Higher is this value, poorer is the quality of the product. It is indicator of fundamental importance as in relation to the level of acidity is established the attitude of fat edible as well as the oil commercial classification. The acidity is manifested by an alteration of lipolytic type, expressed in grams of oleic acid per 100 grams of oil. Its measure is determined by laboratory analysis (acid-base titration). The limit of acidity for extra virgin olive oil is 0.8% but in a quality oil values are much lower (0.1-0.3%). In olive oil you can have a high level of acidity when the product was obtained from fallen olives and/or left in the ground a sufficient time to the triggering of fermentation phenomena. These phenomena are often due to sensory defects (in particular, winey, fusty and mould). The perfect sanitary status of the olives, harvesting at the right level of ripeness and the use of proper techniques of picking, storage, processing and conservation will generally produce an extra virgin olive oil with very low acidity. Very often consumers wrongly associate acidity with the feeling of spicy present in different intensity in almost all extra virgin olive oils. This perception is wrong because the spicy indicates the sensory manifestation of the presence of an important class of aromatic substances called polyphenols, which besides being natural antioxidants are responsible for this sensation.