Merriam-Webster’s Third:

Main Entry: plastein

Pronunciation: *pla*st*n, -_st**n

Function: noun

Inflected Form: -s

Etymology: International Scientific Vocabulary plast- (from Greek plastos

formed, molded) + -ein (as in casein); probably originally formed in German;

from its tendency to pass over into hydrogel

–any of several substances resembling proteins precipitated by the action

of proteolytic enzymes (as pepsin or papain) on the digestion products of

protein