One of the more curious cookbooks I own is a German one entitled “Kochen und Backen nach Grundrezepten” (Cooking and Baking with Base recipes). It was first written in 1932 and has been updated regularily ever since. Each section typically has a standard recipe which indicates the ratios to use followed by suggested variations (just like The improvisational cook). It also has nice summaries of dos and don’ts (just like BakeWise and CookWise), and what really makes the book stand out is that is so compact yet still comprehensive. It’s one of those books I actually use when cooking. Many other books have a little too much text – you have to read a lot to pick up the key points. Anyway – the reason I mention this is that as I read about the new “Ratio” book by Michael Ruhlman (MR books, MR blog), the German cookbook was the first book that came to my mind.

“Ratio: The Simple Codes Behind the Craft of Everyday Cooking” just appeared this month and promises that it “will unchain you from recipes”. That’s a good thing, because by knowing a couple of basic ratios you can cook anywhere without bringing your recipes. I’m quite fond of books like that and look forward to leaf through it once I get my hands on a copy. Bakers have been using ratios for ages, better known as Baker’s percentages, so the concept is not new. When baking bread, knowing that you need 6 dL for each kg flour will make a decent bread (but not necessarily an exceptional one!). Ruhlman extends the concept and describes 33 useful ratios for the kitchen. One examples is cookies, and it’s as simple as 1-2-3: 1 part sugar, 2 parts fat and 3 parts flour. Add flavor according to taste and baking powder and/or eggs for a lighter texture. Now that’s what I call a short recipe! The only thing that puzzles me is why the book has 272 pages… That’s a good 8 pages to explain each ratio But for an experienced cook the only thing you actually need is the ratio. And if you take a close look at the cover it actually displays several of the ratios. I’ve copied them into the table below so they are easier to read. You can find the remaining ratios (covering Stocks & Sauces, Farçir, Fat-based sauces, Custards) in the Barnes & Noble preview of the book. And if you combine these ratios with some of the flavor pairings from “The flavor bible” you should be ready for a lot of fun in the kitchen!

Many cookbooks suggest the following for boiling eggs: 3-6 min for a soft yolk, 6-8 min for a medium soft yolk and 8-10 min for a hard yolk. If you are satisfied with this, there is no need for you to continue reading. But if you’ve ever wondered whether the size of an egg has any impact on the cooking time you should read on. And if you search the ultimate soft boiled egg we share a common goal! From a scientific view point, a cooking time of approximately 3-8 minutes to obtain a soft yolk is not very precise. A number of important parameters remain unanswered: What size are the eggs? Are they taken from the fridge or are they room tempered? Are they put into cold or boiling water? And if using cold water – when should the timer be started? When the heat is turned on or when the water boils? And would the size of the pan, the amount of water and the power of the stove top matter?

A formula for boiling eggs?
I still remember the very first time I heard about a formula to calculate the cooking time for eggs. I was in high school and as a recipe for the ultimate nerd the egg formula gave me a good laugh. Now – many years later – I count myself to this group of nerds And thanks to the internet, google and Peter Barham’s book “The Science of Cooking” – I have been able to find out much more. I haven’t been able to track down the formula I heard mentioned, but the best documented formula nowadays is derived by Dr. Charles D. H. Williams, a lecturer in physics at University of Exeter. He has set up a nice page on the science of boiling eggs and there’s even a pdf with the full derivation of the formula. Given the starting temperature of the egg T_egg, the temperature of the water T_water and the desired temperature T_yolk (all in °C) at the yolk-white boundry, the cooking time t (in minutes) of an egg with mass M (in grams) is given by:

Whenever possible one should use weight measurements in the kitchen, but some times an accurate balance is not available and in those cases we can turn to the Peter Barham’s formula which is published in “The science of cooking”. The circumference of an egg is easily measured around the thick end using a piece of string and a ruler. I used to have a piece of string with three knots at 13, 14 and 15 cm respectively to make it even simpler. The cooking time t (in minutes) for an egg with a circumference c (in centimeters) is given by:

