AI Article Synopsis
- - The study examined how guaiacol, a compound that contributes to off-flavors in Japanese sake, is formed during the brewing process, particularly focusing on rice koji samples.
- - One rice koji sample showed exceptionally high levels of guaiacol and 4-vinylguaiacol, while all samples contained ferulic and vanillic acids, which are precursors in this context.
- - Specific spoilage bacteria, identified as Bacillus subtilis, B. amyloliquefaciens/subtilis, and Staphylococcus gallinarum, were found to convert vanillic acid into guaiacol, indicating that these bacteria play a role in the off-flavor issue during sake fermentation. *
Article Abstract
The formation of guaiacol, a potent phenolic off-odor compound in the Japanese sake brewing process, was investigated. Eight rice koji samples were analyzed, and one contained guaiacol and 4-vinylguaiacol (4-VG) at extraordinarily high levels: 374 and 2433 μg/kg dry mass koji, respectively. All samples contained ferulic and vanillic acids at concentrations of mg/kg dry mass koji. Guaiacol forming microorganisms were isolated from four rice koji samples. They were identified as Bacillus subtilis, B. amyloliquefaciens/subtilis, and Staphylococcus gallinarum using 16S rRNA gene sequence. These spoilage bacteria convert vanillic acid to guaiacol and ferulic acid to 4-VG. However, they convert very little ferulic acid or 4-VG to guaiacol. Nine strains of koji fungi tested produced vanillic acid at the mg/kg dry mass koji level after cultivation. These results indicated that spoilage bacteria form guaiacol from vanillic acid, which is a product of koji cultivation in the sake brewing process.
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| http://dx.doi.org/10.1021/acs.jafc.6b01031 | DOI Listing |
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