There are dozens of types of vinegar. Anything that contains sugar, from grapes to rice, can be made into this common ingredient. It’s a two-step process: First, yeast feeds on the sugar and ferments it into alcohol; second, harmless bacteria called Acetobacter feed on the alcohol and ferment it into a sour-tasting byproduct, which the French first dubbed vinaigre, or “sour wine.” That sourness, or acidity, is essential to our enjoyment of food—look no further than a salad dressing, sauce, or marinade to taste why. But aside from enhancing flavor, vinegar also has the unique ability to alter the color and texture of foods. Read on to learn how it works its magic.
Why does vinegar taste sour?
Acids are volatile molecules that release positive hydrogen ions. These ions have a pro-found effect on the other molecules in foods (more on that later). They can also affect the cells in your body, but fortunately our taste buds help us regulate the amount of free hydrogen ions we eat by making us perceive acids as sour tasting. A small amount makes food taste bright and fresh, while too much tastes unpleasantly sour.
Most vinegars don’t just taste sour, though. The acid in vinegar is primarily acetic acid, which makes up 4 to 7 percent of table vinegars. Distilled white vinegar, for example, is 5 percent acetic acid and 95 percent water; it has the harsh sourness of acetic acid alone. In other vinegars, that harshness is tamed by other acids. Red wine vinegar tastes of tartaric acid, the structure-building acid in wine, and apple cider vinegar has the green apple flavor of malic acid. Depending on the variety, vinegar can contribute sweet, buttery, malty, and savory flavors, as well as woody aromas from aging in wooden barrels, evidenced in balsamic and sherry vinegars.
How does vinegar affect the color of fruits and vegetables?
The hydrogen ions released from vinegar displace magnesium in the chlorophyll molecules of green vegetables, turning bright green chlorophyll a drab olive color. That’s why flavoring broccoli with vinegar discolors it. To keep green vegetables from discoloring, flavor them with non-acidic ingredients instead, such as citrus zest, herbs, and spices.
Vinegar has the opposite effect on plant pigments known as anthocyanins: It brightens red fruits and vegetables like sour cherries and red cabbage. Anthocyanins appear red under acidic conditions and turn blue under alkaline conditions. When boiled in alkaline cooking water (urban water is often made alkaline to prevent pipe erosion), red cabbage turns turquoise blue. Similarly, sour cherries develop a blue outer ring in muffins because baking powder makes the batter alkaline. The trick to keeping anthocyanin pigments bright red is to maintain acidic conditions. Cooking red cabbage with vinegar keeps it red; cherries stay red in muffins if there’s a little vinegar (or another acid, like buttermilk) in the batter.
Vinegar can also preserve the color of white-fleshed produce like apples and potatoes, which discolor when cut. The cut cells release enzymes that cause phenolic compounds previously held within the cells to bond with oxygen, creating brown-tinted melanin pigments in the flesh. Adding an acid like vinegar slows down the enzyme activity and helps prevent browning.