Ok. Here's a paper on using erythritol in ice cream.
It says the hardness comes from crystallization of the the erythritol itself; the freezing point depression factor is actually three times stronger than that of sucrose. The suggested compensations are to combine with other sugar alcohols (sorbitol, sucralose, polydextrose).
The complete sugar reduction is achieved by taking out the crystallisation inhibiting glucose syrup. However, due to erythritol’s strong crystallisation behaviour, a crystallisation inhibitor is indispensable. Several options from the polyol range were tested in the frame of the project. It was found that sorbitol, maltitol, xylitol and their mixtures, all perform quite well alongside erythritol. It was also discovered that all three indeed soften the ice cream structure. This creates a great toolbox where the polyol pair can be varied to modify product hardness and creaminess. The actual second polyol can be chosen according to individual preference as they all will harmonise with erythritol. Texture as well as sensory analysis revealed that the preferred polyol ratio should be in a range of three parts erythritol to two parts of the second polyol.
