crisp vs crispen

crisp is a noun but crispen is not a noun.

Word	Noun	Adjective	Verb	Adverb
crisp	Yes	Yes	Yes	No
crispen	No	No	Yes	No

As verbs, crisp and crispen are synonyms defined as:

Other synonyms of crisp include toast.

crisp (noun)	crispen (noun)
a thin crisp slice of potato fried in deep fat

crisp (adjective)	crispen (adjective)
pleasantly cold and invigorating
brief and to the point; effectively cut short
(of hair) in small tight curls
(of something seen or heard) clearly defined
pleasingly firm and fresh
tender and brittle

crisp (verb)	crispen (verb)
make brown and crisp by heating	make brown and crisp by heating
make wrinkles or creases on a smooth surface; make a pressed, folded or wrinkled line in; `crisp' is archaic