A great loss

Not long ago, I was told that the Swedish physicist Hans-Uno Bengtsson regrettably had passed away. A great loss for many of us that appreciated his unique way of illuminating the science in everyday life, and, to me, the physics in food and drink.

Hans-Uno Bengtsson was associate professor at the Department of Theoretical Physics at Lund University, Sweden. According to Wikipedia, Lund University web pages and people I've talked to, he was also an outstanding lecturer. My experience with his work is his writings on the physics of food and drink, although he published a host of other texts on physics, both scientific and popular. To Scandinavian readers, I'd recommend the two books any time

- "Koka soppa på fysik" ("Cooking soup on physics"[?]), a collaboration with the chef Jan Boris-Möller.
A collection of short texts on various food subjects, connecting apparently unrelated subects in an elegant and subtle way

- "Kring flaskor og fysik" ("On bottles and physics"), together with sommelier Mischa Billing.
A conversation between the two authors leading the reader through a meal, discussing various likely and unlikely subjects on the way.

My fascination about these two books is his special ability to interweave complicated physical subjects into the food and drink in a way that makes me gasp from the physics and maths without being put off (i.e. discussing adiabatic expansion in connection with the little "cloud" that arises when a champagne bottle is opened). In fact, in the bottles vs. physics book, he leaves the calculation in the book, but separates it in such a way that the reader very well may skip this part without loosing the thread. Also, the great aesthetic sense that characterises these two books, reveals a great gift both in terms of language/writing and visually.

Finally, I was fortunate enough to experience him a few times on a food programme on TV ("Mat"/"Food" with Tina on Swedish television), amongst others discussing the most efficient way of cooling your champagne: wrap it in a wet towel, strap it on your motorbike and go for a ride :)

I've been hoping for more food- and drink related contributions by Hans-Uno Bengtsson. Unfortunately that won't be, and as I've understood, I'm not the only one that will miss further contributions from Hans-Uno Bengtsson, who left us far too soon.

Erik

A short note on taste/food as a impulse to making music

Spurred by a recent comment a previous posting about chemistry and music, I thought I'd leave a few thoughts about chemistry/taste/scent/aroma vs. music; most of all just to have them written hem down, really.

At the moment I haven't come any further with this apart from day to day musing. The main idea is that as a large proportion of taste is in fact aroma; what is perceived through the nose receptors rather than the tongue. In our "improjazz" band Quest (www.questmusic.no and myspace music) we've used both visual arts (photography) and text/poetry as impulse to making improvised music. These are both impulses received by our senses (visual and auditory). However, taste and aroma are very powerful impulses in association making. Just imagine how the smell of a dish that you've not tasted since you were a small child, or the perfume of the grandmother you spent a lot of time together with as young, may set you right back to situations years back in time in a way that few other impulses do. To me this happens especially in smelling and/or tasting food I had a lot of as a child, or had in a special situation.

So, my thoughts these days circle around the possibilities that lie in using smell as impulse for me as a musician to create music, in the same way as hearing a poem or seeing a photography/painting/picture. I suppose this leans towards some sort of performance art, although other arts than music aren't my field of expertise in any way.

Finally, one interesting thing I came across through Martin's khymos blog was Aroma jockey. This relates very closely to the thoughts above, but to me it seems like he uses recorded music. I'd love to see where this could lead in cooperation with live musicians.

Erik

Does "light" really mean light? - part II

A follow-up on the last entry, comments and Brian's Diet Coke Floating blog entry

The comments on the last entry on Coke density spurred my curiosity, and I decided to follow up with a few experiments:

1. What's the density of different kinds of Coke? I did a simple experiments, weighing measured amounts of Coke (ca. 100 ml) and got the following result. I did the same measurement for water and corrected this according to standard water density values from a web based water density calculator:
   
   
   
   
   
2. What about water density as function of temperature? The density changes according to the reference values are small, far too small to make a difference (my cans/bottles held between 13 and 21 deg. C), as seen from the density curve as function of temperature (the same density calculator used):
   
   And, of course, the density-temperature difference should not be very different from water to Coke, so at temperatures of high water density, the same should apply to Coke.
   
