It is well known that sugars glucose and fructose are the primary fermentable substrates. However, malic acid can also be fermented but to lactic acid rather than ethanol. This is especially important in red wine, why?​

The correct answer is - due to the different bacteria that produce a different enzyme that is involved in the fermentation of malic acid.

Explanation:

In red wine production, malic acid in present in grapes converted to a softer lactic acid. This process is known as malolactic fermentation. It takes place due to the presence of different types of bacterias such as bacteria of the lactic acid family.

These bacterias produce enzymes which is used to convert the malic acid to lactic acid such a process can occur naturally also.