Former colleagues of mine at the University of Oslo have made a nice flash animation to do calculations with Barham’s formula if you’re not too keen to dig out your calculator. Barham states that his formula gives the time for the centre of the yolk to reach the temperature T_yolk whereas Williams mention in the derivation of the formula that it calculates the time for the yolk-white boundry to reach T_yolk. I’m not able to tell whether the formulas actually differ in this respect or not (comments are welcome on this issue!). A comparison of the two formulas for a set of 50 eggs which I weighed and measured shows that for T_yolk = 63 °C and T_water = 100 °C they are quite similar, except for the larger spread of the circumference measurements (see plot below). For higher T_yolk or lower T_water Williams’ formula consistently gives longer cooking times than Barham’s formula. It remains to be seen which of the formulas will be closer to the truth.

The graph shows the cooking time for 50 eggs (sorted by increasing mass) calculated from the mass and circumference using the two formulas shown above with T_yolk = 63 °C, T_water = 100 °C and T_egg = 4 °C. For the given conditions the two formulas give similar results. The most striking lesson learnt is that measuring the circumference is in fact not very accurate, hence the larger spread of these points.

The doneness of the egg depends on the temperature of the white and the yolk. Egg white starts to coagulate in the range 62-65 °C. At these temperatures it is the most heat sensitive protein, the ovotransferrin, which constitutes 12% of the egg white, which coagulates. The major protein of egg white, ovalbumin, makes up 54% of the white and doesn’t coagulate until the temperature reaches 80 °C. The yolk begins to thicken around 65 °C and sets around 70 °C. Further heating to around 80-90 °C produces the crumbly texture typical of hard boiled eggs. Many of these changes are nicely illustrated in the picture of sous vide cooked eggs below, but the changes are also summed up in the following table:

At sea level, the temperature of boiling water is 100 °C. At higher altitudes, the boiling is lowered. As a rule of thumb, the boiling temperature of water is lowered 0.3 °C for each additional 100 m above sea level. For an accurate calculation, check out his calculator. As we shall see later, the formula can of course also be used prepare eggs at sea level, using water kept at temperatures less than 100 °C. Lastly we must know the starting temperature of the egg which will typically be 4 or 20 °C.

Based on T_water = 100 °C, T_egg = 4 °C and T_yolk = 63-67 °C I’ve prepared plots for the range of 50 eggs used in the previous graph. If the circumference or mass of an egg is known, the boiling time in minutes can easily be determined from the graphs. I’ve also prepared downloadable pdfs with the circumference and mass plots.

Cooking time for eggs with given circumference or mass to reach to reach 63, 65 and 67 °C respectively at the yolk-white boundry with T_water = 100 °C and T_egg = 4 °C (click for larger image or download pdfs with circumference and mass plots)

But is this the perfect egg?
No actually not… keep reading! The problem with using boiling water is that while you do heat the yolk to the desired temperature, you have virtually no control with the temperature of the white. If your water holds 95-100 °C, so will the white (or at least the outer most part of the white). This gives it a firm, rubbery texture. So the problem is, to put it differently, that we want to heat the yolk to somewhere above 65 °C, but we do not want to heat the white above 80 °C. The solution to this problem is to “boil” the egg at a temperature lower than 100 °C, which means not to boil it at all but rather sous vide it! Eggs are perfect for sous vide because you can just drop them into the water bath as they are. No plastic bags or vacuum packaging are required. Douglas Baldwin has cooked eggs sous vide for 75 min at different temperatures ranging from 57.8 to 66.7 °C as shown below. Notice how the egg whites and egg yolks change at the different temperatures.

Composite image of eggs cooked sous vide for 75 min at the indicated temperatures (Photo: Douglas Baldwin. Picture used with permission.)

The surprising thing with some of the sous vide eggs is that they are inverted (or opposite boiled). The white is still runny while the yolk is set. If you would like to try this but don’t have a thermostated water bath for sous vide you can improvise a little. The thermostat most people do have in their kitchen is the baking oven (at least those with electric stoves). Preheat your oven to 70 °C. Then heat 1 L of water to 65-70 °C, put the eggs in, cover with a lid and leave the pan in the oven for one hour. The tricky thing here is that oven thermometers are notoriously wrong so use a separate handheld thermometer to check your oven. With some trial and error you should be able to obtain an inverted egg with a runny white and a yolk that has set.

