sca-cooks Greetings

[Nancy Wederstrandt]

I am working with a cookbook printed in 1590 ish (the date escapes me and I
do not the info at my desk)  In several of the recipes it mentions the
addition of "yest"  as part of the ingredients for sauce.  They only thing
I could figure was that it was yeast and was used as a flavouring agent.
Does anyone have an opinion about this?   Let me know.

Clare R St John