If you’re starting from scratch and not using a culture to speed the fermentation of alcohol into vinegar, your best bet is to start with an ingredient that contains a low level of alcohol (no more than 5-10%) and no added sugar. Apple cider, wine, fermented fruit juice, or stale beer make a perfect starting material. Regarding cider, you can start with fresh apple cider or hard cider. Fresh cider takes a few weeks to convert to vinegar because it first ferments into hard cider before becoming vinegar.
Pour the starting liquid into a glass or stoneware jar or bottle. If you are using glass, try to select a dark bottle. Fermentation occurs in the dark, so you either need a dark container or else need to keep the liquid in a dark place. The advantage of a clear bottle is that you can see what is happening when you check the vinegar, but you need to keep it darkened the rest of the time.
The fermentation process requires air, yet you don’t want insects and dust getting into your recipe. Cover the mouth of the bottle with a few layers of cheesecloth and secure them with a rubber band.
Place the container in a dark, warm place. You want a temperature of 60-80°F (15-27°C). Fermentation occurs more quickly at a warmer temperature. The length of time needed to convert the alcohol to acetic acid depends on the temperature, composition of the starting material, and availability of acetic acid bacteria. The slow process takes anywhere from 3 weeks to 6 months. Initially, the bacteria will cloud the liquid, eventually forming a gelatinous layer on the top of starting material.
The bacteria need air to remain active, so it’s best to avoid disturbing or stirring the mixture. After 3-4 weeks, test a small amount of the liquid to see if it has converted to vinegar. First, smell the covered bottle. If the vinegar is ready, it should smell like strong vinegar. If the bottle passes this initial test, unwrap the cheesecloth, draw off a little liquid, and taste it. If the vinegar passes the taste test, it’s ready to be filtered and bottled. If you don’t like the taste, replace the cheesecloth and allow the solution to sit longer. You can check it weekly or monthly if it’s not ready. Note: a bottle with a spigot at the bottom makes the taste test much easier, since you can remove a little liquid without disturbing the Mother of Vinegar forming at the top of the container.
Now you’re ready to filter and bottle your homemade vinegar. Filter the liquid through a coffee filter or cheesecloth. If you plan to make more vinegar, keep some of the slimy material on the filter. This is the Mother of Vinegar and can be used to speed the production of future batches. The liquid you collect is the vinegar.
Since homemade vinegar typically contains a small amount of residual alcohol, you may wish to boil the liquid to drive off the alcohol. Also, boiling the vinegar kills any undesirable microorganisms. It’s also perfectly acceptable to use the freshly filtered, unpasteurized vinegar. Unpasteurized vinegar will have a shorter shelf life and should be refrigerated.
Unpasteurized (fresh) vinegar may be stored in sterilized, sealed jars in a refrigerator for a few months.
To pasteurize vinegar, heat it to 170°F (77°C) and maintain the temperature for 10 minutes. This can be achieved easily in a crock pot, if you don’t want to babysit a pot on the stove and monitor its temperature. Pasteurized vinegar may be stored in sealed, sterilized containers for several months at room temperature.
Note: This article was an entry in our August – September 2014 writing contest. Click here to find out about our current writing contest.