This study deals with understanding the effects of salt reduction on both the physicochemical and
microbiological properties of soy sauce fermentation and also the application of indigenous yeast starters
to compensate for undesirable changes occurring in salt-reduced processes. Fermentation was tested in
situ at a Korean commercial soy sauce processing unit. Salt reduction resulted in higher acidity as well as
lower pH and contents of residual sugar and ethanol. Moreover, undesired flavor characteristics, due to a
lack of distinctive compounds, was observed. In addition, putrefactive Staphylococcus and Enterococcus
spp. were present only during salt-reduced fermentation. To control these adverse effects, a single or
mixed culture of two indigenous yeasts, Torulaspora delbrueckii and Pichia guilliermondii, producing high
ethanol and 3-methyl-1-butanol, respectively, were tested. Overall, all types of yeast applications
inhibited undesirable bacterial growth despite salt reduction. Of the starter cultures tested, the mixed
culture resulted in a balance of more complex and richer flavors with an identical flavor profile pattern to
that obtained from high salt soy sauce. Hence, this strategy using functional yeast cultures offers a
technological option to manufacture salt-reduced soy sauce while preserving its typical sensory characteristics
without affecting safety.