curdle (v.)

1630s (earlier crudle, 1580s), "to thicken, cause to congeal, change or form into curd" (transitive), frequentative of curd (v.) "to make into curd" (late 14c., from the noun; see curd). Intransitive sense of "to coagulate, thicken" is from c. 1600. To curdle (one's) blood, in the figurative sense of "inspire horror" is from c. 1600. Related: Curdled (1580s); curdling (1690s, almost always of blood and in the figurative sense).