Sujiawa (thin streaks of foam on the moromi)

Sujiawa (筋泡) refers to a specific stage in the fermentation of sake moromi (fermentation mash). Two to three days after the final addition of ingredients (tome-jikomi), thin streaks of foam appear on the surface of the moromi. These are called sujiawa. This stage marks the start of fermentation and is also evidence that ordinary yeast is at work. After sujiawa appear, the foam changes as fermentation progresses. The first foam to appear forms thin, slightly uneven lines. After a few more days, white, light foam spreads across the surface; this is called mizuawa (水泡, water foam). The foam then gradually builds up, becoming iwaawa (岩泡, rock foam), in which it takes on a rock-like shape, and then takaawa (高泡, high foam), in which it rises into a tall mound. Eventually the foam settles, leaving bubbles like soap bubbles; this stage is called tamaawa (玉泡, bubble foam). Once the tamaawa disappear and the surface of the moromi is exposed, this state is called ji (地). The ji stage has several variations: bozu (坊主), where nothing floats on the surface; chirimen awa (チリメン泡, usukawa), where a thin skin can be seen; and atsubuta (厚蓋), where grains of rice float on the surface. Sujiawa is thus an important indicator for understanding the fermentation state of the moromi and reflects the subtle changes that take place during sake production.