The pH of grapes as well as wines can vary enormously since temperature, rainfall, soil type, viticultural practices, and vine varieties can all influence the different natural organic acids and minerals of mature grapes. In general, cool regions produce wines with low pH and hot regions produce wines with high pH. Part of the reason why white wines generally have a lower pH than red wines is that red wines have higher levels of potassium, which is extracted from the grape skin, where this ion is concentrated, during fermentation. See also grape and acidity.