油酸与甘油对玉米醇溶蛋白膜机械性能的影响及机理探讨

主要研究了两种性质不同的增塑剂(油酸和甘油)对玉米醇溶蛋白(zein)膜机械性能的影响和可能的机理,以抗拉伸强度(TS)、伸长率(E)、透水率(WVP)为指标,结果发现油酸和甘油都能显著改善zein膜的机械性能,且添加量都以20%(g/g zein)最优;复合增塑研究发现,当添加20%混合增塑液对zein膜进行增塑时,以油酸∶甘油为3∶1复合增塑的效果最好,其中与未增塑的zein膜相比,TS提高190%,E提高70%。进一步统计学分析表明,油酸与甘油在对zein膜增塑时有正协同作用。对未增塑、20%油酸增塑、20%甘油增塑及20%复合增塑(油酸∶甘油为3∶1)zein膜的玻璃态转化温度(Tg)及红外光谱(FT-IR)分析发现,增塑后的zein膜Tg有所下降,其中复合增塑降幅最大;FT-IR图谱分析发现,复合增塑时甘油的特征峰向高波长方向移动,显示增塑作用加强;蛋白二级结构分析发现,复合增塑后,二级结构虽有小幅改变,但并未达到显著水平,因此增塑剂与zein之间的非共价键相互作用(疏水力和氢键)可能是其增塑的化学基础。     

增塑剂对玉米醇溶蛋白膜阻隔性能影响北大核心

玉米醇溶蛋白具有较好成膜性,但其形成膜较脆,需通过添加不同增塑剂加以改善;但添加增塑剂会使膜阻隔性能受到影响。该实验以甘油、聚乙二醇(PEG)400、单甘油酯为增塑剂,研究在不同乙醇浓度时制备玉米醇溶蛋白(zein)膜阻湿性及阻油性;结果表明,当乙醇浓度为80%、甘油添加量为0.3 g/g zein,PEG–400添加量为0.2 g/g zein,单甘油酯添加量为0.3 g/g zein时,膜的水蒸汽透过率最小,透油率最大。     

制备条件对玉米醇溶蛋白膜机械性能的影响

以玉米醇溶蛋白为原料制备蛋白膜时,研究了乙醇浓度、蛋白质浓度等制备条件对蛋白膜机械性能的影响。在单因素实验基础上,以蛋白质浓度、甘油添加量、聚乙二醇400添加量、半胱氨酸添加量4个因素为变量进行响应面优化,结果表明:当乙醇体积分数为75%、水浴成膜温度70℃、蛋白质浓度0.103 4g/ml、甘油质量分数30%、聚乙二醇400质量分数24%、半胱氨酸质量分数0.80%时,蛋白膜的拉伸强度为7.5MPa,断裂延伸率为202.7%。     

增塑剂对小麦面筋蛋白膜机械性能的影响

本文以单因素对比试验,研究甘油、聚乙二醇和戊二醛对小麦面筋蛋白膜机械性能的影响;结果表明,加入甘油、聚乙二醇能较大的提高蛋白膜的断裂延伸率,加入戊二醛能较好的提高蛋白膜的抗拉强度。     

油酸改性WG-SPI制备复合膜的优化研究及扫描电镜观察

采用响应曲面法研究了油酸改性WG-SPI复合膜成膜过程中各因素对膜性能的影响.以乙醇浓度、甘油添加量、pH、油酸添加量为因素,以抗拉强度(TS)、断裂伸长率(E)、水蒸气透过系数(Pv)为响应值对实验进行响应面设计,建立了TS、E、Pv的回归模型,优化了最佳成膜配方,改性后复合膜的性能显著改善,断裂伸长率提高了21.3%;进一步通过扫描电镜观察,表明改性效果良好.     

可食性绿豆淀粉膜制作工艺的研究

以绿豆淀粉为主要材料,甘油作为增塑剂,羧甲基纤维素(CMC)作为增强剂,以可食性膜厚度、抗拉强度、断裂延伸率、阻水性为指标,研究了甘油添加量、CMC添加量、干燥温度、干燥时间等因素对可食性淀粉膜性能的影响。结果表明以绿豆淀粉为成膜主体,配以0.4 g/g淀粉的甘油和0.06 g/g淀粉的CMC,在80℃烘干4 h,得到淀粉膜的抗拉强度为9.51 MPa,延伸率为114.55%,水滴渗透时间(Ts)为240.98 min/mm。     

增塑剂对乳清蛋白-丝胶复合可食用膜性能的影响

本实验研究了甘油、山梨醇、聚乙二醇200以及甘油,聚乙二醇400(3/1)的混合物作为增塑剂对乳清蛋白-丝胶复合膜性能的影响.结果表明:增塑剂对乳清蛋白-丝胶复合膜的性能有显著影响.同一种增塑剂随着添加量的升高,膜的拉伸强度和透明度降低,断裂拉伸率、水蒸气透过性、含水量和溶解性升高.含有山梨醇和含有聚乙二醇200的膜的拉伸强度和溶解性比含有甘油和含有甘油/聚乙二醇400(3/1)的膜大,但前两者的拉伸率均较小.不同增塑剂制成的膜的水蒸气透过性和水分含量排列顺序为:含有甘油的膜＞含有甘油,聚乙二醇400(3/1)的膜＞含有乙二醇200的膜＞含有山梨醇的膜.甘油和甘油,聚乙二醇400(3/1)的膜相比,后者在一定添加量下拉伸性和阻水性都要优于前者.     

