"Gemeinschaftsgastronomie" appears to be about preparing meals for lots of people who then eat these meals in the same place, whether its business catering, company canteens, care catering etc.

IOW, I think the word "catering" is certainly part of the answer. "Service gastronomy" sounds like a translation, and I've not found a single kosher hit.

Looking at the sentence in its entirety, and assuming "Grossküche" is a "catering kitchen", it might be better to cut to the chase and say "Mr. Schmidt was employed/worked in all areas of a modern large-scale catering kitchen" (although I suppose catering kitchens tend to be big anyway).