If an effect refers to a Food, it means any Food artifact, not just a Food token. For example, when you activate the second ability of Ragost, Deft Gastronaut (which says “{1}, {T}, Sacrifice a Food: Ragost deals 3 damage to each opponent”), you can sacrifice Dubious Delicacy to pay its cost.

You can’t sacrifice a Food to pay multiple costs. For example, you can’t sacrifice Dubious Delicacy to activate one of its own abilities and also to pay the cost of Ragost, Deft Gastronaut’s second ability.