CURDLE

[cur.dle] vb cur.dled ; cur.dling [freq. of

[2]curd] vi (1590) 1: to form curds; also: to congeal as if by forming curds "a scream curdled in her throat"

2: to go bad or wrong: spoil ~ vt 1: to cause curds to form in

2: spoil, sour