Names of branches of neuroscience and related fields dealing with hunger, taste, attachment, and digestion, and their relationship to other perception
Short answer / Intro
This question is (superbly) broad, and I've merely attempted to try to give some pointers, without even trying to be complete in any way.

Background  


  I would like to know what the branches of neuroscience, cognitive science, psychology, and psychiatry related to what happens when the tongue touches...



Neuroscience: neurophysiology
Cognitive science: theoretical neuroscience
Psychology: psychophysics
Psychiatry: ?
Health sciences: Otorhinolaryngology 


In terms of disorders, Hummel et al (2014) say:


  These functions reflect the complaints of patients with smell and taste disorders: Patient complaints include loss of “fine taste”, inability to detect the odour of a partner or child, and the occurrence of, for example, food poisoning. In general the value of these senses is only recognised when they are lost. It is assumed that about 5% of people exhibit functional anosmia.


Anosmia being:


  the loss of the sense of smell, either total or partial. It may be caused by head injury, infection, or blockage of the nose.


In terms of psychiatric illness I'm moving into unfamiliar territory, but there seems to be mention in the literature of a correlation between taste dysfunction and psychiatric disorders (Mott et al., 1993) 

References
- Hummel et al., GMS Curr Top Otorhinolaryngol Head Neck Surg (2011); 10: Doc04
- Mott et al, Dental Clinics North Am (1993); 37(1): 33-71