【作者】 李诚；

【导师】 郑志；

【作者基本信息】 合肥工业大学 ， 农产品加工及贮藏工程， 2015， 硕士

【摘要】 小麦蛋白是小麦淀粉加工过程中的副产物。小麦蛋白含有较多的疏水性氨基酸,还存在较多的分子内、分子间二硫键,导致其溶解、分散等性能较差,难以满足食品加工的要求。采用挤压组织化技术对小麦蛋白进行加工,可以显著改善小麦蛋白的质地、口感和营养价值,有利于人体对蛋白的消化吸收,对小麦蛋白资源充分利用具有重要意义。本文对小麦蛋白挤压组织化工艺参数和添加剂对小麦蛋白的理化、质构、化学键及功能特性进行了研究,主要研究结论如下：(1)采用单因素试验方法,研究挤压组织化过程中工艺参数(加水量、挤压温度、螺杆转速和喂料量)对组织化小麦蛋白外观、理化性质(氮溶解指数、膨化度、复水率)、质构特性(弹性、硬度、粘着性、咀嚼度)和组织化度等影响,确定挤压工艺参数范围为：加水量为40%～45%,挤压温度为150～170℃,螺杆转速为240～3 OOr/min,喂料量为19～23kg/h。通过响应面和多元回归分析方法优化出挤压工艺参数为：加水量44%、挤压温度160℃、螺杆转速280r/min、喂料量21kg/h。该工艺参数条件下制备的组织化小麦蛋白复水率为249.49%,弹性为0.549,硬度为9988.08g,粘着力-60.498g·sec,咀嚼度2650.42,恢复力0.112,膨化度为126.46%,组织化度达到2.33。(2)研究了L-半胱氨酸、单甘酯、海藻酸钠和三聚磷酸钠对小麦蛋白挤压组织化的影响。结果表明：随着L-半胱氨酸和单甘酯添加量的增加,组织化小麦蛋白外观逐渐变的不平整,膨化度和组织化程度逐渐降低,当L-半胱氨酸和单甘酯添加量分别大于0.09%和0.6%时,挤压产品未产生组织化结构。添加海藻酸钠挤压出的产品膨化充分,气孔大小均一,在不同的添加量条件下,产品的膨化度和复水率均大于120%和180%。添加三聚磷酸钠能促进小麦蛋白组织化的形成,挤压产品表面颜色较浅,外观光滑平整,气孔较大且均一；在添加量为0.3%时,产品膨化度达到最高(129.18%),复水率相比未添加的挤压产品高出50%以上。(3)红外光谱(FT-IR)分析表明,在不同添加剂(单甘酯、海藻酸钠和三聚磷酸钠)和挤压工艺参数(加水量、挤压温度、螺杆转速、喂料量)条件下,挤压产品中不稳定的α-螺旋含量均降低至0%,β-折叠、β-转角和无规则卷曲含量均有增加,说明不稳定的α-螺旋全部或部分转化为相对稳定的β-折叠、β-转角和无规则卷曲结构。而添加L-半胱氨酸制备出的组织化蛋白中α-螺旋、β-转角和无规则卷曲含量分别增加了3.37%、2.94%和1.26%,β-折叠含量降低了7.58%。在上述不同工艺参数和添加剂条件下,挤压产品在红外光谱1600～1700cm-1范围内二级结构各子峰峰值所对应的波长基本未产生漂移,说明没有新的二级结构生成。(4)对小麦蛋白原料和组织化小麦蛋白的理化功能性质进行对比研究。结果表明：组织化小麦蛋白的持水力和蛋白质消化率比未挤压原料分别增加70.21%和11.88%。氮溶解指数和游离巯基含量分别降低37.71%和36.10%。蛋白质溶解度分析表明,挤压前后维持小麦蛋白和组织化小麦蛋白作用力的大小依次为：二硫键和非共价键交互作用>非共价键作用>天然状态>二硫键作用。氨基酸分析结果显示,挤压组织化小麦蛋白半胱氨酸损失最大,为15.70%。热力学性质变化可知,组织化小麦蛋白较小麦蛋白原料的热变焓(ΔH)增加了147.63%,说明组织化小麦蛋白中可能形成了新的、键能较高的化学交联键。傅里叶红外图谱中没有新的吸收峰,表明组织化小麦蛋白中没有新的酰胺键(即肽键)生成。蛋白质凝胶电泳结果显示,挤压过程中蛋白质间发生了化学键的断裂、聚合、重组和交联,但没有发生亚基的裂解；扫描电镜结果看出组织化小麦蛋白微观结构呈现出有序的纤维化结构。更多还原

