Shirley O’Corriher, author of the excellent book Cookwise, will host seminars on molecular gastronomy in New York. First topic is “Better cooking through chemistry” followed by “The science of wine”, The science of beer”, “The science of taste” and “The science of cheese”. More info with directions and how to join here.

There is certainly some overlap between molecular gastronomy, kitchen chemistry, gastro physics, culinary physics and everyday chemistry… That’s why I thought the January 2004 issue of Physics Education would be of interest. It features a section on food physics, covering topics such as melting of chocolate, popping of popcorn, photographing food with visible and infrared light etc. Most of the material is for subscribers only (your local university library probably has a subscription!), but the free material includes a nice article by Jon Ogborn (entitled “Soft matter: food for thought”) on foams, gels and emulsions. Did you for instance know that mayonnaise is thixotropic?

This means that it only flows after a certain minimum stress has been applied (figure 6). This is unusual. Liquids usually flow even under the smallest stress.

Non-drip paint is also thixotropic. It retains its shape, but becomes fluid when enough stress is applied, for example when a paint-roller moves through it. Once the stress is removed, the paint becomes stiff again, as it is then only affected by gravity, and does not flowdown the coated surface. It contains large molecules that form a gel, keeping the paint in place. The gel structure breaks down if enough stress is applied, only to re-form quickly once the stress has been removed. So, paint is liquid on the brush and solid on the wall. Try painting with mayonnaise!

Thixotropic materials are also referred to as shear thinningpedia. However, according to this page, the terms thixotropic and shear thinning are easily confused, so here’s the IUPAC definitions:

Shear thinning: If viscosity is a univalued function of the rate of shear, a decrease of the viscosity with increasing rate of shear is called shear thinning, and an increase of the viscosity shear thickening.

The application of a finite shear to a system after a long rest may result in a decrease of the viscosity or the consistency. If the decrease persists when the shear is discontinued, this behaviour is called work softening (or shear breakdown), whereas if the original viscosity or consistency is recovered this behaviour is called thixotropy.

Ketchup is shear thinning (or was it thixotropic?), and an amusing website has even been set up to investigate “The great Ketchup mystery”.

Their conclusion so far is:

… the next time you whack the bottom of a ketchup bottle [consider this:] Even supercomputers can’t predict the outcome.

In Switzerland, associate professor Marc Heyraud at the department of chemistry at University of Neuchâtel organizes a course series on molecular gastronomy, starting November 1st. Totaling 7 days in Neuchâtel and 2 days in Paris (visiting Hervé This), the course covers many different aspects of molecular gastronomy: history, definitions, basic food molecules such as sugars, proteins and fats, taste, texture and temperature. For more information, download this pdf (note that the course and the pdf are in French).

Look out for the upcoming seminar on molecular gastronomy in Belgium on November 20th, 2006. The program includes scientists Peter Barham and Jorge Ruiz, and chefs Kobe Desramault and Sang Hoon Degeimbre. I wish I could take part!

I just came across this fancy egg boiler. It’s designed by Simon Rhymes and bears the name BEM. The egg is cooked in about 6 minutes by the heat from 4 halogen light bulbs with a total output of 500 W.

It sure looks fancy, but I doubt that these eggs can rival the texture of those prepared by the low temperature methods I have described. The reason for this is that the halogen lamps heat up the eggs above the temperature required for the white and the yolk to set. This gives the white a rubbery texture. And even though the BEM has a timer, you still have to figure out (by experimenting?) for how long to cook your eggs…

I think the best part is the cutting ring with a 125 g mass which is raised and dropped to create a crack around the top of the egg. But there is no need to buy the BEM, because a similar egg cracker can be bought separately here for instance! You place the cup on top of the egg, raise the steel ball and drop it. The energy is transferred to the egg, creating a perfectly circular crack. This is actually very neat!

Here’s some pictures of an experiment I did with strawberries and dry ice (solid carbon dioxide). Dry ice is frozen carbon dioxide which holds a temperature of -78 °C. What is fascinating is that dry ice does not melt - it sublimes, which means that it turns directly into carbon dioxide gas.