Although scientifically amusing the inverted egg isn’t really desirable form a culinary viewpoint – the white is a little to runny. Regrettably the formulas presented above aren’t of much help either. They fail because they only take time and not temperature into account. The perfect soft boiled egg in my opinion would have an egg white which is heated to around 70-80 °C and a yolk with temperatures ranging from 64 °C at the yolk-white boundry to about 60 °C in the center. I guess it would be possible to prepare such eggs in a sous vide water bath held at 75-80 °C in less than an hour. A further complication of cooking eggs in real life is that they continue to cook when removed from the hot water. Normally this is alleviated by shocking the eggs in cold water, but if cooked at a lower temperature this could possibly be omitted. I will start experimenting to find a perfect mass-time-temperature combination with a time window that’s as large as possible, and I’ll report the results in a future blog post. And these experiments will also include a test of the recipe for eggs cocotte by Joël Robuchon, found via Chubby Hubby’s post on slow-cooking an egg.

Exotic soft boiled eggs
In his book “Off on a comet”, science fiction author Jules Verne shows that he was actually aware of the possibility of “boiling” eggs at a temperature lower than 100 °C. He has correctly observed that water boils at lower temperature in high altitudes, and that on a fictional comet of appropriate mass, water will boil at 66 °C. The temperature is wisely chosen, because by keeping eggs at 66 °C, you really can’t do anything wrong. From the last paragraph of the excerpt it seems that the eggs were not fully cooked after “a good quarter of an hour”. Of course, there is also no mention about the size of the eggs, so any further speculations end here. But I’ll rather leave it to you to read the excerpt from the Gutenberg e-text version – it’s quite amusing:

The skillet was duly set upon the stove, and Ben Zoof was prepared to wait awhile for the water to boil. Taking up the eggs, he was surprised to notice that they hardly weighed more than they would if they had been mere shells; but he was still more surprised when he saw that before the water had been two minutes over the fire it was at full boil.

“By jingo!” he exclaimed, “a precious hot fire!”

Servadac reflected. “It cannot be that the fire is hotter,” he said, “the peculiarity must be in the water.” And taking down a centigrade thermometer, which hung upon the wall, he plunged it into the skillet. Instead of 100 degrees, the instrument registered only 66 degrees.

“Take my advice, Ben Zoof,” he said; “leave your eggs in the saucepan a good quarter of an hour.”

“Boil them hard! That will never do,” objected the orderly.

“You will not find them hard, my good fellow. Trust me, we shall be able to dip our sippets into the yolks easily enough.”

The captain was quite right in his conjecture, that this new phenomenon was caused by a diminution in the pressure of the atmosphere. Water boiling at a temperature of 66 degrees was itself an evidence that the column of air above the earth’s surface had become reduced by one-third of its altitude. The identical phenomenon would have occurred at the summit of a mountain 35,000 feet high; and had Servadac been in possession of a barometer, he would have immediately discovered the fact that only now for the first time,
as the result of experiment, revealed itself to him–a fact, moreover, which accounted for the compression of the blood-vessels which both he and Ben Zoof had experienced, as well as for the attenuation of their voices and their accelerated breathing. “And yet,” he argued with himself, “if our encampment has been projected to so great an elevation, how is it that the sea remains at its proper level?”

Once again Hector Servadac, though capable of tracing consequences, felt himself totally at a loss to comprehend their cause; hence his agitation and bewilderment!

After their prolonged immersion in the boiling water, the eggs were found to be only just sufficiently cooked; the couscous was very much in the same condition; and Ben Zoof came to the conclusion that in future he must be careful to commence his culinary operations an hour earlier. He was rejoiced at last to help his master, who, in spite of his perplexed preoccupation, seemed to have a very fair appetite for breakfast.

There is in fact no need to head off to other planents to find examples of low temperature prepared eggs. If you go to Japan you’ll find onsen tamago which litteraly translates to “hot spring eggs”. Originally baskets of eggs were lowered into hot springs, but the temperature of hot springs vary so I imagine that there were several types of onsen tamago available (does anyone happen to know the exact temperature of the hot springs used?). After cooking the egg is typically cracked into a bowl of dashi soup with mirin and soy sauce. The challenge of preparing onsen tamago eggs at home is accurate temperature control (just as with sous vide in general). One tip I found was to place the egg on top of rice that has just cooked in a rice cooker. Leave the eggs to “cook” for about one hour while the “keep warm” function of the rice cooker is turned on.

