# In the production of vinegar, where does water come from?

In the production of vinegar, where does the water come from?

I have heard that vinegar production involves these two reactions..

$$\ce{C2H6O {(ethanol)} + NAD+ -> C2H4O {(acetaldehyde)} + NADH + H+}$$

and

$$\ce{C2H4O {(acetaldehyde)} + NAD+ + H2O -> C2H4O2 {(acetic acid)} + NADH + H+}$$

But I don't see where water comes from as an input into the second reaction. Like if it's added manually or if it's produced by something else.

Note- there was an additional part of the question which i've since removed.. some of that is addressed https://biology.stackexchange.com/questions/56995/do-acetic-acid-bacteria-use-the-electron-transport-chain-when-converting-ethanol

• In biochemistry, you typically have plenty of water around. – Ivan Neretin Feb 27 '17 at 12:46
• Vinegar is made in a fermentation process of grape juice (short version). Now take a wild guess where the water comes from... – Fl.pf. Feb 27 '17 at 12:48
• ok thanks, i've edited my question accordingly – barlop Feb 27 '17 at 13:37
• I think this is relevant bbc.co.uk/schools/gcsebitesize/science/triple_edexcel/… ethanol + oxygen → ethanoic acid + water C2H5OH (l) + O2 (g) → CH3COOH (aq) + H2O (l) <--- (CH3COOH being ethanoic acid / acetic acid / C2H4O2 which is key to the production of vinegar) another related- chemistry.stackexchange.com/questions/33135/… – barlop Feb 28 '17 at 3:24
• @Jan i've removed the additional aspect. – barlop Mar 12 '17 at 20:55

Life on Earth evolved in aquaeous solutions. Cells are made up mostly of water; most cells are approximately $70~\%$ water. Water is thus ubiquitous in biochemical reactions. Only few enzymes go great lengths to explicitly exclude water from active sites to prevent undesired side reactions.
• Thanks. . I understand there are these two reactions too bbc.co.uk/schools/gcsebitesize/science/triple_edexcel/… ethanol + oxygen → ethanoic acid + water and ethanoic acid + ethanol <--> ethyl ethanoate + water Is the water produced by those reactions a lot less than the water in the wine? – barlop Mar 3 '17 at 11:58
• @barlop Yes. That water is at best equimolar to ethanol/acetate. Alcoholic fermentation rarely produces more than $15~\%\ \mathrm{v/v}$ and alcohol is less dense and has a higher molecular weight than water so less moles of alcohol give more volume than water. – Jan Mar 3 '17 at 20:44