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7. Question authorities and learn from the experts

A thick, nicely bound cook book with marvelous pictures and a professional layout signals quality and authority. But unfortunately the nice wrapping is no guarantee that the contents is scientifically sound. I would guess that the searing/sealing myth and adding salt to water used to boil vegetables are among the most ubiquitious of the myths. The challenge for everyone is to question the procedures and explanations given in cook books and those that are inherited from your parents and grand parents. Most of them are fine, but some are not. In fact Hervé This has collected more than 20.000 so called “precisions” from French culinary books that he wants to test.

My seventh tip for pursuing molecular gastronomy in your very own kitchen is to question the cook book authorities, but also to learn from the experts in the field. The site Khymos originally started out as a listing of books and web pages that could be useful for anyone interested in molecular gastronomy and popular food science. When giving presentations it was more convenient for me to refer to a webpage than to have people taking notes of all the references. My own collection of books is constantly growing as you can see from the picture (I justed crossed the 100 cm mark), and I am more than happy to share with you my favorite books. Most of what I know about food chemistry and molecular gastronomy is from these books.

Molecular gastronomy should of course never become a theoretical practice only, so remember that “the proof is in the pudding”, as Nicholas Kurti, one of the pioneers of molecular gastronomy often said. Let taste guide your cooking and learn how to conduct simple blind tastings (more on that in part 8). If possible, do an experiment: if there are two or more procedures, follow them and compare the end result.

Despite the many books and articles that have appeared on food chemistry and molecular gastronomy there are still many questions that remain unanswered. Scientifically, molecular gastronomy is tremendously complex. The science of deliciousness lies in the cross section of analytical, biological, inorganic, organic, physical, polymer and surface chemistry. But even though describing and understanding what happes is difficult, everyone is able to judge the end result! This is quite intriguing and because of this it is possible to become an excellent cook - even if you don’t understand the chemistry behind in every detail. This makes me confident that there will always be an “art” and a “love” component in cooking, as Hervé This puts it in his definition of molecular gastronomy.

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Check out my previous blogpost for an overview of the 10 tips for practical molecular gastronomy series. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry, presentation/photography) and links (webresources, people/chefs/blogs, institutions, articles, audio/video) at khymos.org might also be of interest.

I’m happy to finally announce the first edition of a recipe collection devoted mainly to hydrocolloids. Totaling 111 recipes, it’s available for download as a pdf file (29 pages, 433 kB).

Update: The collection has been revised and is now available for download (more than 220 recipe, 73 pages, 1.8 Mb).

The following text is from the introduction I’ve written to the recipe collection:

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

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

One major challenge (at least for an amateur cook) is to find recipes and directions to utilize the “new” hydrocolloids. When purchasing hydrocolloids, typically only a few recipes are included. Personally I like to browse several recipes to get an idea of the different possibilities when cooking. Therefore I have collected more than 100 recipes which utilize hydrocolloids ranging from agar to xanthan. In addition to these some recipes with lecithin (not technically a hydrocolloid) have been included. Recipes for espumas that do not call for addition of gelatin or other thickening agents have also been included for completeness.
All recipes have been changed to SI units which are the ones preferred by the scientific community (and hopefully soon by the cooks as well). As far as possible, brand names have been replaced by generic names. Most of the recipes have been edited and some have been shortened significantly. In some recipes, obvious mistakes have been corrected. But unfortunately, the recipes have not been tested, so there is no guarantee that they actually work as intended and that the directions are complete, accurate and correct. The recipes have been collected from various printed and electronic sources and every attempt has been made to give the source of the recipes.

Since recipes can neither be patented nor copyrighted, every reader should feel free to download, print, use, modify, distribute and further develop the recipes contained in this compilation. The latest version will be available for download from http://khymos.org/recipe-collection.php and will also be announced at http://blog.khymos.org. Feedback, comments, corrections and new recipes are welcome at recipe.at.khymos.dot.org.