The idea was to create a carbonated fruit which gives a sparkling sensation in the mouth. I have used strawberries, but any juicy fruit with a moist surface could be used. Water melons would be perfect!

The chemistry explained in simple terms:

A schematic drawing of the container:

To prevent the plate from touching the dry ice (which would cause the strawberries to freeze), I put in a wooden triangle first.

Put the plate with strawberry halves on top of the wooden triangle. Cover with a kitchen towel (do NOT cover with a tight fitting cover - remember that as CO₂ sublimes, it expands, and this would create a huge pressure ultimately resulting in an explosion), and leave for 30 minutes.

Eat and enjoy!

Update: Carbonated fruit the iSi way!

Spain’s top 10 chefs, including Ferran Adria of El Bulli, were featured at the “Spain’s 10 - Cocina de Vanguardia” in New York. Off the broiler and foodite have nice reports. I particularly fancy their pictures, depicting how laboratory equipment, liquid nitrogen and dry ice is used more and more in restaurant kitchens. I have described a number of tools in this static page. Here’s a couple of pictures from Off the broiler (with my comments added):

Joan Roca uses a Rotavap (rotary evaporator) to capture the volatiles from a mixture of mud and water. The volatiles where then foamed and served with an oyster dish. The nice thing with a rotavap is that by reducing the pressure, you can perform distillations at room temperature.

Methyl cellulose is a versatile thickening agent, although it’s not commonly available for home cooking.

Coconut milk was frozen by first dipping a large spoon into liquid nitrogen, then dipping it into the coconut milk. The shell was then freeze dried. Seems to give a nice texture!

Grilled pineapple with a strawberry sauce that is carbonated using dry ice. This gives the sauce a nice sparkling sensation on the tounge.

Wired has a feature on “Better drinking through chemistry”. This includes a recipe for Eben Freeman’s jellied gin and tonic. This was made for Herve This’ molecular mixology masterclas held at the Ritz in Paris (hosted by Bols, more links here). I found the picture below a long time ago at Drink boy and though it was really cool, but I didn’t quite figure out how it was done. Until now! Enjoy the picture and the recipe.

Jellied gin and tonic, by Eben Freeman
1 frozen lime
2 oz. simple syrup
1 1⁄4 tsp. citric acid
1⁄4 tsp. bicarbonate of soda
1⁄4 tsp. confectioner’s sugar
1 1⁄2 sheets of sheet gelatin
1 oz. gin
2 oz. tonic water
Freeze lime and cut into chips with deli slicer. Coat slices in simple syrup and 1 tsp. citric acid; bake at 150 degrees until crisp. Mix bicarbonate of soda, sugar, and remaining citric acid. Soften sheet gelatin in cold water for two minutes. Warm gin and add gelatin. Pour into a shallow baking pan lined with plastic wrap, add tonic, and refrigerate for two hours. Cut into 1⁄2-inch cubes. Put cube onto lime chip, sprinkle on sugar-soda-acid mixture (the acid combines with the baking soda for a carbonated feeling on the tongue), and serve.

Slightly off topic, but quite amusing: Last night the IgNoble prizes were awarded. Their slogan reads “First it makes you LAUGH, then it makes you THINK”. The 2006 IgNoble prize in chemistry was awarded to a research group studying “Ultrasonic Velocity in Cheddar Cheese as Affected by Temperature”. Just in case you were wondering, melting fat is the reason for the varying ultrasonic velocities observed. And yes - this could be useful for determining mean temperatures in heating/cooling processes acording to the abstract. But why not just use a thermometer?

There was also a nutrition prize awarded to researches who showed that dung beetles are finicky eaters… yuck! My favorite IgNoble this year is the ornithology prize awarded to a team who explored why woodpeckers don’t get headackes!

Ferran Adria’s espresso foam, named “Espesso”, is indeed a fascinating concoction, created in cooperation with coffee producer Lavazza. The word espesso is a combination of espresso and the Italian word spesso, meaning thick. Just luck at the thick lucious foam.

The invention has been commented on thoroughly in the blogosphere. See for instance Skillet Doux and Movable Feast - both feature some nice close-up pictures of espesso (including the one above).

