Again I was lukcy that all the practical details worked out so I could attend this year’s Flemish Primitives in Brugge. For some one who’s not attended, it’s not so easy to grasp the concept and ideas behind The Flemish Primitives (TFP). And I admit, even though I’ve been there twice it’s not so easy to convey it in a short way. First of all the name is rather cryptic (unless you’re into art) as it refers to early Netherlandish painting. The link to food is described as follows by the organizers of the event (my highlights):

In the 15th and 16th century, ’The Flemish Primitives’ were masters in combining their talent with new techniques. Techniques they developed by interacting with other disciplines like manuscripting, sculpting, etc. This way of working changed the painting techniques in all of Western Europe forever. The event ‘The Flemish Primitives’ wants to continue in the same spirit. Respect for food products and beverages, the knowledge of the classic cooking techniques combined with a stimulation of new techniques and creativity. By promoting interaction between scientists, the world’s most famous chefs and artists, the event wants to deliver a creative boost for the food industry and gastronomy in Belgium and the world.

Considering last year’s sucess it was no big surprise that this year’s event was sold out (and the foyer of the Concertgebouw was equally full in the coffee breaks). And with the memories from last year I arrived in Brugge with great expectations. One main difference from previous years was that the scientific parts were much better integrated throughout the day. Scientists were on stage alongside the chefs, explaining their work. Also, contrary to last year’s back stage kitchen, they had now moved the kitchen onto the stage, flanked by a bar, some sofas and laboratory mezzanine. A good decision!

Flavor pairing (or food pairing as they call it) was the main topic of last year, but even this year flavor pairing was mentioned throughout the day by several people. It’s also obvious that Bernard Lahousse and his team have worked hard to get some of the sponsors of the event to incorporate the idea into their printed material (Belcolade and SOSA).

Flavor pairing diagrams like this one were incorporated into the Belcolade (= Belgian chocolate company) handouts. Similar diagrams for a great number of food items can be found at the food pairing website.

As I see it, one of the main objects of TFP is to find (or even create) new sources of creativity for chefs. And art, science and cooking can indeed be a fruitfull mix for creative exchange and development. Working as a chef is all about constantly finding new sources of creativity. Even among the very best, one can find signs of creative fatigue – it suffices to mention Ferran Adria who recently announced that el Bulli would close down for two years (2012 and 2013). He gives several reasons, but The Times Online reports that according to Spanish culinary insiders the “effort needed to keep dreaming up mouthwatering wonders, has worn him down” (more in a recent Q&A from WSJ). Ferran does however promise to be back in 2014!

TFP 2010 included presentations of five novel technologies and concepts. These included the use of very high pressure for processing of seafood and fruit. This is commonly done in the food industry for preservation purposes, but now it was used mainly for the textural and flavor changes induced. A second device shown was a combined vacuum and freezing chamber were the freezing was effected by liquid nitrogen, allowing virtually any temperature between 0 and -150 °C to be reached within minutes. Regrettably I missed part of the presentation of the third device (due to break out sessions that were running alongside the main program – more on those later). But from the pictures it seemed to be a microfluidic device for precise delivery of flavor essences (feel free to fill me out on this one in the comments!). The last machine presented was a kitchen emulsifier for preparation of emulsions as viscous as Nutella. I’ll post pictures and more info on the gadgets in a separate post.

In the preparations to this years event surveys with chefs and consumers had led to the forumlation of 10 statements on the identity of Belgian gastronomy, which in essence are not too different from the Statement on the ‘new cookery’ which was formulated by Ferran Adria, Heston Blumenthal, Thomas Keller and Harold McGee back in 2006. I think they are well formulated and it’s hard to disagree with any of the statements. I also belive that most of them could be adopted by many chefs world wide by substituting their own country into the statements. I bring the statements here in extenso for your convenience:

