Introduction: Root Beer: the Science Behind the Delicious Drink
Root beer has long been a favorite soft drink. Its sweet sassafras root taste was used in the early Americas for culinary and medical purposes. Since then, root beer has spread across the world and has been enjoyed by many.
In this Instructable I'll cover a simple recipe for homemade root beer and then dive into the chemistry behind the drink.
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Step 1: Make Some Root Beer!
To make some root beer (yields about 1.2 gal), you'll need these things:
- Root Beer Extract - 4 teaspoons
- White Sugar - 2 1/2 cups
- Water - 16 cups
- Dry Ice - 2 pounds
To start out, boil the water in a large pot on high heat. Boiling water heats up the H2O as well as the sugar molecules, helping to dissolve the sugar faster. You don't technically need to do this, but I did just because it sped up the process.
After the water is boiling, add all your sugar, stirring slowly to dissolve it. After all the sugar has dissolved, remove the pot from the heat and let it cool.
Once the sugar-water mixture has cooled, add the root beer extract. This stuff is super strong - don't add too much! Stir in the extract and put the pot in the refrigerator. This will prepare it for the carbonation process.
Step 2: Carbonation!
The next step in making root beer is the carbonation. Carbonation is simply dissolving CO2 into a fluid - root beer in this case. There are many ways to carbonate a drink, but for this Instructable, we'll just use the classic dry ice approach.
Dry ice is the solid form of CO2. The cool thing about CO2 is that it will not stay in liquid form under normal atmospheric pressure. Only at 5.2 atmospheres and above will liquid CO2 be possible (above -56.4°C). Further information can be found on the chart above.
It is really simple to do this - just take your pot out of the refrigerator and add dry ice to it. The colder the fluid, the more CO2 will dissolve. Make sure to wear gloves! Dry ice will give you frostbite in a matter of seconds! Once you add the dry ice, the root beer should start smoking very viciously. Just wait until all the smoke clears away (playing with the smoke is actually pretty fun to do while you wait), and you'll have your root beer!
After I did this, I tried putting the root beer into a bottle and then adding the dry ice. I capped the bottle and the pressure increased. The higher the pressure and the lower the temperature, the more CO2 will dissolve. Putting it into a bottle is more dangerous, as the bottle could potentially explode, but in the end, the root beer carbonated better. If you use this method, do so at your own risk!
Step 3: The Science!
While it may seem like you just threw a few things together, the science that went into making root beer is actually pretty cool. When you dissolve carbon dioxide into water, a chemical reaction takes place, forming carbonic acid (H2O(l) + CO2(g) ⇌ H2CO3(aq)). Carbonic acid is what gives soda its tart flavor and is what creates the tingling feeling on your tongue. It is present in your body and is the only acid excreted as a gas by the lungs in order to maintain a balance between the acids and bases.
The root beer taste originates from the sassafrass root, but vanilla, anise, and sarsaparilla root flavorings also attribute to the flavor. However, in the 1960s, the FDA banned sassafrass root as a natural flavor because of the claim that it caused cancer. Since then, artificial flavorings have been used almost entirely, but there are some who still use the natural root for flavoring.
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Is the amount of carbonation less than a normal soda?
When I put the dry ice into the pot without any way to build pressure, the carbonation was definitely less than normal soda, although it was still carbonated just fine. However, when I put the dry ice into the bottle and sealed it (letting excess CO2 escape as needed), the result was comparable to normal soda.