【作者】 佟颖；

【导师】 李新华；

【作者基本信息】 沈阳农业大学 ， 食品科学， 2012， 博士

【摘要】 随着社会经济的高速发展和人们环保意识的增强，化学合成包装材料引发的严重生态问题已受到国际社会的高度重视。植物蛋白膜因形成的膜均匀透明，具有出色的阻氧性和较好的机械性能，营养丰富、可降解、易消化等特点，已成为目前可食性膜的研究热点。谷朊粉（小麦面筋蛋白，WG）是小麦淀粉生产的副产物，主要由麦醇蛋白和麦谷蛋白两部分组成，能与水形成三维立体网络结构，干燥后可形成具有韧性较强、阻氧性和热封性良好、阻油性出色的蛋白膜。由于阻湿性和机械性能较差，直接限制了WG膜在商业上的广泛应用。因此，提高和改善WG膜的阻湿性和机械性能已成为目前制约谷阮粉蛋白膜应用和发展急需解决的关键问题。本文以谷朊粉为成膜基料，选取国内具有代表性的大型小麦面筋蛋白生产企业七家，购买了八种不同质量的谷朊粉，研究了八种不同质量WG的成膜特性及膜性能；在此基础上，研究了成膜条件对WG膜性能的影响，优化了WG膜的最佳成膜工艺；利用麦醇溶蛋白（gliadin）和玉米醇溶蛋白（Zein）对WG膜进行改良，分别优化了麦醇溶蛋白改良膜（简称gliadin改良膜）和玉米醇溶蛋白复合膜（简称Zein复合膜）的制备工艺；并从分子水平研究了麦醇溶蛋白和玉米醇溶蛋白改良WG膜的作用机理。主要研究结果如下：（1）研究了八种WG的成膜特性，考察了不同质量WG对膜性能的影响，结果表明：本研究选用的八种谷朊粉的溶解性、膜液均匀度、干燥速度、揭膜难易程度、膜的色泽和表面光滑程度等成膜性之间差异较大。八种谷朊粉制备的WG膜的抗拉强度、断裂伸长率、水蒸气透过率和透光率等性能之间也有较大差别。河南莲花面粉有限公司生产的谷朊粉（莲花1）因具有蛋白质含量高、脂肪含量低、溶解性良好，膜液均匀，易揭膜和表面光滑等特点，尤其适合制备可食性WG膜。（2）通过单因素和正交试验考察了成膜因素对WG膜性能的影响；优化了WG膜的最佳成膜条件，结果表明：当料液比为1∶15时，WG膜的综合性能最佳；在谷朊粉中添加甘油可以降低膜的脆性，使膜柔韧性增强，且对阻湿性影响相对较小，为WG膜增塑剂的最佳选择。影响WG膜抗拉强度的主次顺序为：甘油浓度＞pH值＞乙醇浓度＞加热温度，当处理组合为pH12、乙醇浓度45%、甘油浓度15%、热处理温度55℃时，膜的TS最大，为3.78MPa；影响WG膜断裂伸长率的主次顺序为：甘油浓度＞pH值＞乙醇浓度＞加热温度，当处理组合为pH11、乙醇浓度45%、甘油浓度30%、热处理温度60℃时，膜的断裂伸长率最大，为189.2%；影响WG水蒸气透过率的主次顺序为：甘油浓度＞pH值＞乙醇浓度＞加热温度，当处理组合为pH12、乙醇浓度45%、甘油浓度15%、热处理温度60℃时，膜的水蒸气透过率最低，为6.98g·mm/m2·d·KPa。综合考虑拉伸强度、断裂伸长率、水蒸气透过率三项主要指标，确定WG最佳的成膜条件为pH12、乙醇浓度45%、甘油浓度20%、热处理温度60℃。在此条件下，WG的拉伸强度、断裂伸长率、水蒸气透过率和透油率分别为3.67MPa、157.9%、7.03g·mm/m~2·d·KPa和0。3.利用玉米醇溶蛋白对WG膜进行改性，制备玉米醇溶蛋白复合膜，考察了添加玉米醇溶蛋白对WG膜性能的影响，结果表明：添加适量的玉米醇溶蛋白可有效地降低膜的脆性，提高膜的韧性、阻水性、机械性和阻氧性。当玉米醇溶蛋白的添加量为25%，乙醇浓度55%，甘油浓度10%，pH12、热处理温度60℃时，复合膜的拉伸强度、断裂伸长率和阻氧能力为4.89MPa、179.1%和21.7mmol/Kg，分别比WG膜（对照）提高33.2%、17.2%和28.1%；水蒸气透过率和透光率为5.20g·mm/m~2·d·KPa和35.6%，分别比对照降低26.0%和75.3%。4.利用麦醇溶蛋白对WG膜进行改性，制备麦醇溶蛋白改良膜，考察了添加麦醇溶蛋白对WG膜性能的影响，结果表明：添加适量的麦醇溶蛋白可有效地降低膜的脆性，提高WG膜的韧性、阻水性、机械性、透光率和阻氧性。当麦醇溶蛋白的添加量为33.3%，乙醇浓度65%，甘油浓度10%，pH11、热处理温度60℃时，改良膜的抗拉强度最大，为5.77MPa，分别比WG膜和复合膜提高了52.7%和18.0%；水蒸气透过率最小，为4.48g·mm/m~2·d·KPa，分别比WG膜和复合膜提高了35.8%和16.1%；阻氧性为18.6mmol/Kg，分别比WG膜和Zein复合膜提高了39.0%和14.3%；透光率为60.3%，分别比WG膜和复合膜提高139.3%和238.8%%。5.通过红外光谱、差示扫描量热谱、热重谱、巯基和二硫键含量、扫描电镜和疏水性分析，探讨Gliadin改良膜和Zein复合膜的改良作用机理，结果表明：向WG中添加麦醇溶蛋白和玉米醇溶蛋白后，Gliadin改良膜和Zein复合膜的表面变光滑，不溶性物质明显减少，且改良膜的表面结构明显优于复合膜；WG的TG曲线分为水分蒸发和WG分解两个步骤；WG膜、复合膜和改良膜的TG曲线均分为空气逸出、水分和甘油的蒸发及WG膜分解四个步骤；在热加工过程中，Gliadin改良膜和Zein复合膜的最大加热温度分别比WG膜低15.01℃和14.88℃。从分子角度分析，认为添加玉米醇溶蛋白和麦醇溶蛋白能够改良WG膜的性能，可能是改良膜和复合膜中蛋白质分子之间的氢键作用减弱，巯基含量减少，二硫键含量和疏水性增加共同作用的结果。更多还原

【Abstract】 With the high-speed development of social economy and people’s increasingawareness of environmental protection, serious ecological problems caused by synthesizedchemical packaging materials has aroused great concerns around the globe. Vegetableprotein films has become the focus of current research interest in edible film filed due to itsuniformity, transparency, excellent POV, good mechanical properties, rich nutrition,biodegradability and good digestibility. Wheat gluten (WG) is the byproduct of wheatstarch production, mainly consisting of gliadin and gliadin; WG can form athree-dimensional network structure with water, after dried, it can form protein films withgood toughness, high POV, good heat sealability and excellent oil resistance. However,because of poor moisture resistance and mechanical property, the commercial applicationof WG films is directly limited. Therefore, enhancement and improvement of moistureresistance and mechanical property is of current urgency for applications of WG films.In this