Crystallization of glazed puddings

Hi everybody! I have crystalization problems!
We use glaze to cover puddings. The glaze´s composition is 86% powdered sugar and 14% albumin. The product is storaged frozen (-18°C) and shelf life must be at least 4 months.
The freezing system is at -35°C, this is the best we can do with current equipment.
We found crystalization begins around 20 days after producing date. Once it appears, crystal size grow and change collor turning light brown.
Our client don´t want to change the taste of the product so they do not accept a sour taste.
I´ve alredy tryed by replacing 10% of sugar with trehalose, but it didn´t worked out. Citric acid (1%) seems to be a good option but it was refused by my client due to sour taste and sticky texture.
Do you have any recommendation?
Do you think pregelatinized starch should help?

How about mixing a glucose syrup in your formulation or any syrup like honey or invert sugar to control it. 80- 90% Fructose sugar in syrup would help also. Having such sugar would retard sucrose recrystallization.

I agree with @Roy using invert sugar is the best way. if you use glucose about 30% of total sugars i think it is enough.

Second way may be this;

Prepare a water and sucrose solution with minimum water then cook it until about 105 C. Cool the solution and use it. This process will invert some of sucrose and prevent crystallization.

Cracking of glaze can be aided with gum Arabic or Gum Acacia, neutral in taste