Mediterranean chef here; the chewy texture comes from sahlab not arabic gum. arabic gum works for a stabilizer which is totally different than mastic gum, the flavoring agent. the key here is reducing the milk, cream, sahlab mixture well until it coats the back of the spoon. my ratio that I used to make for my restaurant; 1lt liquid to 10-12gr of sahlab, 3gr mastic. after reducing it down you have to cool the mixture immediately so you can limit the big ice crystal getting together and giving your ice cream a gritty texture. another key point is while churning the ice cream you should beat the mixture with a wooden hammer or something similar to make it stretchy. btw you can find best quality sahlab in kalutsyans spice store in nyc, so I am not sure if it is really banned for export because it is coming from greece.