响应曲面法优化可食玉米醇溶蛋白膜制备工艺

通过单因素试验和响应曲面法,优化了可食玉米醇溶蛋白膜制备工艺。以乙醇体积分数、固液比、油酸用量和膜液加热温度为因素,以断裂伸长率(E)、拉伸强度(TS)、水蒸气透过系数(WVP)为响应值对实验进行响应面设计,建立了断裂伸长率(E)、拉伸强度(TS)、水蒸气透过系数(WVP)的回归模型,优化的工艺条件为乙醇体积分数82%、固液比(g∶mL)1∶10、油酸用量0.5mL/g玉米醇溶蛋白、膜液加热温度70℃。     

花生分离蛋白可食性膜的制取及性能

以花生分离蛋白为原料,研究了花生分离蛋白质量分数、甘油加入量和增筋剂加入量对花生分离蛋白可食性膜膜性能的影响,通过正交实验确定制取花生分离蛋白可食性膜的最佳配方.结果表明,制取花生分离蛋白可食性膜的最佳配方为:花生分离蛋白质量分数、甘油加入量和增筋剂加入量分别为6.0%、1.5%和0.5%.在此条件下,膜的厚度、延伸率和vWVTR(水蒸汽迁移速率)分别达到0.212 mm、217.0%和20.53 g/(m2·h).     

不同增塑剂对玉米醇溶蛋白膜机械性能的影响

本试验主要研究了几种不同增塑剂对玉米醇溶蛋白膜机械性能（抗拉强度、延伸率）的影响。结果发现：添加复合增塑剂的蛋白膜延伸率较大、抗拉强度差；甘油和乙二醇的延伸率都较其他两种小得多，但乙二醇的抗拉强度比甘油的大；添加油酸所制备的蛋白膜抗拉强度较低、延伸率较大，并且蛋白膜柔软、有光泽和富有弹性。     

Characterisation of gelatin–fatty acid emulsion films based on blue shark (Prionace glauca) skin gelatin

Incorporation of fatty acids (stearic and oleic) into edible films based on blue shark (Prionace glauca) skin gelatin was investigated to modify properties such as water vapour barrier and flexibility due to their hydrophobicity and plasticizing effect, respectively. Addition of stearic acid from 0% to 100% of protein concentration in the film-forming solution considerably decreased water vapour permeability of gelatin–fatty acid emulsion films compared to addition of oleic acid at the same fatty acid concentration. Increasing concentrations of both fatty acids decreased tensile strength, but increased elongation at break due to their plasticizing effect. At the same concentration, oleic acid gave a greater plasticizing effect than did stearic acid. On the other hand, transparency of the gelatin–stearic acid emulsion film was lower than that of the gelatin–oleic acid emulsion film. Faster stirring speed of homogenisation improved properties of only the gelatin–stearic acid emulsion film.     

低共熔溶剂催化油酸制备生物柴油工艺优化及动力学研究

本文以油酸和甲醇为原料,对甲苯磺酸/甲基三苯基溴化鏻形成的低共熔溶剂为催化剂,考察醇酸摩尔比、催化剂用量、反应时间及反应温度等因素对油酸甲酯收率的影响,并通过响应面分析法优化生物柴油的制备工艺。结果表明,对苯甲磺酸与甲基三苯基溴化鏻摩尔比为2:1时所形成的低共熔溶剂（DES-2）具有最好的催化活性;以DES-2为催化剂时,生物柴油的最佳合成条件为：催化剂用量为油酸质量的1.08%,醇酸摩尔比5.8:1,反应时间2.8h,温度373 K,此条件下,生物柴油的收率达97.3%,该结果与模型预测值基本相符。优化条件下,生物柴油合成反应的活化能为34.98 kJ/mol,动力学方程为：。     

Effect of the unsaturation degree and concentration of fatty acids on the properties of WPI-based edible films

The incorporation of lipids into hydrophilic protein films allows the modification of their barrier properties, improving its commercial application as preservation medium on different foods. The main objective of this study was to develop films from Whey Protein Isolate (WPI) together with saturated and unsaturated fatty acids and to determine the effect of concentration and unsaturation degree on surface tension of the coating solution and on water vapor permeability (WVP), mechanical properties (tensile strength and elongation at break), and opacity, of the films. The results obtained showed that surface tension was significantly decreased by adding unsaturated fatty acids (oleic and linoleic acid), whereas the greatest effect on WVP reduction was achieved with stearic acid. The addition of stearic acid resulted in a decrease of elongation and an increase of tension strength; however unsaturated fatty acid content did not modify the elongation and slightly reduce a tensile strength.     

