Alcohol extractions provide the simplest way to distill just about any fruit to its essence -- but pineapple isn't just any fruit. Pineapple contains bromelain, a protease tenderizer. Normally a little bromelain isn't a problem -- it works wonders on tough meat -- but in doughs and batters, it breaks down the gluten needed for structure and strength. Bromelain does the same to gelatin, turning it to liquid. This is why canned foods are sometimes better than fresh: During canning, bromelain is destroyed, making the extract you create from it safe for use in baked goods and desserts.
Strain the juice or water from the pineapple pieces by pouring the canned pineapple over a strainer. Let the pineapple drain for a few minutes.
Fill a 1/2-pint jar half full of drained pineapple pieces. Pour the alcohol over the pineapple to cover.
Seal the jar and set it out of direct sunlight, ideally in a cupboard. Let the pineapple sit for 6 hours if you used 190-proof alcohol; 24 hours if you used 151 proof; and two to three days if you used 100 proof.
Shake the jar every couple hours. Dip a spoon in the extract after the recommended time for the alcohol you used -- shake off the excess extract into the jar -- and taste. Let the pineapple sit a few more hours if you want a stronger flavor.
Line a chinois or fine-mesh sieve with two or three layers of cheesecloth. Set the strainer over a bowl. Pour the pineapple and the extract into the strainer.
Press the pineapple solids with the back of a spoon. Transfer the extract in the bowl to a dark-colored glass jar with a dropper. Store the extract in a cupboard up to a year for the most potency.