Can dry ice be food?

During our summer holiday in the United States this summer, I found over-the-counter dry ice in the supermarket. A truly marvelous thing! This opens up a host of possibilities, both in the home kitchen and as a science teacher.

Dry ice is in fact frozen, solid carbon dioxide (CO₂), the «carbonated» part of carbonated drinks. One fascinating thing about CO₂ is that it sublimes rather than melts – solid CO₂ does not melt to give liquid CO₂, but goes directly over to become gas. Hence, the argument of the producer that dry ice can be used as coolant without getting everything wet. Further, the freezing point of CO₂ is -78 °C (-108 °F), and since this is far colder than that of water/ice the cooling power is larger, but you might get frost burns, so be careful (see precautions below).

Uses
The producer gives a number of suggestions for how to use dry ice, such as:

• Cooling: no wet ice – no water, but note that the low temperature results in water condensing on the outside of the container, especially in humid weather. Stays cold longer than water-based ice
• Freezing: ordinary freezing or flash-freezing (very low temperature gives rapid freezing. Stays frozen longer than water-based ice
• Make carbonated beverages: add dry ice into still beverages to get a fizzy drink (they have a recipe for home made root beer on their web site)
• Special effects – fog or witches brew-like effects
  

The product
The dry ice from this producer comes in solid blocks packed in plain plastic bags. You need to bring some insulated box or bag. Size will obviously vary since the dry ice is stored in insulated containers (using freezer is not of any great help since the ice is far colder than the freezer). Hence, the bag is weighed upon purchase, and the older the dry ice, the greater loss from the bag. This is no problem, as expiry date is no question (as long as it is kept pure and away from other products). As it is meant for use in carbonated drinks, it must obviously be pure enough to ingest (not in solid form however, see below).

My experiences

• Dry ice in blocks is quite hard, but brittle. Use a short and hard knife (I used an oyster knife), a screwdriver or similar to chop off pieces. It should also be possible to shave off to get a more powdery dry ice.
• Dry ice curling: chop off a flat piece and leave it on a table or the floor. After a short while it will start floating with almost no friction against the surface, and you can play around with it. Use gloves or touch is only very briefly

Carbonated drinks (the dry ice must be completely dissolved before drinking)

• Using dry ice for carbonating drinks results in a quite different effect from using SodaStream-type carbonated drinks. One tablespoon of dry ice in a large glass gave a slight tingling sensation on the tongue. Using too much, results in a somewhat bitter taste. Using shavings is better than large chunks, as the latter take a long time to dissolve. The dry ice was either added and stirred with a spoon (i.e. juice) or added after the liquids in the blender for icy drinks, smoothies etc.
• I tried making icy drinks (slush) using larger amounts of dry ice, but did not succeed. My approach was to crush dry ice together with ordinary ice. This resulted in a layer of rock-hard ice in the bottom of the blender. In addition, I guess this might damage the plastic container of the blender due to over-cooling.
• Dry ice might very well be combined with ordinary ice. In crushed-ice drinks, add the dry ice after the liquid contents. When using whole ice cubes, mix dry ice with the liquid and add ice cubes. In all cases, stir or blend well after adding the dry ice.
• Previously, I've tried using a CO₂-charged dessert whip for making carbonated apple juice. Squirting the juice out of the nozzle gave a carbonated juice quite similar to the dry ice version (much of the CO₂ bubbles out in the process). Martin’s carbonated fruit seem to be quite different, but that may simply be due to the longer waiting time. Obviously, the dessert whip is not meant to make carbonated drinks as there are dedicated soda siphons on the market. Note that Martin also have a few posts that mention the use of dry ice.
  
• The cooling effect of dry ice is low, slow and very local when added to a liquid. In fact, water ice seems much more effective for cooling drinks. This is probably due to the escaping CO₂ gas whereas water ice adds cold water to the mixture as it melts.

Tested recipes:

• Dry iced ice tea: works ok, but the bitterness in the tea might be enhanced by the dry ice
• Carbonated juices (pina colada mix, cherry mix): works ok
• Smoothies: I tried a strawberry/banana/coconut drink («Coconut Dream») below and it was good with a slight tingling sensation on the tongue

What might be learned (or rather, taught)
There are lots and lots that might be learned in connection with dry ice. A few topics from the top of my head:

• Gases, liquids and solids
  
• Freezing, melting and evaporation/boiling
• Friction and force (dry ice curling)
  
• Acid-base equilibria (see also "naked egg"-resource which is relevant, CO₂ is produced)
  
• Solubility of gases in liquids
  
• Questions about CO₂ itself

See also the Q/A section below.

