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There seems to be a lot of confusion about what a vinegar mother is and what role it plays in the production of vinegar. It seems to be a prized ingredient which is guarded and cared for surrounded by some type of mystery.
The vinegar mother is a pellicle which is formed by acetic acid bacteria in the liquid. Pellicles are not exclusive to vinegar production but also appear in several other fermentations. Vinegar pellicles are usually present in homemade vinegar but are not necessary for vinegar production.
Vinegar is made by allowing yeast and acetic acid bacteria to grow in a sweet liquid. The yeast produces alcohol and the acetic acid bacteria produce the acetic acid. This process will happen with or without a vinegar mother.
How vinegar is made without a mother
When making vinegar without a mother you are relying on two naturally occurring microbial cultures to grow and then dominate your potential vinegar. These cultures are made up of yeast species and acetic acid bacterial species.
The yeast species can be found mostly on the ripe fruit or vegetable you are using to make your vinegar. They grow best in the presents of simple sugars which makes there population high when the fruit it ripe. Most of these yeast species have a low tolerance for alcohol of about 4%.
The acetic acid bacteria (AAB) are made up of Acetobacter, Gluconacetobacter, Gluconobacter and Komagataeibacter. In commercial production Acetobacter is the main species which is used to convert alcohol into acetic acid but homemade vinegar usually includes them all in varying populations. It is the Gluconacetobacter and Komagataeibacter which are the main producers of the vinegar mother which is so prized in homemade vinegar production.
When making vinegar at home there are two methods available:
Simultaneous alcohol and acetic acid production:
When making vinegar without a mother with this method you are relying on the naturally yeast and AAB to dominate the vinegar base preventing the growth of unwanted species which can produce unwanted flavors in your vinegar.
To do that you must encourage the growth of the yeast and ABB by putting your vinegar in the proper environment which includes the correct temperature, sugar concentration, access to oxygen and regular stirring.
Method of simultaneous alcohol and acetic acid production without a mother
The concern with making vinegar with an unfermented sweet liquid is the opportunity for mold and other unwanted microbial growth in the liquid before the yeast and acetic acid bacteria gain a foothold. If this happens the vinegar will have an off taste and often be unusable.
To prevent this from happening clean all your equipment thoroughly. Wash everything you will need in hot soapy water and rinse well to get rid of any soap residue.
Make your vinegar base
According to WHO (world health organization) vinegar is safe to use and store if it has a pH below 4.0. This translates to about a 4-5% acid concentration in your finished vinegar. To make vinegar which is safe to store and will last indefinitely you will have to prepare the vinegar base with enough fermentable sugar.
The base which most homemade vinegars are made from are fruits like apple, pear and strawberry. These are great bases because they have distinctive flavors which come through in the finished vinegar once the sugars have been consumed. You can also get them pre-juiced from the grocer or farmers market.
For a less intense flavored vinegar you can chop any fruit into small cubes and add it to sweetened filtered water. You will have to add 2/3 cup of white sugar for every quart of liquid you add to the fruit to ensure the yeasts have enough fuel to make the needed alcohol.
You can check the specific gravity of the vinegar base with a hydrometer which will give you a rough idea the amount of potential alcohol the yeast will make for the AAB to convert into acetic acid. With a specific gravity of 1.050 at the beginning and a reading of 1.010 or less at the end you can be sure that the yeasts have converted the sugar into alcohol.
Pour the juice or sweetened water and fruit pieces into your fermenting container and put a breathable cover on it. You can use anything with a fine mesh which will not allow bugs of dirt particles to enter. Secure it with an elastic band.
Aerate the vinegar base
When starting without a mother the various yeast and AAB species will have a low population. This makes your young vinegar susceptible to unwanted bacterial and mold growth. To prevent this unwanted microbial growth you should agitate the surface of the vinegar base and aerate it to encourage the growth of the yeast and AAB.
