When you drink soda, bubbles of carbon dioxide (CO2) cause the tingling sensation on your tongue. In addition to the physical sensation, the CO2 combines with your saliva to produce carbonic acid, which is an important flavor component of carbonated beverages. If you’ve ever taken a swig of flat soda or beer, you’ll know that the carbonation is really important.
For a healthy treat, you can add the sparkling qualities of CO2 to fresh fruit in your own kitchen. You can achieve this with solid CO2 (dry ice), but it has to be measured very carefully due to the pressurized nature of this project. Using effervescent tablets like Alka-Seltzer is a great alternative since they have a long shelf life and produce a known quantity of CO2.
Caution #1: This is a high-pressure project. Use plastic instead of glass, and keep the lid pointed away from yourself and others.
Caution #2: Aspirin is an ingredient in regular Alka-Seltzer. Make sure to buy the aspirin-free version.
1. Add tablets
Add 4 effervescent tablets to the container (Figure A). This will produce a pressure of 20psi at room temperature in the 1-quart container. Don’t add more than 4 tablets, or the excess pressure could pop the lid off. If your container is smaller than 1 quart, scale the number of tablets accordingly.
2. Cut and add cup
Cut off the top of the disposable plastic cup so that it is just a few inches tall. Then cut down one side and halfway across the bottom (Figure B). Push the collapsed cup into the container, with the bottom facing up (Figure C).
3. Cut and place fruit
Cut up some fruit and place on top of the cup (Figure D). Keep the fruit from falling or it will absorb some of the aspirin and the flavor will suffer.
4. Add water and lid
Add ¾ cup water (Figure E), and quickly screw on the lid. Tighten firmly, but don’t overdo it.
5. Chill and enjoy
Chill the container in the fridge for a few hours, or preferably overnight. Slowly open the container, and enjoy your fizzy fruit right away! You can put your fizzy fruit through these steps again for extra fizz.
Updated 9/27/16 with caution about aspirin contained in Alka-Seltzer tablets.