| With the improvement of human living standards,the global collagen industry has shown rapid growth in recent years,and the existing collagen raw materials and collagen products are unable to meet the demand of consumers.Salmon accounts for4.4%of the global seafood supply,and the output shows a trend of rapid growth.Salmon fish meat is a common high-protein fish product and is favored by the market.The salmon skin is not fully utilized,and some are used as edible materials,and some are discarded as waste,resulting in a lot of waste.Therefore,in this paper,salmon fish skin collagen was prepared using salmon fish skin as the research object,and the effects of environmental factors on collagen self-aggregation were investigated at the kinetic level,the pH-regulated collagen chitosan self-aggregation behaviour was investigated at the molecular level,and the effects of different environmental factors on aggregate morphology,particle size and microstructure were explored.This study aims to provide new ideas and theoretical support for the development of high value-added collagen-based products.The main investigations are as follows.(1)Salmon fish skin was used for the preparation of collagen.The experimental results showed that the yield of fish skin collagen was 22.6%(wet basis weight),and the salmon fish skin collagen was typical type I collagen and retained the complete triple helix structure.The thermal denaturation temperature of the collagen was22.3℃.The thermal denaturation temperature of collagen was 22.3℃;the emulsification of fish skin collagen was 65.91-755.97 m~2/g,which was higher than that of bovine collagen 28.4 m~2/g-56.2 m~2/g and salamander sarcoplasmic protein 0.6 m~2/g-3.38 m~2/g;The emulsion stability was 3.50 min,which was higher than that of Mongolian bovine bone collagen for 0.80 min and cobia fish skin collagen for 0.20 min,and the foamability was 16.56%-77.79%,which was higher than that of casein 3.95-10.15%and rice bran protein concentrate 5.2-10.03%;The foam stability of 13.14%was better than that of salamander sarcoplasmic protein 5%and cowhide collagen 10%.The water holding capacity is 18.5±0.73 g/g,which is better than chicken feet collagen1.90 g/g and pigskin collagen 0.21 g/g;salmon skin collagen has better water holding capacity;oil absorption is 14.6 g/g±0.36,Compared with chicken feet collagen 5.30 g/g,chickpea flour protein 4.93 g/g,sorghum flour 3.39 g/g,the relative proliferation rate of MC3T3-E1 cells in 0.4 mg/m L collagen solution was 111.6%.(2)Using salmon skin collagen as raw material,a collagen self-aggregation kinetic model was constructed to evaluate the influence of environmental factors on collagen self-aggregation behavior.The experimental results showed that the collagen concentration was within the range of 0.125-2 mg/m L,the lag time decreased with increasing collagen concentration.At a concentration of 0.5 mg/m L,the rate constant k is the largest.In terms of pH value,when the pH value of the collagen solution is at the isoelectric point,the rate constant k is the largest and the delay time is the smallest.In the pH range of 6-8,as the pH increases,the rate constant k increases,and the lag time decreases(except for the isoelectric point).In terms of ion concentration,when the ion concentration of collagen solution was 0-120 m M,the lag time decreased with the increase of ion concentration.The rate constant k increased with increasing ion concentration in collagen solutions at 0-60 m M ion concentration.The rate constant k decreases when the ion concentration exceeds 60 m M.(3)To explore the change law of collagen aggregates induced by different environmental factors.The experimental results show that:to explore the change law of collagen aggregates induced by different environmental factors,the experimental results show that:in terms of ultra-microstructure,,when the collagen concentration is0.125-0.5 mg/m L,with the increase of collagen concentration,the density of collagen fiber bundles increases,the pores decrease;when the pH value of the collagen solution is 6-8,collagen fiber bundles are produced;when the collagen ion concentration is 0-60m M,with the increase of the ion concentration,the structure of collagen aggregates is more stable and fibrous thicker.In terms of particle size characterization,within the concentration range of 0.125-0.5 mg/m L,with the increase of collagen concentration,the particle size of the main distribution area of the generated collagen aggregates increases,and within the concentration range of 0.5-2 mg/m L,the generated