Elsewhere, food is an exotic test of character, digestive system and morality. The trial-by-combat of the alien banquet in Iain M. Banks' Excession, for instance, or the talking beast which lugubriously points out its best cuts in Douglas Adams' The Restaurant At The End Of The Universe. And sometimes food, or the lack of it, is the engine of the plot. In Adam Roberts' By Light Alone, the majority of the world's population subsist on the photosynthetic nutrition of their hair; only the rich can indulge their base appetites. In Thomas M. Disch's magnificently bleak The Genocides, an alien food-crop overwhelms the Earth and threatens humanity with extinction. In Gene Wolfe's Book of the New Sun, the hero, Severian, consumes not only the flesh of his lover, but also her memories in an anthropophagic rite that's a dark parody of Holy Communion.
But for the practising SF novelist, how people grow or get food, prepare food, and eat and share food, can be a useful shorthand. A window on the ordinary unexamined life of the future, and the inner lives of its inhabitants. Severian, who grew up in a parsimonious Guild, frequently refers not only to food, but to times when he is forced to go hungry. Rick Deckard's wait for a meal at a noodle stall in Blade Runner not only tells us something about his character's loneliness, but also something about the crowded multiculturalism of 2019 Los Angeles. In The Matrix, the mucoid slop served aboard the hovercraft captained by Morpheus underscores the parlous state of free humans; it's so bad that the temptation of a tasty virtual steak is part of the deal with the devil made by a traitor. Soylent Green in Harry Harrison's Make Room, Make Room has nothing to do with the film verson's silly twist, but is a staple food in an overpopulated and undernourished world, made from (geddit?) soy beans and lentils, while the care with which the hero's ancient roommate tends his planters of herbs and onions tells us not only something about their value, but underscores his nostalgia for how things once were.
We're not only what we eat; we're also defined by how we eat it, and how much we value it. But our place at the top of the food chain isn't guaranteed. As the crew of The Nostromo discovered during their last communal meal in Alien, sometimes we're the meat on something else's table.
(Thanks to those on Twitter who responded to my question about famous food moments in SF with some great examples. Soylent Green and That Scene in Alien were by far the most popular.)