Cider vinegar final product

Our final cider vinegar product, pre-filtration and pasteurization.  Pretty gross stuff, but as for vinegar ferments this is the least gross I've seen.  The white film on top is known as "mother of vinegar" and is a mat of yeasts, molds, and bacteria that carry out the production of vinegar. 

So the finished product of our cider vinegar experiment is finally complete after a month of waiting.  As you can see from the above picture the finished product is quite gross and you probably wouldn't want to drink it straight.  All those microorganisms, though not dangerous in themselves, might not be good for your stomach!

To start this project, all I did was place apple juice in a one gallon jar, cover the opening with panty-hose, and let it sit at room temperature for four weeks.

So during the past four weeks this is what happened: Atmospheric yeasts and molds fall into the apple juice and ferment sugars into alcohol (ethanol).  This process of making alcohol is anerobic, meaning without oxygen, and is called fermentation.  Once the yeasts and molds converted all of the sugar to alcohol, Acetobacter sp. of bacteria metabolized the alcohol into acetic acid (vinegar) aerobically (with oxygen).

1. Sugar + yeast -->Ethanol

2. Alcohol + Acetobacter sp. --> Acetic acid

If this process is allowed to continue the Acetobacter sp will begin to convert the acetic acid into water.  If the process of making vinegar is carried out perfectly, the percent alcohol in the juice will produce the same percent of vinegar.  So if 10% alcohol is produced this should make a 10% vinegar.  

Above is a media plate that was inoculated with vinegar before pasteurization.  The large circular colonies with black specked centers are some sort of mold that may have aided in the fermentation of the apple juice.  The tiny white dots outside of the large mold colonies are Acetobacter colonies.  These microorganisms were filtered out and killed through pasteurization before consumption.

As you can see from the above picture, the vinegar is loaded with all kinds of gunk, which are bacteria, yeasts, and molds.  In order to clean up the vinegar I filtered it though a coffee filter to remove the large chunks as much as possible.  Then the filtered solution was pasturized by heating to about 180 degrees to kill the remaining microorganisms.  

Filtered vinegar solution on left and unfiltered on right.  Note how much clearer the filtered solution is.  The clarity of the filtered solution is due to the removal of microorganisms that cloud out the original solution.

After this entire process I finally tasted the vinegar.  Unfortunately it was quite watery which means I let it set out for too long.  The alcohol content probably never got too high because I didn't add any sugar which also led to a low vinegar content.  So I am trying vinegar making again.  For this next batch I used 1/2 gallon of gape juice, 1 cup of sugar, and mixed it with the slurry left over from the first batch of vinegar.  This time I am only going to let it sit for about two weeks or so to see what happens.  If this batch doesn't work well, I'll just try again.  Trial and error is a rule for science as well as success in life...

My next try at making vinegar.  1/2 a gallon of grape juice, 1 cup of sugar, mixed with about 1 cup of slurry from the last batch of vinegar I made.