Eggs boiled in onsen (japanese: hotspring), Nagano, Japan (Photo: Miya.m. Permission: GFDL, cc-by-sa-2.1-jp).

I’ve been told that in Finland some saunas are equipped with egg racks. Depending on where the rack is placed one could probably chose between hard boiled and soft boiled eggs. But the sauna would have to be kept warm for a long time due to the slow heat transfer from the hot air. And talking about eggs and saunas: If the eggs are placed directly on the hot stones they will not only be hard boiled, but actually turn completely brown and aquire a nutty flavor. In Korea such sauna eggs are known as Maekbanseok gyeran.

Other aspects to consider when boiling eggs
An egg has somewhere between 7000 and 17000 pores, meaning that water slowly evaporates (the density decreases from 1.086 g/cm³ by 0.0017 g/cm³ daily). This is also why eggs age faster at room temperature than in the fridge. Beacause of the pores, eggs should not be stored next to foods with a strong smell such as onions (unless of course, you want onion flavored eggs). When boiling eggs it is not uncommon that they crack. The most obvious reason is that they are dropped into the water and hit the bottom of the pot. Another reason for cracking is the expansion of trapped air at the blunt end of the egg. This air cannot escape fast enough through the small pores. Conventional wisdom has it that piercing a small hole in the blunt end will let expanding air escape to avoid cracking. It turns out someone has actually scientifically tested this (with 1000 eggs) and their finding was that there was little cracking for fresh eggs, regardless if they were pierced or not. Piercing reduced the cracking of 5-day old eggs and totally eliminated cracking of 28-day old eggs. The authors theorize that the air pocket grows due to evaporation (meaning there is more air to expand) and that the egg shell of fresh eggs is porous but that the pores gradually become clogged upon storage. Curiously the abstract concludes with the following sentence (this was written in 1973, but it’s still quite unusual for a scientific journal):

Housewives should pierce eggs before boiling them, since if they are fresh it will do no harm and if they are stale it will prevent splitting.

We can safely assume that the advise holds true for men as well! Apart from piercing holes to avoid cracking it is possible to reduce the potential damage from cracking by addition of salt or vinegar to the water. This will help the egg white coagulate faster and thus plug any crack formed.

Picture of egg shell pore (Photo: Jim Ekstrom. Permission: Freeware for non-commercial use).

The suggested temperature range for the roast beef was from 60 °C for a pink interior to 68 °C for grey meat. I settled on 63 °C. I was a little optimistic regarding the timing, so when our guests had arrived and I checked the meat (after 1h 30m) the core had only reached 53 °C. First lesson learnt: meat is a poor heat conductor. I quickly figured that my guests would become very hungry if I were to wait for the core temperature to reach that of the water bath. I therefore turned the water bath up to 68 °C, and put the meat back into the water bath – this time in a normal plastic bag and with a temperature probe at the core. This worked surprisingly well, the pressure of the water pushing out all the air. After another 45 min it had reached 62 °C and I removed the meat from the water bath, saved the juices for the gravy, rubbed the meat with salt and pepper and gave it a quick pan sear with plenty of butter. Despite my bad timing the beef came out extremely moist and tender – I dare say that I have never before achieved such a result with a roast beef in my kitchen! And being my first attempemt at sous-vide with my immersion circulator it was extremely satisfying.

Today I prepared the chicken breast, and I figured that 1h 30m should be sufficient for 700 g of meat. The chicken came out very nice as I served it with fresh pasta, a curry sauce and some salad. Again the meat was moist and tender – and so different from most of the chicken I’ve prepared both at home and been served at restaurants.

