Advanced Biology
Lab: Making Ginger Ale

Fermentation has been used by mankind for thousands of years for raising bread, 
fermenting wine and brewing beer. The products of the fermentation of sugar by 
baker's yeast Saccharomyces cerevisiae (a fungus) are ethyl alcohol and carbon 
dioxide. Carbon dioxide causes bread to rise and gives effervescent drinks their 
bubbles. This action of yeast on sugar is used to 'carbonate' beverages, as in the 
addition of bubbles to champagne).

We will set up a fermentation in a closed system and capture the generated carbon 
dioxide to carbonate our home made ginger ale. You may of course adjust the quantities 
of sugar and/or extract to taste. Note that the lemon called for in step eight is optional. 
And if you want a spicier drink, you can increase the amount of grated ginger.

EQUIPMENT	SUPPLIES
clean 2 liter plastic soft drink bottle with cap funnel Grater (preferably with fine "cutting" teeth 1 cup measuring cup 1/4 tsp and 1 Tbl measuring spoons	cane (table) sugar [sucrose] (1 cup) Freshly grated ginger root (1 1/2-2 tablespoons) Juice of one lemon fresh granular baker's yeast (1/4 teaspoon) cold fresh pure water

Procedure
1.  Add 1 cup sugar to the 2 liter bottle with a dry funnel.  (Leave the funnel in place 
    until you are ready to cap   the bottle.)

2.  Measure out 1/4th teaspoon fresh granular active baker's yeast.

3.  Add yeast through funnel into the bottle, shake to disperse the yeast grains into 
     the sugar granules.

4.  Grate the ginger root on a fine "cutting" grater to produce 1 1/2 Tablespoon of 
     grated root. 

7) Place grated ginger in the cup measure

8)  Juice a whole lemon. 

9)  Add the juice of a whole lemon to the grated ginger.

10)  Stir the lemon juice and grated ginger to form a slurry

11)  Add the slurry of lemon juice and grated ginger to the bottle.  (It may stick in 
        the funnel.  Don't worry, the next step will wash it into the bottle.)

12)  Rinse containers with fresh clean water.

12)  Add the rinsings to the bottle, cap and shake to distribute.

13)  Fill the bottle to the neck with fresh cool clean water, leaving about an inch 
       of head space,  securely screw cap down to seal. Invert repeatedly to thoroughly 
       dissolve sugar.  (The ginger root will not dissolve, of course.)

14)  Place in a warm location for 24 to 48 hours.  (Do not leave at room temperature 
       longer than necessary to feel "hard."  The excess pressure may cause an eruption
       when you open it, or even explode the bottle!)

15)  Test to see if carbonation is complete by squeezing the bottle forcefully with your 
        thumb.  If it dents in as in the picture, it is not ready.

16)  Once the bottle feels hard to a forceful squeeze, refrigerate overnight to thoroughly 
        chill before serving.

17)  Filter the ginger ale through a strainer if you find floating pieces of ginger objectionable.  
       These are found in the first glass or two poured, and, since most of the ginger sinks to 
       the bottom, the last glass or so may require filtering too.  Rinse the bottle out immediately 
       after serving the last of the batch.

NOTE: There will be a sediment of grated ginger and yeast at the bottom of the bottle, so 
that the last bit of ginger ale will be carry ginger fibers. Decant carefully if you wish to avoid
this sediment.

Note that the gas will develop faster in ginger ale, presumably because there is much more 
nutrients in it than in root beer extract.