1. Local ingredients. Work with regional products.
2. High-quality ingredients. Work with products of the best quality available preferably in Belgium. Work with seasonal products in the right season.
3. Producer orientation. Chefs have the power to control the quality of the ingredients by making specific choices and demands. Belgian chefs are partly responsible for the motivation of producers to supply the highest quality.
4. Consumer orientation. Chefs have the power to broaden the palate and to revalue or upgrade specific products by paying attention to forgotten, seasonal and local products, or products with low intrinsic value.
5. Inventiveness and openness. Be open to new techniques and products. Strive for innovation and improvement.
6. Inventiveness and cooperation. Strive for intensive cooperation between chefs, the industry and the scientific community. Information exchange is particularily important, also between chefs.
7. Innovation and tradition. Innovation and tradition are not opposites. Have respect for traditional Belgian cuisine by including this respect or tradition as such in dishes.
8. Tastiness and well-being. Strive for food which is tasty above all, but also keep in mind to provide a state of well-being during and after the meal.
9. Moral responsibility. Strive for the use of products that have been produced in an ethical, ecological and sustainable manner.
10. Multisensorial tastiness. Strive for an optimum and ample stimulation of all senses of the consumer. Create a socially agreeable and exclusive experience.

Apart from all the journalists present this year there were also a couple of food bloggers present. You may already know the blogs which mainly focus on restaurant reviews: Very good food (Denmark), Food snob blog (UK), High end food (Germany), Food intelligence (France), Cuisiner en ligne (France) and Gastros on tour. I had a chat with some of them and they all have non-food day time jobs, just like myself. Like last year I plan to write several posts on various topics from TFP – and I will publish this as soon as time allows. But in the mean time, check out the blogs mentioned for a perspective and covering of TFP 2010 that will probably be different from mine

Update: There were more food bloggers present: Coolinary (Belgium), Der Kompottsurfer (Germany).

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I also visited The Flemish Primitives in 2009. You can read more about that in my four posts from last year: The Flemish Primitives: A travel report (part 1), Chocolate surprise (part 2), Heston Blumenthal (part 3) and Glowing lollipops (part 4). Final note to readers: This year my travel expenses were covered by TFP and the tourism bureau of Brugge.

If Richard Wiseman’s fork balancing trick is not challenging enough, why not try the fork balancing trick I did for part 8 (where I encourage experimentation in the kitchen) of my Ten tips for practical molecular gastronomy series. You only need two forks, two skewers, a wine cork and a little patience. If interested you can read more about the physics behind the balancing fork trick.

As the name suggests, the TGIF posts are a little less serious than what I otherwise post here at Khymos. I hope you enjoy it

Miss Silvia is full of surprises! She’s been around the house for a year, but only now did she reveal one of her hidden capabilities. Did you know that you can make scrambled eggs with the steam wand of your espresso machine? Me neither. It’s a brilliant idea and one can wonder why no one has done this before. I mean, espresso machines have been around for a while. And as it turns out – according to Kelly’s comment below this was done in San Francisco back in the 90’s. It seems as if the credits for rediscovering these scrambled eggs should go to Chef Jody Williams (and thanks to Jessica at FoodMayhem for posting this). I’ve tried it several times and it works very well. I’d even say that this gives you another reason to purchase an espresso machine with a proper steam wand! Many other reasons can be found in my first post about Miss Silvia.

This is how I make the scrambled eggs: I crack 3 eggs in a 600 mL pitcher (normally used for steaming milk) and press the steam button on my Rancilio. After approx. 10 seconds I empthy the wand of water and wait for another 30 seconds to allow pressure to build up before I start steaming the eggs. Notice that I didn’t even whisk the eggs with a fork – the whirling effect of the steam wand is strong enough to get the eggs properly mixed. With my Miss Silvia it takes about 50 seconds before the steam breaks through to the surface. The eggs actually set in the pitcher and I used a spoon to scoop the eggs out and put them on a plate. Scroll to the end of the post for a video illustrating the whole process.

Make sure you clean the steam wand very well after using it for eggs. The best way of softening the protein residues is to immerse the steam wand in cold water.

I have tried to add a little milk to 3 eggs before steaming, but interestingly I wasn’t able to get this mixture to set properly. I say interestingly, because even though the scrambled eggs failed I figured that steaming perhaps could be a good way of preparing custards. Holding the pitcher one has pretty good control of the temperature, and also very efficient aeration. It could even that this is a more robust way of preparing a custard? This needs experimenting – and you are more than welcome to join me! And why stop with custard? How about a sabayon? Basically any egg based sauce could be prepared with a steam wand.