It will not take long for the yeasts to dominate the culture when it is given adequate oxygen. Yeast can double their population in a short period of time once they get past their lag period. With repeated doublings of their population other microorganisms find it hard to compete and either die off or fail to grow.
The AAB need oxygen to grow. When the vinegar base is aerated oxygen enters the liquid and the AAB are put in contact with more of it. This helps the AAB to multiply as the yeast produces the alcohol. At the AAB grow they acidify the vinegar base making it harder still for unwanted microbial growth.
Ferment until the sugar is consumed
The yeast will continue to grow until it has consumed most of the fermentable sugar in the vinegar base. At this point you will notice that the liquid will begin to smell acidic and little or no effervescence will be noticeable when stirring the vinegar.
It is now safe to leave your vinegar alone. The yeast has consumed most of the sugar and will have started to die off. You will be able to tell by looking to see if there is a layer of dead yeast cells on the bottom of your container. At this point the AAB are very active producing acetic acid.
You can continue stirring your vinegar or you can leave it alone. If you leave it alone the AAB will begin forming a pellicle otherwise known as a vinegar mother. It will start as a layer of whitish film on the surface of the vinegar and thicken over time.
Filter and age your vinegar
Begin tasting your vinegar after a month or so. When it has reached a pleasant flavor pour some into a container for use. Filter the rest into a clean container to remove the lees (the sediment on the bottom).
Filtering the vinegar off the lees will help prevent it from developing a yeasty flavor as your vinegar ages. Age it by transferring it into another clean container with a wide mouthed lid. Unless the AAB have completed the conversion of all the alcohol into acetic acid you will get another pellicle forming on the top. Let it thicken as the vinegar ages.
Aging helps to smooth out the flavors of your vinegar just like aging smooths out the flavors in wine. Some vinegar is aged for years such as balsamic and rice vinegar. As long as it has reached the proper acid concentration level it will not spoil.
Pre-fermentation of the alcohol prior to acetic acid production:
Vinegar made from an alcoholic base are vinegars like red wine vinegar, rice wine vinegar and mead vinegar. All these types of vinegars are easier to make than with unfermented sweet liquids.
The presents of the alcohol helps to inhibit the growth of molds and other unwanted bacterial growth. This helps keep off flavors out of the vinegar. It also provides different flavors which are not present in vinegar made from unfermented sources.
To make vinegar from an alcoholic base you can start with commercial wine, beer or any other alcoholic liquids or you can produce your own out of any sweet liquid.
Prepare the alcoholic base
When you make vinegar from wine or other spirits you have to prepare the solution to provide the best opportunity for the acetic acid bacteria to flourish. You do this by diluting the liquid to be in a range between 5-8% ABV.
Acetic acid bacteria grow best in a solution with an alcohol content between 5-8%. Outside of this range they will either not have enough fuel to raise the concentration of the liquid above 5% acetic acid or the high concentration of alcohol will inhibit their growth delaying the conversion to vinegar.
Alcohol By Volume (ABV) is a measurement used to indicate how much alcohol is in a solution expressed as a percentage. To adjust the percentage of alcohol to optimum levels for vinegar production use the following formula:
For example:
If you have 100 fl.oz. of wine with a 10% ABV and you want your vinegar base to be 8% then:
Additional liquid = (10% / 8% – 1) X 100 fl.oz
Additional liquid = 0.33 X 100 = 33 fl.oz
Your will have to add another 33 fl.oz of non-alcoholic liquid to lower the ABV to 8%.
Aerate the vinegar base
When starting with an alcoholic base it is not as critical to aerate the liquid. The alcohol will protect it from unwanted bacterial growth as the AAB begin to convert it into acetic acid. Aerating your vinegar will speed up the acidification process producing vinegar much faster than otherwise.
AAB need oxygen to grow so to encourage their growth stir the liquid to help to oxygenate it giving the AAB access to more oxygen. Once the liquid begins to smell acidic you can leave it to ferment or continue aerating it.
