classification, Charles Neal has written about a French classification system. In France and Spain, the system has an intermediate category called acidulée or acidulada respectively, which is sometimes used to classify cider apples that are semi-tart and have low tannin content. Similar to the English system, acidity and tannins are considered. Apples are classified as follows: In the US, there are four regions where cider apples are grown in orchards: the Northeast, Mid-Atlantic, Midwest, and Northwest. Out of the twenty most commonly grown cider apple varieties, half originate from England, two come from France, and the rest originate in America. Most special cider cultivars for European ciders are bittersweets and bittersharps, which have high tannin content. There are not a lot of cultivars with high tannins readily available in the U.S. Most ciders in the United States are made from culled dessert apples that are generally sweets and sharps. There is no systematic classification of North American apple cultivars for cider-making purposes. However, there is a database for apple varieties called the U.S. National Plant Germplasm System (NPGS). Other classification considerations Beyond the Long Ashton or English system and French system for classifying cider apples, there are other considerations for characterisation. Other measurements taken of apple varieties towards use in cider classification include pH, polyphenol composition, Yeast Assimilable Nitrogen (YAN), and soluble solid concentration (ºBrix). The sharpness of an apple is affected by pH and titratable acidity. Most cultivars must reach pH levels of around 3.3 to 3.8 to aid in the fermentation process, and additions of malic acid may be necessary if the cider apple is over this desired threshold. Soluble solids as measured in units of degrees Brix can be used to quantify the potential alcohol that a yeast can ferment from the initial juice of the cider apple. This is carefully considered in cultivars from areas where there are tax regulations on the percentage of alcohol by volume that is contained in these products. In the United States, "hard cider" legally falls between the 0.5% to 8.5% alcohol by volume tax bracket. Cideries that exceed a soluble solids level of 17 °Brix will be subject to higher tax levels that are classified under cider wine. In the United Kingdom, cider falls in two duty brackets, with a flat rate for up to 7.4% ABV, and a higher duty rate for ciders between 7.4% to 8.5% ABV. Foaming