts such as calcium carbonate will precipitate. And these particles can act as nucleation sites. If after boiling water there are particles present, these should be filtered away before freezing. The easiest way to get rid of salts is to use distilled water.

I’ve done a couple of experiments and it seems there is no quick fix. The water in the ice cubes pictured above was boiled for several minutes before freezing, but plenty of bubbles formed as you can see. I also tried the layer-by-layer method, but even in a thin layer of only 2-3 mm I could detect many bubbles. So clearly I need to do more experiments.

What are your experiences with making clear ice cubes?

Osmosis in the kitchen

Wednesday, April 9th, 2008

Lettuce should be fresh and crisp but upon storage water will eventually evaporate. The pressure inside the cells drops and the leaves shrink and become less appetizing. The simple yet effective remedy is to immerse the lettuce leaves in plain, cold tap water. The water will then diffuse back into the cells again. The process is known as osmosis [wikipedia].

For the following experiment I purposly left some lettuce (Lactuca sativa var. crispa, sold in Norway under the name “Rapid”, it’s a Summer Crisp/Batavian cultivar) to really dry out as you can see from the picture.

After approximately 4 hours in water the leaf looks like this. Notice that along the rim the leaf was so dry that the cells were damaged “beyond repair”.

To illustrate this relatively slow process I set my camera to take a picture every minute and left it for almost 4 hours. I then stiched it together and the resulting time lapse movie shows the process speeded up 720x (click if the embedded video won’t work).

The wonderful thing about this simple experiment is that it actually illustrates the essence of a recently rewarded Nobel prize (and I should thank Erik Fooladi for pointing this out to me)! The 2003 chemistry prize was awarded “for discoveries concerning channels in cell membranes”. The swedish Nobel foundation have excellent pages with further explanations for the public and for specialists alongside an illustrated presentation (recommended!). There are even two animations of which the first is also available on youtube (embedded below, poor resolution, download the original for higher resolution!). It shows how water molecules move through cell membranes:

TGRWT #10: Pizza with blue cheese and pineapple

Tuesday, March 25th, 2008

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This piece of art was recently sold at an auction for $ 35 million USD! No … just kidding. Read on to find out more!

For the 10th round of TGRWT I decided to modify one of my favorite pizza recipes. As it already has some blue cheese I decided that I would just add som pineapple to the sauce and see how that would work out. Knowing that pineapple works quite well on pizza (at least I have childhood memories from a pizza place called “Aloha” where they served a “Hawaiian delight” pizza with pineapple, ham and cheese) I was quite optimistic about this combination.

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Normally I don’t use a recipe for the dough. I only remember to use 1 dL water per person. Everything else is added ad lib. But to give you a proper recipe I measured all the ingredients. Using 4 dL water gives approximately 1 kg dough in total. This gives 3 pizzas with a diameter of about 26 cm, serving 3-4 people. If you like you can roll the dough out thinner and make 4 pizzas and stretch the sauce and toppings correspondingly.

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Pizza dough
4 dL water
5 g salt
5 g fresh yeast
580 g flour (plain white)
20 g olive oil

Add salt and yeast to luke warm water (~37 °C) and stir to dissolve yeast. Add flour in portions, reserving about 40 g. Mix/knead well for a couple of minutes. The dough is quite sticky. Add the olive oil. Mix/knead more. Add the remaining flour and fold the dough a couple of times. Cover and let rise for 1-2 hours.

Addition of 2% oil helps to give a lighter texture. But mix/knead the dough first so you form the gluten network before you add the oil. Otherwise the oil will cover the glutenin and gliadin proteins and inhibit the formation of gluten, rendering the dough less elastic.

pizza-sauce-bluecheese.jpg

Pizza sauce
45 g sardines (I used King Oscar “Mediterranean style”)
3 t capers
2 T tomatoe paste
1 clove garlic
4 pineapple rings

Mix everything in a small food processor. (You can also add some olives if you like.)

Blue cheese sauce
75 g blue cheese
75 g crí¨me fraí®che

Crumble the blue cheese, add the crí¨me fraí®che and mix until smooth.

