Making Vinegar at Home

Maple Vinegar Aki Kamozawa and H. Alexander Talbot

Vinegar is one of those ingredients that people don't think of as often as they should. It is mostly just seen in salad dressings and pickles, which is a shame, because there is a whole world of flavor there just waiting to be tapped into. There are often times, especially during the holidays, when there is leftover wine after a festive dinner. Many of us will cork the bottle, with or without various safeguards to preserve the contents, and set it aside for the next day. Occasionally the bottles are forgotten, and when you finally open them again you find that the wine has evolved into something quite a bit different from what you were expecting. In these moments the change is often viewed with disappointment, as a delicate beverage has transformed into something sharper and edgier. Frankly, though, a smart cook will see the change as an opportunity. Good wine makes good vinegar and good vinegar is a stellar cooking ingredient.

Vinegar is a living ingredient created through the process of fermentation. The final product will contain elements of the original stock, which add a depth of flavor that differentiates a naturally fermented vinegar from a manufactured one. The term "vinegar" actually refers to the two-step process of fermentation from a carbohydrate to an alcohol to an acetic acid. Sugar is converted into alcohol, which is then fermented into vinegar. Not all acetic acids are vinegar, although all vinegars are made from acetic acid. When creating a fruit-based vinegar, wild yeasts are added to convert the sugars into alcohol. Starch-based vinegars add an extra step, wherein the starch is converted into sugar first, a triple fermentation process. "Alegars" are made from sour beer. Strongly flavored beers that have expired and are no longer fit for consumption as a beverage can make wonderfully flavorful and complex alegars.

Vinegar stocks are made using a base material that is fermented with yeast to create alcohol. Brewer's yeast is used for cereals, grains, and molasses. Wine yeasts are used for fruit juices and honey. A sugar concentration in the range of 10-18 percent is considered ideal for making vinegar stock. This is because concentrations of alcohol at 9-12 percent are considered optimal for vinegar production. Acetobacter aceti is the bacteria used to create vinegar from alcohol. It is widely found in nature and requires oxygen to function. The bacteria are added to the vinegar stocks to begin the second fermentation process. Vinegar can be made from stock with alcohol concentrations as low as 5 percent, although these conditions can result in over-oxidation, while at higher concentrations, over 15 percent alcohol, acetobacters are inhibited by the amount of alcohol present and can even be killed off by it. If you're using leftover wine, the alcohol levels range from 10 percent to 15 percent. Not to worry, if you don't want to mess about with testing kits and you're working with some leftover wine at the high end of the scale, say a California cabernet clocking in at 15 percent or more, just add a splash of water and let it ferment. It may take longer than something in the optimal range, but it will become vinegar eventually and you will be rewarded for your patience by the flavor of the finished vinegar. .

Acetobacters tend to be very temperature-sensitive. They are happiest between 59 and 94°F, with an optimum range of 80 to 85°F for acetification, and they die off at temperatures over 140°F. A clean, sterilized container for storing your vinegar during the fermentation process is a must. Small oak barrels can be purchased online, although we've found that large glass cookie jars with loose-fitting lids are an economical alternative. Acetobacters need oxygen to function, so airtight containers will not work for the fermentation period. Pure, soft water should be used for any dilution of the vinegar stock. The chlorine and fluoride found in municipal water can have an adverse effect on the fermentation process, so filtering your water is recommended. Once the fermentation process has begun, the vinegar stock should be left alone in a dark spot because acetobacters are sensitive to UV light for at least two to three weeks. The vinegar-in-progress should not be stirred or agitated during the fermentation period.