   
3. Experiments should always be tested for repeatability, so I used two cans of coke. Also, I tested whether the same would happen for Coke bottles (500 ml plastic bottles), and if the same would happen for Coke Zero. The pictures below tell the whole story. The difference between Coke Light and Coke Zero, from the ingredients list, seems to be the sweeteners. Coke Light contains Sucralose and Acesulfame K, while Coke Zero contains Aspartame and Acesulfame K.
   

What seems really strange to me is the measurement of Coke light and Coke Zero having densities lower than water, especially the light variety which is well below any temperature dependent variations. How can it be that a water solution with dissolved matter has lower density than water? Carbon dioxide? I don't think so. Carbon dioxide is still matter dissolved in water and should contribute to a higher density rather than lower (regardless of its density in pure, gaseous form).

Anyway, the safe explanation to the floating Coke light is of course the air pocket (both in cans and bottles), and I think I'll stick to this as the main explanation rather than densities of Coke. Ordinary Coke is a clean cut case, anyway.

Erik

Does "light" really mean light?

In a simple demonstration playing around with light products floating/sinking in water a fascinating contrast emerges.

Try submerging the following two pairs of products: ordinary and light mayonnaise, and diet coke (or other cola vs. cola light).

Light mayonnaise floats lower than ordinary mayonnaise. In the case of the soft drink, cola light floats while ordinary cola sinks! What's going on?



Explanation
The term in question is density:

Mayonnaise
The main ingredients in mayonnaise are water and fat/oil:
Ordinary mayo: 80% fat, 16% water
Light mayo: 40% fat, 50% water

Fat floats in water. A larger proportion of fat makes the mixture closer to pure fat and vice versa.


Cola
Cola can be considered as water with some dissolved material. Ordinary cola is, as such, a sugar solution with a few other additives (taste, aroma, colour etc.).

Cola light contains the artificial sweeteners Sucralose and Acesulfame K. Both are far sweeter than table sugar, sucrose (650 times and 180-200 times, respectively, ref. Belitz). Thus, far less sweetener is needed. If we assume that all other ingredients are the same, then far less material is dissolved in the light version. The same total volume with less material --> lower density. Thus: pure cola light would float up in ordinary cola taken that they didn't mix.


In both the mayo and cola cases, there is some air (or trapped gas) inside the tube/can. This makes the tube/can float higher than in the case of the pure mayo/cola. However, as long as the volumes are the same, this doesn't make any difference. If it wasn't for the air, both cans would in fact sink, and the experiment wouldn't be.


A question of using and understanding scientific concepts
The concepts relevant to this is not only "light", but also (amongst others) "(chemical/dietary) energy" and "density". If something floats, we usually say that it's "lighter than water". However, two kilograms of wood is heavier than one kilogram of water, but it still floats. To me as an adult, it's probably easy to grasp, but placing this in an educational context makes it important to use the correct terms. So, "cola has higher density than cola light" would be more correct.

It's quite easy to put this to the test: measure both the volume and weight of a can/bottle of cola and compare. The one that sinks (highest density) weighs the most taken the same volume. Another version of this experiment is concealing the labels, letting the students know the content without telling which is which. The task is then to use knowledge and reasoning to deduce which is which.

Using the term "diet" rather than "light" would of course make the whole case less diffuse, but then a fascinating aspect in the experiment and following discussion is lost. This is the reason for using "light" instead of "diet" in the first hand. However, this may be a nice way of introducing the energy concept of (chemical) energy, kcal and kJ, and contrast this against "light" used in different contexts.


Natural sciences are evidently not only concerned with nature itself, but just as much the language describing nature.

Erik


Refs.:
- Belitz et al., Food Chemistry 3rd ed., Springer 2004
- A Swedish version of the cola experiment at SkolKemi pages of University of Umeå

Do we need to know about dispersions: addition

Slightly embarrassing, I forgot to include Hervé This' work on dispersions.

