可食性玉米醇溶蛋白保鲜膜的研究

本文对甘油、虫胶、甘油－早胶混合物与玉米醇溶蛋白复合制成的可食性薄膜进行了研究,以抗张强度、阻湿性、透明度及耐水性成膜性能评定指标。结果表明：添加甘油可改善膜的阻湿性、透明度及耐水性。添加一定量虫胶后能提高膜的阻湿性和透明度。将甘油和虫胶按一定比例混合后添加于玉米醇溶蛋白溶液中可以改善膜的各项性能指标。     

添加丁香精油对玉米醇溶蛋白膜性能及结构的影响

以玉米醇溶蛋白为原料制备可食性膜,将丁香精油添加到玉米醇溶蛋白膜中,研究其对玉米醇溶蛋白膜物理性能及微观结构的影响。结果表明,丁香精油体积分数在0.5%～2.0%范围内时,随着体积分数的增加,玉米醇溶蛋白膜的厚度、断裂伸长率和水蒸气透过系数逐渐增加。丁香精油体积分数为0.5%～1.0%时,玉米醇溶蛋白膜的拉伸强度显著增加（P＜0.05）。添加丁香精油改善了膜的机械性能,增加了阻光性和透湿性。通过红外光谱和扫描电镜分析表明,添加丁香精油并未显著改变玉米醇溶蛋白的结构,且添加丁香精油的成膜液在干燥过程中会产生微孔,使得玉米醇溶蛋白膜的表面粗糙不均匀。     

可食性玉米醇溶蛋白膜的制备及其在食品保藏中的应用研究

研究了玉米醇溶蛋白膜的制备及其在食品保藏中的应用,以所提取的醇溶蛋白为原料,加入增塑剂,按一定的料液比加入乙醇溶解,然后进行流延成膜。对乙醇浓度、料液比及增塑剂对可食性薄膜性能的影响进行了研究,利用TA—XT2i质构仪对所得薄膜机械性能进行了测定,结果表明用90％的乙醇、料液比为10：1,添加40％油酸增塑,所得薄膜最佳,其抗拉强度、弹性、韧性分别为493．0g、3．12mm、261．34g·s。试验以荷兰瓜为研究鲜对象,考察了玉米醇溶蛋白膜的保鲜效果,结果表明玉米醇溶蛋白膜可减少果蔬的水分散失。     

复合增塑剂对玉米醇溶蛋白膜性能的影响

以木糖醇和甘油为复合增塑剂制备出木糖醇/甘油/玉米醇溶蛋白膜。通过TGA、扫描电镜、红外光谱及电子织物强力机研究玉米醇溶蛋白膜的热性能、微观结构及力学性能。结果表明:在160℃之前膜性能稳定,与纯玉米醇溶蛋白膜相比,添加复合增塑剂后玉米醇溶蛋白膜表面产生了多孔结构,随木糖醇含量增加孔洞结构有增大的趋势,抗拉强度略有下降,伸长率有所提高。     

硫酸盐对玉米淀粉糊化性与成膜性影响

玉米淀粉糊化过程中,硫酸盐能够影响玉米淀粉糊化与成膜性能。分别添加亚硫酸钠、硫代硫酸钠0,0.05,0.1,0.2,0.4和0.8 g至5 g/100 mL淀粉悬液中,90℃糊化40 min,测定糊化性指标;添加同水平硫酸盐制备玉米淀粉-甘油-海藻酸钠复合膜,测定膜机械性能、透明度、水溶性,并用DSC,SEM检测膜热稳定性与形貌表征。结果表明:亚硫酸钠的添加使淀粉膨胀度由9.56(g/g)增加至15.53(g/g),溶解度由0.07(g/g)增加至0.45(g/g),凝沉性减弱,无水析出。硫代硫酸钠的添加未改变淀粉膨胀度,溶解度由0.07(g/g)增加至0.34(g/g),凝沉率由7%增加至12%。DSC分析表明:两种膜热稳定性好;SEM显示膜较粗糙,表面结晶减少。两种硫酸盐的添加使淀粉溶解性、透光率、吸水性及膜水溶性、断裂伸长率增加,膜透明度降低。     

可食性玉米醇溶蛋白成膜工艺的研究

玉米蛋白膜是一种绿色包装,它具有良好的阻气性、阻油性、保香性、防湿性和防紫外线性,因此我们开发玉米蛋白膜具有重大的意义。本文对玉米醇溶蛋白的成膜条件进行了研究。结果表明,玉米醇溶蛋白在80%乙醇中溶解效果良好,在40℃恒温条件下,可以在光滑的不锈钢板上形成具有一定强度的可食性薄膜。此外,添加油酸与甘油可以对膜的透明度与抗张强度有一定改善。     

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。     

木薯氧化淀粉-壳聚糖复合膜的成膜特性研究

利用木薯氧化淀粉为成膜主要材料,添加增塑剂甘油和增强剂壳聚糖,制备了一种新型可食性淀粉膜.通过研究膜组分和成膜工艺参数对抗拉强度、断裂伸长率、水溶性和透明度等膜性能的影响,确定了制膜最佳工艺条件.正交实验结果表明,氧化淀粉的用量对膜的力学性能起主要影响作用,当m(木薯氧化淀粉):m(壳聚糖):V(甘油)=6:2:3时,在60℃下烘干4h,可制得较为理想的淀粉膜,抗拉强度为4.86MPa,断裂伸长率为130.88%,水溶性和透明度分别为50.31%和87%.     

