On some level, I’ve often been disappointed by a lot of the SF I’ve read and watched along these lines. Not that I necessarily want some sort of long infodump of alien farming, but food sourcing gets elided quite often.
Take, for example, the Replicators on Star Trek. I kind of hate them. They’re a cheap answer to a major element of civilized culture. On TNG, it even gives them the “high ground” to look down their nose at another species that still, you know, eats actual meat. Because in their enlightened future, they don’t need to deal with any messy reality of food production. How do we feed ourselves? We talk to a hole in the wall, and it appears like magic.
But taking magic tech out of the equation, the practical realities of how people produce, store and prepare food– especially on long, deep space flights– should be a worldbuilding element the writer is aware of, even if they never talk about it much.
A fantastic resource Space Opera writers should check out is Mary Roach’s Packing for Mars. In it, Roach digs into every little practical “but what about this?” question that NASA was thought of (and they really thought about all of them), and solutions they’ve come up with, as well as the ones they still struggle with. Food supplies for a manned mission to Mars is a major concern.* The whole book is worth the time.
Alien foods are another thing to consider, specifically in terms of humans eating alien foods. Now, biochemistry is not even remotely a strong suit of mine, but I’m given to understand that it’s highly unlikely we’d be able to digest alien biomatter, let alone extract useful nutrients out of it. Presuming no negative reactions**, it would just pass through our systems untouched.
However– they still may be interesting to eat. Spices, for example. We don’t really get useful nutrients out of pepper or cinnamon or cumin, but they all make food more interesting. Alien spices can create unique culinary opportunities. And that’s also where xenobiodiversity can come into play, especially in terms of interspecies trade. In the future you build, the trade of raw materials will, of course, be crucial, but there’s nothing unique to, say the gold or molybdenum*** found on Earth compared to the gold or molydbenum on Starkasia or Paxica or wherever else people go in the galaxy. But paprika? Now that’s something you can’t get anywhere else. That could be worth quite a lot out there.
*- As is the human waste element, which Roach gets into as well. There were NASA scientists who suggested the possibility of having the problems solve each other: the waste material could be purified and used as a raw protein base to be repurposed as a food supply. Scientifically possible. But astronauts in the discussion shot this down: “We’re not eat shitburgers on the ride home.”
**- Which, I would imagine, would be more likely to be allergic reactions rather than toxic ones.
***- Or whatever matters. “Molybdenum” is just a fun name.