Research On Extraction, Antioxidant Activity And Physicochemical Property Of Black Soldier Fly Larva Proteins

Hermetia illucens, whose English name is black soldier fly, possesses abundant fat and protein in its larva body. This article attempted to optimize the extraction process and determine the antioxidant activity and physicochemical property of black soldier fly larva proteins(BSFLP, for short). The main results are showed as follows:(1) The methods of extraction by lye, enzyme, salt and Tris-HCl buffer were used and comparatively analyzed in extracting BSFLP. Then, the optimum levels of Na OH mass concentration, liquid-to-solid ratio, and extraction temperature and time were determined by means of single factor tests. And the experiment and analysis of BBD response surface was conduct based on the results from univariate tests and the actual situation. The results indicated that among the four extraction methods of BSFLP, the optimal one was lye extraction, and its optimum extraction conditions were Na OH mass concentration 2.44 g/100 m L, liquid-to-solid ratio 22 m L/g, extraction temperature 53 ℃ and extraction time 2 h. The relative error between the corresponding extraction ratio of verification test and predictive value only 0.28%, so the response surface model was fitting high and the optimum extraction process was feasible.(2) The results from the preparation of BSFLP and the determination of its in-vitro antioxidant activity revealed that The isoelectric point of BSFLP was at about 4.8, and BSFLP extracted using this method was in high purity, so the method of alkali dissolution and acid precipitation was available to extracting proteins from larvae of black soldier fly; the total reducing power of BSFLP was about 0.013 times as strength as that of VC, and 1.319 times as strength as that of OVA; the activity of scavenging superoxide anion of BSFLP was stronger than that of OVA but weaker than that of VC; and the IC50 s of scavenging superoxide anion, hydroxyl radical, DPPH radical and ABTS radical, chelating ferrous ions, and inhibiting peroxidation in linoleic acid system of BSFLP were respectively 2.577 mg/m L、3.965 mg/m L、0.228 mg/m L、0.876 mg/m L、5.050 mg/m L, which were all also between those of VC(or EDTA) and those of OVA, therefore BSFLP was good at in-vitro antioxidation.(3) The results from the analysis of nutritional component in black soldier fly larvae, their defatted flour and BSFLP and the determinations of the physicochemical property of BSFLP demonstrated that the protein contents of black soldier fly larvae and their defatted flour were 32.79% and 57.7%, respectively. Therefore black soldier fly larvae could be served as the raw material of proteins. And some protein isolates containing at least 91.31% protein were yielded with a bulk density of 0.085 g/ml, an oil-absorbing capacity as high as 8.66 g/g, typical functional groups of protein, and outstanding nutritional characteristics. The composition of the amino acids was suitable and superior to that of the defatted flour. The protein solubility, foaming capacity, foam stability, emulsifying capacity, emulsion stability, water-holding capacity, and gelling capacity were all affected by p H and Na Cl concentration, and almost all of the highest values thereof were obtained at a high p H and a concentration of about 0.5 M Na Cl; whereas the lowest values were obtained near an isoelectric point and at a high Na Cl concentration. The results showed that BSFLP had a favorable physicochemical property for use in the feed and food industries.