Hervé This has done some beautiful systematic work on dispersions which he has termed "Modelling dishes". He has several publications on this, but one of these is a paper in British Journal of Nutrition: "Modelling dishes and exploring culinary ‘precisions’: the two issues of molecular gastronomy". It's (at the moment, at least) free for download through IngentaConnect.

Although probably not suitable for the everyday school teacher (but who knows), this is great stuff for those with a more-than-average interest in science vs cooking.

Erik


Post addition, February '09: the Swedish book "Den tekniske kocken" (The Technological Chef") uses in a very consistent manner the different dispersion terms, and show graphically what sorts of dispersions are important in various foods and dishes (although the book recieved a harsh review, "worst cookbook of the year", in Matälskaren).


Reference: This, H., Brit. J. Nutr. 2005, 93, S139.

Do we need to know about dispersions?

Most of the matter and materials that surround us aren't pure compounds or true, homogeneous solutions. If we want to give a science education that is relevant and connected to everyday life, why then is so much of the labwork we do focussed on pure substances and solutions? ...and will the home-/professional cook benefit from knowing a little about dispersions?

A look in the kitchen cupboard and fridge revealed, apart from water and air, the following pure compounds and true homogeneous solutions: sugar, salt, natron (sodium bicarbonate), some of the soft drinks, and some refined vegetable oils. All the other stuff is dispersions, i.e. more or less stable mixtures of compounds/phases that don't mix.

Dispersions and colloids
A related word is colloids, but to my knowledge the word dispersions has lately been adopted as a collective term for colloids, aerosols, foams and emulsions. A dispersion is a homogeneous mixture of two or more phases that are immiscible (won't mix). What is mixed are solids, liquids and gases. The table below gives an overview. In fact, it's quite an enlightening exercise to have a look around and try categorizing the stuff around you. Bread is a foam; cheese, most vegetables and meat are gels; milk, butter and mayonnaise are emusions, just to mention a few.


Click picture for full size version in new window. Click here for Norwegian version


Why dispersions?
In Norwegian school science books and science teacher training literature, matter is divided only into pure compounds and mixtures, see below. The problem with this is that students (and teachers) don't get a language to deal with the stuff that surrounds them. To most of us, foam is a known phenomenon, and emulsions are also known to some. However, these are secondary terms rather than the primary term dispersion.

Conclusion
The term dispersion is not mentioned in the Norwegian curriculum for primary,secondary and high school (Kunnskapsløftet, eng.: "The Knowledge Promotion"). Do I think the term dispersion should have been included in the curriculum? Maybe, maybe not. This new curriculum isn't meant to give detailed instructions to what should be taught, but to what competences the students should have inherited after a certain level. It's up to the school/teacher to fill he subjects with a content as long as the students achieve these competences.

So, if we want the kids to experience a science education related to their everyday life, rather than stuff they'll meet only in science lab, maybe we should start talking about (and playing with) dispersions.

Also, for those of us who would like to benefit from scientific knowledge when we cook, this may afford a good way of viewing ingredients and foods (i.e. previous entries on Tomato foam and Egg white foam).

Erik

Post comment:
Addition to this post in the following post "Do we need to know about dispersions: addition"

Five cardinal rules in cooking

Inspired by Martin's blog entry "Ten tips for practical molecular gastronomy", I came to remember Östen Dahlgren's five cardinal rules in cooking:

1. Be critical of recipes
2. Stop and think - should I really do [it like] this?
3. Keep in mind how the heat is distributed/transferred
4. Keep in mind what is soluble in what
5. Taste while you're cooking - often
   

(my translation)

Dahlgren has written the book "Laga mat - Hur man gör og varför" ("Cooking - How to do it and why"), which is a Swedish counterpart to McGee's "On food and Cooking".
Dahlgren's list is a simpler version of the ten rules that Martin lists up. Although less comprehensive, the short list is easier to keep in mind whenever you're cooking, and I think that's a virtue. I could have commented further on each point, but I think I'll keep it short this time.

