Enlightening video lecture on argumentation at Penn State University

Twice a semester Pennsylvania State University holds its Ed Waterbury Lecture on science, technology, mathematics, engineering and mathematics education. This autumn, one of my main sources of inspiration concerning argumentation in science was the invited lecturer.

Prof. Sibel Erduran from University of Bristol is a renown researcher, author and lecturer in fields such as science education, argumentation in science education and philosophy of chemistry. Her contribution to a seminar at the University of Oslo a few years ago was the starting point of my interest in argumentation in science education. In fact, this was the main impulse for me getting involved in what we now call "the Kitchen stories project" (see below).

Her 1 hr lecture + Q/A session at Penn State University was on the topic of argumentation in education (mainly middle school) and professional development of teachers, titled "Modeling Epistemic Practices in Teachers' Learning: The case of argumentation". This lecture is available on the university's web pages (open access, hopefully online for a long time).

Sibel Erduran: "Modeling Epistemic Practices in Teachers' Learning: The case of argumentation"

Dancing the structure of a molecule + scent vs music revisited

Some time ago I caught a glimpse of a headline about some researchers "dancing their natural science projects", more specifically a biochemist dancing the structure of certain biochemical compounds. I thought the idea was rather far-fetched and didn't give it further thought. After seeing it just recently I find myself being so very wrong... Second part of the post contains a few recent thoughts about a project on scent vs. music.

Have a look at the video below. In the start of the video I didn't see the point, but after a while things started to dawn on me.

Lipids Dance! from Kerstin Wagner on Vimeo.

After watching the video I realised that this did indeed illustrate behaviour of the molecules in question in a very vivid way. I'm of the opinion that one should look for as many possible ways of describing and explaining a phenomenon as possible. If a student tells you they don't understand what you're saying there is seldom any help in repeating the same words one more time. You need to find new words, some other metaphor, another mental representation.

One major and one minor literature reference on Molecular gastronomy

At last(!) there is a comprehensive and broad focussed review on molecular gastronomy (MG) in the scientific literature. Also, I stumbled over another scientific paper on the same topic from 2007 which has missed my attention until now.

An important (and seminal?) contribution

Martin at khymos has written a short post on the most recent and comprehensive addition to the scientific publications on MG: "Molecular Gastronomy: A New Emerging Scientific Discipline" written by eight(!) researchers in the field, and is open access. What a gift!

Since it was mentioned already in a paper from 2008 (van der Linden, McClements & Ubbink, ref. here), I've been waiting for this paper for at least a year. It is incredibly welcome that others than Hervé This writes about MG in scientific papers, and now we have several contributions with slightly different viewpoints on the same phenomenon.

Low-temperature cooking might save restaurants money

Last year, I had the pleasure to act as a co-supervisor for two students at in their final project for the Food and beverage management study at the University of Stavanger. The focus was low-temperature cooking.

The students, Eirik Nestavoll and Martin M. Stokkan (both chefs), attended this as a continuing professional development study. The aim of their experimentally angled final project was whether "new cooking methods" might give economic gain to hotels.

Thorvald Pedersen's recent book: "Molekylær gastronomi"

Thorvald Pedersen has been writing about food and cooking from a scientific perspective for years (mostly in Danish as far as I know), probably well before the term molecular gastronomy gained much attention.

Now he's published his third book on the subject and has dared to use the debated and, according to some, oft misunderstood and misused name Molecular gastronomy. In fact, Pedersen has suggested his own definition of the term, being different from Hervé This' and Harold McGee's:

• Pedersen: "The science of choosing, preparing and eating good food"
• This: "The scientific discipline that looks for the mechanisms of culinary transformations and processes, from a chemical and physical point of view"
• McGee (1 and 2): "The scientific study of deliciousness"
  

This debate has been running on the MG mailing list also, by the way.

Anyhow, the book has been out for a few months and I got it for present. I've always loved reading Pedersen because he's got this way of making everything warm and cosy, very Danish in a way (Danes seem to be far more relaxed and life-enjoying than us Norwegians, or Swedes for that sake). Reading his books and articles are almost like having one's grandfather telling stories. For that reason, I think Pedersen is even more enjoyable to read than This and McGee language-wise. He seems more relaxed somehow, maybe because he has nothing to prove, being a professor emeritus in chemistry.

The book is shorter than his previous books "Kemikeren i køkkenet" (Chemist in the Kitchen), a collection of his articles in the Danish magazine Dansk Kemi (Danish Chemistry) and "Kemien bag gastronomien" (The Chemistry Behind the Gastronomy) which is more of a textbook in food/cooking science or molecular gastronomy.


