Food Science Question #151 — Vinegars
Foreword: I was thinking the other day that it might be fun to start a conversation about food science in the format of my first book, 150 Food Science Questions Answered.
I’m going to start off with one of the questions and answers that didn’t make the final cut into the book. If you have a food science question you want answered, I’ll do my best to answer it.
Let’s get started with this little co-creative experiment!
Q: Is There a Real Difference Between Vinegars?
The Answer: Yes
The Science: All vinegars are made up of water and between 5 and 20% acetic acid, the acid present in all vinegars that gives them their characteristic bite. But each type of vinegar is produced in different ways that lead to unique levels of acidity, flavors, colors, and thickness.
Traditional wine vinegars, like sherry or marsala vinegar, are produced by taking a high-alcohol wine and adding a culture of acetic acid bacteria to the wine. These bacteria can metabolize the ethanol in the wine to acetic acid in the presence of oxygen. The fermenting mixture is allowed to age for several months to several years in wooden barrels.
The result is a rich, deep flavor formed from the complex biochemical reactions that occur from the long-term fermentation process. Balsamic vinegar undergoes the same process, except the vinegar is fermented from a raw grape juice that’s been boiled down to thick, viscous syrup containing at least 30% sugar. Fruit vinegars like apple cider vinegar, on the other hand, are brewed directly from unconcentrated fruit juice.
White distilled vinegar is cheaply produced using an industrial method developed in 1949. Grain is fermented with yeast to produce alcohol that is then distilled into a high-proof vodka. A second fermentation is conducted by diluting the alcohol and bubbling oxygen into the solution in the presence of acetic acid-producing bacteria and nutrients.
The resulting vinegar is produced within 1 to 3 days and has an acetic acid content of between 15% and 20%, which is further diluted down to 5% to 10% for commercial purposes. The resulting vinegar is nearly pure acetic acid and water with few impurities.
Rice vinegar is produced by inoculating steamed rice with spores of Aspergillus oryzae, an edible mold, or symbiotic cultures of that mold and alcohol-tolerant yeast. As the mold grows on the rice for several days, it produces amylase enzymes that break down the rice starches into sugars. The fermented rice is mixed with water and pitched with yeast (if not using the symbiotic culture) to produce a rice wine.
Acetic acid bacteria are then added to the rice wine to ferment the alcohol to acetic acid. As a result of this process, both Chinese and Japanese vinegars are typically less acidic and sweeter than Western varieties.
Malt vinegar is made by allowing barley grains to first germinate, a process known as malting. The malted barley grains produce amylase and protease enzymes that break down the carbohydrates and proteins in the grain into sugars and amino acids.
The grains are steeped in hot water and filtered to give a sugary wash that’s brewed with yeast into a malt ale. The malt ale is then fermented with acetic acid bacteria to produce malt vinegar.
Kitchen Takeaway: Vinegars are not completely interchangeable. Each type of vinegar adds a punch of acidity to a dish with different accompanying flavors. While all vinegars contain acetic acid, the method of production of each vinegar can vary much in the same way as wines, lending distinct flavor nuances to food.
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by the author.