Malt vinegar is a type of vinegar made from malted barley, which is a grain that has been allowed to partially germinate. The germination process produces enzymes that convert the grain's starches into sugars, which are then fermented into alcohol. This alcohol is then converted into acetic acid, which is the main component of vinegar. The term 'alegar' is a Spanish word meaning 'to make sour, ' and is often used to refer to malt vinegar.