De or het gistmengsel?

The correct Dutch article is:

het gistmengsel

Rule Words ending in -sel: usually het. See the rule

How to use gistmengsel

the gistmengselhet gistmengsel
this gistmengseldit gistmengsel
that gistmengseldat gistmengsel
our gistmengselons gistmengsel
your gistmengseljouw gistmengsel
every gistmengselelk gistmengsel
which gistmengsel?welk gistmengsel?
a big gistmengsel / the big gistmengseleen groot gistmengsel, het grote gistmengsel