Traditional methods for brewing sour beers involve fermentation with lactic acid bacteria and yeast. The most common approach in recent years has been using the kettle souring method to pre-sour the wort prior to fermentation. In this method, sterile unhopped wort is inoculated with bacteria, which is held at a precise temperature for 24-48 hours, to allow the development of lactic acid. The wort is then boiled (with hops as desired) and then transferred to a fermenter and inoculated with a brewing yeast strain