Abstract
Deep seawater (DSW) is pumped up from a depth of 320 meters off Muroto in Kochi Prefecture, Japan. Since DSW is known to be less polluted and contains various minerals, it has been used for a variety of fermented foods in Japan. To investigate the effects of DSW in Japanese “sake”-fermentation, we carried out small-scale (1-2 L) fermentation tests. The addition of DSW elevated levels of aroma components, including isoamyl acetate, ethyl caproate and ethyl caprylate. For further elucidation of the mechanism underlying this phenomenon, we used cDNA microarray analysis for studying yeast gene expression during fermentation. The addition of DSW substantially increased the transcript levels of several genes known to be involved in the biosynthesis and metabolism of amino acids and fatty acids. It is therefore suggested that the rise in transcription of these genes resulted in the increased aroma production. The sensory evaluation revealed that the addition of DSW in fermentation resulted in significantly superior flavor profile of the final products compared with the addition of NaCl, a major component of seawater. Interestingly, the microarray analysis demonstrated the addition of NaCl by itself induced stress during fermentation as indicated by mRNA levels in “sake” yeast. The addition of DSW appeared to ameliorate the negative effect induced by NaCl. Taken together, these results indicate that addition of DSW in the fermentation processes provides unique advantages for the “sake” production.