短小芽孢杆菌脂肪酸羟基化发酵特性与培养条件优化

利用一株具有转化油酸进行羟基化的短小芽孢杆菌(Bacillus pumilus)突变株M-F641发酵生产具有重要功能的ω-羟基脂肪酸。以细胞生长、NADPH生成及油酸转化产物为测定指标,研究了培养基的最佳碳源及其发酵工艺条件;在单因素实验的基础上,采用响应面分析法,以油酸转化率作为指标,优化了发酵工艺条件,并对优化后的发酵条件进行了验证。结果表明,最佳碳源为葡萄糖,其最佳初始质量浓度为20 g/L,最佳发酵条件为:温度30℃、pH 7.4、装液量60mL/250 mL。在此条件下油酸转化率为74.58%,ω-羟基脂肪酸产率达22.3%。在优化的发酵条件下羟基脂肪酸生产效率得到了显著的提高。     

反油酸对人脐静脉内皮细胞活力的影响

目的：观察反油酸对人脐静脉内皮细胞(HUVEC)增殖活力的影响。方法：采用50、100、200、400、600μmol/L 等5 个浓度的反油酸作用于人脐静脉内皮细胞,以正常组为阴性对照组,NaOH 组(200μmol/L)为阳性对照组,MTT 法和台盼蓝排斥实验检测其对内皮细胞的毒性。结果显示：反油酸组内皮细胞增殖活力明显低于正常组,且高浓度组(400、600μmol/L)对细胞增殖抑制率明显高于低浓度组(50μmol/L);而NaOH 组与正常组比较却无明显差异。此外,反油酸组活细胞率降低。结论：反油酸对内皮细胞有明显毒副作用,其生长抑制率与反油酸浓度和作用时间呈正相关。     

不同增塑剂对大豆蛋白包装薄膜机械性能稳定性的影响

大豆蛋白膜是以大豆分离蛋白（soybean protein isolate,SPI）为主料,添加适量增塑剂形成具有一定机 械性能的包装薄膜,但其在贮藏过程中机械性能的不稳定是制约其在实际中应用的主要因素。因此本实验选取甘 油、山梨醇、油酸3 种增塑剂制备SPI膜,以贮藏期间抗拉强度、断裂延伸率、水蒸气透过率、水溶失率的变化为 评价指标,探讨添加不同增塑剂的SPI膜在贮藏期间机械性能变化规律。结果表明,以甘油、山梨醇和油酸组合 （2∶1∶1,m/m）作为增塑剂制备SPI膜时,SPI膜机械性能稳定性最佳,与空白组（单独由甘油增塑的SPI膜）相 比,抗拉强度稳定性提高了64%,断裂延伸率稳定性提高了65%,水蒸气透过率稳定性提高了27%,对水的稳定性 提高了20%。本实验可为SPI包装薄膜在实际中更广泛的应用提供一定的理论依据。     

Transport of Oleic and Acetic Acids from Emulsions into Low Density Polyethylene; Effects on Adhesion with Aluminum Foil in Laminated Packaging

Three test emulsions were prepared by adding oleic acid and/or acetic acid to a fatty food simulant (oil-in-water emulsion) from rapeseed oil, using Tween-80 as emulsifier. These test emulsions and the blank were packed in laminated material and stored for 4 wk at room temperature (21°C). Sorption of oleic acid into LDPE and the rate of acetic acid permeation through LDPE were highest for emulsions containing both oleic and acetic acids. A complete delamination within 4–7 days occurred for all acid-containing test-emulsions, probably caused by formation of a weak boundary layer (WBL).     

植物甾醇酯的脂肪酶促催化合成及其分析表征

运用中心组合设计,以酯化率为考察指标,对脂肪酶(由Candida rugosa生产)催化合成植物甾醇油酸酯进行优化研究。通过甾醇酯化率的响应面分析,研究反应温度、反应时间、底物物质的量的比(油酸:植物甾醇)和酶量及其交互作用对酯化反应的影响,构建相应的回归模型,并进行验证。结果表明：反应温度41℃、反应时间19h、底物物质的量的比2.4:1、加酶量7%为最佳条件,验证实验酯化率可达77.43%。并采用红外光谱和气相色谱-质谱对甾醇酯进行有效检测分析及结构表征。     

Evaluation of mechanical and water barrier properties of transglutaminase cross‐linked zein films incorporated with oleic acid

In this study, four concentrations of transglutaminase were used in zein films incorporated with four oleic acid concentrations, and subsequently, the mechanical and water barrier properties were evaluated. Enzyme concentration significantly affected mechanical and barrier properties of the films. Transglutaminase concentration at 1% improved tensile strength of control sample from 17.5 to 26.9 MPa while solubility decreased from 6.4% to 4.4%. Incorporation of oleic acid into transglutaminase‐treated zein films irrespective of enzyme concentration decreased water vapour permeability and solubility with the 1% transglutaminase‐treated zein films incorporated with 3% oleic acid registering the lowest permeability (0.37 g mm m^?2 h^?1 kPa^?1) and solubility (2.8%) values while elongation at break was not significantly improved. The use of transglutaminase at 1% concentration in cross‐linking zein films coupled with incorporation of controlled concentrations of oleic acid can be an effective approach in improving mechanical and water barrier properties of zein‐based films.