collagen The particle size of the main distribution area of the aggregates decreased;when the pH of the collagen solution was at the isoelectric point,the particle size of the main distribution area of the collagen aggregates was the largest.When the ion concentration of collagen solution was 60 m M,the particle size of the main distribution area of collagen aggregates was the largest.In terms of infrared characterization,at 0.125-0.5mg/m L,the amide A band and amide III band of collagen aggregates shifted red with the increase of concentration,and the collagen skeleton became stable;at pH 6.39,the amide III band of collagen aggregates showed red shift.When the ion concentration increased from 0 to 60 m M,the absorption peak wave number of the amide I band of collagen aggregates decreased,and the stability of collagen aggregates skeleton was enhanced.In terms of secondary structure,when the collagen concentration increased from 0.125 mg/m L to 0.5 mg/m L,theα-helix of collagen in the aggregates increased,and when the collagen concentration exceeded 0.5 mg/m L,theα-helix of collagen in the aggregates decreased;When the pH was 4-8,theα-helix of collagen in the aggregates increased with the increase of pH,and when the pH of collagen was 10,random coils appeared and the stability decreased.Theα-helix of the aggregated collagen increased when the ion concentration increased from 0 to 60 m M,and when the ion concentration was 120 m M,theα-helix of the collagen in the aggregate decreased and the aggregate stability decreased.In terms of aggregate functionality,in the concentration range of 0.125-2 mg/m L,as the concentration of collagen increases,the emulsification,foaming,and foaming stability of collagen aggregates increase,while the emulsification stability decreases.The emulsification,emulsification stability,foaming,and foam stability of collagen aggregates decreased relative to the experimental groups at pH 4 and 10 without self-aggregation.The emulsification and emulsification stability of the aggregates at the isoelectric point,Foaming,foam stability is the lowest.The ion concentration of 0-60 m M promoted the increase of emulsification and emulsion stability of collagen aggregates,and the ion concentration of 120 m M inhibited the increase of emulsification and emulsion stability.When the ion concentration is 0-60 m M,the foaming property of collagen aggregates increases,and when the ion concentration is too large,the increasing tendency of the foaming property of the aggregates slows down.As the ion concentration increases,the foam stability of the aggregates decreases.(4)The aggregation process of salmon skin and chitosan regulated by pH was investigated from the molecular point of view.The experimental results showed that when the pH of the solution system was less than 6.39,the particle size of the collagen experimental group and the collagen chitosan experimental group had the same trend,the particle size increases.When the pH of the solution system is greater than 6.39,and the collagen group and the collagen/chitosan concentration ratio are 4:1,unsaturated adsorption of collagen and chitosan occurs.With the increase of pH,the particle size decreases,and stable aggregation is not formed.When the concentration ratio of collagen/chitosan is 2:1,1:1,1:2,under the action of electrostatic attraction,collagen and chitosan are saturated and adsorbed,the particle size increases,and stable collagen is formed.Chitosan aggregates.(5)Analyze the change law of the morphology,microcosm and structure of collagen chitosan aggregates generated by pH regulation.The experimental results show that:when pH is greater than 6.39,collagen chitosan aggregates have UV absorption at 230 nm and 280 nm.The peaks indicate that collagen and chitosan react to form collagen-chitosan polymer.The triple-helix structure of collagen in all collagen-chitosan polymers remained intact,and compared with collagen,the amide I band of collagen-chitosan aggregates was red-shifted,and the collagen skeleton structure was more stable.With the increase of pH,theα-helix of collagen in collagen/chitosan aggregates increased and the structure was more stable.In addition,when the pH was greater than 6.39,collagen and chitosan aggregated,and chitosan was attached to the surface of collagen.In terms of functionality,when the pH is greater than 6.39,the emulsification stability and foam stability of the formed collagen chitosan are better than those of collagen under the same conditions. |
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