Food is an artifact type. Even though it appears on some creatures, it's never a creature type.

You can't sacrifice a Food to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate Maraleaf Rider's ability.

Whatever you do, don't eat the delicious cards.

White Glove Gourmand doesn't need to have been on the battlefield when the Human died. For example, if a Human dies during combat on your turn and you cast White Glove Gourmand during your second main phase, its last ability will trigger at the beginning of your end step.

White Glove Gourmand's last ability will trigger only once during your end step, no matter how many Humans died under your control this turn. However, if no Humans have died under your control so far this turn as your end step begins, the ability won't trigger at all. It's not possible to cause a Human to die under your control during the end step in time to have the ability trigger.