What is Wine?
Parts of a Grape
Skin
There are two principal types of grapes: white grapes and black grapes. Black grapes have deeply color that can vary from deep purple to almost black. Black grapes have higher levels of skin tannin than white grapes and tend to be on the sweet side. The skin of white grapes has a golden color. Most often white grapes are going to have more tart and much lighter, crisper flavor.
Red and rosé wines are made from black-skinned grapes. Almost all white wines are made from white-skinned grapes. But it’s possible to make white wine from black grapes, if the juice is extracted and the skins are removed straight away. So, technically speaking, white wines can be made from either white or black grape varieties.
Pulp
The section of a grape where juice is contained is the pulp.The pulp contains sugars, organic acids, phenolic and nitrogenous compounds, aroma compounds, minerals and pectic substances. The color of the pulp is the same regardless of the grape skins.
Alcoholic Fermentation
Alcoholic fermentation is a biological process by which sugar is converted into alcohol and carbon dioxide. Microscopic organisms (yeast) are required in order for this. In most cases this process continues until the yeast have eaten all of the sugar. The alcohol stays in the newly made wine and in most cases the carbon dioxide escapes into atmosphere.