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。     

提高玉米醇溶蛋白膜机械性能的研究进展

玉米醇溶蛋白膜的阻隔性能强于其他植物蛋白膜,但机械性能较差,使其应用受到了限制.影响玉米醇溶蛋白膜机械性能的主要因素有成膜液中各组分性质、制膜工艺及贮藏条件等.通过添加增塑剂、交联剂和改进成膜工艺,可提高玉米醇溶蛋白膜的机械性能.     

乳酸对玉米醇溶蛋白基面团品质提升的作用

以玉米醇溶蛋白、玉米淀粉、沙蒿胶为原料制备玉米醇溶蛋白基无麸质面团（简称Z面团）,以玉米淀粉和沙蒿胶所制面团（简称NZ面团）为对照。通过调控面团中乳酸含量（L）和原料粉含量（F）的比例（简写为L/F,mL/g）,比较乳酸含量对Z面团与NZ面团粉质性能的影响规律,表明玉米醇溶蛋白是影响Z面团粉质性能的关键组分。面团中L/F为2∶50的Z面团（Z2）稳定时间最长,弱化度最低,粉质质量指数最高,加工品质良好。探究在乳酸调节下,Z面团中玉米醇溶蛋白的理化性质与结构变化,发现乳酸会引起玉米醇溶蛋白的脱酰胺反应和蛋白质水解,促进α-玉米醇溶蛋白二倍体向单倍体转变,改变玉米醇溶蛋白的表面疏水性和二级结构组成。基于以上研究,将Z面团制为面条,考察乳酸含量对玉米醇溶蛋白基面条蒸煮品质的影响,其中Z2面条不易断条,蒸煮损失最少,质地良好。综上,适量的乳酸可改善玉米醇溶蛋白基无麸质面团粉质性能,提高玉米醇溶蛋白的表面疏水性,增加β-折叠占比,优化玉米醇溶蛋白基面条蒸煮品质。     

Zein molecules in aqueous acetic acid solution: Self-assembling behaviors and formation mechanism of gluten-free doughs

The assembly behavior of biopolymers is affected by the type of solvent used. Previous investigations have focused on the self-assembly of zein molecules in aqueous ethanol. In this study, the self-assembly behavior of zein molecules in aqueous acetic acid solutions and their application in the development of zein-based gluten-free doughs was investigated. Zein molecules in low concentrations of acetic acid (30%–60%, v/v) assembled into irregular entities, in medium concentrations (70%, v/v) there was intermediate transition, and at high concentrations (80%–100%, v/v) they formed regular spheres. Interestingly, protein fibril formation was found to occur in 50% zein solutions in 50% and 60% acetic acid, as self-standing gels with solid-like properties resulted and the findings were verified using rheology. The 50% zein solutions in 70% acetic acid could form viscoelastic masses after anti-precipitation with the addition of excess water. Gluten-free dough with wheat-like properties was obtained by mixing the viscoelastic zein masses with wheat starch at room temperature. SEM observations showed that the formation mechanism for zein-based doughs involves the dispersion of starch granules in a three-dimensional zein network. These results will help to improve our understanding of zein assembly behavior regulation, and provide technical support for the development of zein in gluten-free food products.     

Preparation and Physical Properties of Zein-Coated High-Amylose Corn Starch Film

The objective of this study was to prepare the edible composite films using high-amylose corn starch (HACS) and corn zein and to determine their physical properties. HACS was gelatinized using the specially designed high-pressure container. HACS film containing 20 g sorbitol/100 g as a plasticizer had suitable physical properties. The HACS film coated with corn zein containing 20 g oleic acid/100 g had moderate physical properties and barrier properties.     

Technical Note: A Method to Quantify Prolamin Proteins in Corn That Are Negatively Related to Starch Digestibility in Ruminants

Compared with floury or high-moisture corns, dry corn with a greater percentage of vitreous endosperm has been demonstrated to be negatively related to starch digestibility and milk yield of lactating dairy cows. Starch granules in corn are encapsulated by hydrophobic prolamin proteins that are innately insoluble in the rumen environment. Corn prolamin proteins are named zein, and laboratory methods to quantify zein exist but are seldom employed in ruminant nutrition because of their arduous nature. In this study, advances in cereal chemistry were combined with rapid turbidimetric methods yielding a modified turbidimetric zein method (mTZM) to quantify zein in whole corn. Ten dry corns containing unique endosperms were evaluated using the mTZM. Corns with flint, dent, floury, or opaque endosperms were found to contain 19.3, 11.3, 5.8, and 4.9 g of zein/100 g of starch, respectively. The ability of mTZM to differentiate corn endosperm types as defined by least significant difference was 2.6 g of zein/100 g of starch. Ten high-moisture corns of varying moisture content were also evaluated using the mTZM. Zein content of high-moisture corns as defined by mTZM ranged from 8.3 to 2.8 g of zein/100 g of starch with a least significant difference of 1.2 g of zein/100 g of starch. The mTZM determined that zein contents of high-moisture, floury, and opaque corns were markedly less than those of flint and dent dry corns, indicating that mTZM has the ability to quantify starch granule encapsulation by hydrophobic prolamin proteins in whole corn.     

