Effect Of Crosslinking On In Vitro Digestibility And Absorption Of Collagen Film

Edible film as a new kind of packaging material,can prevent the loss of moisture and volatile substances in food and improve the quality of food.Because of its convenience and no pollution,edible film is getting more and more attention recently.Collagen film,the only commercialized edible protein film,has been widely used in the meat industry because of its high nutritional value and good tensile strength.Given that different extraction of collagen may reduce the mechanical properties and thermal stability of collagen film,a variety of cross-linking methods for collagen film to improve the performance have been developed in recent years.However,the effects of these cross-linkings on the digestibility,safety and nutrition of the film were not still well known.In this study,bovine type I collagen extracted from cowhide was used as a raw material to prepared collagen films,followed by cross-linking by different methods,and then the digestibility and safety were evaluated by in vitro digestion model and cell model.First of all,the collagen film was cross-linked using four physical or chemical cross-linking methods,including ultraviolet irradiation,dehydrothermal treatment,tannin and glutaraldehyde,and then was digested in vitro.The results showed that partial denaturation of the protein caused by physical cross-linking caused the collagen film a good digestion performance,while glutaraldehyde and tannin reduced the digestibility of the collagen film to varying degrees.In terms of microstructure,after continuous immersion and hydrolysis action,collagen film with different cross-links had no difference in the degree of degradation.Glutaraldehyde residues were toxic to cells,while using other methods to cross-link collagen membranes provided nutrients to the cells.Secondly,by adding CMC,MCC or their blending to the collagen film,respectively,the electrostatic interaction and wet Maillard reaction are used to crosslink cellulose and collagen,and then was subjected to in vitro digestion.The results showed that due to the strong electrostatic interaction and Maillard reaction between cellulose and collagen,the addition of cellulose reduced the digestibility of the collagen film;the degree of hydrolysis was lower and the particle size after degradation was bigger.The structure of MCC-collagen was easier to be digested than the other two cross-linking methods,and the hydrophobicity was lower.The Maillard reaction product was potentially cytotoxic and reduced the survival rate of cells.The structure of cellulose-collagen,led to poor nutritional performance because cellulose cannot be digested and absorbed.Finally,by selecting four different commercial collagen film and laboratory-made control collagen films subjected to in vitro digestion,the digestion performance was compared.The results showed that commercial collagen films,especially collagen film No.3,had a higher degree of hydrolysis and loss of dry matter,and a smaller particle size after digestion.However,the amount of collagen dissolved or absorbed by film No.3 was low,which may be due to the different collagen content in the collagen film.All commercial collagen films were non-cytotoxic,and film No.2 showed good nutritional performance,high hydrophobicity after digestion,and protein structure changes during digestion similar to the control film.In summary,the commercial collagen films generally have good digestive performance,while the laboratory-made film through heat treatment,ultraviolet cross-linking collagen film have the best digestive performance due to protein partial denaturation.Dialdehyde residues and the Maillard reaction products may make collagen films potentially toxic and require further research to determine their safety.