What is soluble in what? Blueberry juice in chili oil
(Photo: Erlend Krumsvik)

Furthermore it seems to me that the various tips in Martin's list demand quite different degrees of knowledge and experience. "Learn how to control the texture of food" and "Learn how to control taste and flavor" demand quite a lot of either knowledge or experience (or both) from the cook. On the other hand, "Know what temperature you’re cooking at" doesn't demand much more than the skill of using a thermometer. Of course, Dahlgren's list also operates on different levels, but maybe less so than Martin's. Or is it maybe me seeing things a little too much through my own eyes here, being more accustomed to Dahlgren's rules knowing them for a longer time?

One of my personal favourites is by the way Martin's 9. tip, being imperative in science and science education: "Keep a written record of what you do! ".

Maybe should we go for a happy marriage, making one complete list for the Molecular Gastronomy enthusiasts and a shorter one for everyone else? A future post, either here or at Martin's blog, should certainly have two such differentiated lists. A joint venture?

Erik

A kindred spirit

My first experience with the annual ASE (The Association for Science Education) conference was at The University of Birmingham 3.-6. January. A paradox was that I had to go all the way to England to find that one of the most interesting experiences was to be a Swedish lecturer.

A packed programme with hoards of parallel sessions, spanning most thinkable and unthinkable science education issues; from the highly inspiring/enthusing to the one that give you the feeling "I never thought it was possible to completely ruin something so inherently fascinating". However, one experience left all of the other sessions in the shadows: Hans Persson at the Swedish National Centre for Education in Physics (and The Stockholm Institute of Education) had two sessions: "Creativity in the Science Classroom" and "Curious About Science?". His approach to science teaching was so fresh, vital and inspiring that the session ended in the audience giving standing ovations (the first time I've experienced such after a conference lecture).

What makes this special? First of all, the strong focus on students' interest/attitudes towards science in addition to the knowledge. Interest before knowledge, maybe. If you don't enjoy dealing with science, you won't learn much. Other key factors are having courage to be truly playful and enthusiastic, and utilising every aspect of everyday life to impart science. I also share his quite strong criticism of the kind of science teaching that is separated from everyday life, i.e. lab equipment which its sole purpose is for use in science education, but which doesn't exist anywhere else (note that this primarily applies to primary and secondary school, college/university level may be quite a different ballgame).

The other thing that makes this stand out is that he managed to convince me that he's got a firm foundation for this approach, possibly both theoretical/ideological and empiric, both from primary/secondary school and teacher training. His book on concept building is sure to find it's way to my bedside table soon (only in Swedish, unfortunately, but he's published books in English as well).

Anyway, I don't think I've seen such a fresh approach to science education during my five years in the game, and I decided to post this although strictly it doesn't deal with food and science education (although he touched in on that as well).

A visit at his web page, which bears the subtitle "How can we awaken interest in science and then keep that interest alive?", gives a small glimpse of his thoughts and work. I find this so important that I've put the link in the permanent links list in the right hand margin.

Erik

Link: www.hanper.se (both English and Swedish, but the Swedish pages are somewhat more comprehensive).

Christmas dinner trimmings - a hot potato? (part two)

Many a Christmas dinner, we end up with the potatoes falling apart in the dish and pale olive-green Brussel sprouts. Does it have to be like this? Using a little scientific knowledge in the kitchen can help.

Part two - green vegetables
Brussels sprouts and the broccoli: Do you prefer a fresh, vivid green colour, or a dull olive green? The colour in green vegetables is due to chlorophyll, which is a compound well suited to play around with. The green colour in chlorophyll is due to a magnesium atom (in fact, an ion) attached to a porphyrin ring, and acid can substitute this magnesium altering the colour. Try adding a little lemon juice or vinegar to the water next time you cook green vegetables if you want to do a “sabotage experiment” just to see what you may want to avoid. This kind of sabotage experiments are, in my opinion, just as important as the “successful” ones.