Toppings
1-2 onions, in rings
50 g pepperoni
100 g cheddar, grated

Assemble the pizza as follows. Roll out approximately 330 g dough and place it on a suitable pizza peel (if you forget this you won’t be able to transfer the pizza to the baking stone). Add pizza sauce, blue cheese sauce, onion rings, pepperoni and cheddar cheese. Transfer to a preheated pizza stone and bake at 250-300 °C until nicely browned. Depending on temperature this typically takes around 5-10 min.

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The key to a good pizza is turning up the heat! I usually set my oven around 250 °C, but you can go even higher if you like. Secondly you want to use a pizza stone (also known as a baking stone) to get that nice oven spring and a crisp crust. The picture at the top of this blog post is just a close up of my pizza stone! The black speckles are the carbonized remains of cheese and pizza sauce. I’ve blogged about the science of pizza stones previously:

A baking stone is made from a porous ceramic material. It’s heat capacity is good (much higher than that of a metal plate/sheet) and as a result, when the cold dough is placed on the baking stone, it still has enough heat to make the pizza rise immediately. Secondly, the fact that the baking stone is porous lets it absorb moisture from the pizza. This is what gives the nice crisp crust as it transports moisture away from the pizza.

pizza-stone.jpg

Verdict:
The original version of this pizza (without pineapple) is one of my absolute favorites and tinkering a little with the recipe doesn’t change this. But even so I felt that the pineapple diluted the pizza sauce and that the sweetness took away too much of the saltiness of the pizza sauce. Unfortunately, when making the pizza sauce, I discovered that my tube of tomato paste was empty so I used ketchup in stead. In retrospect I see that this wasn’t a good choice as ketchup is quite sweet. Therefore it’s not fair to say that all the extra sweetness came from the pineapple, but it nevertheless contributed with a lot of sweetness.

The overall flavor was very nice though, and my wife thought this pizza was better. Personally however I prefer the “original”. But perhaps next time I’ll try to add pineapple chunks in stead of churning it together with the sauce so as to concentrate the pineapple flavour more and allow it to come in small “flavor packs” now and then. I think that might work better.

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Serve with red wine and a fresh salad!

Look out for “The Gastronomer”

Wednesday, February 13th, 2008

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(Photo: Mette Randem)

The Norwegian journalist, writer and food lover Andreas Viestad, known to many abroad for his books “Kitchen of light”, “Where Flavor Was Born: Recipes and Culinary Travels Along the Indian Ocean Spice Route” and two seasons of “New Scandinavian Cooking” on television (DVD of season one and two is available), has his debut today in The Washington Post with a new column dubbed “The Gastronomer”. Andreas has let me know that “It will be about food and science – as seen from the kitchen rather than the lab. It is an attempt to create a sort of maverick gastronomy, with recipes”.

The first column entitled “Like Water for Chocolate” is about chantilly butter and chocolate chantilly. Elaborations of Hervé This’ classic recipe in other words!

Andreas is not a scientist, but he has a remarkable capacity for absorbing the writings of Hervé This et al. and transform this into practical advice for the amateur home cook (and my guess is that many pro’s could learn a lot as well). So if you’re looking for extreme cooking á la Adrií , Andreas is not your kind of guy:

Spending hundreds of dollars on sous-vide equipment or ordering stuff weeks in advance and toiling for two days to make a “very interesting” side dish is for people in search of a hobby, not for people who want to make something nice for dinner.

A couple of years ago Andreas invited me to proof read one of his books from a chemical perspective. The book entitled “How to boil water” (only available in Norwegian) had a similar approach as his new column – it was about how the results of food science and molecular gastronomy could be applied to “normal” cooking at home. It was quite interesting, but also challenging, because as a scientist I’m used to a different level of precision when science is involved. But then on the other hand, what Andreas writes is much more readable and entertaining than what most scientists write!

Andreas has attended several of the Erice meetings (the International Workshop of Molecular Gastronomy) and he’s frequently in contact with Hervé This and Harold McGee from whom he gets a lot of inspiration. Although the chantilly is not exactly science, Hervé has told Andreas that:

From a scientific point of view it is nothing, a mere detail, but Pierre tells me it is one of the most useful things I have ever come up with.

In my opinion the chantilly is indeed a very good place to start! Hereby his new column is recommended! And if you have never made a chantilly, why not give the chocolate chantilly a try? I’ve posted a very short recipe previously, whereas Andreas has published a very comprehensive recipe in today’s column. Enjoy!

