Studies On The Characterization Of Silkworm Pupa Protein Modified By Physical-enzymatic Methods

China is the world's largest producer of silk and has a long history of sericulture.As the main purpose of sericulture is silk,silkworm pupa has become the main by-product.We can produce more than 500,000 tons of fresh silkworm pupa,but the silkworm pupa is basically used as feed in a fairly long period of time because of lacking of technology,which led to a huge waste of resources.In order to improve the utilization value of silkworm pupa protein,the sensory odor of silkworm pupa was removed by microorganism fermentation,and this study modified the silkworm pupa protein by using the methods of micronization pre-treatment-controlled enzymatic hydrolysis and ultrasonic pre-treatment-controlled enzymatic hydrolysis.And also researched the changes of its functional properties,the nutritional value and biological activity before and after modification.The aim was to provide theoretical basis for using silkworm pupa protein efficiently.Canidia albican had the best effect,which was screened out from 8 strains used the sensory odor after fermentation with silkworm pupa as the index.Through the single factor experiment,we selected the optimal condition was that the inoculation rate was 2%,the fermentation temperature is 35 ?,the fermentation time was 40 h.We analyzed the odor components under different fermentation conditions by GC-MS.The results showed that the odor components of silkworm pupae were significantly reduced after fermentation.The solubility could be 1.84?2.32 and 2.69 times higher than untreated after treatment of ultrasonic,enzymolysis and micronization-enzymolysis.The emulsification could be improved 3.6%,15.05% and 21.52%.The foaming and foam stability could be improved evidently.The degree of hydrolysis could reach 22.59%,which is 1.58 times as high as that of untreated after micronization,enzymolysis and micronization-enzymolysis.The protein recovery could reach 56.68%,which is 1.82 times as high as that of untreated.The molecular weight of silkworm pupa protein modified by different treatments was small,and the content of disulfide bond could be reduced by 19.70%,and the content of sulfhydryl could be increased by up to 55.30%.The secondary structure were obviously changed.The structure of ?-helix,?-fold and ?-angle were reduced,the random coil was more than 90%after treatment.The solubility could be 2.03?2.32 and 3.59 times higher than untreated after treatment of ultrasonic,enzymolysis and ultrasonic-enzymolysis.The emulsification could be improved10.94%,15.05% and 40.40%.The foaming and foam stability could be improved evidently.The degree of hydrolysis could reach 24.55%,which is 1.72 times as high as that of untreated after ultrasonic,enzymolysis and ultrasonic-enzymolysis.The protein recovery could reach 75.99%,which is 2.44 times as high as that of untreated.The molecular weight of silkworm pupa protein modified by different treatments was small,and the content of disulfide bond could be reduced by 20.39%,and the content of sulfhydryl could be increased by up to 59.59%.The secondary structure were obviously changed.The structure of ?-helix,?-fold and ?-angle were reduced,the random coil was more than 90% aftertreatment.Amino acid analysis and nutritional evaluation,its antioxidant activity,inhibition rate of Angiotensin Converting Enzyme(ACE)in vitro and proliferation of mouse spleen cells were carried out to evaluate the biological activity of the modified silkworm pupa protein.Results showed that the value of Essential Amino Acid/Nonessential Amino Acid(EAA/NEAA)was improved 10% and the highest was 66.86%,and the value of Essential Amino Acid/Total Amino Acid(EAA/TAA)was higher than that the Food and Agriculture Organization/World Health Organization(FAO/WHO)recommended model 36%.The value of Amino Acid Score(AAS)and Essential Amino Acid Index(EAAI)also had improved,the EAAI were all higher than 90%.1,1-diphenyl-2-picrylhydrazyl(DPPH)scavenging rate and Fe2+ chelating capacity could reach 70% and 80%,and the reducing power were also improved.In short,its antioxidant capacity had been greatly improved.The IC50 of inhibition rate of ACE in vitro minimum could be reduced to 2.00mg/mL,which was5.93% of the protein untreated.At the dose of 50 ?g/mL,proliferation of mouse spleen cells could improve 100%.In a word,the nutritional value,the antioxidant activity,the inhibition rate of ACE in vitro and proliferation of mouse spleen cells were significantly improved after modification.