I’m reading The Greedy Queen by Annie Gray. The author introduced the way people made gelatine in Victorian times:
Jellies at this time were set with gelatine extracted from calves’ feet. Rendering the gelatine took days, and was even more involved than making a stock, involving similar amounts of clarification and straining, plus a bit of flavouring with wine and sugar, and with the added pitfall of ensuring that the final thick liquid would set firmly – but with a perky wobble – when chilled. This basic wine jelly was used as the basis for some incredible dishes, often made in specialised moulds which enabled cooks to fill internal cavities with set creams.
I'm lost from "pitfall" onwards. As defined by the dictionaries, "pitfall" basically means a trap. But what does the whole thing have to do with a trap? Is this sentence saying that something is added to set the gelatine? If not, what's it saying? And does "this basic wine jelly" in the following sentence actually refers to the aforementioned gelatine? Can anybody clarify the idea for me?