Precautions
Main point: dry ice is harmless if you avoid ingesting it in frozen state and if you’re careful with skin/eye contact.

Ingestion of solid dry ice may result in severe frost damage due to the low temperature of the dry ice. The same might happen from direct skin contact, but it may be handled if small pieces are thrown back and forth between the hands, minimising the contact time. Textile gloves work well. Upon sublimation the CO₂ increases its volume by 540 times. Ingesting a tea spoon of dry ice would then produce 2.7 l gas in the stomach, which might result in internal injury. Dry ice might damage certain plastic items, varnished material etc., due to the low temperature.

Conclusion
In my vocabulary dry ice might very well fall into the category of food, but this depends on how it is used. Use it as a cooland or reagent in a lab, and it is a chemical. Use it for a somewhat more tingling smoothie, and it’s food.

Finally, I have only explored a few possibilities. I expect that many others are more proficient in finding even more tempting culinary applications than these simple icy drinks and smoothies (as have already been suggested in Martin's and other blogs, follow links and comments at his relevant entries mentioned above).

Erik



A few questions and answers
Q: What is the «smoke» coming from dry ice, either pure or in drinks?
A: The fog is not dry ice, but condensed or frozen water from the air (or the drink). The air above the dry ice is cooled to an extent that water in the air condenses or freezes; miniature snow crystals.

Q: Why is expiry date not a relevant issue?
A: CO₂ is among the most stable compounds around. Hence, it will not deteriorate apart from sublime («disappear»). However, if other products that might give off odour etc. are in the vicinity, these might condense on the surface and the dry ice is increasingly contaminated.

Q: Why do pieces of dry ice float freely on hard surfaces?
A: In contact with a warmer surface, gaseous CO₂ is liberated creating a «gas cushion» between the table and dry ice. The same effect being used in hydrofoil boats and what you see if you spill drops of water onto a hot cooking range. As long as gas is produced in the interface, this «gas cushion» results in almost no friction.

Q: Does dry ice float or sink?
A: In water (or other beverages), dry ice will float due to the porous, and thus gas-filled, structure. CO₂, however, is more dense than air and sinks in air (the CO₂ will escape only slowly in a glass filled with CO₂ gas if it is not stirred)

Q: Is it possible for private persons to get dry ice in Norway?
A: Yes, from producers AGA (retailers, choose «industry dealer» when prompted) and Yara Praxair (retailers) through their network of retailers. However, it seems to be quite expensive, at least compared to the $0.99/lb in US supermarkets.

Freeware for calculation of food ingredients, nutrients, energy etc.

If you can live with reading some Norwegian, this freeware program will calculate whatever you like in terms of nutrient content, energy etc.

Albeit not among the most recent news (at year and a half old), it might be appropriate to comment on Mat på data 5.0 v2 ("Food on computer") which was last year taken over by the public Food Safety Authorities (Mattilsynet) and rendered free. A great step forward for those who teach food&healt in the Norwegian (Scandinavian) countries, and of course others with interest in having a closer look at food and diet.

Study up to three foodstuffs/dishes simultaneously in detail
Just plug in the ingredients and amounts. It even allows for a large number of ready-made/processed dishes and semi-processed foods, and with an impressive detail in varieties of various foodstuffs (i.e. 15 different varieties of potatoes or potato dishes). Whenever you choose a food or dish, you can choose the amount by grams, number (i.e. no. of tomatoes), volume, or portions (i.e. two slices of pumpernickel bread, one glass of milk). The output is energy content and all the different nutrients, both in numbers and graphically (a couple of varieties). A copy-function for exporting to word processing software etc. in included. The screenshots below show information on the following small meal:

• One egg fried in butter
• Two slices of pumpernickel (black) bread
• Five cherry tomatoes
  

Create your own dish and/or meal
If you have a recipe of your own its no problem regiserking this in the database, and you can then compare your own chocolate cake recipe with the one you buy in the supermarket, or compare your modified version with grandma's. Also, it is possible to register a whole meal as one single entity (i.e. your regular breakfast of cereals, milk and cup of coffee).

Analyse/create a week's diet
If you have registered meals (see above), these might be put together to set up a week's complete diet.

Finally, it also includes some general recommendations for nutrient and energy intake based on a person's age, sex, activity level etc.

It may be downloaded for free from http://matportalen.no/Emner/matpadata. English translation (of the download page, not the software unfortunately).

Truly, a gift.

Erik

Back, ...at last

after a long break in order to finish my doctoral thesis, this summer I plan to start blogging again. Lots of energy and creativity to spare now, so hopefully there'll be some contributions before end of summer.