Martin Lersch
Oslo, August 2007

When chopping onions, propanethial-S-oxide is liberated. If this compound is not a chemical, what is it then?

There are many misconceptions about chemicals, and one of the most common ones is that food should be “free” of chemicals. For example, in the article “The future of cuisine?” the journalist writes:

“… the ingredients used in molecular cooking are natural, free of chemicals…”

Most of the hydrocolloids used in molecular gastronomy are certainly of natural origin, I don’t disagree about that. But “free of chemicals” is ridiculous… All ingredients used in the kitchen are chemicals (in a broad sense), albeit some very complex and not always very pure onces!

One of my motivations for being involved with molecular gastronomy and popular food science is to promote the understanding that all food is made up of atoms and molecules. Therefore I would like to present to you the organisation Sense about science which tries to combat common chemical misconceptions. According to their site which is well worth a visit they “promote good science and evidence for the public”. As a chemist I found the section Making sense of chemical stories particularily interesting. I think the report Misconceptions about chemicals (downloadable pdf) should be downloaded and read by every journalist writing a story about molecular gastronomy (or any other everyday science topic for that sake). And I think it should be quite interesting for the readers of this blog as well. Here’s a short summary:

You can lead a chemical-free life
The chemical reality is that you cannot lead a chemical-free life, because everything is made of chemicals. Chemicals are substances and chemistry is the science of substances – their structure, their properties and the reactions which change them into other substances. Claims that products are “chemical free” are untrue. There are no alternatives to chemicals, just choices about which chemicals to use and how they are made.

Man-made chemicals are inherently dangerous
The chemical reality is that whether a substance is manufactured by people, copied from nature, or extracted directly from nature, tells us nothing much at all about its properties. In terms of chemical safety, “industrial”, “synthetic”, “artificial” and “man-made” do not necessarily mean damaging and “natural” does not necessarily mean better.

Synthetic chemicals are causing many cancers and other diseases
The chemical reality is that many of the claims about chemicals being ‘linked’ to diseases simply tell us that that a chemical was present when an effect occurred, rather than showing that the chemical causes the effect. Caution is needed in reporting apparent correlations: it is in the nature of scientific experiments that many disappear when a further test is done or they turn out to be explained in other ways.

Our exposure to a cocktail of chemicals is a ticking time-bomb
The chemical reality is that, although the language of “cocktails” and “time bombs” is alarming, neither the presence of chemicals nor the bioaccumulation of them, in themselves, mean that harm is being done. We have always been exposed to many different substances, because nature is a “cocktail of chemicals”. Modern technology enables us to detect miniscule amounts of substances, but the presence of such a small amount of a specific substance does not mean that it is having any discernible effect on us or on future generations.

It is beneficial to avoid man-made chemicals
The chemical reality is that, insofar as there is a ‘need’ for anything, synthesised and man-made chemicals have given societies choices beyond measure about what they are exposed to and the problems they can solve.

We are subjects in an unregulated, uncontrolled experiment
The chemical reality is that there is an extensive regulatory system that strictly controls what chemicals can be introduced: what experiments can take place, what can be used, for which purpose and how they should be transported, used and disposed of.

Apart from the “free of chemicals” misconception there is the whole natural/organic vs. synthetic/conventional food debate. But I think I’ll leave that for a separate post.

Update: Several commenters below have pointed out that Sense about science is funded by various lobby groups. An article by George Monbiot explores this in great detail. It’s OK to be aware of this, but I still feel their statements regarding “Misconceptions about chemicals” are very much to the point and well worth reading.

[”Sense about science” was found via The Sceptical Chymist. Thanks!]

The Scientist in an interview with Hervé This reports that:

Recently, New York University Assistant Professor of Chemistry Kent Kirshenbaum teamed up with chef Will Goldfarb to bring experts together to discuss the intersection of science, cooking and eating. Often they are talking about the same thing, but with different vocabulary, says Kirshenbaum, who specializes in the architecture of polymer chains. “I think of these as reagents. He thinks of them as ingredients.”