Update (added on October 25th)
In the comments there was a question about what would happen with egg whites. I had 3 leftover eggwhites so I added some sugar and tried to steam them. They fluffed up very fast and I was not able to control the process. I spooned the result onto a plate and as you can see the result was quite regrettable. The whites lost a lot of liquid.

I also tried to make a simple sabayon using 1 egg yolk, 30 g sugar and 60 mL of white wine. I got a frothy texture, but when I poured into a glass it separated quite fast. I think the main problem here is scale – on such a small scale it’s really difficult to control the temperature. I presume that this could be easier to control by tripling the amounts.

[Found via the Norwegian food blog Ordentligmat]

After 7 days of feeding my sour dough starter “took off” and was ready for baking. Even with a water bath set to 28 °C it took longer than expected. I started off with 100% hydration as this is convenient when you have to feed your starter frequently. Using only whole grain rye flour and water, I fed my starter every 12 hours (I’ve included details of the “feeding schedule” at the end of this post). This time interval is based on the growth cycle of yeast, where the yeast after an exponential growth phase reaches a plateau after 8-12 hours. This is the best time for feeding the starter.

There seems to be a consensus that a wet starter (i.e. 100% hydration) favors growth of lactic acid bacteria (LAB) which in turn produce acids. The low pH after 2 days in my starter suggests plenty of LAB activity, so the main challenge for me was to get the yeast growing. Considering the fact that the yeasts found in sourdoughs prefer areob conditions for growth, I should have whisked in more air with each addition of water. And I wonder if this is the origin of the widespread myth that you “catch wild yeasts from the air”. I’m quite sure whisking helps, but what you do is not to catch yeast, but rather feed oxygen to your starter. This needs testing though! Most starter recipes call for discarding of half or even more of the starter before each feeding. Even though it seems wasteful I wonder if an important effect of this is to dilute the acid produced by the LAB (the flour may also act as a buffer). This acid will to some extent slow the growth of yeasts (even though the sourdough yeasts are far more acid tolerant than the conventional brewer/baker’s yeast Saccharomyces cerevisia).

Bubbles indicating that the starter is active

Regarding temperature the growth optimum for LAB lies around 32-33 °C whereas the growth optimum for yeast is somewhat lower at 28 °C. The sourdough FAQ has further temperature recommendations which are illustarted in the graph below (data from sourdough FAQ). Holding this together with the notion (see for instance p. 272 in “The handbook of dough fermentations”) that lower temperatures (20-25 °C) favor acetic acid production (= stronger flavor) and higher temperature (> 32 °C) favors lactic acid production (= milder flavor) it immediately becomes clear why a starter kept at roomtemperature has little yeast activity and smells of acetic acid. It need not be ruined, but is desperately in need of dilution, aeration and higher temperature.

Effect of temperature on growth of lactic acid bacteria and yeast based on data for optimum growth and no growth from the sourdough FAQ

I’ve kept the starter alive since August and baked with it at least once a week. I make sure that I keep 50-100 g which I store in the fridge. I’ve also frozen a sample just in case. I’ve changed from 100% hydration to 67% hydration, as this simplifies the calculations a little. On the evening before baking day I feed the starter to a total starter weight of approximately 900 g. The next day I bake bread as follows (the exact numbers were calculated using an internet sour dough calculator with the following input: 3200 g total dough weight, 25% starter, 67% hydration of starter and final dough and 1.8% salt):

Sour dough bread
949 g water
1417 g flour *
800 g starter (67% hydration, 25% of total dough)
34 g salt

* for instance 300 g rye whole grain, 200 g rye fine, 300 g whole grain wheat and then plain all-purpose wheat flour up to 1417 g.

