Há estudos para tudo: Este é sobre mergulhar algo numa taça (tipicamente) partilhada com outros que já foi trincado uma vez por nós (surpresa: O conteúdo de germes aumenta consideravelmente, apesar de que não de forma igual em todos os meios testados - chocolate, molhos de salsa, etc.). O estudo ainda se pronuncia sobre morder a rodar o pedaço de comida antes de voltar a mergulhar (com vídeos - Seinfeld inclusive):
http://metro.co.uk/2016/08/08/science-says-that-its-officially-not-ok-to-double-dip-anything-anymore-6054805/#ixzz4GnJg9700
Citando:
"Research conducted by Harvard University’s Healthbeat journal has found that bacterial counts in dips surged after a person took a bite from a crisp and then dipped it back in again.
And the number of bacteria varied with the particular dip – with salsa harbouring way more bacteria after a double-dipping incident than cheese or chocolate sauces.
‘This research does raise the possibility that a person who is sick might spread a disease by re-dipping a chip,’ says the journal’s editor, Dr Robert Shmerling."