What is a grisette beer?

Grisette is a historical style of Belgian beer, starting somewhere in the 1700’s or early 1800’s. Although there are higher gravity versions, most grisettes were brewed to be around 3-5% ABV. The beer was moderately hopped to around 0.36-0.89 oz/gal, depending on the gravity of the beer and the source of the hops (English vs Belgian vs Bavarian).

Why is this not a classic grisette recipe?

The second reason that this might not be a classic grisette recipe is the use of flaked oats. I have no reason to say that this was (or was not) employed in historic grisettes. But with such a low OG beer and highly attenuative yeast, I think it is a reasonable addition to build some body into the final beer while staying lighter with the grist.

Was grisette fermented with lactic acid bacteria?

While the beer was probably fermented with a mixed culture, the beer was generally meant to be served fresh and the hopping rate would have limited the activity of lactic acid bacteria on shorter timescales. Much of the research into Grisette has been done by Dave Janssen and presented on his blog Hors Catégorie Brewing: