Study Of In Vitro Digestion And Antioxidant Activity Of Black Soldier Fly Larvae Proteins

Black soldier fly(BSF,Hermetia illucens L.),an insect with high protein and abundant essential amino acid,has been proposed as a high-quality protein resource.In this study,the amino acid composition and in vitro digestibility of the BSF larvae proteins(BSFLP)based on two drying methods(conventional oven drying and microwave drying)were investigated.In addition,four kinds of proteins(albumin,globulin,prolamin,and glutelin)were isolated by a sequential extraction method from the BSF larvae and the in vitro antioxidant activity and physicochemical property of the protein fractions were investigated.Based on the research above,albumin was selected for its best solubility and antioxidation,and the protein ingredient was determined by HPLC/MS.The main results were showed as follows:(1)Total crude protein and four kinds of protein fractions(albumin,globulin,prolamin,and glutelin)were isolated by alkali and a sequential extraction method from the BSF larvae,respectively.Experiment results showed that the crude protein of defatted BSF larvae were 54.00%and the proportion of four fractions to defatted BSF larvae were 23.58%,19.46%,1.52% and 8.44%,respectively.The physicochemical properties of four isolated proteins were investigated.Experimental results showed that albumin exhibited the lowest foaming stability while globulin showed the biggest foaming stability and the lowest water-holding capacity.Prolamin exhibited the highest emulsifying property and the lowest foaming capacity.Glutelin showed the biggest water-holding capacity and foaming capacity.The physicochemical properties were affected by Na Cl concentration,and almost all of the highest values were obtained at a concentration of about 0.2M NaCl.The experimental results indicated that the BSF larvae proteins had good physicochemical properties and could be utilized as foaming agent,emulsifying agent in the future.(2)The effects of two drying methods(conventional oven drying and microwave drying)on amino acid composition,in vitro digestibility and morphologies of BSFLP were discussed.Experimental results showed that their amino acid score(AAS)could reach the requirement of FAO/WHO(2013) for indispensable amino acids(IAA).The proportion of essential amino acids to total amino acids(E/T)of both conventional dried BSFLP(CD-BSFLP)and microwave dried BSFLP(MD-BSFLP)were more than 40%.Both of the in vitro digestible indispensable amino acid score(DIAAS)values of the BSFLP were more than 75%.The results of scanning electron microscopy(SEM),thermo-gravimetric analysis(TGA)and differential scanning calorimetry(DSC)of the samples showed that microwave drying polymerized the protein particles and made them harder to digest.In conclusion,the BSFLP prepared by conventional drying(60?) had higher DIAAS and better digestibility.(3)The in vitro antioxidant activity,including reducing power,hydroxyl radical,ABTS radical,DPPH radical and superoxide radical scavenging ability of four isolated proteins were investigated.The results showed that all the protein fractions had antioxidant activity,and the values increased with the protein concentration.In addition,albumin had the strongest reducing power,hydroxyl radical scavenging ability,DPPH radical scavenging ability and superoxide radical scavenging ability.Glutelin had the strongest ABTS radical scavenging ability.Based on the research above,albumin was selected for its best solubility and antioxidation,and the protein ingredient was determined by HPLC/MS.Experimental results showed that there were eighteen kinds of protein components in albumin and six of them were significant to vital movement which including myosin heavy chain,alpha-actinin,calmodulin,ATP synthase subunit beta,polyubiquitin and chymotrypsin.