Extraction Of Euglena Protein And Improvement Of Its Functional Characteristics

Euglena is a unicellular microalgae,which contains a lot of nutrients such as protein,carbohydrates,vitamins andβ-carotene.At present,there are few studies on the extraction and functional characteristics improvement of Euglena protein.Whenβ-1,3-glucan is extracted from Euglena,the remaining liquid cannot be used reasonably,resulting in a waste of resources.In this experiment,Euglena protein was extracted by foam separation,and then the functional characteristics of Euglena protein were improved by ultra-high pressure method and Maillard reaction.The specific research contents and conclusions are as follows:(1)Euglena protein was extracted by foam separation method,and the optimum p H,liquid volume,temperature and dilution ratio for foam separation were determined.At the same time,the functional characteristics of Euglena protein were investigated,the structure of the protein was analyzed by FT-IR and UV-Vis spectra,and the amino acid composition of Euglena protein was determined by amino acid analyzer.The results showed that the optimum conditions for the separation of Euglena protein foam were p H 5.50,liquid volume 300 m L,temperature 30℃and dilution factor 15,at which the recovery rate and enrichment ratio were 94.27%and4.18,respectively.At 60℃,the water-holding capacity of Euglena protein is 7.27 g/g,and the oil-holding capacity is 14.74 g/g at 40℃.With the increase of protein content,the foamability and foam stability of Euglena protein increased first and then decreased.FT-IR and UV-Vis showed that the protein of Euglena had a typical protein peak.The contents of essential amino acids and hydrophobic amino acids in protein are 35.28%and 50.80%,respectively,which indicates that foam separation is a feasible and simple method.The results of this paper provide experimental basis for the research and development of Euglena.(2)The emulsification performance of Euglena protein was improved by ultra-high pressure method,and the optimum conditions of ultra-high pressure modification were determined with emulsification as an index.At the same time,the secondary structure,particle size,surface hydrophobicity and Zeta potential of Euglenoid protein before and after modification were characterized.The results showed that the optimum process for improving the emulsification of Euglena protein by ultra-high pressure was as follows:protein mass fraction was 0.41%,holding time was 20.59 min,and holding pressure was 133.88 MPa.Under these conditions,the emulsification of protein was 89.09 m~2/g.In order to verify the best optimization process and conditions of this experiment,considering the actual situation,the protein content was 0.40%,the holding time was 20.50 min,and the holding pressure was 135MPa.Under these conditions,the emulsifying property of Euglena protein was 86.74m~2/g.Compared with the unmodified Euglena protein(58.27 m~2/g),the emulsifying property of the modified Euglena protein was significantly improved.After modification,the content ofβ-sheet of Euglenoid protein decreased,while the content ofα-helix and random curl increased,indicating that Euglenoid protein changed to looser structure,disorder increased,particle size decreased,surface hydrophobicity increased,and Zeta potential increased,indicating that ultra-high pressure method can effectively improve the emulsification of Euglenoid protein.(3)The antioxidant activity of Euglenoid protein was improved by Maillard reaction.Euglenoid protein was used as raw material and reacted with glucose by hydrothermal Maillard reaction.With DPPH·scavenging rate,·OH scavenging rate and total reducing ability as indicators,the effects of four single factors,namely different substrate ratio,reaction time,reaction temperature and p H,on the antioxidant activity of Euglenoid protein were explored.The results showed that the optimum conditions for Maillard reaction to improve the antioxidant activity of Euglena protein were as follows:m(protein):m(glucose)was 1:3,reaction time was120 min,reaction temperature was 100℃,and p H was 11.00.Under these conditions,the DPPH radical scavenging rate of the protein was 45.73%,the hydroxyl radical scavenging rate was 61.28%,and the total reducing ability was 1.36.The DPPH radical scavenging rate of unmodified Euglena protein was 31.66%,the hydroxyl radical scavenging rate was 45.84%,and the total reducing ability was 0.82.Comparatively,the oxidation resistance of the unmodified Euglena protein was obviously improved after Maillard reaction.