Effect of heat treatment on the enzymatic stability of grass carp skin collagen and its ability to form fibrils in vitro

BACKGROUND: The molecular configuration, molecular weight distribution and thermal transition enthalpy (ΔH) of grass carp skin (GCS) collagens after heat treatment under different conditions were measured using circular dichroism, gel filtration chromatography and differential scanning calorimetry (DSC). The enzymatic stability of collagen was evaluated using different enzymes, while the ability to form fibrils in vitro was assessed by morphological observation of collagen fibrils and turbidity testing. RESULTS: The ΔH values, in-solution molecular aggregation and the stability to enzymatic hydrolysis of GCS collagen decreased irreversibly and progressively with the duration of heat treatment at 33 °C, which was the onset endothermic temperature obtained from the DSC curve. A strong positive linear correlation between the enzymatic sensitivity of collagen and the degree of thermal denaturation was found. A decrease in fibril diameter and D-periodicity length with denaturation could also be observed in the SEM and TEM images. CONCLUSION: The onset endothermic temperature (To ) rather than the denaturation temperature (Td ) is the threshold temperature for configurational stability of GCS collagen in acidic solution, and the biological properties would obviously change if the collagen was heat treated at this temperature.