This instructable will discuss the basics of vinegar manufacture. You could, for example, try to turn wine into vinegar by just leaving it out, but the results will be more variable than a controlled process.
Step 1: Mother
The basis of vinegar production is the mother. This is a thin film of gelatinous bacteria that forms on top of the liquid. This is what is floating around inside the jar when you buy raw vinegar. The mother is also referred to as mycoderma aceti. It consists of cellulose and acetic acid bacteria.
Many acetobacter species are found in vinegar mothers particularly acetobacter aceti. These are gram negative obligate aerobes that are benign and found where there is wild alcohol production like flowers, fruits, insects, water and soil. They feed on ethanol and convert it to acetic acid, which was first proved by Louis Pasteur in 1864. The bacteria grow best at temperatures ranging from 75-85 degrees Fahrenheit and in the pH range 5.4-6.3.
You can order a vinegar specific mother online, use the mother from a bottle of unfiltered/raw vinegar or cultivate your own. Once the mother is established it will last indefinitely as long as it is fed. You can also share it with friends by suspending it in a solution of alcohol (wine, beer, etc) and water.
Step 2: Local Mother
You can make your own mother with a trap. Take a plastic bottle and add equal parts sugar and water. Also add fruit like apples or banana peels and add a dash of vinegar. Leave the top off the bottle and hang outside in a the shade. In a few weeks a cloudy substance will form. This is the mother forming. Natural yeast on the fruit will convert some sugar to ethanol for the bacterial on the visiting insects to convert to vinegar. You will need to test the mother to see what kind of vinegar flavors it produces. Some will be better than others. Trying many traps in different locations through trial and error should yield a desirable mother.
Step 3: Recipes
Vinegar can be made from beer, wine and other alcoholic beverages as long as it is diluted to under 10% alcohol. For this example red wine will be used. The flavor of the wine will directly effect the flavor of the vinegar. This doesn't mean it has to be expensive, but it should taste good. Filtered water is best because the chlorine and flouride in municipal water can adversely effect acetification.
All at once method:
Place 0.5 cup unfiltered vinegar, 4 cups wine, and 2 cups water in the jar all at once.
Place 2 cups wine and 1 cup filtered water in the jar and let sit for 1 week. Add 2.5 cups of wine, on 3 different days, over the course of the next week for a total of 7.5 cups added.
The initial level of alcohol will correspondence with the final level of acidity. This should be taken into account when starting and maintaining the process.
Step 4: Jar
Add the liquids to a sterilized 1-2 gallon vessel. It can be made of glass, ceramic, plastic, wood or stainless steel, but not of reactive metal. A container that blocks light is best. A wide vessel works well because it increases the surface area for oxygen uptake. A spigot on the bottom of the container is also good for tasting and draining the product.
After the liquid is placed in the container cover it with cheesecloth and wrap it with a rubber band. This will keep out insects but allow oxygen in. Store in a warm dark place like a kitchen cabinet that is not often opened. Try not to disturb the mother.
Step 5: Done
Vinegar production usually takes 6-18 weeks. Testing for completion consists of smelling and tasting the liquid. This is based on preference and when it smells and tastes good to you it is complete. If there is a strong smell of nail polish remover this is ethyl acetate and could mean the vinegar has gone bad and the process needs to start over. If a particular pH is desired the vinegar can be tested with strips or an electronic pH meter.
C2H5OH + O2 = CH3COOH + H2O
Step 6: Ethyl Acetate
Ethyl acetate generates an acetone like off-odor, the most common source of which are spoilage microbes. Nonetheless, it can accumulate abiotically from the esterification of ethanol in the presence of acetic acid. At concentrations below 50 mg/liter, ethyl acetate may add a subtle fragrance. However, above about 100 mg/liter, it begins to have a negative influence, possibly due to suppression of the fragrance of other aromatic compounds such as fruit esters. At above 150 mg/liter, ethyl acetate generates an obvious acetone like off-odor. In other words a little bit is OK and can add a fruitiness, but too much means a production failure.
Step 7: Bottle and Maintain
You should smell the vinegar regularly to monitor its progress. When you are satisfied with the product you can drain it off and add new wine and water to the mother. Some people keep adding wine to the pot and take off small amounts of vinegar at a time.
Pass the vinegar through a coffee filter and pasteurize by heating to 140-160F for 10 min. Using a water bath or temperature set slow cooker will help maintain temperature. Water can be added at this point to reach the desired strength. Store in a sterilized glass bottle.
Once the vinegar is decanted and pasteurized it can be left to mellow for a number of months.
If not pasteurized the vinegar can be stored in the refrigerator for a few weeks.
As the mother multiplies new mother will sit on top and old mother will sink to the bottom. You can fish out the old mother with clean hands every month or so.