Prevent crystallization in frozen food

hi,

Which high sugar?

Did you try adding some acids as citric acid to control crystallisation?

Would you be more clear about the product you are formulating.? ..So we can see how to sort it out Guesswork troubleshooting based on scant information is a waste of time.
There are so many varieties of frozen desserts ..

The product is a raw chocolate lava cake. The sugar content in formula is around 25%

Hi! No, I didn't! Do you have any recommended dose to suggest me?

Raw chocolate lava cake...Upon further thought you might be making unbaked lava cake..There is not enough information about its composition that will assist in sorting out the issue directly until now we can only propose ideas based on granulation issue with other confections.
If granulation is the problem then adding another granular sweetener like trehalose will not solve it .
You should prepare a sugar syrup mixture composed of sucrose ,glucose, and enough water then heat to dissolved the solids to around 80% Brix before using it to sweeten your dessert if that is acceptable to your formulation. .?

Victoria, you still need to add more information.
Are you blast freezing first? What is your packaging?
What are the ingredient criteria, ie: clean label etc.?

Victoria,

I will go with @Roy's suggestion. Heat the sugar to produce syrup which is partly invert sugar then freeze your product quickly. Invert sugar is less prone to crystalization then slow freezing causes crystalization.

[quote="Vic, post:5, topic:6284, full:true"]
Hi! No, I didn’t! Do you have any recommended dose to suggest me?
[/quote]

it depends your formula and your mixture pH. Try 0,02% and check the result.

Try to maintain min 20% reducing sugars in your product.