Babies will generally show disgust in response to unpleasant tastes. Disgust expressions, which begin in the first few months, can include an open mouth, raised upper lip, and a wrinkled nose.
Lewis, M. (2000). The emergence of human emotions. In Lewis, M., & Haviland-Jones, J. M. (Eds.), Handbook of emotions (2nd ed.). New York: Guilford Press.