A guest project by Rich Faulhaber, contributing Evil Mad Scientist.

“Infusing unsuspecting whole fruit with gaseous CO2 in the entire Tri-State Area!”

In an effort to make fruit fun for the kids, I built a carbon dioxide injector from parts in my garage with the purpose of carbonating whole fruit! With a common house water filter housing, a 16 Oz paintball CO2 canister, an old gas regulator, and some miscellaneous valves and fittings, I was able to bring this fizz fruit apparatus to life, and the kids love the results.

The principle
Carbon dioxide dissolves well in water, hence the reason you find it as the source of fizz in all your favorite soda drinks. When you open your soda and let it sit out on the counter you will find that after some period of time the soda loses its fizz and becomes “flat.” The rate at which the drink loses its fizz depends on pressure, temperature and the surface area of the liquid and the environment. Skipping the thermodynamics lecture, let me just tell you that the process works in reverse as well. To reverse this process, one needs only to have a high pressure CO2 environment, a medium to infuse (i.e., the fruit) and enough time to let the gas diffuse across the fruit skin and dissolve into the water inside. Refrigerating the fruit helps tremendously in the process as well.

Parts list

• 16 Oz paintball cylinder (or a more proper CO2 tank if you happen to have one)

• Gas Regulator
• Household water filter housing
• Some hose
• Toggle or ball valve
• Miscellaneous fittings to hook it all up
• Fruit

This type of water filter housing is designed to withstand water pressures in excess of 100 psi, and it comes with two ports and an o-ring seal. These can be bought for about ten dollars at Lowes or Home Depot. Its ports are standard 3/4-inch type. Use Teflon tape (plumbers tape) on all the threads. Thread in a plug on one side and a valve on the other. I used a toggle valve with a quick disconnect to make everything easier. The hose can by any standard type rated for at least 100 psi. Small bundles are available in the plumbing section of your hardware store.

For gas handling I used an old single stage regulator. These can be quite expensive new but often times you can find deals at garage sales or in surplus stores. You don’t need anything fancy, just something to step down the pressure to something manageable– well below 100 psi. My CO2 source is a standard-issue paintball cylinder.

Procedure:

1. Pre-chill the fruit in the refrigerator. Get it nice and cold. My favorites are grapes, oranges and blueberries. However, just about any fruit with a large water content will work.

2. Open the house water filter by unscrewing the lid. Place your cold fruit inside.

3. Connect the CO2 tank to your water filter housing. This is where the quick disconnects come in handy.

4. Adjust the regulator output to about 40-60 psi, the higher the better but make sure all your connections are extra tight and sealed or “it might get dangerous.” If you think you have a leak somewhere, you can apply some soapy water where you think the leak is and look for bubbles. If you see bubble just tighten until they stop forming.

5. Start pressurizing the house filter by opening the toggle valve. On top of the water filter housing there is a pressure relief button. Depress this while you fill to get some of the residual air out.

6. Once pressurized, shut the toggle valve and disconnect the CO2 line. You can store the unit in the fridge or somewhere out of sight.

7. Then, you wait. Depending on the fruit, temperature, and pressure, carbonation should occur between 20-60 minutes. If you go too long at too high a pressure the skin of the fruit can burst and it will be a big mess, if you go too short and at too low of a pressure, the results will be unimpressive. Experiment with your fruit, pressure, and duration until it suits your tastes.

8. Open the toggle valve to release the pressurized gas then unscrew the lid to the housing and enjoy your newly carbonated fruit.

And of course, the kids love the “poppy fizz” inside the fizzy fruit.