Erik

The first(?) example of molecular gastronomy in music

More music than science lately, but this one is inevitable:
Recently, the improvisational electroacoustic jazz band Food released their fifth record named "molecular gastronomy"!

Furthermore, seeing the track list, I was baffled by the rather specific concepts taken directly from molecular gastronomy (MG), such as khymos (Martin Lersch's blog), spherification and texturas (ref. the Texturas series by Ferran Adrià at el Bulli) and heston (Blumenthal, at The Fat Duck).

At first, I wondered whether this was a joke, serious, or somewhere in between. Qualitywise, this is by no means a joke. Both from previous recordings and this one, Iain Ballamy (sax) and Thomas Strønen (drums/perc) prove that they are among the foremost in their field, no doubt. Other band constellations they are engaged in confirms this as well.

So, is it possible to hear the gastronomy in the music? (ref. previous posts on food and chemistry/food vs. music). That's a difficult question, and I'm not sure whether I should look for it either. My experience with using other senses than my ears as impulse to improvisation is that things become rather banal if one lets the impulses become too evident in the music. One example when we (Quest) played together with the Norwegian poet and author Lars Amund Vaage reading his poems about sheep farmers from the book "Det andre rommet". The one percussion instrument to be extremely careful about in that context, at least in my opinion, was the (cow) bell.

Anyway, I guess taste, aroma etc. are such unfamiliar impulses to use in music compared to visual (i.e. pictures) and text, that the effect of these may be difficult to discern (I'd really love to have a chat with the Food-guys about this).

I'll surely spend time listening to this, food/gastronomy references or not. Strønen is no doubt a favourite in terms of combining energy, cool-factor and elegance. Coupled with the long mellow saxophone lines of Ballamy and keyboards/effects, the result is simply great music.

Erik

Post-comment after more listening, 16. December 2007:
----------------------------------------------------------
After running the album a few more times, the question of hearing the food in the music is still a long shot to me. What is pretty clear, however, is that the music is closely connected to many of the track names; it's easy to relate/associate the music to the words. Examples are the machine like percussion (especially the bells) in "apparatus", the less rythmic and soft lines of "texturas", and the last track "alchemy" which is a synthesis (or maybe a distillate) of several of the other tracks. So, the search for food/gastronomy in music goes on, or maybe it's already there, the fault being in my mind or expectations?


Track list:
----------
khymos
apparatus
red algae
lota
spherification
texturas
nature's recipe
heston
the larder chef
alchemy

Food, science and pupils'/students' experience of success

Cooking is a discipline that is often heavily focussed on a successful result. Sometimes this is a good thing, but other times focus on achieving is not necessarily the best strategy in terms of learning. In these cases, a science perspective may be just what is needed.

In Norway, cooking in school has had a rather strong feminine focus, possibly because the approach has been home cooking and home related questions rather than a more masculine gastronomical /restaurant perspective.* This focus prevails, and I don't complain about that. On the contrary, I think a home focus is the right approach in a school setting.

One thing I find that these two approaches have in common, though, is that achieving a successful result (dish) often is the main focus, and in that respect I think there are things to be done. My point is:

if the pupils/students end up with is a bread that hasn't leavened, would that be regarded as a failure? If the goal is achieving an optimal product, the answer is probably yes. If learning is the goal, I'd say no. In fact, it may be an excellent impetus to learn something about baking, yeast, leavening etc.

In fact, nothing spurs me more to experiment than when a recipe tells me by all means to avoid doing something, such as getting egg yolk in when whipping egg whites, or whipping the double cream past the whipped cream-stage. Sometimes, "sabotage experiments" may very well be the ultimate way of learning and experimenting with food (and may result in surprisingly good or interesting products as well).

Through science and research, we learn that a result is a result is a result...; a negative result may be as informative as a positive one. If it is true that "a drop of success will create a pound of persistence", then why not turn what could be seen as a failure into an interesting result from which one may learn from? Maybe this could spur towards a more gender neutral home economics (in Norway: Food&health) teaching?

Also, in many cases the unlikely results and the odd combinations may be the ones that lead to new experiences and wonderful dishes, such as the unlikely purple mashed potatoes made by all blue potatoes (there are no colourings added and the picture is not manipulated).

Photo: Erlend Krumsvik


(* The masculine/feminine thing is more of an observation, rather than an opinion of mine. Personally, I'd really like to see a more equal gender distribution among both the mentioned groups/perspectives, such as a male home economics teacher in primary school...)

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.