There's a lot of edible stuff in The Hitchhiker's Guide to the Galaxy: beer, tea, Pan-Galactic Gargle Blasters, and Vegan Rhino cutlet, to name a few. We're not including whale (oh, poor, sweet whale) or petunias, though some people around here might like to eat that in cake form. Because there are lots of foods and drink in this book (though not as much as in the sequel, The Restaurant at the End of the World), we can't say that all the food symbolizes one thing. However, we have broken this group down into two categories:
Tastes Like Chicken (or Used in the Same Social Situations)
Janx Spirit, Pan-Galactic Gargle Blasters, and Vegan Rhino cutlet may sound disgusting to us, but they serve pretty regular roles in galactic life. In this book, things out in space happen pretty much the way they do here. Janx Spirit is basically alcohol, and people drink it in space for the same reason they drink it on Earth. There's even a party game in the book involving Janx Spirit, but frankly, we're not going to think about it too much, since—our apologies—it involves Ford's body (1.94-101).
The Vegan Rhino (unfortunately, no, not a rhinoceros following a strict vegan diet) is served during a big party that the mice throw for Arthur and his friends. As Zaphod notes, the mice "have been gassing us and zapping our minds and being generally weird and have now given us a rather nice meal to make it up to us" (31.16). So this meal could be seen as a peace offering or as a gift. However (and this is something that Zaphod misses at first), this is also a pretty typical business lunch where the mice want to lay out their offer. So, really, this gift of Vegan Rhino is double-edged. It's just something to soften up Arthur and his friends, making it all the more appropriate that in the end, Vegan Rhino is really just an "evil smelling meat" (31.16).
I Never Thought of Putting it There
If our first category is "alien food used in regular Earth-style situations," our second category is all about reversing that: Earth food used in alien situations. For instance, when Ford takes Arthur to the pub, he gives him beer. Because he wants to be Arthur's friend, you ask? Not so much. Ford gives Arthur beer to use as "muscle relaxant" (2.43). Peanuts, to Ford, aren't a little snack to be eaten at a baseball game; they are a replacement supplement for the "salt and protein" that Arthur probably lost. These are pretty alien understandings of common foods.
As for tea, well, instead of drinking it in space, aliens use it to power their improbability machines: "The principle of generating small amounts of finite improbability by simply hooking the logic circuits of a Bambleweeny 57 Sub-Meson Brain to an atomic vector plotter suspended in a strong Brownian Motion producer (say, a nice hot cup of tea) were of course well understood…" (10.4).
Notice how Adams starts off with lots of important-sounding scientific-type words—principle, logic circuits, sub-meson, atomic vector, plotter, Brownian motion—and then hits us with something super common, especially to British people: tea. So sometimes we find regular food stuff where we least expect it. It's sort of like Adams is showing us how weird our foods and habits are by putting them in an unusual, alien context.