TGRWT #8: White chocolate soufflé with caviar

Wednesday, January 30th, 2008

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As a late (but just in time for the deadline) response to TGRWT #8 which was announced by Chadzilla in December last year – here is finally my write up on a recipe and a little on the background of this flavor combination which has become a classic in molecular gastronomy.

Heston Blumenthal introduced it around 2002 at The Fat Duck. It’s well worth reading what Heston wrote about this combination back then. He describes how salt can help bring out the flavor of many desserts. At one point he tried caviar and white chocolate – the effect was stunning. He then wanted to find out why this combination was so successful:

I gave some caviar and chocolate to Franí§ois Benzi, who works for Firmenich, the flavourings and perfumes company based in Geneva. He was so surprised at the way that the caviar and chocolate melded together that he excused himself for half an hour while he tried to discover the reason behind the success of this union.

When he returned, the response was that both the chocolate and caviar contain high levels of amines. These are a group of proteins that have broken down from their amino acid state but not so far as to become ammonia. Amines contribute to the desirable flavours that we find in cooked meats and cheeses, among other things.

Some might object to using caviar but remember that there is no need to turn to sturgeon caviar as this species is endangered. I used caviar from Capelin which costs less than $4/€3 for a box of 50 g. As I have never tasted the “real” stuff I’m not the right person to judge about similarity or difference in aroma. And in case you also wondered about the terminology – roe is the fully ripe egg masses of fish whereas caviar refers to processed, salted roe. I decided to make a soufflé and based the recipe loosely on one of the soufflé recipes in my Larousse Gastronomique.

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White chocolate soufflé with caviar
40 g white chocolate
30 g flour
1 dL milk
35 g caviar
3 eggs, separated
nutmeg

Melt chocolate on very low heat. Add 1/3 of the flour and stir, heating gently. Add a 1/3 of the milk and mix thoroughly. Add another 1/3 of the flour, then more milk and so on. Add finely ground nutmeg. Add 3 egg yolks and heat until right before the mixture sets (yeah – I admit – this is not very precise…). Then add the caviar. Beat egg whites stiff and fold them in. Pour into greased soufflé dish and bake at 220 °C for about 15 min.

Verdict: Aromas blend well together, but when eaten alone it’s perhaps a little bland. But I’m quite sure that it could be succesfully incorporated into a menu together with something acidic. The texture was nice, but the soufflé quickly falls together once it’s removed from the oven (I’ll have to post more on the chemistry of soufflés some other time – Hervé This has written a lot about this).

If you try to make this – note that white chocolate doesn’t behave excately like butter when you add the flour. It all got very thick, very fast – that’s why I started adding milk early. I also guess you have to be really careful when heating the whtie chocolate, but I didn’t do any stress tests here.

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This is what the mix looks like before I folded in the egg whites.

For my first attempt at this recipe I used 20 g flour and 15 g caviar. The result was that the caviar sedimented before the soufflé had set, besides the fact that one could hardly taste the caviar at all. On my second attempt however, there was enough flour to keep the caviar suspended until the soufflé set. And one could actually also taste the caviar.

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And now on to the chemistry behind:
I promised that I would come back with more information about the chemistry behind this pairing, but there isn’t very much information out there. There is one paper on aroma development in block-milk which used in the production of white chocolate. This paper lists a couple of volatiles, but only with their relative peak areas. Turning to caviar (or roe), there is a recent paper on flavor characterization of ripened cod roe, and this paper includes qualitative information about odor intensity.

Comparing the list of volatiles, the following volatiles which contribute substantially to the odor of ripened cod roe are also found in block milk (followed by odor thresholds in water, given in ppb, taken from this page):

2-butanone (50000 ppb)
2-methylbutanal (1 ppb)
3-methylbutanal (0.2-2 ppb)
pentanal (na)

Of these, the first has a high odor threshold, so it’s not likely to be an impact odorant in block-milk (and white chocolate). The methylbutanals however probably contribute to the overlapping aroma of roe and white chocolate. I didn’t find any threshold value for pentanal.

