All penguins - of all types - have been discovered to have no taste for sweet, bitter, and umami flavors of edible matter. Of course they can't taste anything sweet, even if it happens to be a sweet-tasting rock - but this finding is linked inextricably to eating. As it turns out, its likely penguins lost their taste for several types of food over the course of their migration to cold climates and evolution to the creatures they are today - friendly, tasteless waddlers though they are.
As tastes such as these don't often appear in the bitter cold, penguins simply did not need to have the genes to detect them. That's what a team of researchers has concluded after sequencing the genomes of a couple of penguin tribes: Adelie and emperor penguins.