Many people believe that all alcohol burns off in cooking, but I remember reading a USDA report about the extent to which all alcohol does not burn off. Please discuss.
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Contrary to the common belief that alcohol completely evaporates during cooking, a study from the U.S. Department of Agriculture (USDA) confirms that significant amounts can remain depending on the preparation method. Retention ranges from as high as 85% to as low as 5%, but alcohol is rarely fully eliminated.

Alcohol Retention by Cooking Method

The following data, based on the USDA Table of Nutrient Retention Factors, illustrates the percentage of original alcohol that remains in a dish after various types of preparation:

Preparation Method - Percent Alcohol Retained
Added to boiling liquid and removed from heat - 85%
Flambéed (flamed) - 75%
No heat (stored overnight) - 70%
Baked (25 mins, not stirred) - 45%

Baked or simmered (stirred into mixture)
— 15 minutes 40%
— 30 minutes 35%
— 1 hour 25%
— 2 hours 10%
— 2.5 hours 5%

Key Factors Influencing Retention

Cooking Time: This is the most critical factor; the longer a dish is cooked, the more alcohol evaporates.

Surface Area: A larger cooking vessel (like a wide pan) provides more surface area for evaporation, resulting in lower alcohol retention than a deep, narrow pot.

Heat Level: Higher temperatures accelerate evaporation, but even boiling does not immediately remove all alcohol.

Method of Incorporation: Stirring the alcohol into the mixture helps it evaporate faster than if it is layered or added at the end.

Ingredients: Thick sauces or breadcrumbs can trap alcohol molecules, slowing down their evaporation.

While the residual amount is often not enough to cause intoxication for most adults, it can be significant for individuals in recovery, pregnant women, or those avoiding alcohol for religious or health reasons.