@skylark I didn't have salt and I think a contrast of texture, which acts to produce a varied, non-linear force on the periodontal ligaments helps to stimulate the digestive secretions.

"Chewing of foods stimulates the receptors in the periodontal ligament (Scott et al. 1998) sandwiched between the tooth and the alveolar process of the jaw bone, although interestingly these are not stimulated by empty chewing, i.e., teeth grinding (Anderson et al. 1996)."

Carpenter, G. H. (2013). The Secretion, Components, and Properties of Saliva. Annual Review of Food Science and Technology, 4(1), 267–276. doi:10.1146/annurev-food-030212-182700