I should also mention that I made 68 °C eggs this morning. I left them in the water for 1h. The egg white was very soft – almost runny – whereas the yolk had set but was still very pliable. Comparing this with the eggs over at Fooducation it’s clear that even with constant temperature time does play a role. My 1h @ 68 °C eggs had a white that looked more or less like the white of Erik Fooladi’s 6h @ 65 °C eggs. The are probably several reasons for this, but I guess that the kinetics of protein coagulation are mcuh more complex that one might expect at first. But that’s a different story.

Several comments to my last post asked about pricing and where to buy immersion circulators. Basicallyl any laboratory supplier sells these. And even the simplest models have temperature stability of +/- 0.1 °C or less. Amazon also has a couple of models available from Fischer/Thermo Scientific ranging from around $900-2000.

The products of the Maillard reaction provide tastes, smells and colors that are much desired and lend their charachteristics to a variety of foods. In this post I will focus on the factors that influence how fast the Maillard reaction proceeds. And more specifically I’ll give examples on how the Maillard reaction can be speeded up. This is not about fast food, nor is it about saving time. It’s more about controlling the browning reaction by speeding it up or slowing it down in order to get a desired end result.

The Maillard reaction is, to put it simple, a reaction between an amino acid and a sugar (there’s more on the chemistry at the end of the post). To speed it up you can do one or more of the following:

Chances are you have already utilized this in the kitchen without knowing. When eggs or milk are used for glazing, they act as a protein source for the Maillard reaction, giving a nice brown color. Milk also provides lactose which is a reducing sugar. You’ve probably also observed that temperature does influence browning. Water content is indirectly related to temperature – as long as there is water present, temperature will stay below 100 °C. But once the bread crust dries out the conditions are just right to get the Maillard reaction running.

The same principles are applied to microwaveable pies. The microwaves primarily interact with water and hence only bring the temperature up to the boiling point of water. In order to get sufficient Maillard productcs at these temperatures reducing sugars and amino acids are added to the crust (as exemplified in this patent where dextrose and whey solids are used). Not so surprisingly there is also a patent on how to avoid excessive browning in cookies which calls for addition of a polycarboxylic acid ester to lower pH and hence slow down the Maillard reaction.

Pretzels are an extreme example of how the Maillard reaction can be tweaked. Before baking the pretzels are brushed with lye, a dilute solution of sodium hydroxide, which is very basic. The high pH speeds up the bottleneck of the Maillard reaction (see end of post for details).

A pinch of baking soda can bring out a new taste dimension when browning onions

Another basic ingredient found in most kitchens is baking soda (sodium bicarbonate, NaHCO₃). It’s used as a leavning agent which requires addition of an acid to function. Since it is a weak base, it can be used to increase the pH and hence the speed of the Maillard reaction, for instance when browning onions. This basic task, which isn’t always so easy after all, benefits greatly from a pinch of baking soda (and surprisingly it seems that this hasn’t been done before!). To illustrate this I’ve made a time lapse video of chopped onions being fried with and without baking soda. The frying took 11 min, but things are speeded up about 10x.

Samples taken throughout the experiment are shown in the picture below. Even after 4 min there is a visible difference. After 11 min, the small addition of baking soda has yielded onions which taste remarkably sweet with strong caramel notes, compared to the control which tastes like fried onions.

Another example of how baking soda is used to speed up the Maillard reaction is dulce de leche, a popular sauce/caramel candy in Latin America. It’s made by slowly boiling sweetened milk. Baking soda is not a required ingredient, but is often included. The baking soda gives dulce de leche a darker color and also contributes to the flavor.

Photo by audinou from flickr.com.

It should perhaps be added that baking soda is frequently used in Chinese cooking, for instance in tempura batters and marinades. Once there, the baking soda will certainly speed up the Maillard reaction, but it also affects the texture of meat – I’ll have to return to that topic later.

To round of this post I will briefly touch upon one of the reasons why pH influences the Maillard reaction. The first step involves a reaction between a reducing sugar (depicted as R(C=O)H) and an amino acid (depicted as R’NH2) followed by loss of water to yield a Schiff base. The Schiff base rearranges to the Amadori product (not shown). Of these first steps the formation of the Schiff base is the bottleneck (rate limiting step). The reactivity of the amino acid is influenced by the pH. A simplified reasoning goes like this: At low pH the amino group is protonated, yielding it less nucleophilic. At higher pH, the nitrogen becomes more nucleophilic and at very high pH the amino group can even be deprotonated. It should be noted that the fate of the Amadori product is also in large determined by pH and hence pH will affect more than just the rate, but this is far beyond the scope of this blog post.

