5

Probably a silly question, and I have never heard of an incident, but then again that does not rule out a safety issue. Basically, if I want to put a covered pot in the oven with beer or wine (or some other alcohol), is there a safety concern, or a pre-oven step that must be done? The reasoning is that if the alcohol cooks off as a gas, could it be trapped in the oven, and heat up until it explodes or starts a fire?

For now, I usually add the beer or wine to the pot on the stove, and let it heat up uncovered for a few minutes before the oven.

  • 2
    One other point: you don't really drive off much alcohol by bringing it up to boiling point on the stove. Previous answers here have linked to some real data on that. So it's not much less alcoholic when you put it in the oven for this step. – Chris H May 8 '17 at 5:50
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This is a little speculative but too much of an answer for a comment.

We've had a few discussions here about the relative rates of boiling off water and alcohol. The result is that the alcohol vapour (starting from even pure beer/wine) will be mixed with quite a lot of water vapour so will be dilute even before it mixes with air.

Apparently you need between 3.3% and 19% alcohol in air for it to be flammable. A source of ignition is also required (e.g. the flame in a gas oven). Gas ovens have to be fairly well ventilated for there to be enough oxygen to support a flame. So much of the alcohol would escape. Any that does reach the flame is likely to be consumed there unnoticed before much can build up.

An electric element (not the air in the oven) does get hot enough to ignite alcohol. It can ignite spitting fat and that doesn't cause a problem except a smoky kitchen. If you've boiled off enough to replace 3.3% of the air with alcohol you've also replaced quite a bit with water vapour too. An oven would have to be very well sealed to allow this buildup in the first place.

I have seen an old oven door fail when grilling. In that case the (forgotten) food itself ignited and was spitting flames at the glass, which burst. It didn't cause a fire outside the oven.

I haven't considered the case of strong spirits. There's probably a way to arrange pure/flambé alcohol to ignite in an interesting way.

  • Regardless of weak or strong spirits used, liquid concentration will not equate to vapor concentration for ethanol in water. Over a broad range of concentrations, ethanol vapors are enriched significantly. Convection and partial condensation could easily produce a flammable mixture and as the flame front travels, further leaning of the mixture could happen progressively to sustain the flame. – user110084 May 7 '17 at 20:22
  • You wouldn't get partial condensation if ethanol or water in an oven. It's too hot. If the mixture is lean to start with making it leaner isn't going to make it more flammable. From liquids at or just below 100C water evaporates almost as fast as alcohol, and there's more water to start with(@user110084) – Chris H May 8 '17 at 5:45
  • Agree on condensation inside a hot oven. Water will will not evaporate as fast as alcohol across a wide range of concentrations because at any given temperature, ethanol would have a higher vapor pressure than water. Only at the azeotrophic composition (just under 96% w/w or 80% v/v) would you get equal evaporation rates. A 14% v/v wine will boil at well below 100C at sea level. Obviously, this is a continuously changing system since the wine composition changes as it evaporates as does its boiling point. And vapor composition will also change. – user110084 May 8 '17 at 7:48
  • @user110084 except between the boiling points the difference in value pressure is rather low, limiting the concentration of alcohol in the air/water vapour/ethanol vapour mix. – Chris H May 8 '17 at 7:57
  • @Chris_H Yes. So the key issue about safety concern is quantity of alcohol used rather than high or low proof since small quantity of alcohol would not support combustion for long and the amount of energy released would be insignificant. I would hesitate to use whole bottles of wine. – user110084 May 8 '17 at 8:15
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I have never heard of any issues either, but let's do some math together:

Assuming you used a large bottle of wine, e.g. one liter of red wine for a bœuf bourguignon. And you picked a wine with 13.5 percent (by volume) alcohol, which is a rather high percentage. Then you end up with 13.5 ml of pure alcohol (or 10.6 g). That's a scant tablespoon.

Now while one can produce a neat flash using a comparable amount of alcohol for a flambé dish (e.g. using two tablespoons of rum), you will have problems to get the concentration of alcohol in your dish to create a similar effect. The following points are preventing it:

  • The alcohol in a dish won't boil off or evaporate completely (as discussed here before) and during the process it will be diluted by water, which does not need to boil to turn into gas. So you will have only part of the alcohol available to potentially catch fire and that part will be very diluted.
  • Only if the alcohol is concentrated enough will it be able to catch fire at all - that's why you need high-proof types for flambé.
  • The alcohol is much more volatile than the water/steam, so you won't be able to create a scenario where the water boils off or escapes the oven and the alcohol remains. You can safely assume that the alcohol "goes first ".

Conclusion:
Unless you decide to pour high-proof alcohol straight into your oven, there is no risk of a fire or explosion. I probably wouldn't use a bottle of whisky to deglaze the roasting pan, though.

  • 2
    You appear to by off by 10x on the amount of ethanol; it's 0.135 x 1000 ml = 135 ml! But alternate sanity check: can you ignite wine or its vapor, even heated in a pan on a burner (a la crepes Suzette sauce?) That doesn't work for me at all unless using spirits of ballpark 80 proof (40% ethanol.) I wouldn't worry about some beer or wine in cooking, myself. – Catalyst May 1 '17 at 10:10
  • With ethanol in particular, percentage ethanol in liquid can be very massively different from that when vaporized. It is unrealistic and unwise to assume that a 1% ethanol solution in water will produce a 1% ethanol vapor with 99% water vapor. Wine with say 14% v/v wwould vaporized into a roughly 70:30 mixture (70% v/v). – user110084 May 7 '17 at 19:53
  • We do not have a simple 2-component system of just air and ethanol, but a 3-component one (treating air as a single component). The air-ethanol flammability limits do not apply. The crepes suzette example is useful, 40% v/v ethanol should not ignite, when vaporized it should produce a 73% vapor body which should not burn, but it does because of diffusion and vapor leaning as the flame front progresses. – user110084 May 7 '17 at 20:23
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There is a bit of a misconception that you can get vapor ignition only with high proof spirits. This is very different from reality because ethanol-water is a non-ideal mixture and vapor concentrations look nothing like liquid concentrations with rare exceptions. In fact, with high proof, the initial vapor is likely too rich to support combustion and ignition is typically delayed until there is enough diffusion.

It is true that with small quantities of low proof, you will not have enough alcohol to sustain a flame for very long and there would not be much energy released. If you make mulled wine and put a lit candle close to the pan, you can experience this. This is quite helpful: non-ideal mixtures

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