Studies On The Preparation Of Soy Protein From High-temperature Denatured Soy Meal

High-Temperature Denatured Soy Meal(HTSM) is obtained by low temperature desolventizing after soy oil immersion. The meal which contains 45% protein, has good worthiness of exploiting and utilizing. However, it is difficult to obtaine protein from the meal because of higher denaturation of protein. At present, the meal is mainly used as feed. The objective of our study is to utilize HTSM better, by improving the NSI of HTSM and preparing protein with fine flavor and color. The NSI of HTSM treated with hydrothermal treatment, homogenizing and ultrasonic method was compared in this paper. Thermal treatment conditions were choosed and optimized. The flavor, color and functional properties and of the protein, obtained by continuous thermal treatment, were analyzed at last. The results were showed as followed:(1) The physicochemical properties and NSI of HTSM and WSF were compared and functional properties of protein from two materials were studied. The NSI of HTSM was 22.74% with the extraction pH8.0, while the NSI of WSF was 80.39%. Compared with protein extracted from WSF, the protein extracted from HTSM, which had larger size and molecular and worse solubility, was not completely denatured.(2) The effect of hydrothermal treatment, high-pressure homogenizing and ultrasonic treatment on NSI of HTSM was compared in this paper. It was found that all of the three treatments could improve NSI of HTSM. The optimum conditions of extraction determined were as follows: The temperature of treatment was 120℃, the pressure of the treatment was 0.1MPa, and the duration of high-temperature treatment was 20 min. Under these conditions, the NSI of HTSM was 65.58%. Under the pressure of 600bar, homogenizing for 3 times, the NSI was 51.34%; The ultrasonic power was 400W, the duration of ultrasonic treatment was 30 min. Under these conditions, the NSI of HTSM was 63.56%.(3) HTSM was treated with continuous thermal treatment. The time, temperature and pH of the treatment were optimized. It was found that: The continuous thermal treatment could greatly improve NSI of HTSM. Under the optimum conditions, the NSI of HTSM was 80.79%. The product had fine solubility, emulsifying ability and flavor, but darker color. The color of protein could be improved better when ethanol wash and addition of NaHSO3 were implemented together. Under the optimum condition, the color of protein from HTSM was closed to protein from WSF.(4) The functional property of protein obtained by continuous thermal treatment was studied systematically. The results showed that: the protein, which had larger of molecular and size, was a kind of completely denatured protein aggregate. The solubity of the protein was lower than the protein from WSF, but it had better emulsifying ability and oil holding capacity. The surface hydrophobicity index was higher than nature protein, but lower than the protein of WSF obtained by continuous thermal treatment.