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Root Beer Lab

Root beer was made by our forefathers by soaking Sassafras (a type of tree) root in water, and adding sugar and yeast (yeast for carbonation). In the early 1900's however, scientists discovered that safrole, a chemical found in Sassafras root, was a carcinogen (which means it is a cancer causing agent). Now, a mixture of other herbs and spices makes up "root beer extract" which is what we now use to make homemade root beer.

Respiration is the breakdown of sugar (glucose) to form ATP (a form of energy for an organism). There are two types, aerobic and anaerobic (also called fermentation). Yeast cells (a type of fungus) obtain energy from glucose (sugar) by a specific anaerobic process called fermentation.  There are two types of fermentation, lactic acid fermentation (which occurs in muscle cells when they are oxygen deprived), and alcoholic fermentation, which is involved in the making of food products. Alcoholic fermentation begins after glucose diffuses into the yeast cell. The glucose is broken down into two, three carbon molecules called pyruvic acid. The pyruvic acid is then converted to CO2, ethanol, and energy for the yeast cell. Fermentation is used to make a variety of food products, including the making of beer, wine, bread, cheese, sauerkraut, and baked goods. It is the carbon dioxide produced by the yeasts that give root beer its "fizz."  This fizz is produced in store bought root beer by a carbonation machine that forces  carbon dioxide into the root beer mixture, without the aid of our little yeast friends.

Equation for respiration:

C6H12O6 + O2 ---> CO2 + H2O + ATP

IB Standards: 

Materials:

Clean empty 2 liter plastic bottles + caps; Large Bowl; Funnel; Mixing spoon; Water (preferably spring water); Brewer's yeast (the dry kind), Rootbeer extract; Sugar; Measuring spoons; and cups.

Procedure:

  1. Dissolve 1/8 heaping teaspoon of yeast in 2/3 cup of very warm water. Let stand for 5 minutes and ensure yeast is thoroughly dissolved. Being in warm water activates the yeasts, and wakes them up from being dried out. Spring water, incidentally, makes better root beer than tap water.

  1. Add warm water mixture, 2.25 cups sugar and 1 tablespoon Rootbeer extract and mix in a 1 gallon container.

  1. Pour half of the mixture from Step 3 in two soda bottles then top off each bottle with plain water to within 2 inches from top of bottle.

  1. Seal with a resealable cap and shake.

  1. Store the bottles at room temperature in approximately 65-70 degrees Celsius for 4-6 days in a dark place; the firmness of the bottle indicates the amount of carbonation. Refrigeration will stop the fermentation process and kill the yeast. Total aging of at least one week is recommended. Two weeks will improve the flavor. Be sure to check the bottles every day for tightness, if they get too pressurized, they will explode. Never use glass bottles!

  1. Filter the Rootbeer to remove yeast if necessary.  Chill root beer and taste! 


Analysis:

  1. Describe the appearance of the root beer during the bottling process.

  1. Describe the appearance of the root beer after fermentation. How is it different from #1?

  1. Why is the yeast necessary in this experiment (what purpose does it serve)?

  1. Why is the sugar necessary?

  1. Explain how the root beer came to be carbonated.

  1. Why did we put the yeasts in the warm water for 5 minutes?

  1. Explain the process of anaerobic respiration (fermentation)?