Of course recipes can't be copyrighted, but you running into this issue proves just how much you screwed up at trying to understand your audience.
Don't blame them for filling DMCA requests, blame yourself for not building something that they'll want to use and contribute to.
Think about it for a minute. Does Github grab your source code without asking you and then offers people the option to fork it? No! Devs upload their source code to Github because they get a value out of it.
The same goes for food blogs or anything else. If your target audience can't get any value out of your product, then you're dead before launching.
As devs, we need to keep this in mind: people won't care if they can't get value. Just because it took you days/weeks/months/years/decades to build does not mean it will produce value for anyone. Only studying your target customers and building on top of this knowledge will.