Studies On The Functional Properties And Application Of Protein And Bioactive Peptides From Shrimp Shell Wastes

Oriental shrimp(Fenneropenaeus chinensis)is the main shrimp export of China owing to its delicious taste and abundant nutrition.The shrimp industry in China can produce approximately 1,480,000 t of shrimp,most of which are processed as peeled and headless shrimps for export,resulting in more than 300,000 t of shrimp head and shell wastes annually.These wastes are usually dumped without beneficial use so they become an environmental pollutant.With high nutritive value and potential biological activities,shrimp shell wastes(SSW)are good candidates for functional foods and drugs through the bioconversion.In order to facilitate the utilization of SSW and provide a theoretical basis for the new functional food and drug development,in this study,the physicochemical properties and the?-amylase inhibitory and antioxidant activities of the peptide released from SSW were investigated.At the same time,the extrusion effect on the characteristics of protein isolates from SSW were investigated and the effect of different ethanol extracts from different plant crops(corn silk,oolong tea and black soybean seed coat)on the physicochemical and antioxidant properties of SSWP-chitosan-extracts(SSWP-C-E)films were also evaluated.First,in order to obtain shrimp shell wastes hydrolysates(SSWH)with?-amylase inhibitory activity,response surface methodology coupled with a Box-Behnken design(RSM-BBD)was used to optimize the neutrase concentration(A:4-6%(w/w)),liquid-solid ratio(B:10-20 mL/g)and hydrolysis time(C:3-5 h).The optimum conditions were enzyme concentration of 5.4%(w/w),liquid-solid ratio of 13 mL/g,time of 4.1 h,temperature of 50°C and pH of 7.0.Under these conditions,the?-amylase inhibitory rate was 43.4%,which was in agreement with the prediction model with a coefficient of determination(R~2)of 0.9676.SSWH showed significant ability to scavenge diphenyl picryl hydrazinyl(DPPH)free radicals,reduce iron(III)and inhibit lipid peroxidation.SSWH consisted mainly of small peptides with molecular weights less than 4 kDa and high essential amino acids(278 mg/g),which indicated its high nutritional value based on the recommended standard protein(FAO/WHO).In addition,different conditions of extrusion variables(temperature and moisture content)were applied to SSW,and its effects on the physicochemical,functional properties and antioxidant activities of shrimp shell wastes protein(SSWP)were investigated.The results showed that extrusion caused a marked improvement in the protein content and yields compared with the control,and it also resulted in the changes of SSWP on the amino acids composition,functional properties,thermal properties and morphological properties.The protein from extruded SSW showed better antioxidant activities than the untreated one.When the six samples were compared by principal component analysis,the SSWP sample obtained from the conditions of 25%moisture content at 150°C(T3M2)were observed to have the highest comprehensive principal component values.As for the study of active films,SSWP mixed with chitosan were used as the sources of biopolymers and different concentrations(1,3 and 5%)of oolong tea extracts(OTE)corn silk extracts(CSE)and black soybean seed coat extracts(BSSCE)were added as natural antioxidants.The film properties were determined by measuring physical properties and antioxidant activities.The structural properties of films,as observed by SEM and DSC were strongly affected by the addition of OTE,CSE and BSSCE.The thermal stability of SSWP-C films incorporated with OTE,CSE and BSSCE were improved with the increasing concentration of extracts.The SSWP-C films incorporated with OTE,CSE and BSSCE exhibited lower light transmission in UV light,lower percent transmittance and higher transparency value compared to the control film.The findings of this study showed that the incorporation of OTE,CSE and BSSCE into SSWP-C films enhanced the DPPH radical scavenging activity,reducing power and inhibition on lipid peroxidation.In summary,this study could help provide a theoretical basis for shrimp shell wastes bioactive peptides and protein used in functional food application and related drug development.