In very small quantities, diacetyle enhances the flavour of the wine and gives it a pleasantly creamy and smooth taste with slightly nutty and caramel-like notes. Concentrations of up to 1 mg/litre in white wines and up to 5 mg/litre in red wines are considered to be sensory inconspicuous to moderate. This can mask the fruity flavours in the wine. Only at higher levels of diacetyl is this considered a wine defect called lactic acid tartness. Confusingly, this is sometimes also referred to as butyric acid tartness, but it has nothing to do with butyric acid. To a greater extent, a buttery impression can go hand in hand with a milky appearance; however, the two perceptions are not the same.