Analysis of the cooked aroma and odorants that contribute to umami aftertaste of soy miso (Japanese soybean paste).

Soy miso, the traditional Japanese fermented soybean paste prepared using soybean koji, is used for imparting umami aftertaste to cooked dishes. The objective of this study was to identify the key odorants of cooked soy miso and their influence on umami aftertaste perception. Volatile compounds of soy miso and two rice misos were prepared using simultaneous distillation-extraction, and the key odorants were identified by using the gas chromatography-olfactometry/aroma extract dilution assay approach, and soy miso was compared with rice misos. Forty-one aroma-active compounds were detected in cooked soy miso, and malty, green, roasty and sulfury aromas were identified as the characteristic aromas. Finally, sensory evaluation was conducted to assess the contribution to the umami aftertaste of six key compounds with the highest flavour dilution factor. Results revealed that dimethyl trisulfide, which was newly identified in cooked miso, contributes to the umami aftertaste and palatability of cooked soy miso.

Mycoviruses related to chrysovirus affect vegetative growth in the rice blast fungus Magnaporthe oryzae.

Mycoviruses causing impaired growth and abnormal pigmentation of the host were found in the rice blast fungus, Magnaporthe oryzae. Four dsRNAs, dsRNA 1 (3554 bp), dsRNA 2 (3250 bp), dsRNA 3 (307 bp) and dsRNA 4 (3043 bp), were detected in isolate S-0412-II 1a of M. oryzae. By picking up single conidia of S-0412-II 1a, cured strains of the fungus were isolated that had completely lost the mycovirus. The cured strains had normal mycelial growth and pigmentation, suggesting that this mycovirus modulates host traits. The buoyant densities of isometric virus particles (∼35 nm diameter) containing these dsRNAs in CsCl ranged from 1.37 to 1.40 g cm⁻³. The single ORF (3384 nt) of dsRNA 1 encoded a gene product highly homologous to the viral RNA-dependent RNA polymerase of members of the family Chrysoviridae. It is noteworthy that mycovirus S-0412-II 1a was detected not only in host cells but also in culture supernatant. Furthermore, abnormal aggregation of mycelia was observed after adding the mycovirus-containing culture supernatant to an uninfected strain of M. oryzae and mycoviral dsRNAs were detectable from the aggregated mycelia. This novel dsRNA mycovirus was named Magnaporthe oryzae chrysovirus 1.