Here is a small summary of the different kind of fermentation to better understand the article.
The three main type of fermentation are:<p>- Alcoholic fermentation (beer, wine,etc.): without oxygen, yeast produce ethanol from sugar, like when you leave some fruits rotten without too much oxygens...but fruits rotten because fungi proliferates quicker due to the presence of oxygen<p>- lacto-fermentation (cheese, yoghurt, etc.): without oxygen and in a warm environment, lacto-bacillus produce lactic acid from sugar<p>- acetic fermentation (vinegar) : WITH oxygen (seldom one), acetobacter bacterias produce acetic acid from ethanol<p>Louis Pasteur said "Fermentation is Life without oxygen", so whenever there is oxygen, you'll see the usual rot produced by fungi (yes, very crude simplification). So the main aspect of fermentation is to ensure an anaerobic environment, often with water or when you remove oxygen from a recipient by aspiring it.<p>The other types of fermentation are more seldom: propionic fermentation (from lactic acid to propionic acid like in the gruyere cheese), butyric fermentation (like in rancid butter), malolactic fermentation (from malic acid to lactic acid, because the malic acid, found in grappes and apples gives a very acidic taste and is used to lower that acidic taste in some wines).