

Usually not worth it; you’ll need to gently distill (in proper glass, this is important) the beer like it is done for ABV measurement and measure density of leftovers. Or do quantitative chromatography. You’ve got to know hands-on chemistry real well for this. Let me know if you need the procedure.
In my childhood, we had these kinds of root vegetables sliced and caved in on one end, and a spoonful of honey was placed on top and in the cavity. Somehow this sped up conversion to overnight, and it was a treat. I guess, similar process could be used to convert them for brewing.
Although the whole idea sounds a bit like potato for vodka. Nothing wrong with that too, but the flavor might me less than interesting in the end. Worth trying I guess. I wish I had some of those now, not unripe ones from the store.