Does Arabic gum help keep frozen yogurt soft?
Basically you can't actually make soft-serve style yogurt in a regular freezer. It's just too cold.

However, you can make it softer by doing one or more of the following:


adding additional sugar. After a certain concentration, sugar prevents ice cream, sorbet and frozen yogurt from freezing as hard.
Adding some concentrated source of alcohol. I often use an ounce or two of spirits or liqueurs in my ice creams (usually a 5-6 cup batch), which prevents the mix from freezing as hard because of alcohol's very low freezing point.
Adjusting the fat ratio. I don't know the exact magic ratio of fat, though I'm sure someone else can find it for us. I've found that low fat and very high fat ice cream tends to freeze very hard.
Adjusting the amount of air in your batch. The churning process that an ice cream maker would buy you adds a fair amount of air between the crystals and results in a softer batch.


An ice cream machine can also produce a result that you can serve up quickly after making so that you never get to the "hardening" stage that American-style ice creams go through when you put them in the freezer after churning.

I don't use gums in my ice creams, but the advantage that they give you has more to do with stabilization of the ice crystals, not softening, as far as I understand. They primarily help cope with the conditions of transport, as you tend to slightly melt the ice cream/frozen yogurt when you take it home from the store and then you refreeze it.