Mix water and flour mixed until all flour is wetted. Leave for 15-20 minutes (during which the autolyse proceeds – this eases subsequent mixing). Mix (see more comments below regarding method/machine for this) until dough is smooth, and while mixer is running add sour dough starter. Once the starter has been properly incorporated into the dough, add the salt. Cover and leave to rise until volume has increased 30-100% (I know – this is not very accurate…). I have left it in on my bench top, but while this worked well on warm August days, it seems to be less than ideal on colder October days. Leaving the dough to rise on top of the fridge might be a conventient compromise here as my current waterbath is not large enough to hold the mixing bowl with dough. The reason I use a starter with a 67% hydration is that I can be more sloppy when adding the starter to the sourdough as it will not change the hydration of the dough. After proofing and slashing I bake the breads on a baking stone which is preheated to 250 °C. Right beneath the baking stone I have a small oven proof dish that I fill with boiling water. This helps to moisten the air in the oven and it simulates the steam injection port of professional baking ovens. There are several reasons why this is important. Moist air is a better heat conductor than dry air, and it prevents the surface from drying out too early while baking, resulting in a better oven spring. Furthermore the moist air condenses on the cold surface of the dough which improves gelatinization of the starch. This in turn gives better crust formation. After 10 min at 250 °C I open the oven to let the moisture out, take out the dish with water, turn the heat down to 220 °C and close the oven door. I bake the breads to a core temperature of about 93-95 °C.

Here I bake two 800 g loaves on a baking stone. Notice the dish with water for steam generation.

I should comment on mixing. When kneading by hand I’ve had a tendency to add to much flour. In fact I think this is one of the reasons why I quit baking bread several years ago – I found that the breads I made generally were a little to dry with a poor crumb, and at that time I didn’t really sit down and think about these matters. In retrospect however there’s no doubt that baking bread and adding flour ad lib until the dough feels good to touch is NOT recommended. Well anayway not unless you stop adding flour while the dough is still quite sticky. The thing about doughs with a high percentage rye is that they are quite sticky, and they should be. This is the best argument you’ll ever get for buying a kitchen gadget: bread doughs are too sticky to be kneaded by hand! There you have it! I’ve settled with the Assistent from Sweden. It was formerly sold under the Electrolux brand, but is now marketed indepentendly, yet it is still produced at the very same factory as always. In the US the machine is known as the Magic Mill. It has a huge 7 L bowl that rotates. The roller is attached to a flexible arm, so if the dough is to hard to work the arm just moves to the middle of the bowl. This significantly reduces the chances of overheating the motor. There are of course other alternatives from Kitchen Aid, Hamilton Beach and Viking Range which seem robust, but I have no experience with these. However, I doubt that the average Kenwood can cope with more than 3 kg of bread dough (but please correct me if I’m wrong ).

Unlike most other machines, the bowl of the Magic Mill/Assitent rotates while the roller pushes the dough to the sides of the bowl

Sources for further reading

I’ve read quite a bit about sourdoughs, and what I’ve been looking for a simple correlation between temperature, hydration and fermentation time. An excellent source of information with lots of practical advice is the FAQ from rec.food.sourdough.

I think the best resource I’ve found sofar is Lorenz and Bruemmer’s chapter “Preferments and Sourdoughs for German Breads” and Teija-Tuula Valjakka, Heikki Kerojoki and Kati Katina’s chapter “Sourdough Bread in Finland and Eastern Europe” in “The handbook of dough fermentations”. I will have to study these more carefuly.

There are quite a number of academic publications which also touch upon the effect of temperature on acid development. Here are some snippets:

“Controlled production of acetic acid in wheat sour doughs”:

…temperature has no significant effect, and that fructose is more efficient in influencing the FQ than dough yield.

FQ = fermentation quotient = lactic acid / acetic acid

“Volatile compound and organic acid productions by mixed wheat sour dough starters: Influence of fermentation parameters and dynamics during baking”:

… Low temperature (25 degrees C) and sour dough firmness (dough yield 135) were appropriate for LAB souring activities but limited yeast metabolism. Raising the temperature to 30 degrees C and semi-fluid sour doughs gave more complete volatile profiles …

“Sourdough: a tool for the improved flavour, texture and shelf-life of wheat bread” (Ph.D. thesis of Kati Katina):

The production of acids depends also on other things such as fermentation temperature, time and dough yield. Optimum temperatures for the growth of lactobacilli are 30-40 °C depending on strain (Stanier et al. 1987) and for yeasts 25-27 °C. In general, a higher temperature, a higher water content of sourdough and the utilisation of wholemeal flour enhances the production of acids in wheat sourdoughs (Brummer and Lorenz 1991, Lorenz and Brummer 2003).