"Molekylær gastronomi" is divided based on short articles into two main parts (following the introduction):

• The preparations. Articles on various foods (not dishes); carrots, potatoes, onions, fish, meat. Each article has one or two recipes, mainly taken from classic(?) cookbooks , exemplifying the main point in the article
  
• The meal: starting off with an article on flavour and goes on to describing three meals of increasing complexity, from outdoor cooking during his time as boy scout, to a tasting menu at the fat duck
• Also, the book is scattered with 27 small boxes on various themes such as plant cell structure, starch, how to identify fresh fish, colours in food, viscosity etc.
  

In terms of what he writes, most of the results refer to McGee and a few other sources, including his regular food column in Dansk Kemi (the Danish research on gourmet salting for juicy and tender meat is especially interesting, and I've planned to write a post on this). Hence, if you've read McGee, there are not many new astounding discoveries.

One interesting thing is how he uses the tables of nutrients given the various foods. Most commonly people use such tables looking for amount of sugar, fat, whether a food contains gluten etc., that is health purposes. Pedersen however, uses this information for cooking purposes, and he gives the relative amounts of nutrients by dry weight as well. This is really useful, because various foods are easier to compare. One example is looking for amount of starch in different sorts of potatoes, which might have different percentage amount of water. Given values by dry weight makes it much easier to compare (there seems to be something wrong in the potato tables however, as the amount of nutrients add up to more than 100%).

In my opinion, the book is worth buying just for the sheer enjoyment of reading it. Also, I warmly recommend his food column "Kemikeren i køkkenet" in Dansk Kemi, mentioned above, freely downloadable (single pdf files).

Deciphering an old preserves recipe

Teaching food preservation methods combined with science often results in the classical why-questions; why does the recipe tell us to do things this way, and why is that so important (...and is it really that important?)

Autumn means ripe fruit, berries and vegetables, and many of us look forward to harvesting for the coming year. Only a few areas of the world have the benefit of continuous supply of fruit and vegetables (especially we up here in the north), and this has lead to loads of ways to preserve food. Nowadays, however, many of these methods are used for culinary purposes rather than survival. Recently, Martin wrote about cherry jam (I have given a few on his post as well). Also, Hervé This has written about culinary proverbs and old wives tales, "culinary precisions" as he terms them, some being sound advice from a scientific viewpoint, some being directly misleading, and others probably not making that a big difference.

So, I thought this might be a good time to take a recipe for sugar-preserved pears and have a closer look at it, step by step. It is in fact a quite fun exercise.

Traditional sugar-preserved pears «the old fashioned way» (generic recipe)

1. Heat jar in oven or water by slowly increasing the temperature to above 100 °C and keeping it at that temperature for a certain amount of time (i.e. 15 minutes). Cool.
   
2. Peel pears. Cut in half and remove seeds and core
   
3. Make syrup from water and sugar by boiling the syrup until the sugar is dissolved. Leave to cool
   
4. Fill a jar with the pears. Fill up with syrup, cold or lukewarm, but not hot
   
5. Put the lid loosely on, do not tighten
   
6. Place jar in a pot with cold water almost up to the rim of the jar. Heat slowly and keep at boiling point for a certain amount of time (i.e. 8 minutes)
   
7. Remove jar from pot and
   Either: leave to cool for a certain amount of time (i.e. 15 minutes). Then tighten the lid
   Or: Tighten the lid while boiling hot
   
8. Turn jar upside down and
   Either: store upside down
   Or: leave upside down for a certain amount of time (i.e. 15 minutes)

Taking a closer look
Firstly, the main reason for all these operations is to keep the pears edible for a long time, more specific until the next time ripe pears are at hand (a year, usually...). The two main ways that fresh fruit is spoilt are chemical (enzymes and reaction with oxygen from the air) and biological (microorganisms: bacteria, moulds and yeasts). Even though the methods were developed before the discovery of microorganisms and enzymes, the results of these were evidently clear. The source of enzymes is the fruit itself, whereas microorganisms are ubiquitous: the fruit itself, hands, tools, jar and in the air. So a perfectly sterile fruit would over some time be contaminated by just sitting in the air.
Two important facts: microorganisms thrive and multiply at temperatures between 10 and 40 °C, and die at high temperatures. The trick is thus to avoid the 10-40 °C window. Also, microorganisms need water to thrive and multiply.

So, how much of this procedure makes sense from a scientific point of view? I've marked the steps being most «fishy» with a red asterisk:

1. Heat jar and lid in oven or water by slowly increasing the temperature to above 100 °C and keeping it at that temperature for a certain amount of time (i.e. 15 minutes)
   Makes sense, but cooling leaves the jar and lid ready for infection. However, they're dry and not prone to being infested
   
   
2. Peel pears. Cut in half and remove seeds and core
   No effect other than possibly infecting the pears from hands, tools and surrounding air
   
   
3. Make syrup from water and sugar by boiling the syrup until the sugar is dissolved. Leave to cool
   Sugar has a preserving function due to its dehydrating effect on microorganisms (a later post will deal with this). Sugar won't kill microorganisms, but inhibit growth. If the syrup is thoroughly boiled, microorganisms in the water and sugar are killed. Cooling the syrup is not recommended if it can be avoided (10-40 °C window)
   
   
4. Fill a cold jar with the pears. Fill up with cold or lukewarm, but not hot, syrup
   Warning: we are in the 10-40 °C window. From a microbiological view, the best would be to add hot/boiling syrup. However, this might damage the fruit, such as turning the surface mushy (in the case of plums, the skin would most likely break).
   
