# Question #fc6b1

Jun 5, 2017

It isn't.

#### Explanation:

A decomposition reaction is the separation of a single compound into two or more simpler compounds.

The major reaction in the souring of milk is the conversion of milk sugar (lactose) into lactic acid.

The reaction takes place in several steps.

The balanced equation for the overall reaction is:

$\underbrace{\text{C"_12"H"_22"O"_11)_color(red)("lactose") + "H"_2"O" → 4underbrace("CH"_3"CHOHCOOH")_color(red)("lactic acid}}$

The lactic acid causes the milk to have a sour taste.