Can humans eat it? Do they have food at all? What do they have as a staple foodstuff?
On the planet of Risayn the locals are almost exclusively pescatarian. Since First Contact, Earth-style sushi has become an incredibly popular dish in cities and smaller settlements alike, though they often use other ingredients instead of rice, which isn’t well known to the inhabitants. It is seen as an important cultural link between Earth and Risayn and is often served when humans and the locals meet.
I really like the concept of cross-over between dishes resulting in a cultural link. Very cool idea!
Now this one is interesting to me. Is it a cultural taboo on eating land-bound animals, or just a lack of suitable land creatures for consuming?
The planet is mostly water and the denizens are amphibious so they mainly eat fish. They do have some very primitive agriculture but on the whole they consume fish far more than anything else
It’s very sour. Humans can eat it because my aliens are genetically related to humans, but unless they like very sour food they might not enjoy it. And it’s probably bad for their teeth.
How do your aliens eat it? Or is it just a case of them being more adapted to highly acidic foods/diet compared to humans?
Pretty much the second part - humans are a branch of theirs, and their world is largely Earth-like but a bit hotter and more deserty. It’s like the idea behind SE Asian food being spicier than French food, or US Southern food being more oily than Californian fare.
They are more tolerant of extremes in general, and through some weird circumstances are basically the only large animal on their planet, so they are more vegetarian and have cultivated a lot of proteinaceous plants. Spices and added flavor in general are a big part of their process. They have spicy, savory, and sweet foods too, but everything is just shifted one or two notches more sour.
As a result they really love fermented, citrus-based, and vinegar- heavy foods when sampling earth cuisine. An example of a dish they might make in Earth-terms might be like beans with extra lime-juice, brown rice with rice vinegar, nopales tacos with a strongly vinegar-based hot sauce, and orange juice or lemonade.
Two-hundred-ish years in the future, humans have become really good at tinkering with food genetics to boost their productivity.
Which is probably a good thing, because the majority of humans live in giant space stations, and so being able to grow food which is tolerant of extremes in temperature, gravity, radiation, etc. is really helpful in keeping everyone fed. Even so, getting truly fresh food is something of a small luxury - you can probably afford it, but not for everything.
One side effect of this is that almost no meat or animal products actually come from animals as we would recognize them. Even seafood products are derived from massive cell-culture farms, rather than complete organisms. Depending on your point of view this may or may not be a good thing; there definitely are people out there who claim to be able to tell the difference.