to curdle or thicken almond milk or cow's milk as it is cooked (see Molina)
IPAspelling:
pɑpɑtsɑ
Alonso de Molina:
papatza. nitla. (pret. onitlapapatzac.) cortar almendrada o leche, quando la cuezen. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 79v. col. 2. Thanks to Joe Campbell for providing the transcription.