The initiative of Kent Kirshenbaum and Will Goldfarb resulted in The Experimental Cuisine Collective which was officially launched on April 11th with a workshop entitled “Experimental Cuisine: Science, Society, and Food”.

Their mission statement is an elaboration and expansion of Hervé This’ original and revised definitions of molecular gastronomy (ie. not excluding the technological and political aspects of molecular gastronomy, and including the social context):

Provide a venue for scientists, food academics, culinary and pastry professionals, journalists, and the dining public to gather and exchange knowledge.

Contribute to a rigorous scientific understanding of the physical basis for cooking processes.

Enhance understanding of the social contexts for cooking and the societal ramifications of new food technologies.

Accelerate the discovery of scientific and experiment-based approaches to innovative culinary practices, unorthodox flavors, and new dining traditions.

Provide technical expertise for chefs.

Advocate for a balance between modern cuisine while maintaining a healthful and sustainable approach to food preparation.

Disseminate knowledge about human diet and health; inform the public regarding the molecular basis of nutrition and the chemical constituents of food; and foster research that will improve people’s ability to obtain and choose healthful foods on a local and global level.

Introduce curricula on food and cooking as an approach for generating enthusiasm among school children for studying the physical sciences.

Celebrate taste.

Their mission statement sums up many of my interests related to molecular gastronomy and popular food science and I look forward to their contributions! And I really hope they will publish their results and findings on the web.

The New York Academy of Sciences has an interesting series on the Science of Food. On April 10th Hervé This, a pioneer of molecular gastronomy, talked about “Dinner: The Final Frontier”. An interview with This and the other speakers is now available for free download:

Dialogos de Cocina took place in San Sebastian, Spain, on March 12 and 13. Monday’s program featured a session on Technology, Technique and Science which should be of great interest to the molecular gastronomy community. The sessions have been made available as webcasts available in English, French and Spanish. Look out for the following topics:

Monday, March 12

16.00-16.30
Other Ways of Thinking, Toni Massanes (Fundación Alicia).

16.40-17.10
Other Ways of Understanding, Antonio Duch (Fundación Azti).

17.20-17.50
Other Ways of Doing it, Harold McGee.

18.00-18.30
Other Ways of Seeing it, Davide Cassi.

18:40-19:40
What can Science Offer us in Addition to Techniques and Technology?,
Round table discussion with Toni Massanes (Fundación Alicia), Antonio Duch (Fundación Azti), Harold Macgee (writer), Davide Cassi (scientist), Heston Blumenthal (chef).

Update: Kate Hill at IACP (International Association of Culinary Professionals) has written an extensive report on the meeting.

Cookware made from cast iron has a reputation for keeping food warm for a long time. Is that really true? Best way to find out is by an experiment. I decided to compare a cast iron pot with one of stainless steel. These are the pots I used:

For the first experiment I filled them each with 2,5 L of water, put the lids on and brought both to the boil and let them boil for a minute so the pot itself would be warm throughout. Then both were placed on cork plates and left to cool. The temperature probe was carefully inserted under the lid in order to reduce the heat loss, and removed once the temperature had stabilized. For the second experiment 5 L of water were used. The measured temperatures are shown in the graph.

Contrary to what I had expected, the stainless steel pot keeps water warmer! After approximately 1,5 hours there is a 10 °C difference between the two. As expected, when using 5 L of water, it stays warm longer. Physical data for the two pots are given in the following table:

The heat capacity of the cast iron pot is more than double that of the stainless steel pot. But this is negligible compared to the heat capacity of water: 10.5 kJ/K (2,5 L) and 20,9 kJ/K (5,0 L). Also, there is only a small difference in their surface area which cannot explain the large difference in temperature loss observed.