Espesso has been available in Europe since 2002 (anyone know where?), but was just recently introduced in the US. Appearantly, the foam is served warm in Europe, but has been served cold in Chicago, at Lavazza’s three locations there.

According to the reports, espesso is made from espresso and a “secret” ingredient. The ingredients are mixed and left to settle for 12 hours under pressure. The product is then dispensed from the iSi Gourmet Whip (more info here, the propellant gas is nitrous oxide, N₂O). As a chemist I certainly wonder what the “secret” ingredient is? If it is true that espesso has been served both warm and cold, they would need to use a thickening agent which is not very sensitive to temperature. Also, it appears that the foam once served is not stable for more than a couple of minutes.

My best guess would be xanthan and guar gum, or possibly a combination of the two. These hydrocolloids show thixotropic properties - when subjected to pressure/agitaion they soften, but then they jellify again afterwards. In other words - they could be easily dispensed through a siphon and would then solidify in the cup. Also, xanthan and guar gum are relatively temperature independent with regard to their thickening properties. Check out the INICON manuals on texture for great (and FREE!) information on these and several other hydrocolloids.

Update: The Lavazza homepage now features a video and a tool to find your nearest Espesso!

According to Emma Marris at The Sceptical Chymist, Harold McGee, author of my favorite book “On Food and Cooking” has suggested that the term “molecular gastronomy” should be ditched.

He noted that most chefs labeled as molecular gastronomists rejected the label and say that their experiments rarely take place on the molecular level. […] These chefs aren’t looking into molecules, says McGee, “they are cooking with ingredients. They are artists, not chemists.”

Currently, there is a career opportunity for chefs with an interest in science. Heston Blumenthal at The Fat Duck is hiring:

Research Chef Stage - Applicants should give a minimum commitment of 3 months, but a longer stay of up to six months is preferred. The successful applicant will be an enthusiastic chef or culinary student with an interest for the science behind cooking. A background in chemistry or other related science is desirable, but not necessary.

I received an email last week from a supertaster (read more: BBC, Wikipedia) with an interesting question: Certain foods contain bitter substances that only a fraction of the population can taste. Examples include a group of compounds called cucurbitacins, found in melon and cucumbers, and propylthiouracil in broccoli. The question was whether these compounds could be neutralized by any means.

A very simple chemical that neutralized/modifies bitter taste is salt - and the best thing is that you don’t have to be a supertaster to test this. For a simple experiment, take tonic water, taste it and then stir in some salt (start with 1/2 teaspoon). Taste it again - if you can still taste the quinine, add a little more salt. At one point the bitter taste has almost disappeared! This principle might work for cucumbers and melons as well, but of cource there could be totally different taste mechanisms responsible for the bittertaste in the two cases.

It might sound strange to add salt, but in Asia, it is not uncommon to eat different fruits with salt. I am aware of unripe mangoes, guavas and honey dew melon are eaten with salt, a salty spice and soy sauce respectively. Also - some people add a small amount of salt to the water when brewing coffee - this reduces bitterness and rounds of the taste. One last example is how salty food can make a young red wine with plenty of tannins more pleasent to drink. Tannins (polyphenolic compounds) can be both astringent and bitter, depending on their molecular weight (low molecular weight tannins are predominantely bitter whereas larger molecules are more astringent).

BTW, this has also been treated scientifically. See for instance: Breslin, P. A. S; G.K. Beauchamp, “Suppression of Bitterness by Sodium: Variation Among Bitter Taste Stimuli” Chemical Senses 1995, 20, 609-623 (link).

If two different foods share one or more volatile molecules, chances are they can taste pretty nice when eaten together. A further discussion of the science behind can be found here. I justed wanted to share a picture of the simplest possible way this can be done. White chocolate/black caviar (top left - this is one of Heston Blumenthals signature combinations!), strawberries and coriander leafs, pineapple and blue cheese, and banana and parsley. Definitely very strange, but when eaten together, the tastes more or less blend together. Convince yourself and try this at home!

Any readers with fantasy to create exciting dishes based on such flavor pairings? Suggestions and links are welcome!