【Abstract】 Wheat gluten is the by-product of the production of wheat starch. Because wheat gluten is rich with hydrophobic amino acids, intramolecular disulfide bonds and intermolecular disulfide bonds, it shows poor solubility, poor dispersion, and it is difficult to meet he requirement of food processing. The texturization process with extruder could significantly improve the texture, taste and nutritional value of wheat gluten and make wheat gluten well digested by human. Therefore, process parameters of extrusion texturization and the physiochemistry, texture property, chemical bonding and functional properties of the wheat gluten were studied, and the results were as follows:(1) Single factor experiment was used to research the influence of the process parameters of extrusion texturization (water addition, extrusion temperature, screw speed and feed speed) on the appearance, physiochemical indexes (nitrogen solubility index), expansion ratio and rehydration ratio), texture properties (springness, hardness, adhesiveness, and chewiness), and texturization degree of the wheat gluten. The determined process parameters of extrusion texturization were as follows:water addition 40%-45%, extrusion temperature 150-170℃, screw speed 240-300 r/min and feed speed 19-23 kg/h. Based on the single factor experiment, response surface method (RSM) and Multiple Regression Analysis Method were employed to optimize and verified the process parameters of extrusion texturization. The results showed that optimal process parameters were as follows:water addition 44%, extrusion temperature 160℃, screw speed 280 r/min and feed speed 21 kg/h. Under these conditions, the expansion ratio of the wheat gluten was 126.46%, the rehydration ratio was 249.49%, the coefficient of springness was 0.549, the coefficient of hardness was 9988.08 g, the coefficient of adhesiveness was-60.498 gsec, the coefficient of chewiness was 2650.42, the coefficient of resilience was 0.112, the expansion ratio was 126.46%, and the texturization degree was 2.33.(2) The influence of L-cysteine, monoglyceride, sodium alginate and sodium tripolyphosphate on the extrusion texturization of wheat gluten was studied. The results showed that with the addition of L-cysteine and monoglyceride increasing, the appearance of wheat gluten became uneven and the degree of expansion and texturization reduced gradually. When the addition of L-cysteine and monoglycerides were greater than 0.09% and 0.6%, respectively, the extrusion products had not formed the texturization structure. Owing to the addition of sodium alginate, the extrusion products were puffed fully and filled with uniform pores. Adding different quantity of sodium alginate, the expansion ratio and rehydration rate of products were larger than 120% and 180%, respectively. Besides, the addition of sodium tripolyphosphate could improve the generation of texturization structure of wheat gluten and the surface of the extrusion products were light-colored and smooth with uniform pores. Once the amount of sodium tripolyphosphate was 0.3%, the expansion ratio of the products was the highest (129.18%) and rehydration rate was more than 50% higher than that of products without sodium tripolyphosphate.(3) With the optimal additives (monoglyceride, sodium alginate and sodium tripolyphosphate) and the optimal process parameters of extrusion texturization (water addition, extrusion temperature, screw speed and feed speed) above, the fourier transform infrared spectroscopy (FT-IR) showed that the content of unstable α-helix of the products was decreased to 0%, and the content of β-sheet, β-turn and random coil of the products were all increased. It was indicated that in whole or in part of unstable α-helix were transformed to relatively stable β-sheet, β-turn and random coil. After added L-cysteine, the contents of α-helix, P-turn and random coil of texturized proteins were increased by 3.37%,2.94%, and 1.26%, respectively, and the content of P-sheet was decreased by 7.58%. Under the all above conditions, the correspondent wavelengths of respective peaks of secondary structure of obtained products hardly drifted in a range of 1600-1700 cm-1 wavelengths, which indicated that there was no generation of secondary structure.(4) The changes of the physicochemical characteristics and functional properties of wheat gluten and texturized wheat gluten were also studied, and the results were as followed:after extrusion, the water holding capacity and the digestibility of texturized wheat gluten were increased by 70.21% and 11.88%, respectively, and the NSI and the content of free sulfhydryl were decreased by 37.71% and 36.10%, respectively. The protein solubility analysis showed that the order of the maintenance of intermolecular forces of wheat gluten and texturized wheat gluten before and after extrusion were as follows:disulfide bonds and non-covalent bonds, non-covalent bonds, native state and disulfide bonds. The amino acids analysis showed that cysteine was decreased 15.70% which was the maximum loss amount in the extrusion process. According to the changes of thermodynamic properties, the thermal enthalpy (AH) of texturized wheat gluten was increased by 147.63%, which indicated that new chemical bonds with higher bond energy were formed in the texturized wheat gluten. There was no new absorption peak in FT-IR spectrum, indicating that no new peptide bond existed in the texturized wheat gluten. The result of protein gel electrophoresis indicated that the breaking, polymerization, recombination and cross-linking of chemical bonds between the proteins were generated during the process of extrusion. The images of scanning electron microscope (SEM) showed that the texturized wheat gluten had an orderly fiber structure.更多还原