Enzymatic fermentation of Uruka under hydrostatic pressure conditions

Uruka is a traditional Shiokara food made from the fermented viscera of ayu (sweetfish), which has high salinity. A common recipe involves anaerobic fermentation of salted ayu viscera densely packed in a container and capped during fermentation for several months or years under cool and ambient conditions. As the mechanism of Uruka fermentation remains unclear, we examined the microbiota of Uruka using 16S rRNA gene amplicon sequencing. As we were unable to identify the predominant microbes involved in Uruka fermentation, hydrostatic pressure conditions were applied to determine whether Uruka was fermented enzymatically or microbially. The results indicated that the fermentation of Uruka was enzymatic rather than microbial.