Study On The Crosslinked Effects And Antibacterial Of Collagen Films By Laccase Mediator System

Firstly,the macro-sized acid-swollen collagen from bovine hides were prepared for film matrix to explore the improvement of laccase mediator system(LMS).A dosage gradient of 3,6,12,24,48 U Lac/g ASC was added to the ASC dispersion followed by gallotannins(GT,0.1 mg GT/g ASC),respectively,named as GT-Lac films.The Lac films were prepared with the same procedures of the GT-Lac films,at the same gradient of Lac dosage in the absence of GT,while the pure ASC film was prepared neither GT nor Lac.These samples were incubated in 30? for 2 h to achieve crosslinking and dried at room temperature.A contributing factor was the appropriate dosage of Lac(?12 U/g),whose tensile strength increased from 33.42 to 44.82 MPa and denaturation temperature raised from 99.42? to 103.05?.Their microstructure gradually became compact and barriers properties were also enhanced.On the other hand,GT-Lac films exhibited higher tensile strength(39.06 to 45.33 MPa)and higher denaturation temperature ranging from 102.67 to 109.07? as well as tighter structure and water-resistance than Lac films.Together,two film groups exhibited better integrity,tensile strength,and young's modulus than those of commercial collagen casings(MCC)in dry state.For exploring the crosslinking effect of LMS on ASC with various structural GT,the GT solution mixed with sulfuric acid was let to stand at 100? for 0,2,4,6 and 20 h to gain hydrolysis GT(HGT).Then,their hydrolysis degrees,determined by colorimetric method with rhodamine agent,referred to 0%,45%,61%,83%and 100%.Then,the nano-sized acidswollen collagen(NASC)were prepared from ASC using high pressure homogenization processing.The HGT films were prepared with different HGT(1 mg/g NASC).HGT-Lac films were prepared with different HGT cooperate with 12 U Lac/g NASC,while the pure NASC film was prepared neither HGT nor Lac.These samples were incubated in 30? for 2 h to achieve crosslinking and dried at room temperature.The low dose HGT showed few effects for NASC on their properties.The HGT-Lac films showed higher tensile strength(89.96 to 100.77 MPa)when the hydrolysis degree was 61%,and denaturation temperature(91.97 to 101.64?)as well as lower wettability.Finally,some representative NASC films were selected to study the preservation of cod fresh sausages.These sausages were stored at 4? for 0,2,4,6 and 8d,and the total viable count(TVC)on the surface and inside of the sausages were measured.The results showed that NASC films could maintain integrity on packaging effect.In terms of antibacterial properties,the shelf-life of fresh sausages covered by NASC films were expanded.In addition,the antibacterial properties of 4HGT-Lac films(hydrolysis degrees 61%)was higher than ?-polylysine film and MCC.In conclusion,LMS whose mediator was HGT of hydrolysis degrees 61%,had an effective catalysis and acted as a positive role for ASC crosslinking,improving their weak mechanical properties,thermal stability,and antibacterial properties.Our study provided new idea to improve the collagen films,and theoretical basis for the study of LMS.