paper, WG was chosen as substrate for film preparation. Eight kinds of WGwith different qualities were purchased from seven large-scale domestic representativecompanies who produce WG protein. We investigated the film-forming ability andproperties of the aforementioned eight WG films with different qualities; based on this, theeffects of film-forming conditions on the WG film properties were studied, and the optimalfilm-forming preparation technology was obtained; Then, we used gliadin or Zein tomodify the WG films and optimized the film-forming preparation technology of gliadinimproved films and Zein composite films; finally, we investigated the working mechanismof gliadin and Zein on the improved films on the molecular level. The main results were:(1) The film-forming ability of eight WG films and the effect of quality on the WGfilm properties were studied. The results suggested that:The resolvability, film liquid uniformity, drying rate, difficulty of film-uncovering,film color and surface smooth degree of the chosen eight kinds of films were significantlydifferent. The tensile strength (TS), fracture elongation rate (E), water vapor permeability(WVP) and transmission of the eight WG films prepared from the eight WG protein werealso obviously different. It was found that the Lotus1WG protein produced by HenanLotus Flour Co. Ltd. was the most suitable one for the edible WG film preparation due toits advantages of high protein content, low fat content, and good resolvability, uniform filmliquid, easy film-uncovering and smooth surface etc.(2) The effects of film-forming factors on the WG film properties were investigatedvia single factor test and orthogonal test, the optimal film-forming conditions wereoptimized. Results indicated that: when the solid-to-liquid ratio was1:15, WG filmsshowed the best comprehensive properties; glycerin can reduce the film brittleness andhence enhance the film flexibility, but affected the moisture resistance relatively little.Hence, it can be a best plasticizer for WG films. The sequence of factors influencing the WG film TS was as follows: glycerinconcentration> pH value> concentration of alcohol> temperature of treatment, with thetreatment combinations of pH12, the concentration of alcohol of45%, glycerinconcentration of15%, temperature of treatment of55℃, the maximum of TS reached3.78MPa. The sequence of factors influencing the E (elongation at break) of WG films:glycerin concentration> pH value> concentration of alcohol> temperature of treatment,with the treatment combinations of pH11, the concentration of alcohol of45%, glycerinconcentration of30%, temperature of treatment of60℃, the maximum E (elongation atbreak) of WG films reached the maximum of189.2%. The sequence of factors influencingthe WG films WVP: glycerin concentration> pH value> concentration of alcohol>temperature of treatment, with the treatment combinations of pH12, the concentration ofalcohol of45%, glycerin concentration of15%, temperature of treatment of60℃, the WVPof WG films can reach the minimum of6.98g·mm/m~2·d·KPa.Considering the three main indexes of TS, E (elongation at break), and WVP, theoptimal film-forming conditions was determined as follows: pH12, the concentration ofalcohol of45%, glycerin concentration of20%, temperature of treatment of60℃. Underthese conditions, the TS, E, WVP and oil permeability of the WG films were3.67MPa,157.9%%,7.03g mm/m~2d KPa and0.