What is the additive they put in apple juice to change it from cloudy to clear?
(after reading this: http://www.ncbe.reading.ac.uk/ncbe/protocols/inajam/pdf/jam01.pdf)

They usually use pectinase  (http://en.wikipedia.org/wiki/Pectinase) to break down pectin molecules to help mechanical filtration.

They also use gelatins to help clump up particules to help mechanical filtering.