I must admit that I’m a little confused as some of these snippets seem to contradict. It might be that I’m overlooking something important though and that I’m taking results out of their context. Any insight from my readers on this will be greatly appreciated!

Starter details
Here’s the details from my notebook on how I fed my sourdough starter. As I mentioned above, I wonder if discarding dough in the process actually does make sense after all.

• July 29, evening: 50 g rye + 50 g water
• July 30, morning: 25 g rye + 25 g water, evening: small bubbles (!), 50 g rye + 50 g water
• July 31, morning: 50 g rye + 50 g water, evening: pH measured to 3-4 with strips, fed with 50 g rye + 50 g water
• August 1: morning: 50 g rye + 50 g water, tested for bread baking, result: not active enough, feeding continued evening: 50 g rye + 50 g water
• August 2: morning: 50 g rye + 50 g water, evening 50 g rye + 50 g water
• August 3: morning: 50 g rye + 50 g water, evening: no bubbles, discarded all except ~100 g, fed with 50 g rye + 50 g water
• August 4: morning: 50 g rye + 50 g water, evening 50 g rye + 50 g water
• August 5: morning: 50 g rye + 50 g water, evening: big bubbles, the starter is active, CO2 production evidenced by tickling in nose, fed with 60 g rye + 60 g water and 2 x 100 g samples taken for fridge and freezer as fallback points
• August 6: morning: 50 g rye + 50 g water, first successfull bread made with the starter

I show my raw data to illustrate that it’s not straightforward, even with temperature control.

A fool proof starter – is it possible?
What I’m hoping to achieve can be summarized as follows: A “fool proof”, robust and quick method to obtain a sourdough starter that’s as simple as possible, using only flour and water (possibly with addition of some fruit) without having to waste anything of the starter. Temperature is maintained using a thermostated water bath. Preferably it should be possible to adjust the fermentation quotient (ratio of lactic acid/acetic acid) and the total titrable acid content by means of temperature, time and hydration/dough yield.

Inspired by the Swedish bread blog Pain de Martin which I recently discovered I decided it was time to have a go at sourdough breads! Although one of my favorite types of bread it’s a long time since I gave it a try and even longer since I actually succeeded. Leaving apple peel covered with water for two weeks in a cool place (15 °C) I got a light apple cider which I used to make a starter some years ago. I followed a recipe from the Norwegian artisan bakery Åpent bakeri and it gave a marvelous bread. But since then I’ve tried to repeat this twice without success. No wonder that even Rose Levy Beranbaum in her book “The Bread Bible” writes that she didn’t intend to include a chapter on sourdough at all. There’s no doubt that sourdoughs are tricky, but I was a litte surprised and disappointed that someone who sets of to write a 600+ page book on bread even considered to skip sourdough… Luckily she changed her mind and the introduction has a fascinating nice-to-know fact: 1 g flour contains about 320 lactic acid bacteria and 13000 yeast cells!

I believe one the reasons why sourdoughs seem to live their own lifes sometimes is that they need to be kept in a warm place. My kitchen isn’t that warm so I figured it was time to use my immersion circulator and give sourdough another chance (who says you can only use immersion circulators for sous vide anyway? – I think my next project will be to make yoghurt!). With a thermostated water bath keeping a sourdough starter at constant temperature is as easy as 1-2-3. But surprisingly I haven’t seen any blogposts yet from people using their sous vide water baths for sourdough starters (although some have built their own water baths for this purpose using aquarium equipment).


