YAS medium

YAS medium (known in Japanese as YAS baichi) is a type of culture medium used in sake brewing, mainly to test for contamination by acid-producing bacteria. It is used to assess the state of microorganisms in koji, shubo (yeast starter), and moromi (fermentation mash). YAS medium plays an important role in detecting the growth of harmful microorganisms, such as lactic acid bacteria, in the moromi, and it contributes to stable brewing quality. This allows brewers to take measures to prevent problems during the sake-making process.