I have different types of vinegar and I'm wondering what factors influence how much acetic acid is present in different vinegars (e.g wine vinegar/white vinegar/apple cider). I was thinking maybe it has something to do with different fermentation processes. Any thoughts?
Vinegar comes from French "vin aigre", aka sour wine. The transformation of wine into vinegar happens when some (possibly unwanted) aerobic bacteria transform the alcohol into acetic acid by oxidation. So any alcoholic mixture which allows growth of those bacteria can be turned into vinegar, like cider, sake...
The amount of acetic acid depends on the alcohol content which in turn depends on the initial concentration of sugar. It is also dependent on the time allowed for fermentation.
In fact it is much more complicated than that. Have a look at Wikipedia for more info.
My 3.785 L, extra strength 6% "Acitity" vinegar (V), means (1), and I just found this out myself. Vinegar produced by the Generator Method, which produces anhydrous acetic acid. The pure Acetic acid (Ac) crystalizes to a solid at less then 16.7 C. (2). You can imagine how easy it is to make any concentration you want, when you have a powder to mix with water = distilled vinegar. That means that in that 3.8 L bottle only about 270g is actually Acetic Acid. However because Acetic Acid is a weak acid in water with a pH of ~ 2.2 (= ) for 6% acidity. Some of that Acetic Acid (moles of Ac - mole of protons = moles of acetic acid left) dissociates so, there is some (equal to ~moles of protons) Acetate in there as well.
Link 1 seems pretty interesting regarding the making of vinegar 1 - http://www.madehow.com/Volume-7/Vinegar.html 2 - http://antoine.frostburg.edu/chem/senese/101/organic/faq/ethanoic-acid.shtml