The other day my dad and I placed the strawberries and the glaze on a strawberry cake. He used strawberry juice for the glaze instead of water to avoid watery taste.
If I remember correctly the red cake glaze was made of Carrageen and tapioca starch. The instructions said to mix this with water and sugar or wine. As I said we used strawberry juice. The sugar content should be similar. He noticed that the cooking glaze wasn't as thick as it should be and we added more of the mix. It still wasn't binding well enough so he added cornstarch and it finally was binding in the pot.
The next day the glaze was still a bit runny and not firm and cut-resistant. He also said that he tried it once with black currant juice and it didn't bind at all. We we're wondering what the reason for this is and thought about acidity, but wine (that is also ok to use with the mixture) would also be quite acidic.
What is the reason for fruit juice not binding well with starch and Carageen?