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.

For this round of TGRWT I decided to use the recipe (Chocolate Carbonara with Parmigiano Reggiano Cream and a Chocolate-Dipped Grissini Wrapped in Prosciutto di Parma) by Masaharu Morimoto which I’ve blogged about previously. I was quite intrigued by that recipe and wanted to try it! So here it is, converted to metric units with some small adjustments. The original recipe called for 4 eggs, but this rendered the pasta dough to hard. I added two of the whites which were left over from the sauce. BTW this is why one of should better weigh out eggs instead of count them (too bad I didn’t think about his from the beginning so I could have weighed the eggs I used). The original recipe called for bread sticks with chocolate and prosciutto di Parma which I skipped (but which nonetheless sounds like a good accompaniment – as you’re probably aware of meat and chocolate also go very well together!).

Chocolate tagliatelle
450 g plain flour
4 eggs + 2 whites (adjust according to size of eggs)
55 g cocoa powder
1 T olive oil (leave out? – see comment in text)

Knead. Let rest for 30 minutes or more. Use pasta machine to work through dough until smooth. Roll out to desired thickness and cut into tagliatelle or spaghetti.

To start with the dough was not very elastic, so I immediately regretted that I had added the olive oil (which I optimistically added to the dough, hoping that it would perhaps help bind the crumbles together – only to discover that more eggs were needed anyway). The reason for this is that the olive oil interferes with the formation of gluten because it covers the proteins glutenin and gliadin and prevents them from reacting with each other to form gluten. So next time I would try without the olive oil (or at least wait until after the dough had rested before adding the oil to allow time for the flour to be completely hydrated).

I used a manual pasta machine to knead through the dough and make tagliatelle strips of the dough.

The color is wonderful and handling sheets like this certainly sparks new ideas. How about a chocolate lasagna with a custard cream?

When partly dry, the surface easily cracks.

Parmesan cream
5 dL cream (38% fat)
4 egg yolks
100 g sugar
50 g grated parmesan

Bring cream to boil. Remove from heat. Add sugar and parmesan while stirring. Add egg yolks. Whisk and heat to 80-85 °C. Serve with chocolate tagliatelle.

Verdict: Very nice! Because of the rich cream, it’s a good idea not to serve a large plate of it though. As was the case last time I tried the cocoa/parmesan combo, it was as if something was missing. Probably something acidic like lemon or lime. The cream is quite sweet, so the dish would probably work best for a dessert (but a guest I served it too said he wasn’t quite sure whether it was a starter or a dessert). I think a lemon or lime sorbet/sherbet would be nice with it! Or why not try Morimoto’s breadstick with prosciutto?

Tasting the parmesan cream by it self was quite surprising, because – believe or not – it reminded me of vanilla! In fact I’m quite sure that many would be convinced that it was vanilla cream (with a special little twist added). Certainly the color and the texture look a lot like vanilla, but the flavour also reminded me of vanilla. This was perhaps the most fascinating discovery and I’ll certainly have to explore this further. The weird thing of course is that once I start googling for parmesan and vanilla I find both recipes and menu examples (Sour dough loaf with parmesan, vanilla & truffle butter, Fava Bean Custard with Parmesan/Vanilla Foam & Grilled Belgium Endive). There is nothing new under the sun

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 François 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.

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.

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.

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 François 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.

Most popular blogpost
The most popular post by far this year has been the post on how to achieve a “Perfect steak with DIY “sous vide” cooking”. This is also the post which was most commented, counting 42 comments so far. I really enjoy that this topic has become so popular. Low temperature cooking can make a huge difference in people’s cooking, yet it doesn’t require any sophisticated equipment apart from a thermometer. It’s perhaps the best example of a technical application of molecular gastronomy in a home kitchen.

Most popular static page
The khymos site got a jump start in January as the static page on “How to prepare the perfect boiled egg” made it all the way up to the front page of digg.com (many readers left comments here). It’s amazing how this can drive up the traffic on a site!

