You usually get the purest extracts when you make them at home. Commercially produced strawberry extract, for example, contains artificial coloring, fruit juice and glycerin. Pure strawberry extract isn't difficult to make, it just isn't feasible for large-scale production -- at least not at prices most consumers will pay. Making small-batch strawberry extract at home is easy, but has one drawback: time. It takes at least one month to make strawberry extract, and up to two moths for a stronger flavor. Extracts last indefinitely, but the flavor diminishes after about a year.
Rinse the strawberries for several minutes under cool running water, and let them drain in a colander for a few minutes.
Sterilize a clean jar and lid by boiling them for 10 minutes, or washing them with 1/4 tablespoon of all-purpose bleach mixed with 1 quart of water and then rinsing it off.
Slice the strawberries 1/4 inch thick. Pack them in the sterilized jar.
Cover the strawberries with 80-proof alcohol. Neutral spirits like vodka produce the purest taste; use brandy, rum or whiskey for additional flavor.
Seal the jar and place it in a cool cupboard for one to two months. Shake the jar once a week. Steep the strawberries one month for a moderate strawberry flavor and two months for a strong flavor. Taste the strawberry extract after one month.
Strain the strawberry extract through a sieve lined with three or four layers of cheesecloth and into a measuring cup. Pour the extract into a sterilized dark bottle with a rubber stopper. Store the extract in a cupboard.