Starch when come into contact with the water, gelatinization takes place and converted into gel/paste like structure. Hydrocolloid helps to retain more water, water holding capacity can be increased and thus starch retrogradation can be minimized.
Pasting properties of commercial native starches are described in detail in attached paper (unfortunately it is written in Polish). The work on food grade modified is in press in the same journal at the moment. Regarding interaction between starch and food hydrocolloids I recommend you to look for papers prepared by Sikora M. et al.
It is my pleasure that you have found my answer helpful. In the near future, the new paper on pasting properties of food grade modified starches is going to be published in the “Żywność, Nauka, Technologia, Jakość” journal (unfortunately once more in Polish).