碱热活化改性高温豆粕制备大豆蛋白胶黏剂

Preparation of Soybean Protein Adhesive from High-temperature Soyben Meal by Thermo-alkali Activation

为解决高温豆粕因其蛋白变性而导致的交联活性差的问题,提出高温豆粕的碱热活化策略,采用FT-IR、XRD、XPS、热重等方法研究了NaOH用量对活化改性高温豆粕及其胶黏剂的结构与性能影响。研究结果表明:高温豆粕在碱和热共同作用下,大豆蛋白球型结构被打开,释放出被包裹的活性基团,部分大豆蛋白的肽键水解形成可参与交联反应的胺基和羧基离子,从而能与交联改性剂发生有效交联,使活化高温豆粕制备的大豆蛋白胶黏剂形成良好的交联网络结构,并具备与低温豆粕所制备胶黏剂相当的胶接耐水耐热性能。碱热活化改性结果显示:高温豆粕碱热活化的最适宜NaOH用量为2%(质量分数),此时改性高温豆粕的乙醛值为4.28 mg/g,相应胶黏剂的黏度59.8 Pa·s、“热水浸泡”湿态胶合强度1.48 MPa、“煮-干-煮”湿态胶合强度0.96 MPa,相应胶黏剂固化产物的沸水不溶率79.73%、热分解残留率40.87%,最大分解速率温度306.1℃。

In order to solve the low crosslinking activity resulted from protein denaturation of high-temperature soybean meal(HTSM), the thermal-alkali activation of HTSM was proposed, and the effects of sodium hydroxide(NaOH) dosage on the structure and properties of HTSM and HTSM-based adhesive were evaluated based on the FT-IR, XRD, XPS, TGA analysis and other traditional methods. The results revealed that thermal-alkali activation could not only unfold HTSM’s globular structure to release the buried active group but also hydrolyze partial peptide into amino and carboxyl groups. Then, the crosslinking reactions between reactivated HTSM and crosslinking agent was increased, and the obtained soybean protein adhesive had equivalent thermal and water resistances with the adhesive prepared by low-temperature soybean meal due to the formation of sufficient crosslinked networks. The results of thermal-alkali activation showed that the most preferable NaOH dosage was 2%(mass fraction), and the acetaldehyde value of HTSM was 4.28 mg/g(reactivated HTSM). Correspondingly, the adhesive viscosity was 59.8 Pa·s, the soaked wet bonding strength was 1.48 MPa(63 ℃ for 3 h), the boiling-dry cycled wet bonding strength was 0.96 MPa, the boiling-water-insoluble content was 79.73%, the mass-residue ratio was 40.87%, and the temperature for maximal degradation rate was 306.1 ℃.