A considerable quantity of malic and tannic acids are present in all apples. It is these that give the apples and juice the tart taste. It might be thought that the sweeter varieties are sweet on account of a greater amount of sugar, but this is not the case. Apples are sweet or sour depending on the amount of acids present. The color of the cider depends upon tannic acid. If the pulp be exposed to the air from twelve to twenty-four hours before pressing a darker color of the cider results. The action of the tannic acid together with the air causes darkening. Also, part of the cloudiness of cider is due to albuminous matter; tannic acid assists in precipitating this out and making it settle. Hence a juice high in this acid will be of a darker color and is more likely to be clear.