Most time consuming post
The single post which took the most time to research and prepare was without doubt the one were I presented the collection of hydrocolloid recipes. I spent quite some time searching for recipes and an equal amount of time formatting and converting them all to metric units and shortening down the text. Reception has been good, and since it was published in August, it has been downloaded more than 7000 times. I hope to publish a revised edition in 2008, and I am of course always eager to hear from you, especially if you have some recipes that you think should be included.

Most fun to write
I blog because I enjoy it. But if had to chose which posts were most fun to research and to write, I think the list would include “Perfect steak with DIY “sous vide” cooking”, “Two flavour pairing case studies”, “New perspectives on whisky and water” and “First experiments with sodium alginate”.

TGRWT
The first round of the food blogging event “They go really well together” was launched in April. Since then 7 rounds have been completed with almost 90 submissions in total! I’ve had a lot of fun both preparing dishes and browsing through the round-ups. The current round is on white chocolate and caviar, and since December has been a busy month for most people (including myself), the deadline has been extended to February 1st. So if you’ve never participated before – why not try out one of the “classic” flavor pairings of molecular gastronomy?

DMBLGiT
I admit that I am a passionate amateur photographer, and I have submitted a couple of pictures to the monthly “Does my blog look good in this” contest. But with around 100 contributions every month, and most of them of very high quality, I haven’t had great expectations of winning. Therefore it was a pleaseant surprise that my picture of cherries (used to illustrate “Ten tips for practical molecular gastronomy, part 6″) made it all the way to the top of the August 2007 round of DMBLGiT (click to view gallery).

2008 blog forecast
One of the first things I’ll do in 2008 is to complete the series of post with “10 tips for practical molecular gastronomy” which I started in January. Apart from this I have a number of unfinished projects that only need a little more research and experimentation – so let’s hope that I can find some time for this besides my full time job and my family!

A great thing about blogging is that it allows me to interact with the readers – you. So far there are 514 comments to my 112 posts – thank you very much for taking time to comment my posts! Some of you also contact my by email, and I try my best to answer all emails, but if you haven’t heard back from me – don’t hesitate sending me a reminder to webmaster (at) khymos (dot) org!

Because of all the spam comments (67,506 so far!) it’s difficult to say something about the number of people actually visiting the site, but there’s at least a couple of hundred unique visitors every day which is very nice and encouraging. So to all my readers I just want to say Happy New Year! (and in case you missed it, go back and read “Happy New Year with the Science of Champagne!” from last year).

In the last minutes of the TGRWT #6 I decided to make a simple apple cake and add some lavender. The cake was nice, but I could clearly have used much more lavender. This makes me curious about what experiences the rest of you have made combining apple and lavender.

Apple cake (with too little lavender)
100 g butter
170 g sugar
rind of 1/2 lemon
4 eggs (~210 g)
275 g flour
1 t baking powder
1 dL milk (or cream)
ca. 20 lavender leaves
3-4 apples, thinly sliced
3-4 t sugar

Mix butter and sugar. Add eggs and lemon rind. Mix flour and baking powder and add to the rest. Stir in milk and add lavender. I used leaves for the batter and ca. 15 to decorate the top. Pour batter into greased pan. Insert apple slices. Sprinkle with sugar. Bake at 175 °C for 45-55 min until golden. Cool. Serve with whipped cream.

Having initiated the TGRWT event I figured I should try to see if there was any OAV data available for coffee, chocolate and garlic. I was lucky to find OAVs for coffee (both arabica and robusta beans) and cocoa. To compare coffee and cocoa I sorted the flavour compounds in a descending order based on the OAV, keeping only the 20 first compounds. I turned out that 7 out of 20 key odorants in coffee and cocoa are shared, corresponding to 28/25% and 39% respectively of the total “odor activity” (= sum of OAV of top 20 odorants). Here’s the whole list:

(I hope the authors stuck to the IUPAC naming conventions as I did not take the time to check if synonyms were present in the compounds lists)

To compare this with a random pairing I search for more OAVs and found data for parmigiano reggiano and mango, so I repeated the excercise. Among the 20 odorants with the highest OAVs respectively for coffee and mango there was no overlap. A neglibile overlap was found between cocoa and mango: one odorant (linalool) was present in both with OAVs corresponding to 0.03% and 0.05% of the “odor activity” respectively. The fact that there is no overlap between coffee or cocoa and mango does not imply that they don’t go well together, only that their key odorants don’t match. Parmigiano reggiano and cocoa however had a lot in common, as seen from the table below. In fact 6 out of 20 key odorants, representing 36% and 89% of the “odor activity” for parmigiano reggiano and cocoa respectively.