(3) Zein was used to modify WG films, Zein composite films were prepared, and theeffect of Zein on the WG films properties was investigated. The results showed that:Appropriate additive amount of Zein can effectively reduce the film brittleness,improve the film toughness, water resistance, mechanical properties and POV. When theadditive amount of Zein was25%, the concentration of alcohol was55%, the glycerinconcentration was10%, the pH value was12, the temperature of treatment was60℃, theTS, E and POV ability for the WG composite film were4.89MPa,179.1%and21.7mmol/Kg, increasing by33.2%,17.2%and28.1%respectively when compared with WGfilms (as the control group); the WVP and the transmission were5.20g·mm/m~2·d·KPa and35.6%, decreasing by26%and75.3%respectively when compared with WG films.(4) The gliadin was used to modify WG films, gliadin improved film was prepared,and the effect of gliadin on the WG film properties was investigated. The results showedthat:Appropriate additive amount of gliadin can effectively reduce the film brittleness,improve the film toughness, water resistance, mechanical property, transmission and POV.When the additive amount of gliadin was33.3%, the concentration of alcohol was65%,the glycerin concentration was10%, the pH value was11, the temperature of treatmentwas60℃, the TS of the improved film reached the maximum of5.77MPa, increasing by52.7%and18.0%compared with WG films and composite films respectively; the WVPwas minimum of4.48g·mm/m~2·d·KPa, increasing by35.8%and16.1%compared withWG films and composite films respectively; the POV is18.6mmol/Kg, increasing by 39.0%and14.3%compared with WG films and composite films respectively; and thetransmission rate was60.3%, increasing by139.3%and238.8%respectively, comparedwith WG films and composite films;(5) By analysis of infrared absorption spectroscopy, differential scanning calorimetryspectrum, thermal gravimetric spectrum, mercapto-group and disulfide bond contents,SEM micrographs and hydrophobicity, the modification mechanism of gliadin improvedfilms and Zein composite films were explored. The results showed that:After the addition of gliadin or Zein into WG, the surface of gliadin improved filmsand Zein composite films became smooth, the content of insoluble matter was significantlyreduced, the surface structure of improved films were obviously better than the compositefilms; The TG curve of WG was divided into two stages as water evaporation and WGdecomposition; the TG curves of WG films, composite films and improved films weredivided into four stages of air escape, water evaporation, glycerin evaporation and WGfilm decomposition; in the process of heating treatment, the maximum temperatures oftreatment of gliadin improved films and Zein composite films can be decreased by15.01℃and14.8℃compared with WG films.From a molecular perspective, it was proposed that the reasons why the addition ofZein and gliadin can modify WG film properties possibly were the comprehensive result ofthe weakening hydrogen bond interaction between the protein molecular, the decreasingcontent of mercapto-group, the increase of disulfide bond contents and hydrophobicity inthe gliadin improved films and Zein composite films.更多还原