Fresh apple peel in water. This particular experiment failed – the cider smelled OK, but there was quite a lot of mould on the surface after two weeks so I didn’t dare to proceed …

It was Martin’s post on an apricot starter that triggered my desire for sourdough (but careful – never close your jar with a rubber as shown in his picture!). I got a bag of dried apricots and gave it a try. There was some bubbling and it smelled quite nice, but the bread dough never rose properly. I later found out that in a comment to the first post and a later post on the same topic it was pointed out that the apricots should not be treated with sulfur dioxide or a sulfite (used to conserve the fruit, appears on labels as E220-228 in Europe). That’s very obvious once you think about it, because the sulfur dioxide/sulfite is there to kill microogranisms and increase shelf life. For a sourdough however you want living microorganisms! The solution to this is to use untreated dried apricots. I haven’t been able to find any yet, but I’ll definitely give it a new try once I find some! Other options of course are to use dried or fresh apples, pears, grapes – preferably not treated with pesticides or sulfur dioxide – as the surface of these fruits are host to many yeasts.

A relatively firm rye starter with 150 g water and 200 g whole grain rye flour (left) shows signs of yeast activity after 24h at 28 °C (right).

Having failed with the apricot starter I decided to give a traditional rye sourdough a try, using a recipe from the book “Brød” (=bread) by “Åpent bakeri”. I got a nice bubbling after 1 day, but the starter was pretty dry. As I discarded a portion and fed more flour and water to the starter it seemd as if it died… I (believe) I followed the recipe very accurately (except for the very first day where I opted for a hydration of 75% instead of 60%), but the final dough never rose, so I had to cheat and add bakers yeast in order to actually get the breads baked. Acid production was fine however and the resulting flavor was very delicious and I got the crumb that I desired! However, with all these problems I figured it was time to turn to the scientific litterature and read more on sourdouhs … More on what I found out in a follow up post.

One last thing: Despite my limited experience with sourdoughs I’ve already been a little annoyed by recipes for starters that require one to discard a significant portion of the sourdough every day before feeding the start with more water and flour. One obvious way around would be to start at a much smaller scale so that every feeding can be done without having to waste any sourdough. In fact Kurt Janz already has a post with detailed instructions on a less wasteful sourdough (and he BTW has one of the most comprehensive sites on sourdough I’m aware of including a sourdough calculator). The only reason I could think of why one perhaps would want to use more than a couple grams of flour to start with would be to outnumber any unwanted yeasts or bacteria from the air or the equipment. Is this the case? Are there any other reasons? To circumvent this one would simple have to work very clean and wash all equipment properly.

Just a small reminder that the deadline for the current round of TGRWT #17 is a little later than usual: May 8th. I took the picture above for last month’s TGRWT (where it was combined with chicken) and came to think that it actually qualifies for this month’s TGRWT as well. It’s rose foam on a spoon with apple, celery and almonds, and the foam is sprinkled with a little pepper.

As an experiment I tried to freeze the leftover rose foam and was quite surprised by the resulting texture. It was easy to scoop due to the incorporated air and had a nice mouth feel. There were no ice crystals and the texture was almost a little chewy. What would one call this? Ice cream? Sorbet? No – there is no cream and the texture is much lighter. Frozen sorbet? Foamed sorbet? Frozen foam? Any suggestions? I think I’ll make a variation of the frozen foam for TGRWT #17

Frozen rose foam

Frozen rose foam is easily scooped due to all the air bubbles

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).

I recently found an interesting article on how an electric field can be used for maturation of wine (New Scientist news coverage of the article). Applying a AC field of 600 V/cm for 3 minutes resulted in an accelerated aging of wine and according to the authors of the paper, it made “harsh and pungent raw wine become harmonious and dainty”. They observed changes in concentrations of higher alcohols, aldehydes, esters and free amino acids. But I was quite surprised that they don’t say anthing about astringency and polyphenols (tannins). I’d expect some changes there as well, but alas it’s so much more difficult to measure the polyphenols than the low molecular compounds. A sensory panel identified both positive and negative effects of the electric treatment which helped identify an optimum treatment. Apparently several Chinese wine manufacturers are testing the technology on a pilot scale now. Many people have a romantic impression of how wine is made, but the extensive catalogues of “corrective chemicals” available to the modern wine maker should perhaps make you reconsider the romatic idea of wine making. Even professor Hervé Alexandre at the University of Burgundy has given the technology a thumbs up: “Using an electric field to accelerate ageing is a feasible way to shorten maturation times and improve the quality of young wine”. Who knows – maybe you’ll soon be drinking a wine that has been zapped?