This leaves me with two eplanations:

My guess is that the difference in emissivity is more important (but please correct me if I’m wrong). With an infrared thermometer, one should therefore be able to measure a difference between pots of cast iron and polished stainless steel (even though they’re at the same temperature!) due to the difference in emissivity. Any one who can do the experiment and report back?

Conclusion: There are many good reasons to use cast iron, but keeping food warm is not one of them!

In a recent survey 72% of chefs say they may want to experiment with molecular gastronomy in 2007. That’s an impressive number and considering the attention molecular gastronomy gets in media I bet many home cooks would want to experiment in the kitchen as well. Here’s a list of things to consider if you want to make a scientific approach towards cooking:

1. Use good and fresh raw materials of the best quality available.

2. Know what temperature you’re cooking at. A dip probe thermometer with a digital read out is a cheap way to bring science into your kitchen.

3. Get a basic understanding of heat transfer, heat capacity and heat conductance. “Heat” in this context des not imply high temperature since it also applies to the understanding of freezing/thawing.

4. Learn how to control the texture of food. Some key points: temperature induced changes (freezing, heating), emulsifiers, thickeners, gelling agents, moisture content, pressure/vacuum, osmosis.

5. Learn how to control taste and flavor. Some key points: flavor pairings, spice synergies/antagonies, influence of temperature (Maillard reaction, caramelization, temperature stability, volatility), taste enhancers, taste suppresants, solubility of flavour compounds in fat/water, extraction.

6. Remember that prolonged exposure to a flavor causes desenzitation, meaning that your brain thinks the food smells less even though it’s still present in the same amount. Therefore, let different flavours enhance each other. Similarly, variation in taste, texture, temperature and color can open up new dimensions in a dish. This is referred to as “increased sensing by contrast amplification”.

7. Be critial to recipes and question authority - they do not necessarily represent “the truth”. Nevertheless, you can certainly learn a lot from the experts.

8. Dare to experiment and try new ingredients and procedures. Do control experiments so you can compare results. When evaluating the outcome, be aware that your own opinions will be biased. Have a friend help you perform a blind test, or even better a triangle test to evaluate the outcome of your experiments.

9. Keep a written record of what you do! It would be a pity if you couldn’t recreate that perfect concoction you made last week, simply because you forgot how you did it.

10. Have fun!

Heat causes many changes in food, but few appreciate how important it is to know at what temperature they are cooking and at what temperature the desired change occurs.

These tips for molecular gastronomy relate to the technical and scientific aspects of food preparation and eating, and I plan to elaborate on each of the points in separate blog posts. However, according to Hervé This’ definition of molecular gastronomy, one should also investigate the social and artistic components of cooking. A good example of this is the “Five Aspects Meal Model” developed at Grythyttan in Sweden (Gustafsson, I.B. et al. Journal of Food Service, 2006, 84.). Although intended for a restaurant setting, the general idea can also be applied for home cooking.

The meal takes place in a room (room), where the consumer meets waiters and other consumers (meeting), and where dishes and drinks (products) are served. Backstage there are several rules, laws and economic and management resources (management control system) that are needed to make the meal possible and make the experience an entirety as a meal (entirety – expressing an atmosphere).

Or to put it differently: average food eaten together with good friends while you’re sitting on a terrace with the sun setting in the ocean will taste superior to excellent food served on plastic plates and eaten alone in a room with mess all over the place.

One last thing: once you’re finished in the kitchen with your culinary alchemy, your gastro physics, your cutting edge science cuisine, your molecular cooking, your hypermodern emotional cooking, your science food or whatever fancy name you attach to it - remember the social and artistic components when you serve the food. Just so people won’t refer to you as a techno chef, a mad scientist or a modern day Willy Wonka. After all, molecular gastronomy is about the science of deliciousness, not technical wizardry.

Questions and topics for future blog posts are welcome at webmaster [a] khymos.org (substitute @ for [a]) or as a comment below.

