essential roles of microbes and oxygen in the traditional Orléans process (p 773) Modern methods for growing baker’s yeast and producing penicillin were adapted to vinegar manufacture after World War II, and now produce finished vinegar in a day or two The Virtues of Acetic Acid Acetic acid contributes two different flavor elements to foods One is its acidity on the tongue, and the other is its characteristic aroma in the nose, which can intensify to a kind of startling pungency, particularly when the vinegar is heated The vinegar molecule can exist in two forms: as the intact molecule, and broken into its main portion and a free hydrogen ion The hydrogen ion gives the main impression of acidity, while only the intact molecule is volatile and can escape from the vinegar or food, travel through the air, and reach the nose Both the intact and “dissociated” forms coexist side by side, in proportions that are determined by their chemical surroundings If the food is already acidic — thanks to the presence of tartaric acid in wine vinegar, for example — then less of the acetic acid dissociates, more is intact and volatile, and the vinegar aroma is stronger Acetic acid is an especially effective preserving agent A solution as weak as 0.1% — the equivalent of a teaspoon of standardstrength vinegar in a cup of water/5 ml in 250 ml — will inhibit the growth of many microbes Acetic acid has a higher boiling point than water, 236ºF/118ºC This means that vinegar will get more concentrated if it’s boiled Because half of its molecule is more fat-like than water-like, it is a better solvent than water for many chemical relatives of fats, including the aroma compounds in herbs and spices This is why cooks flavor vinegars by ... of the acetic acid dissociates, more is intact and volatile, and the vinegar aroma is stronger Acetic acid is an especially effective preserving agent A solution as weak as 0.1% — the equivalent of a teaspoon of standardstrength vinegar in a cup of water/5 ml in 250...“dissociated” forms coexist side by side, in proportions that are determined by their chemical surroundings If the food is already acidic — thanks to the presence of tartaric acid in wine vinegar, for example — then less of the acetic acid dissociates, more is intact... — the equivalent of a teaspoon of standardstrength vinegar in a cup of water/5 ml in 250 ml — will inhibit the growth of many microbes Acetic acid has a higher boiling point than water, 236ºF/118ºC This means that vinegar will get more concentrated if it’s boiled