The grapes undergo a chemical process called fermentation.
Fermentation is a chemical metabolic process in which an organic substrate is broken down by enzymes, bacteria, yeasts usually accompanied by the released of gas and heat.
Fermentation usually is an anaerobic respiratory process that supplements when there is no oxygen.
The products are usually organic acids or alcohols and carbon dioxide gas.
The sugar in grape is acted upon by yeast.
The product is an alcohol, release of gas and heat.