The degree of overlap between parmesan and cocoa is in fact better than for coffee and chocolate when judging by the percentages (albeit with one less odorant), so this pairing will certainly be included in a future TGRWT event! A quick google search revealed that chef Masaharu Morimoto has come up with a recipe combining cocoa and parmesan:

Chocolate Carbonara with Parmigiano Reggiano Cream

Chocolate Pasta:
1 pound all-purpose flour
4 eggs
½ cup cocoa powder
1 Tablespoon olive oil

Pasta Sauce:
2 cups cream
4 egg yolks
½ cup sugar
½ cup Parmigiano Reggiano

For the Chocolate Pasta:
Sift flour and cocoa powder together and knead in the eggs and olive oil for 15 minutes. Rest for another fifteen minutes then roll and cut in a pasta machine. Heat up a pot of lightly salted water and boil pasta until al dente.

For the Pasta Sauce:
In a medium sauce pot scald the cream. In a separate bowl, whisk together egg yolks, Parmigiano Reggiano, and sugar. Temper this mixture into the hot cream and bring to a light simmer, whisking constantly to prevent curdling.

Unfortunately I couldn’t find any OAVs for garlic, so I haven’t been able to verify the triple pairing forming the basis for TGRWT #1. The claim was that coffee has dimethyl sulfide in common with garlic, and methyl pyrazine in common with chocolate. The table above confirms that coffee and chocolate have several methyl pyrazines in common, but dimethylsulfide is not among the 20 key odorants in coffee. This puzzles me, but there could of course be other volatile compounds that garlic shares with coffee. There should also be quite a difference between raw garlic (not to mention between whole, crushed and possibly even minced) and roasted garlic. If I overlooked something (or perhaps a paper with OAVs for garlic), please drop me an email about this. The OAVs of garlic could easily be calculated if data on volatile compounds in garlic and threshold concentrations are available.

I did a search on coffee, cocoa and garlic on The Good Scents Company website as described previously and found the following compounds either naturally occuring or used for recreating the aroma of coffee, cocoa and garlic:

So there are obviously similarities similarities between coffee, chocolate and garlic, but the question is whether these compounds are key odorants or not.

It’s only fair enough to add that the concept of odor activity values has it’s limitations. Some are related to matrix effects, because thresholds are not necessarily recorded in a matrix mimicking the food product. Possible synergies between flavour compounds are disregarded (examples are known where sub-threshold concentrations are detected in the presence of other volatile compounds). Also, the underlying assumption that the odor intensity increases linearily is not quite correct. The typical intensity vs. concentration curve is more ‘S’ shaped with an expansive, linear and compressive region as shown below. At low concentrations (expansive region) synergism (also known as hyperadditivity or mutual enhancement) is observed. At high concentrations (compressive region) antagonism (or subadditivity or mutual suppresion) is observed. This means that a high OAV overestimates and a low OAV underestimates the impact of the individual compounds. This also means that the odor activity percentages calculated for the pairings above should be take with a pinch of salt. In between these extremes normal additivities are observed.

Even though OAVs are not phsychophysical measures of the perceived odor intensity, they compare quite well with models that take different aspects of sensing into accout. The validity of the found OAV can also be tested by a recombination of the flavour compounds to see how good it imitates the original product studied. I can recommend the freely downloadable article “Evaluation of the Key Odorants of Foods by Dilution Experiments, Aroma Models and Omission” (DOI: 10.1093/chemse/26.5.533) for those interested in reading more about the science.

Despite the drawbacks and limitations I think OAVs can and will be helpful when studying the flavour pairing hypothesis.

Tips: You can read more about OAVs in books which are (partly) available through Google books.