Learn Dutch: Er valt geen enkele kruimel te vinden. - Not a single crumb can be found.

Adding enkele makes the negation absolute and emphatic. While geen kruimel just means "no crumb", geen enkele kruimel emphasizes that there is "not a single crumb" left.

Why does enkele end in an -e in this sentence?

The phrase geen enkel(e) follows standard adjective rules. The noun kruimel is a de-word (de kruimel). Because it follows geen and modifies a de-word, it gets an -e, making it geen enkele kruimel. If it were a het-word, you would use geen enkel without the -e.

What does the combination valt te vinden mean?

While valt literally means "falls", the grammatical structure valt te + an infinitive verb means that something "can be" done. So valt te vinden means "can be found". It is very similar to saying is te vinden (is to be found).

Why do we need the word Er at the beginning?