Whilst not directly related to a jar of homemade emulsion....the following Kodak publication has some brief information on freezing unprocessed film. They suggest -18 Celcius for long term storage of unprocessed Motion Picture film.
(My domestic freezer reaches around -25 Celcius.)

http://www.kodak.com/global/en/consu...fo/e30/e30.pdf

As the publication pints out this won't stop gamma/cosmic ray fogging.

Emulsion.