If you leave it alone it will most likely form a pellicle on the surface which thickens over time. This is what is referred to as a vinegar mother and can be used to make vinegar with other sweet or alcoholic liquids.
Age your vinegar
When making vinegar from wine or other spirits the aging process is a valuable step. It will help lower the alcohol level of your vinegar, smooth out the flavors and add additional flavors as the various AAB species grow.
There are several methods of aging vinegar:
- Open air container
As the alcohol content goes down so does the population of AAB. This slows the rate the alcohol level declines. Aging in an open air container helps to reduce the alcohol content by giving the AAB access to oxygen.
- Air locked container
This type of aging allows the CO2 to escape but will not allow anything back into the container. This prevents the AAB from getting any more oxygen and slows their growth. This will produce a vinegar which has a higher alcohol content for a longer period of time. This low oxygen environment favors different AAB which helps to develop new flavors which cannot be found in commercial vinegars.
- Closed non-reactive container
When aging vinegar in a sealed container like a glass jar ensure you use containers which can withstand pressure as the growth of the AAB will continue to produce CO2 which can be dangerous if the container explodes.
Closed to the air the vinegar flavors will blend together over time making your vinegar less harsh and young tasting. Once it has been aged a year or two the flavor will change as the various organic acids stabilize and meld together into a more even flavor.
- Closed wooden cask
Aging in a wooden cask provides another level of flavor possibilities. The vinegar reacts with the wood in the cask adding wood tones to the vinegar. Some of the more volatile compounds in the vinegar escape through the wood along with some of the liquid. Over time this makes a vinegar with a completely different taste, texture and feel.
The best example of this type of aging process is balsamic vinegar. It is aged at least 5 years before it can be considered true balsamic vinegar but it can be ages 10, 20, 25 or 50 years.
How to prevent mold growth
Mold growth in vinegar will give the vinegar a bad taste and makes it unsuitable for consumption. Preventing the growth of mold at the beginning stages of vinegar production is of prime importance as once the liquid has acidified mold will not grow.
Besides stirring your vinegar regularly until it has started to acidify it is important to:
Start with clean equipment
Wash all your equipment in hot soapy water or run them through a dishwasher with heat dry. This will eliminate enough of the unwanted mold and unwanted bacterial species on your equipment.
Protect it from contamination
Using a tightly woven clean cloth to cover the vinegar and secure it with an elastic band. This will keep out any floating contaminates as well as flies or other bugs from entering the vinegar.
When stirring your vinegar use a clean spoon and wash it in between uses.
Provide adequate heat
Yeast and acetic acid grow quickly when put in the right environment and heat is one of the most important. With adequate heat the yeasts will quickly dominate the culture leaving little room for mold to gain a foothold.
Start your vinegar in a warm location between 20-25˚C. This will give the yeast and AAB a fast start.
Pre-acidify your liquid base
A liquid which is acidic is protected from mold growth so if you pre-acidify your liquid then the chances of mold growth is minimized.
To do this you can:
- Add powdered acetic acid or lactic acid available through wine, beer or cheese making stores
- Add 1 part finished vinegar to 4 parts liquid
These will help protect your vinegar from mold growth but they will change the flavor of the finished vinegar. When adding straight acetic acid or lactic acid to a liquid the flavors which would have been developed in the process of getting to that acidity will have been skipped.
It is like the difference between sourdough bread and quick rise bread. The quick rise bread makes a nice fluffy loaf but it is missing many of the flavors which are found in a good sourdough.
Adding finished vinegar will add the flavor of the vinegar you added. If you are making cherry vinegar adding apple cider vinegar to acidify it will add a distinct apple flavor to your cherry vinegar. Even white distilled vinegar has a distinctive flavor so be careful when choosing your acidifying vinegar.
Using finished vinegar not only adds flavors but also can infect your vinegar with vinegar eels. Production vinegar often has these small creatures growing in them. Although these are not harmful in any way they are a little disconcerting and can change the flavor of your vinegar.