Study On Extracting Technology Of Selenium-containing Protein From Se-enriched Pleurotus Ostreatus And Development Of Foods For Special Dietary Users

Discovered in the nineteenth century, selenium has been shown by many scholars as nature essential trace elements of the body growth. Although the inorganic selenium is difficult to be absorbed by human body with relatively higher toxicity,Ostreatus can be an intermediate carrier of selenium which is planted by the biological transformation method and transfer inorganic selenium into organic selenium. It is reported that selenocysteine, as the main form of selenium in the physiological organism, penetrate and associate the formation of protein. Furthermore,the selenium can exert their biological fuctions in the form of enzymes. Thus,utilization of selenium protein in selenium-enriched Ostreatus as the vegetable protein resources in the food industry is worth to be further developed. Currently, most protein extraction process using alkaline method, which is highly efficiency and is simple to operate. On the other hand, the loss of nutritional value during extraction and the destruction of protein structure could the main reason obstructing its application in the commercial field. Although the enzymatic extraction method could lead to a milder reaction and raise nutritional value of protein, it has not been large-scale applied in the industrial production because of the high cost and inadequate technology. Therefore, the development of extraction method for selenoprotein in selenium-enriched Ostreatus has realistic significance for utilization of selenium protein and broaden selenium-enriched food chain.In this paper, selenium-enriched Ostreatus is considered as raw materials mainly processed with ultrasonic-assisted alkaline method and double enzyme method to extract selenoproteins. This study focuses on the selecting optimum conditions forformer methods to explore detection methods of proposed content of selenium in selenoproteins. In the meanwhile, a comparative analysis of the functional properties,physical and chemical properties, nutritional value and the thermal denaturation temperature of selenoproteins has been launched. Finally, the utilization of selenoproteins, as selenium supplements, combined with beef jerky contributes to producing a new type of special diet products. And the main findings are as follows:At first, using Ultrasonic assisted alkaline extraction methods to extract selenoproteins. The single factor experiment shows that 50 min of ultrasound test time and ultrasonic power 160 W is the optimal ultrasound condition. The orthogonal test is launched with single factor of different extraction temperature, extraction time, alkali concentration, and solid-liquid ratio. Then, the result of variance analysis shows that the extracting time 6.5h, alkali concentration 0.090 mol / L, solid-liquid ratio 1:25,extraction temperature 55 ? is the best combination which leads to 41.13% protein extraction and has significant effect(P <0.05) on industrial production.Secondly, extracting selenoproteins use double enzyme method. According to the experiment, Cellulase, and alkaline protease is considered as the optimum sugar enzyme and optimal protease enzyme. The statistical analysis illustrates that repeat test of enzyme dosage 2%, solid-liquid ratio 1: 25, p H5, extraction time 2h, and the extraction temperature of 55 ? conditions leads to protein extraction rate of 13.72 ±064% which is the optimum parameter based on single factor experiment for selenoproteins extraction using enzyme methods. To explore extraction rate of selenoproteins from selenium-enriched Ostreatus, this study uses single factors test of p H, solid-liquid ratio, and the extraction temperature to explore the best industrial parameters which is p H9.0, enzyme dosage 1.5%, extraction time 4h, solid-liquid ratio 1:15, and the extraction temperature 55 ? based on single protease method.These significant factors(P <0.01) lead to protein extraction rate of 45.36%.Utilization of the best parameters, obtained from former experiments, in double enzyme method test results in protein extraction rate of 51.65% which is 10.5%higher than ultrasonic-assisted alkaline method.Furthermore, referring to3,3-diaminobenzidine(DAB) colorimetry, organic selenium content in selenoproteins is 100.94 ug / g.To explore the thermal denaturation temperature, nutritional value and functional properties of selenoproteins, a comparative analysis between ultrasonic-assisted alkaline method and double enzyme method has been launched. The result shows that thermal denaturation temperature of ultrasonic-assisted alkaline method and double enzyme method is 63.26 ? and 64.73 ? respectively. The nutritional value of enzyme method extraction is slightly higher than that of alkaline method which is52.1and 55.1 of amino acid score of ratio coefficient(SRC) respectively. Furthermore,the result illustrates that the protein solubility, emulsifying, foaming and foaming stability and water holding capacity of protein extracted by enzyme method are considerably higher than those extracted by ultrasonic-assisted alkaline method.However, it shows lower emulsification stabilizer in enzyme extracted protein.According to single factor and orthogonal test, the best selenium-enriched beef jerk, a new kind special dietary products associated with selenoproteins, formula is:100g raw beef materials, adding selenoproteins in amount of 28 g, curing time 24 h,baking temperature 75 ?, baking time 4h. Selenium-enriched beef jerk obtained by such parameters not only reflects the best flavor, but also provide nutrients, especially the selenium, needed by the body.