Here’s some of the upcoming molecular gastronomy events. The field is really exploding and this list is far from complete. Feel free to add other events in the comments section.

Videos from the MG seminar in Belgium held on November 20th last year have generously been made available for free on the net. There are four videos to watch: presentations by Prof. Peter Barham (‘Molecular Gastronomy? The science of taste and flavour’) and Prof. Jorge Ruiz (‘Methods in the kitchen: the science behind’) plus demonstrations by Kobe Desramault and Sang Hoon Degeimbre.

Also, Bernard Lahousse (who is in charge of food for design and a co-organizer of the MG smeinar) has let me know that the next seminar will be held on March 16th with the title “A world of Pinot noir” - focus is on wine, but with live MG demos. Stay tuned!

Have you ever though about how far you can shoot a champagne cork? The swedish physicist Hans-Uno Bengtsson has actually done the necessary calculations in the wonderful Swedish book “Kring flaskor och fysik” (which translates to something like “Among bottles and physics”, it was written together with sommelier Mischa Billing). Assuming a bottle pressure of 6 atmospheres, a cork length of 25 mm (the part in contact with the bottle), a radius of 9 mm and a mass of 7.5 g, this gives an initial cork velocity of approximately 20 meters per second or 70 km/h! This translates into a maximum shot length of around 40 m (if we neglect air resistance). In case you prefer not to shoot the cork, you could of coarse turn to a saber or a heavy kitchen knife instead to open the bottle.

When opening a bottle of champagne, you might have noticed the cloud forming right above the bottle neck (see picture below). This is due to a significant temperature drop, caused by gas expansion when we open the bottle. Assuming an adiabatic expansion (meaning no heat exchange with the surroundings), Hans-Uno Bengtsson has calculated a temperature drop of 112 °C! No wonder the vapor around the bottle neck immediately freezes forming a small cloud.

(picture by polarunner at flickr.com)

If this doesn’t satisfy your craving for champagne science, there’s a whole book on the subject: “Uncorked - The Science of Champagne” by Gérard Liger-Belair. He’s an associate professor of physical sciences at the University of Reims Champagne-Ardenne and probably knows more about champagne bubbles than anyone else! In addition to many fascinating pictures of bubbles, the book has many interesting facts. Did you know that:

(these facts should be perfect conversation starters!)

(photo by Gérard Liger-Belair)

An interesting article by Gérard Liger-Belair, “Effervescence in a glass of champagne: A bubble story” is available from Europhysics news.

Happy New Year!

The day of St. Lucia is celebrated in Scandinavia and some countries in southern Europe on December 13th. In Scandinavia a traditional kind of bun, lussekatt, is normally made and eaten on this day.

Lussekatt (Photo by Jonas Bergsten)

What is exciting about this from a chemical perspective is that they are made with saffron, the world’s most expensive spice (a recipe can be found here). Because of the high price, saffron is sometimes adulterated with turmeric. There is however a simple chemical test to check whether your saffron has been adulterated or not.

The color of saffron comes mainly from crocin, a carotenoid with a sugar attached that makes it water soluble (this is why the color is so easily extracted into water containing foods):

The aroma arises mainly from the degradation of picrocrocin to release the terpene safranal:

The yellow color of turmeric comes from curcumin.

Upon reaction with a base, curcumin turns bright red whereas crocin is unchanged. Because of this it should be possible to detect whether saffron has been adulterated with turmeric. In the picture below, strips of coffe filters where inserted into suspensions of saffron and turmeric in water (two of each), and those on the right where then held over a bottle of aqueous ammonia. An immediate reaction takes place between ammonia and curcumin, producing a bright red color. I should quickly admit that I haven’t had the opportunity to test this on an “authentic” adulterated sample!

BTW, the color change is very fast as is obvious from the video below (click here if it doesn’t play in the window below):

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).