مشخصات پژوهش

Edible films based on red tilapia (Oreochromis niloticus) washed mince in the presence of cryoprotectants at different levels were prepared by casting method using glycerol as plasticiser. Films containing cryoprotectants, except for 4% sucrose, had lower tensile strength (TS) accompanied with higher elongation at break (EAB), compared with the control film (P < 0.05). Water vapour permeability (WVP) of films increased (P < 0.05) but no changes in transparency value were observed in the presence of cryoprotectants, compared with the control film (P < 0.05). Light transmission of films in UV range (200e280 nm) was lowered in films containing cryoprotectants, but increased in the visible range (350e800 nm). Intermolecular interactions between cryoprotectants and protein molecules were found in the film as determined by FTIR spectroscopy. Thermo-gravimetric analysis revealed that films containing 2% sucrose and 2% sorbitol exhibited the lower degradation temperatures with the lower weight loss, compared with other samples. Film with cryoprotectants had a smoother and more homogeneous surface without cracks. However, cryoprotectants at higher level caused the gritty surface. Thus, cryoprotectants present in the fish mince or surimi acted as plasticising agent and directly affected properties of films.