Moving from industrial scale wine upgrading to kitchen scale gadgets: In his latest “curious cook” column Harold McGee writes about different gadgets that supposedly can change the flavor of wines. To the better of course. He mentions the Wine wand which is supposed to speed up aeration of wines. The promotional explanation on the web page sounds quite dubious, take for instance the claim that the wine wand can “accelerate the aerating process of wine by replicating the natural frequencies of air and oxygen, and infusing them into the wine”. Complete nonsense! Harold McGee however mentions that he did several blind tests and found that there were differences. I guess we can’t exclude the possiblity that there could be some kind of reactive surface on these wands. From the pictures there seem to be some small (glass?) beads in a hollow cylinder. I can’t find any information about the surface. Perhaps it’s been activated or coated with a metal? In that case we could have plenty of surface chemistry going on. If it’s only glass however – well – then I’d just leave the wine to mature in it’s glass bottle.

The other object he mentions is the Clef du Vin or wine key which is more interesting from a chemical perspective. The active part consists of a metal disc which (in a preferred embodiment to quote the patent jargon) consists of 95% copper, 3% gold and 2% silver. According to the description in the patent application, the device is capable of an “accelerated and gauged oxidation-reduction of the wine”. Dipping the disc into a glas of wine for one second is supposed to equal one year of cellar aging. Metals can catalyze many reactions, and there are many reactive compounds in wine so I wouldn’t be surprised if something happens. Considering the fact that sulfurous compounds (such as hydrogensulfide for instance) are very potent, and that sulfur has an affinity to several metals such as gold, copper and silver it seems plausible that the metal disc may actually remove some sulfides from the wine by adsorption and in turn influence the flavor. However, in the course of one second only a small fraction of the wine has been in contact with the metal disc, so I can’t really see how this should be sufficient. It would in a way be strange if only desirable reactions are catalyzed (i.e. only undesirable compounds are degraded/removed). Anyhow – I’d really like to see a peer reviewed paper on this. For someone with spare time and access to a GC-MS this should be a nice project

A stainless steel “soap” is believed to remove garlic stains from your fingers

Interestingly there is a totally different product that relies on the same chemistry: the steel soap. It is typically shaped like a standard soap bar and consists of plain normal stainless steel. It’s supposed to remove garlic, onion and fish smell from your fingers. It works by rubbing your hands against it under running water. I have one, but to be honest it’s hard to really say if it works or not – perhaps some have more experience with it? I had a friend of mine analyze my stainless steel soap by XPS and he gave me the following elemental composition for the six most abundant elements: 70.6% iron, 18.5% chromium, 8.2% nickel, 1.4% manganese, 0.7% molybdenum and 0.3% copper. This is more commonly known as 18/8 steel where 18 denotes 18% chromium and 8 denotes 8% nickel and it’s what all your forks and knives and other stainless steel tools are made of (which of course means that just about any stainless steel object you have in the kitchen should serve the purpose to remove odor from your fingers). Of the metals present here molybdenum in particular is used industrially for desulfurization of oil. Based on a paper on hydrodesulfurization I speculate whether the mechanism could be something like this:

A proposed mechanism for desulfurization on the surface of a “steel soap”

A sulfur compound exemplified here with a thiol (R-SH) reacts with the steel soap surface and the S-H bond is cleaved. Then the S-C bond is cleaved homolytically to yield radical species. The alkyl radical abstracts hydrogen from the surface and escapes whereas sulfur remains bound to the surface. The surface could be regenerated by removal of sulfur with hydrogen. All in all the chemistry of a steel soap seems plausible to me, but I’m not sure whether the effect is significant effect when it comes to removing that garlic smell from my fingers.

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.

I have recently come to know Miss Silvia. She’s from Italy, weighs a good 14 kg and even my wife welcomed her in our kitchen! As home brew espresso afficionados will know by know, I’ve become the proud owner of an espresso machine from Rancilio! She’s been around for a number of years, and is one of the most popular among prosumer espresso machines available before you take the step up to double boiler machines that allow simultaneous brewing and steaming. Every place that is (proud of) serving espresso uses these machines, but their price is well beyond most coffee lovers budget. The good news however is that even single boiler machines can produce excellent espresso!

