Sciencemadness Discussion Board

The use of organic solvents in cooking

Aurus - 29-5-2010 at 14:03

I live on an island on the Mediterranean and, sometimes, when we want to cook sausages, we pass two of them on a spit and hold them over a plate or a saucepan in which we have alcohol (of the ethyl variety). We light the alcohol and we happily cook the sausages. Now, today, I realised we had run out of ethanol at home, and I decided to have a little twist. Instead of using alcohol, I decided to use acetone. Indeed, I cooked the sausages, but when the time came to eat them, dinner companions did not want to eat a food cooked over acetone.

My idea is that a solvent, provided it does not contain any halogens or sulphur and is not made up of too much carbon, should be safe to use, as it will combust to carbon dioxide and water. What do you think? I don't know if they bake sausages in this way in other countries.

Possibilities for cooking include:
  • Ethanol

    1. Methanol
    2. Acetone (Propanone)
    3. Alkanes (C5-C10)

    This is applied chemistry :)

    Sedit - 29-5-2010 at 14:15

    Go with EtOH or glycerol.

    Aurus - 29-5-2010 at 15:43

    I intended this more as an intellectual exercise, although I did it as a little experiment. Would it be safe to eat with solvents considered poisonous? What would the combustion products be? I concur with you, though.

    Magpie - 29-5-2010 at 15:54

    The denatured alcohol used for cooking stoves may contain all manner of poisons added as denaturants. Using that as experimental evidence for safe use based on millions of experiments, your logic does seem sound.

    And many people must cook their food over wood fires, and some do by choice while camping. Seems there would be all kinds of nasties coming off those fires. Most people just say "..mmm good!" :D

    [Edited on 29-5-2010 by Magpie]

    chief - 29-5-2010 at 16:50

    Depends on what wood they accidentally use or not ...
    ==> Some plants may give off poisonous fumes, eg. oleander ...; there are said to have been even fatalities from using a oleander-piece to stirr the tea ...

    not_important - 29-5-2010 at 17:07

    Methanol was the traditional fuel in Sterno and other "canned heat" products. Liquid alkanes are also used, a potential problem is traces of them giving the food a kerosene flavour.

    psychokinetic - 30-5-2010 at 01:32

    The use of a pure substance could pose more products than the mix of products coming from a woodfire.

    The other problem I can think of is the possibility of any unburned fuel reacting with the food. . . .

    Aurus - 30-5-2010 at 05:25

    Interesting. As the chemicals present both in charred food, and I suppose, combustion products of wood, are supposed to cause cancer, cooking must have become much safer now that it is done in kitchens. Probably, if you eat something cooked over alkanes or acetone once in a while, the effect mustn't be worse than eating marshmallows.

    watson.fawkes - 30-5-2010 at 08:48

    Quote: Originally posted by Aurus  
    Now, today, I realised we had run out of ethanol at home, and I decided to have a little twist. Instead of using alcohol, I decided to use acetone.
    Acetone, as a chemical, is a metabolic product of lipid (fat) digestion. In small quantities it's basically non-toxic, so to that extent unburned acetone residue is nothing to worry about. I would worry more about partial combustion products, particularly formaldehyde. The two points of advice that come from this are (1) low-carbon-number fuels are better the high-number ones and (2) make sure your fire is hot and not smoldering, that is, promote complete combustion.

    That's not the whole story, though. Acetone, as an industrial product, is anything but the pure chemical. There are all sorts of impurities that matter little for industrial use but matter a lot for culinary use. The one that pops into mind immediately is lead, which would gladly volatilize and deposit itself in your food.

    As for cooking over wood, the initial heat from a wood fire comes primarily from the combustion of gases released from the pyrolysis of the wood. A major component of that pyrolysis is methanol (wood alcohol from destructive distillation). As before a hot wood fire is going to leave less residue than a not-so-hot wood one. Alternately, you can cook over charcoal, by which I mean actual charcoal, after the pyrolysis fire is over and you just have glowing coals.

    Formatik - 30-5-2010 at 23:29

    Combustion of acetone in air forms next to other products, acrolein (Berl, H. Fischer, Z. El. Ch. 30, 34). Burning glycerin and fats also forms some acrolein, but these are better known. Methanol combustion in air will also form some formaldehyde. Which we know has carcinogenic potential. Between acrolein and formaldehyde, formaldehyde is the gentler poison.

    But ethanol is no saint. Wether you ingest it or burn it, it will form some acetaldehyde. Acetaldehyde has been found to cause single-strand and double-strand breaks in DNA (read about it here). These usually get repaired, but still double-strand breaks promote cancer (see here).

    Usually, whatever you burn will form some toxic, carcinogenic combustion products. All hydrocarbons that are burned form formaldehyde. It's probably a question of how much is formed, and how much you are exposed to that puts you at a higher risk of disease. Incomplete combustion products tend to be worse (also think of carbon monoxide). It would be nice if there were a chart somewhere comparing formaldehyde and toxics from simple fuels.

    Aurus - 31-5-2010 at 06:11

    It would be interesting to find a website or a book that talks about partial combustion products. Do you know of any?

    Formatik - 31-5-2010 at 10:54

    I don't. Typically, the more incomplete the combustion, the more room there is for a toxic product to form via side reactions. Looking through books which may cover incomplete combustion at your university might reveal books which cover the phenomenon. Google books might be useful for information, like from this book, which mentions formaldehyde concentration from natural gas burners was highest with lower air-gas ratios. It also mentions using formaldehyde odor to detect carbon monoxide. They theoreticize smothering of the flame with a utensil too close to the burner also caused formation of some of those (this point also relates to one above made in the post above mine).

    Aurus - 31-5-2010 at 14:10

    This also poses the question of the hydrocarbons and other products coming out of the exhaust when driving a car. For example, how much formaldehyde is the average pedestrian exposed to? However, I assume catalytic converters will convert much of the partial combustion products into the usual CO2 and H2O.

    densest - 31-5-2010 at 15:40

    @Formatik - don't alcohol dehydrogenases convert ethanol to acetaldehyde as the first step in human metabolism of ethanol? As with many poisons encountered in the environment, small amounts can be detoxified and in this case used as a calorie source.

    Formatik - 31-5-2010 at 16:18

    The metabolism product, right. Sure, we can use ethanol as a metabolic calorie source, but it is one of the least healthy ones.

    Aurus - 1-6-2010 at 03:29

    About that, it is interesting that the two carbon compounds (ethanol, acetaldehyde and acetic acid) are the least toxic, compared to methanol, propanol, formaldehyde etc. I have heard of this metabolic process that uses two-carbon parts. Maybe that's why.