   
5. Put the lid loosely on, do not tighten
   Makes sense. During heating, the contents expand and trapped and dissolved air is expelled (gas solubility is lower at higher temperature). The air above the fruit expands when heated and needs to go somewhere
   
   
6. * Place jar in a pot with cold water almost up to the rim of the jar. Heat slowly and keep at boiling point for a certain amount of time (i.e. 8 minutes)
   We are in the 10-40 °C window for quite some time during slow heating. The historic reason is most likely that old glass types had tensions/stress that would result in the jar cracking from shock heating or cooling. Modern glass production methods solve this by i.e. annealing. My experiences with ordinary jam jars is that they manage shock heating and cooling quite well. If the fruit survives, rapid heating is preferable.
   
   
7. * Remove jar from pot and either leave to cool for a certain amount of time (i.e. 15 minutes). Then tighten the lid, or tighten the lid while boiling hot Leaving the jar open at this point is certainly not a good idea. Cooling results in the air above the fruit contracting, sucking in air from the surroundings (see note). Even though microorganisms might die when entering, thermally stable spores might enter which might develop at a later point. Tightening the lid right away is by far preferable. If you use modern jars with aluminium lids that pop down due to reduced pressure inside the jar, this should happen when the jar cools (if you buy a jar of jam and the lid doesn't pop when you open it, return it and get another). If the lid pops up before or during storage, consume immediately («oh, what a disappointment» ;)).
   
   
8. Turn jar upside down and either store upside down or leave upside down for a certain amount of time (i.e. 15 minutes)
   Makes sense. Getting the lid sterile is always a difficult task. Turning the jar lets the hot contents come in contact with the lid, sterilising it getting rid of a majority of the microorganisms present. One might speculate whether keeping the lid seals moist might also be a reason (why wine is stored lying), but a biologist friend of mine meant that the atmosphere above the fruit would result in a moist enough atmosphere for that purpose, and that the sterilising effect of killing microorganisms is the point here. If that is true, it should not make a difference which way the jars are stored.

Remember that operations conducted in a kitchen are far from sterile procedures. For this reason, many such recipes rightfully ask for two and sometimes three actions with apparently the same purpose.

Finally, while hard cheeses with unwanted mould often are safe to eat if the mould is removed by cutting away a layer of the cheese, stored preserves such as jams, sugar preserved fruit and syrups should be discarded if the seals are broken or visible mould is seen. In the cheese, the microorganisms cannot travel due to the dry and solid structure, whereas diffusion is jams etc. occurs rather easily and the whole jar might very well be contaminated even though the visible mould is removed.

What might be learned/taught
Loads of microbiology. However, since I'm primarily a chemist, I won't venture too far into this. To me, taken that microorganisms are everywhere and that they die when they are heated, the most important things to teach would be (again, from the top of my head):

• temperature-volume relationships of gases and gas-liquid relationships (popping lids, see note below)
• critical thinking, don't always believe what you read
  
• working systematically, always questioning why should I do this? (see Five cardinal rules in cooking)

In fact, this experiment/recipe might be among the few cases where one can test and predict something rather complicated based on a very limited amount of knowledge, but are often stated as among the most important treats in enquiry based science teaching (quite a paradox, really). Such situations are scarce, and I'm thrilled every time I stumble upon one.

Erik


Note: Heat expanding air is easily illustrated by putting a blown-up balloon into the freezer; it contracts. Take it out, and it expands back to (almost, at least) original size. However, when the jar contents are boiling, the headspace will in fact be filled by mostly steam from the preserves. When this water condenses (in the closed jar), the volume of the steam (now liquid water) is reduced by a factor of ca. 1300(!), resulting in a considerably lowered pressure.

Addendum (6. August)
some statements about sterilisation are modified as common canning does not result in sterile product (hence the need for preservatives such as sugar, salt, acid/vinegar etc.). This way of canning/preserving more resembles high pasteurization which is common in some milk products.

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

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.

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

New paper by Hervé This!

Hervé This, co-founder of the term Molecular gastronomy, has published another paper: "Food for tomorrow? How the scientific discipline of molecular gastronomy could change the way we eat
" (EMBO reports, see free html or pdf versions). I've had a brief look, and there are lots of interesting and important issues to be discussed further. He discusses the role of molecular gastronomy in everyday life (and education, although briefly), and confronts the fact that a scientific view on food still has a long way to go if we want to reach people's everyday cooking, and not the high-end restaurants only.

Highly recommended, and I'll give some education-related comments on this in near future.

Erik