| Currently,with the promotion of coordinated green sustainable development in the food industry,food preservation technology is becoming increasingly important.People's pursuit of quality of life and the high-tech desire of the food preservation industry have made packaging materials of high research value in the choice of raw materials and performance improvement.Besides,natural macromolecules are safe,environmentally friendly,and degradable,and they have good medicinal functions for the modification treatment and composite applications of some macromolecules.Therefore,natural macromolecular substances have become the preferred raw materials in the preparation of film.In this study,collagen and glucomannan were used as raw materials.Chemical and physical methods were used to modify the raw materials.The atomic force microscope was used to explore the characteristics of the modified molecular self-assembly behavior and surface structural integrity after film formation.The main contents and results of this study are as follows:? The collagen was modified with glutaraldehyde and UV/riboflavin,and the self-assembly effect of collagen molecules under different conditions was observed with an atomic force microscope.The results showed that as the concentration of glutaraldehyde increased,the self-assembly effect of collagen was significantly enhanced.The width and height of collagen changed with the increase of glutaraldehyde concentration: 36.45 ±4.45nm-64.35 ± 2.58 nm and 2.26 ± 0.19nm-4.93 ± 0.29 nm.Roughness tended to decrease first and then increase.Compared with the UV/riboflavin treatment group,the UV/riboflavin treatment group had obvious self-assembly crosslinking effect.In addition,the duration of UV irradiation had a greater impact on the height of collagen than on its width.The changes in the width and height of collagen under different UV irradiation durations were: 41.36 ± 4.30nm-55.47 ± 4.53 nm and 3.10 ± 0.39nm-6.20 ± 0.85 nm,the percentage changes w: 25.44% and 50.00%.Studies on the effects of concentration and time on collagen have found that concentration has a greater effect than irradiation time.After UV/riboflavin treatment,the maximum width and height of collagen were changed to 106.98± 3.37 nm and 11.17 ± 1.33 nm,respectively,but there was no significant change in the fluorescent treatment group.? Atomic force microscope was used to observe the cross-linking of glucomannan at different concentrations,and the concentration of single glucomannan molecule was selectedfor subsequent research.The concentration of glutaraldehyde,p H value,and UV/riboflavin parameters were adjusted to modify glucomannan.The results showed that as the concentration of glucomannan increased,the glucomannan molecules gradually showed an intertwined network structure,and when the concentration was 2?g/ml,it showed a clearer single-chain structure.After treatment with glutaraldehyde,the glucomannan molecules showed a clear porous network membrane structure.Under different concentrations of glutaraldehyde,the changes in height and roughness of glucomannan molecules were: 1.38 ±0.11nm-1.65 ± 0.12 nm and 0.43 ± 0.00nm-0.55 ± 0.04 nm.With the increase of p H value,the height and roughness changes of glucomannan molecules were: 1.14 ± 0.07nm-1.61 ±0.02 nm and 0.27 ± 0.00nm-0.69 ± 0.01 nm.The pore size of the sugar film decreased from98.07 ± 0.81 nm to 33.11 ± 0.75 nm.When p H=11.59,the pore diameter increased to 74.44 ±0.71 nm,showing a tendency of destruction.When the UV/riboflavin treatment group reached 60 min,glucomannan molecules showed a porous network membrane structure.? The collagen and glucomannan were compounded,and the thickness,roughness and pore density of the compound were investigated using an atomic force microscope.In this study,different proportions of compounds were prepared,and the appropriate ratio was selected to observe the cross-linking effect of glutaraldehyde and UV/riboflavin on the complexes.The results showed that when the final concentrations of collagen and glucomannan were 20?g/ml and 2?g/ml,respectively,the complex showed a good composite form.After glutaraldehyde treatment,the thickness of the composite was reduced from 1.78±0.18 nm to 1.12±0.08 nm,and the roughness was reduced from 0.51±0.02 nm to0.41±0.02 nm.After UV/riboflavin treatment,the thickness of the composite increased from1.63±0.17 nm to 3.55±0.21 nm,and the density of pores showed a gradual decrease.? Considering the difference between molecular and macroscopic factors,the collagen/glucomannan composite membrane was prepared.Fourier transform infrared spectroscopy was used to characterize the reaction of the composite membrane molecules under different conditions,and to further explore the principles of physical and chemical methods.The results showed that intramolecular and intermolecular hydrogen bonding occurred between the two molecules in the composite membrane after the crosslinking treatment.In addition,the glutaraldehyde treatment consumed functional groups in the composite film,so the crosslinking effect was more obvious.After the glutaraldehyde treatment,the surface of the composite film was smoother than that of the UV/riboflavin treatment;the thickness and roughness of the composite film were 46.55% and 57.76%smaller than that of the UV/riboflavin treatment group,respectively.? Collagen/glucomannan composite membrane was prepared to investigate the effects of glutaraldehyde at different concentrations on the surface structure,water absorption and solubility of the composite membrane.Meanwhile,the UV/riboflavin treatment group was selected as the control group.The results showed that with the increase of glutaraldehyde concentration,the roughness of the composite membrane showed a downward trend,the water absorption showed a trend of increasing first and then decreasing,and the solubility showed a trend of increasing gradually.The UV/riboflavin treatment group was dissolved within 24 h after immersion in distilled water,so the treatment of glutaraldehyde reduced the hydroscopicity and solubility of the composite membrane.After comprehensive evaluation of the above methods,both glutaraldehyde and UV/riboflavin treatments could produce a good cross-linking effect between collagen and glucomannan at the molecular level.The investigation of the performance of macroscopic composite membranes showed that the effect of glutaraldehyde on the composite membrane was greater than that of UV/riboflavin treatment.By exploring the molecular mechanism of the crosslinking treatment,this study further improved the comprehensive application of the composite in the process of film formation.This research will lay a solid foundation for the future research and development for better performance of food packaging. |
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