The first time I offered the science of espresso any thought was when reading Jeffry Steingarten’s accounts of his espresso adventure (in “It must’ve been something I ate”) which brought him all the way to Italy and Illy and then back again to Manhatten where he set up 14 home espresso machines in his kitchen. This is also where I first was made aware of the fact that 7 g of coffee should be used for a single espresso (which is considerably more than the 5-6 grams found in the Nespresso capsules).

Since I decided to buy an espresso machine I have been devouring sites written by and for coffee enthusiasts: CoffeeGeek, Home Barista and Espresso! My Espresso! to mention a few. You’ll be surprised how much one can possibly write about espresso!

Considering the fact that there is a world championship for baristas, it might seem boisterous to claim that I have pulled a couple of decent espresso shots in the last few weeks. They certainly vary in quality, but by preparing and drinking espressos daily I learn more and more as I taste my way through different types of coffee. One thing I feel quite confident of is that preparing an espresso is the the most sophisticated extraction done in any kitchen. Consider these parameters:

coffee beans
roasting
grinding
dosing
tamping
water pressure
water temperature
extraction time
extraction volume

Luckily all of this has been researched in great detail and the last five generally should not be varied at all. To brew a perfect double espresso you should use water at 92-94 °C and a pressure of 9 bar. During an extraction time of 25-27 seconds you should get 60 mL of espresso – no more, no less! To provide enough back pressure you need to tamp the ground coffee relatively hard in the filterbasket. A pressure of 10-15 kg is recommended. As you can see all these parameters are fixed. So the only things left for the barista to vary is the grinding, the dose and of course the choice of coffee beans (including roasting). Since the recommended amount of coffe for a double espresso is 14-16 grams (some extend the range to 12-18 g), you’re basically left with grinding and the choice of coffee beans. Sounds simple, but there’s a lot that can go wrong. I’ll come back to all of this in part II. The espresso should neither be too bitter nor too acidic. And it should have a nice and stable crema.

“Crema, the dense, reddish-brown foam that tops an espresso, is composed mainly of tiny carbon dioxide and water vapor bubbles surrounded by surfactant films. The crema also includes emulsified oils containing key aromatic compounds and dark fragments of the coffee bean cell structure.”

There is one family whose name is forever linked to espresso – the Illy’s. The above quote is from Ernesto Illy’s article “The complexity of Coffee” which appeared in Scientific American, June 2002 (previously available from illyusa.com, now available through the internet archive – it’s highly recommended!).

The illy company was founded by Francesco Illy (1892–1956) in 1933. In 1935 he invented the precursor to espresso machines as we know them today. His son Ernesto Illy (1925-2008) studied food chemistry and worked with illy for his entire career. Francesco’s grandson Andrea Illy (1964-), also a chemist by training, currently acts as chairman of the board. “Espresso is a miracle of chemistry in a cup,” says Andrea Illy (this is as close to pure molecular gastronomy as you will ever get!). The (scientifically) interested reader will probably enjoy the definitive textbook on the subject: “Espresso Coffee: The science of Quality” which Andrea Illy has co-edited. The more artistically minded might prefer “Illy Collection: A Decade of Artist Cups”.

Further reading, listening and viewing
“Discovering La Dolce Vita in a Cup” (NY Times interview with Ernesto Illy from 2001). There is also a video interview with Ernesto Illy available on DVD, “The Complete Dr. Illy Milan Interview”.

Andrea Illy talked about “The Science of Coffee” at the New York Academy of Sciences (podcast) and was also interviewed by CoffeeGeek.

When it comes to preparation of espresso (which I will digg into in part II), “Espresso Coffee: Professional Techniques” by David C. Schomer is the standard textbook most people refer to, in addition to the videos “Caffe Latte Art” and “Techniques of the Barista”. Schomer developed Espresso Vivace with Geneva Sullivan and operates espresso bars in Seattle. The homepage features an extensive archive with articles on espresso by David C. Schomer.

Previous posts in the extraction series: water, ethanol and oil.