You do not need to store in the fridge, but it will extend the shelf life.
I've found large bottles of soy will last longer in the fridge. If the bottle
is small or you use it quickly enough, why bother.
--
Dan
Oops, reread and I notice the OP was talking about low sodium which might
have a shorter shelf life. However, just looking at my bottle of Marukan
Ponzu (sudachi citrus marinade,) it does say 'Refrigerate after opening for
quality.'
--
Wilson 44.69, -67.3
I buy large bottles of lite soy and have noticed that over the length 4 months,
the flavor changes. It does seem to darken some and seems more bitter.
--
Dan
A few decades ago it was common to see a small bottle of shoyu (soy
sauce)
on the kitchen tabletop of most Japanese homes.While you will still
see it to some extent,
especially out in the country, the practice of keeping it in the
refrigerator has become more
the norm. While soy sauce can be stored for a long time at room
temperature it's not the
same once opened. Ponzu was always kept in the refrigerator since it's
not used as
frequently as Shoyu. BTW, an opened Shoyu bottle in the summer WILL
attract fruit flies.
Musashi