Hydrogels of collagen hydrolysate (H) of mean Mw 15–30 kDa obtained from waste collagen from meat casings manufacture, cross-linked with 15% (based on H) polymeric dialdehyde
starch (DAS), have a marked tendency to ageing, which shows in hydrogel gradually increasing rigidity and decreasing thermo-reversibility.
Methods of thermal analysis (DSC, TG) proved that ageing of hydrogels is not related with a non-equilibrium state of the cross-linking
reaction but is rather given by increasing density of inter-chain hydrogen bonds between polypeptide segments of H. Plasticizing
effect of DAS on H is not too pronounced but the difference between glass transition temperature of dry xerogel Tg = 189.5±2.5°C and temperature of starting degradation (DAS component) 241.4±12.7°C offers certain space for processing these
xerogels into biodegradable (edible) packaging material by usual plastics technologies. Films obtained from the reaction mixture
by casting and drying at room temperature after thermal processing (105°C for 4 h) dissolve at room temperature only after
350 h. This effect can be employed for time-controlled releasing of active substances from such biodegradable (edible) packages.