The term vinegar originates from the French phrase for “sour wine,” and one of the methods to produce vinegar is to ferment fruit beyond the point where it's merely alcoholic, and it turns quite tart instead.
WHAT CAUSES THE ACIDIC PH OF VINEGAR?
Lactic fermentation is a process that involves anaerobic bacteria consuming sugar and converting it into lactic acid, ethanol, and more bacteria. When the fermentation involves only the lactic bacteria (as in yogurt or vegetable fermentation), the culturing halts at the point where there are no more sugars to consume, and the bacteria die off.
In fermented drinks like water kefir or kombucha, or in fermented fruits, yeast is also present. This could be added to the mixture for fermentation, present in the material being fermented, or present in the culture. The yeast stimulates the additional production of alcohols during fermentation. If the fermentation is aerobic (exposed to oxygen), an extra type of bacteria, acetobacter, comes into play. This bacteria converts the available alcohol into acetic acid, which is why vinegar is acidic. Acetic acid also prevents other organisms from living in it, which is why vinegar can be used as a natural preservative.
Another process for creating vinegar involves fermenting distilled alcohol. The resulting colorless liquid is then diluted to a standard strength and filtered of all impurities.
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There are two ways of describing the strength of vinegar:
- Its acidity, which is measured as a pH value.
- Its concentration (sometimes referred to as grain strength), which is the amount of acidity in a given volume of liquid and is measured in percent.
HOW IS VINEGAR PH MEASURED?
To measure the pH of vinegar, simply use a pH strip. The resulting color will tell you how strong the vinegar is. Distilled white vinegar usually measures around pH 2.4, with a strength of 5%. The lower the pH, the more acidic the vinegar is. A pH level of under 7 is classified as an acid.
DETERMINING THE ACIDIC STRENGTH OF VINEGAR
To ascertain the quantity of acetic acid–which determines if vinegar is an acid or base–in the vinegar liquid, you need specific equipment.
You can buy acid test kits at a beer- and wine-making supply shop for only a few dollars but these are designed to test the acidity of wine, and generally will not measure an acidity of more than 1%. To be described as “vinegar,” a liquid must have at least 4% volume of acetic acid.
Test kits for measuring this quantity of acid usually run around $50 to $100. Essentially, you would add the vinegar being tested to a flask, and dilute it with water. You then addphenolphthalein, a chemical that will change color at different levels of acidity.
In a special tube flask marked with measurements in milliliters, you put a solution of sodium hydroxide, a caustic chemical that must be handled with care. This is called the titrating solution and is slowly dripped into the vinegar-phenolphthalein mixture until the vinegar solution turns pink. At this point, you can measure how much of the sodium hydroxide you have used.
Ideally, the procedure is repeated three times for accuracy. Once you have a reliable value for the volume of titrating solution, you mustdo some math to translate that amount into a standard measurement of grams of acetic acid in a liter of vinegar. That would be the percent strength of vinegar.
THE MEANING BEHIND THE PH OF VINEGAR
This level of precision is not something you would typically employ as a home hobbyist making vinegar in the kitchen. If you've produced vinegar using wine or fruit scraps, view it as a delightful addition to salad dressings or recipes.
People have utilized vinegar for preservation for centuries without such testing. If you opt to use homemade vinegar for pickling projects, you should at least measure the vinegar ph level and ensure it is no higher than 4.0. This pH will guard against most harmful bacteria and against the formation of mold.
Ready to try your hand at making vinegar? Kombucha is a perfect starter! It’s great for gut health and has a slightly sweeter flavor, a bit like apple cider vinegar, but with a bit more nuance. Grab a kit and you can not only make kombucha vinegar, you can also make a healthy delicious fermented drink for the family!