Dahlenborg et al. (2011) observed a volume increase in white chocolate shell, that was stored against a hazelnut filling, of approximately 40% after 36 weeks storage at cycled temperatures.
Further, Galdamez et al. (2009) observed an increase of approximately 25% in chocolate shell weight after storage against hazelnut oil at 23 _C for one week, which corresponded to an increase of 61 wt% regarding the fat phase of the shell.
We suggest that a possible reason for a swelling could be crystal growth in the CB matrix, due to Ostwald ripening and re-crystallisation into more stable polymorphic forms.