Why does saliva clean so well?
Saliva has alpha-amylase (ptyalin), which hydrolyzes carbohydrates (so starch starts to taste sweet in just a few seconds), kallikrein, an enzyme that breaks down protein, and lingual lipase, which helps disintegrates fats (lipids).

So next time you clean off a splattered insect from your wind-screen (windshield, should you prefer), think of it as external digestion, as practiced by flies and by starfish. Or perhaps you might not want to consider that thought...