Chlorophyll molecular structure at pH = 7 (neutral/basic) to the left, and pH<7

Fruit and vegetables contain a little acid, so if we use pure water or steam the, this acid is in fact sufficient to alter the colour in a negative way. As a remedy, try adding a couple of teaspoons of (sodium) bicarbonate/natron per litre of water. This makes the water slightly basic. The water will turn green as well, but there is more than enough chlorophyl left for the vegetables. Short cooking times is also recommended, as chemical reactions take time, and the replacement of magnesium is no exception. This is probably the reason that the colour change is more visible in Brussels sprouts than broccoli, the sprouts cook longer and thus more of the chlorophyll is degraded.

Left: cooked with a little bicarbonate (pH ca. 9), right with a little lemon juice or vinegar (pH ca. 4.5)

So, in the two posts conclusion: treat the potatoes and vegetables the opposite way.

Happy New Year

Erik

Background info:
McGee, H. (2004): McGee on Food and Cooking – An Encyclopedia of Kitchen Science, History and Culture. London: Hodder and Stoughton.
Belitz, Grosch og Schieberle (2004): Food Chemistry (3. utg.). Berlin: Springer.

PS: have any idea why the water turns green on adding bicarbonate? Please let me know.

Christmas dinner trimmings - a hot potato? (part one)

Many a Christmas dinner, we end up with the potatoes falling apart in the dish and pale olive-green Brussel sprouts. Does it have to be like this? Using a little scientific knowledge in the kitchen can help.

Part one - potatoes
In Norway, Christmas dinner is often accompanied, amongst several things, by boiled potatoes and Brussels sprouts. The potatoes are often of a mealy sort, and peeled before cooking rather than after.

Mashed potatoes are a result of the outer parts of the potato being cooked too much before the inner parts are tender. Potatoes contain pectin, the cement which holds the cells together. Pectin is soluble in hot water, and when mealy potatoes are boiled, the pectin dissolves in the water. The cement is gone, and the potato fall apart in it’s separate cells. There is, however, an enzyme in the potato that helps the pectin molecules to cross-link internally, so the pectin stays in the potato. This enzyme is active between 50 and 60 °C. The solution is: leave the potatoes in water at this temperature for 20-30 minutes before heating further up, and your potatoes will not fall apart (use a standard cooking thermometer). But beware; the cooking time will be longer. Cooking bacalhau a couple of weeks ago, I had a fascinating experience (in Norway it goes by the name bacalao. Bacalhau is a Portuguese/Brazilian fish dish, in this case a hot pot with tomatoes, potatoes, onion, clipfish, black olives and olive oil). The potatoes were pre-cooked as described above, peeled and cut in large pieces, and added to the hot pot. After 75 minutes simmering, the potatoes were still not tender, and the guests had to wait another 15 minutes. One and a half hour’s simmering before the potatoes were tender! The potatoes, by the way, kept their shape perfectly even when the dish was reheated.
If you deliberately want the potatoes to fall apart, i.e. to thicken soup, you should do the exact opposite: put the pre-peeled potatoes directly in boiling water.

One problem with such pre-cooking is the off-colour (enzymatic browning). This can be fixed by adding a little acid, a tea spoon of vinegar or some lemon juice, or an antioxidant; a C-vitamin tablet or a tea spoon of pure ascorbic acid does the trick. The acid retards the reaction, while the ascorbic acid (C-vitamin) sacrifices itself in the reaction.

A drawback is that vitamin-degrading enzymes are also efficient at temperatures between 50 and 60 °C, so focusing on texture results in lower vitamin content. For everyday dinner I’d put unpeeled potatoes directly in boiling water to deactivate the vitamin-degrading enzymes, alas deactivating the pectin reinforcing ones as well.

Part two will deal with the Brussel sprouts - how to achieve a fresh green colour rather than a pale olive-green colour. A Norwegian version of this post can be found at www.naturfag.no/mat.

Merry Christmas(-dinner)

Erik

Background info:
McGee, H. (2004): McGee on Food and Cooking – An Encyclopedia of Kitchen Science, History and Culture. London: Hodder and Stoughton.