By MIKA OMURA/ Staff Writer
August 26, 2021 at 07:30 JST
Plates for sampling soy sauce (Asahi Shimbun file photo)
Suggest storing a bottle of soy sauce outside the fridge in Japan and you're likely to receive a lukewarm reception as it's widely believed that the sauce starts going bad if not refrigerated.
Though it's true that once the bottle has been opened, soy sauce becomes darker in color and loses its flavor and aroma over time, despite the common wisdom, keeping soy sauce at room temperature has its advantages.
"'Shoyu' becomes less savory when it's cold. You can enjoy the aroma of shoyu more at room temperature when you use it as a dip or pour it on food," a publicist at soy sauce maker Yamasa Corp. said.
The darkened color and loss of flavor occur when the sauce is exposed to heat, oxygen and other conditions.
When kept in a conventional container or a PET bottle, it's unavoidable to keep the sauce from being exposed to air after opening, so people have been encouraged to keep the bottle in a fridge to at least reduce the influence of heat.
But the increasing use of airtight containers to bottle soy sauce by brands has begun breaking that habit in the last 10 years or so, as they allow the condiment to be kept at room temperature.
Soy sauce giant Kikkoman Corp. said roughly half of its household products now come in airtight containers.
The company's Kikkoman Freshly Pressed Nama-Shoyu can maintain freshness for up to 90 days after opening. Its label states that it must be kept at room temperature.
"The quality will remain the same for 90 days whether it is kept at room temperature or put in a refrigerator," said Mika Inoue, a manager in charge of the company's shoyu and mirin (sweet sake) division.
As a plastic container within the bottle forms a double-layered seal around the soy sauce in bottles with airtight seals, the sauce is kept from being exposed to air during use to prevent oxidation.
Oxygen, in fact, has more influence than heat on soy sauce degradation. By eliminating oxygen as a factor in how soy sauce degrades, double-layered bottles allow the sauce to maintain its quality at room temperature, industry experts say.
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