One group of compounds which was not mentioned in the paper on cod roe odor from 2004, but which was mentioned in a Russian paper from 1967 are amines (Golovnya: “Gas-chromatographic analysis of amines in volatile substances of salmon caviar”). Considering the fact that trimethylamine has a threshold in the range of 0.37-1.06 ppb, and that trimethylamine is found in block-milk suggests that it might contribute significantly to the odor of both white chocolate and roe. I guess the reason trimethylamine (and the whole range of other, closely related amines) is not found in the odor analysis in the 2004 paper has to do with the analytical method used.

The fact that amines are crucial is further supported by the Guardian article I quoted from in the beginning where Heston Blumenthal describes how he turned to Franí§ois Benzi, a flavor chemist at Firmenich, to find out why white chocolate and caviar is such a good match. Benzi concludes that it is due to the presence of similar amines in white chocolate and caviar.

Clarification of stock and other liquids

Monday, September 3rd, 2007

In a comment to the last post, Chad asked how the clarification with laboratory glass ware works. Here’s how. Basically it’s a filtration. But if you would use a normal filter paper (such as a coffee filter) and let gravity pull the liquid through the filter, it would take ages. By applying a vacuum to the back side of the filter, the stock is sucked through (or pushed if you like by the atmospheric pressure). The are several possible sources of vacuum. The simplest and cheapest is a water aspirator or a handpump. More expensive solutions include a membrane pump or an oil pump. The particles you want to remove are from 0.0001 mm and upwards to > 1 mm. The best thing would be to first pass the stock through a cheese cloth or a muslin, followed by one or more filtrations using filter paper. This would gradually yield a perfectly clear solution. Pictures of a Bí¼chner funnel, Erlenmeyer flask and a water aspirator can be found on the tools page of Khymos. Pictures of a complete setup can be found by googling. If doing this in a kitchen, you would want to have an Erlenmeyer flask of at least 2-3 L as this is where the clearified stock is collected. The Bí¼chner funnel should preferably have a diameter of 12 cm or more.

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The fascinating thing about a filtration like this is that you can also remove color. At the EuroFoodChem XIV conference I was told by Jorge Ruiz of Lamaragaritaseagita that you can make perfectly clear tomato juice by succesive filtrations, starting with a coarse filter and moving to finer filters. All in all, 3-5 filtrations should be sufficient.

Molecular gastronomy at EuroFoodChem XIV

Sunday, September 2nd, 2007

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The conference venue was right next to the Eiffel tower

I’ve just returned from the conference Euro Food Chem XIV which took place in Paris from August 29th to 31st 2007. One of the topics was “Molecular Gastronomy: objectives, development, international collaboration”, which as you might have guessed, was the reason I went there. There were several oral presentations and a whole number of poster presentations of interest to molecular gastronomists. It was great meeting again people who attended the 2004 Erice meeting. I also had the pleasure of interacting with several of Hervé This’ former and present students who share the same enthusiasm for molecular gastronomy and the application of scientific thinking to home cooking.

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Hervé This and myself at the conference dinner (Photo by Daniel Kalnin)

Molecular gastronomy was only one of four topics at the conference, but fortunately Hervé This had arranged a special “Chefs meet scientists” session on the second day of the conference which attracted a large number of people in addition to those attending the EuroFoodChem conference.

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The auditorium was packed for the “Chefs meet scientists” session

Following an introduction by Hervé This, there were presentations of molecular gastronomy activities in France, Spain and Portugal. These activities are directed towards both chefs and the general public. Representatives from Air liquide, a manufacturer of liquid nitrogen, had a presentation of various uses of liquid nitrogen for “cooking” purposes, followed by shorter presentations of tools, techniques and ingredients. The molecular gastronomy blogging community was well represented, and I was delighted to meet the people behind Food for design (Bernard Lahousse from Belgium), Jocooking (Joana Moura from Portugal) and Lamargueritaseagita (Jorge Ruiz Carracal from Spain) – their blogs are hereby recommended!

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Hervé This fills in on Joana Moura’s presentation

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Representatives from Air liquide demonstrating liquid nitrogen applications. In the picture a stainless steel disk has been cooled and is then used as an “inverted griddle”

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Anne Cazor from Cuisine Innovation explains clarification of stock using traditional organic chemistry glass ware

All in all the conference and in particular the “Cheefs meet scientists” session and talking to people was truly inspiring and an excellent opportunity for me to catch up on what is moving in molecular gastronomy these days!