This question came up last night in a conversation about whether it is okay to serve food prepared with alcohol to children. My initial thought was that much of the alcohol burns off during the cooking process. It seems though, the answer is not as simple as that.
Based on a study published in the Journal of the American Dietetic Association back in 1992, the amount of alcohol retained in a food actually depends on the cooking method and length of time.
The following is a list of preparation methods and cooking times indicating what percentage of alcohol is retained:
(The following information was prepared by Rena Cultrufelli of the USDA, one of the study coauthors)
- No heat application, immediate consumption (Alcohol Retained 100%)
- No heat application, overnight storage (Alcohol Retained 70%)
- Alcohol ingredient added to boiling liquid, and removed from heat (Alcohol Retained 85%)
- Flamed (Alcohol Retained 75%)
- Baked, approximately 25 minutes, alcohol ingredient on surface of mixture/not stirred in (Alcohol Retained 45%)
- Baked/simmered, alcohol ingredient stirred into mixture:
15 minutes (Alcohol Retained 40%)
30 minutes (Alcohol Retained 35%)
1 hour (Alcohol Retained 25%)
1.5 hours (Alcohol Retained 20%)
2 hours (Alcohol Retained 10%)
2.5 hours (Alcohol Retained 5%)
So, essentially the longer you cook the dish, the less alcohol will be left in the food.
With regard to serving children foods with alcohol in them, its probably best to avoid it. There are several possible substitutions for alcohol in recipes, the most obvious ones being broths, vinegars or fruit juices, depending on what you are making. There is also a very good list of substitutions at this link.
Or, if you know you will be cooking for a child, you could set aside a small amount of what you are cooking, and cook that one with one of the substitutions separately.
Augustin J, Augustin E, Cutrufelli RL, Hagen SR, Teitzel C. Alcohol retention in food preparation. J Am Diet Assoc. 1992, Apr;92(4):486-8.