So, you like vinegar. Not just the store white distilled brand but many types. Or maybe you just love apple cider vinegar and hate the bland tasting store brand. Home made vinegar is a lot like garden grown vegetables: yours always tastes better. There are many reasons that homemade vinegars can be great but a big one is you don’t have to use the lowest cost cider or wine like large manufacturers. You can use the $20 bottle of wine that no mass producer would touch with a 10 foot pole. Or the cider from the local orchard store. How about the strawberries from the bush in your backyard? The possibilities are endless.
I would be remiss to say there are a lot of guides online to making vinegar. Their quality ranges from excellent to awful and misleading. This several part series will hope to be the former type and give you a good and detailed guide on making vinegar. I make it regularly from small to large production batches and know many of the secrets, tricks, and pitfalls.
What is vinegar?
This is a basic but good starting question. Most people will think vinegar is “spoiled wine” or spoiled cider. In fact, the term vinegar comes from the French vin aigre or sour wine. What vinegar essentially is though is acetic acid. Like wine is ethyl alcohol in water (with flavor of course), vinegar is acetic acid in water. Acetic acid (named for acetum the Latin name for vinegar) is a relatively weak acid but one that can nonetheless corrode quickly. It is harmless and even healthy for us in small concentrations.
How is vinegar made?
Most people know yeast make alcohol by fermenting sugar but very few know the deed for vinegar is done by bacteria. These are good bacteria, not the type that make us sick. Acetic acid bacteria (AAB) are the workhorses of all vinegar fermentation forming the famous ‘mother of vinegar’ and using oxygen in the air to convert alcohol to acetic acid. Caring for AAB and understanding their needs is crucial to a successful vinegar fermentation.
Vinegar: Acidity is to vinegar as ABV is to alcohol
Most people know that alcohol content is measured in alcohol by volume (ABV). Beer is weak, around 4-5% while wine is typically 12%-14%. Vodkas and rums are 40% or so. The ‘proof’ system of measurement is just the ABV times two so 40% ABV vodka is 80 proof.
Vinegar has similar measurement system known as acidity. Typical store bought vinegar is 5% acidity. The legal minimum in almost every country is 4%. Typically, the highest acidity vinegar is wine vinegar which can be 7-8%. Acidity is measured in grams of acetic acid per 100 mL. So a 5% white distilled vinegar has 5 g of acetic acid per 100 mL of water. Vinegar also has an alternate measurement system like proof known as ‘grain’. Grain is calculated by multiplying the acidity times 10. So 5% vinegar is 50 grain vinegar. The grain system is mainly used by manufacturers, however, and almost never listed on a retail label. The term grain comes from the old days in the 19th century where the vinegar acidity was measured by how many grains (about 1/15th of a gram) of a strong base (like sodium hydroxide) it took to neutralize it. Granted the volume of vinegar and strength of the base were standardized so everyone go the same amount of grains in neutralizing vinegar of a given strength and quantity.
What about pH?
The most common way to measure acidity is pH and this is done with a pH meter. Most substances have pH readings in the range of 1 to 14 where a pH below 7 is considered acidic and a pH above 7 is considered basic. pH is a logarithmic scale so a vinegar with a pH of 3 is 10 times as acidic as one with a pH of 4. We measure pH with vinegar primarily to determine if it is safe. A pH below 4 is essential to guarantee harmful bacteria and mold will not contaminate our vinegar. However, never try to estimate acidity with pH. The relationship between acidity and pH varies by type of vinegar and is not consistent. We will cover this in more detail in a subsequent post.
How much alcohol to make vinegar of a given acidity?
The rule of thumb is in vinegar fermentation, for every 1% ABV of the starting alcohol you can get 1% acidity in the final vinegar. In practice you get about 0.8% acidity for every 1% ABV due to various losses. However it is a good way to start. So if you want 5% vinegar it is best to start with at least 6.25% ABV alcohol.
How strong can I make vinegar?
Typically, the AAB will not ferment anything with greater than 10% ABV so 8-9% is typically the upper level home fermenters can hope for and even this level takes time with batches of successively increasing strength.
What can I make into vinegar?
Anything you can make into alcohol! This includes juices (grape, cider, or any other fruit), cereals (the origin of malt vinegar and many Chinese vinegars) and even starchy foods like sweet potatoes though you have to convert the starch of the cereals or tubers into sugar first. Also sweet liquids like maple syrup, honey, and coconut juice are also candidates.
The trick is to get it to alcohol first, usually by adding yeast. In the next segment we will discuss the basics of making vinegar by starting on how to get your alcohol ready, or how to make alcohol from juices or starches to make vinegar!