玉米-小麦淀粉/玉米醇溶蛋白双层膜热学及微观特性

研究了玉米-小麦淀粉成膜液与玉米醇溶蛋白成膜液不同配比制作的5 种可食用复合膜理化特性的差异, 并分别通过扫描电子显微镜观察、热重分析、差示扫描量热分析、X射线衍射分析、傅里叶变换红外光谱分析对其 热学特性和微观结构进行研究。结果表明：添加一层玉米醇溶蛋白后,双层膜阻水性提高,机械性能得到改善,由 扫描电子显微镜观察结果可知双层膜间结合紧密,热重分析和差示扫描量热分析结果显示双层膜热稳定性得到提 高,X射线衍射结果表明生物大分子之间相容性较好,傅里叶变换红外光谱分析结果发现双层膜间产生了新的氢键 等作用力,为玉米-小麦淀粉/玉米醇溶蛋白双层膜在食品包装中的应用提供了重要的参考依据。     

Starch Cooking with Limited Water as Affected by Zein and Guar Gum

DSC (Differential Scanning Calorimetry) peak temperature of starch was decreased by adding zein, but was increased by adding guar gum. Adding zein increased the initial rate of starch cooking, but adding guar gum decreased it. Kinetic studies were carried out at 115, 125, and 135°C. At25°C, zein absorbed less water than waxy corn starch, especially at water activities >0.6 where guar gum absorbed more water than starch. The strong binding of water by guar gum increased DSC-peak-temperature and decreased the initial rate of starch cooking. The relatively weak binding of water by zein decreased DSC peak temperature and increased the initial rate of starch cooking. Although water sorption data at cooking temperatures are difficult to measure, the kinetic data at these temperatures and DSC data could be used to supplement the sorption data.     

玉米后熟期间醇溶蛋白结构和理化特性

将新采收的玉米在温度15 ℃及25 ℃、相对湿度55%条件下进行恒温恒湿贮藏,研究玉米后熟期间玉米醇溶蛋白结构特征及理化特性,并分析二者之间的构效关系。结果发现,玉米在15 ℃及25 ℃后熟56 d期间内,玉米醇溶蛋白的游离巯基含量降低,二硫键含量升高,表面疏水性降低,Zeta电位的绝对值增加,粒径和分散指数降低。玉米后熟期间玉米醇溶蛋白中氢键缔合下降,更多有序的β-折叠转化至无序结构,且后熟作用导致玉米醇溶蛋白热稳定性和α-玉米醇溶蛋白亚基的分子质量降低。此外,玉米后熟显著改变了蛋白的理化特性,在15 ℃后熟42 d和25 ℃后熟28 d,玉米醇溶蛋白的溶解性和持水性均达到最大,在2 个温度下后熟14 d时乳化活性和起泡性均显著增加,而后熟作用导致持油性下降。玉米后熟过程中玉米醇溶蛋白理化特性的改善可能与蛋白质聚集程度降低及其柔性结构相关。结果表明,适当的玉米后熟能够修饰玉米醇溶蛋白结构,进而改善其理化特性。     

Influence of ensiling time and inoculation on alteration of the starch-protein matrix in high-moisture corn

The fates of hydrophobic zein proteins, which encapsulate corn starch to create vitreous endosperm, have not been investigated in high-moisture corn (HMC). To assess influences of ensiling time and inoculation on zein proteins in HMC, quadruplicate samples of 2 random corn hybrids (A and B), containing 25.7 and 29.3% moisture, were ground, inoculated with (I) or without 600,000 cfu/g of Lactobacillus buchneri 40788 (Lallemand Animal Nutrition, Milwaukee, WI), and ensiled for 0, 15, 30, 60, 120, and 240 d. Nutrient composition [crude protein (CP), starch, acid detergent fiber, and neutral detergent fiber], fermentation (pH, lactate, and acetate), and protein degradation markers (buffer-soluble CP, isopropanol-soluble CP, and NH₃-N) were evaluated. At 0 and 240 d, α, γ, δ, and β zein subunits were profiled using HPLC. Data were evaluated as a split-split plot using the PROC MIXED procedures of SAS. Ensiling time and inoculation decreased pH, and altered lactate and acetate contents of HMC. Lactate and acetate contents of A, AI, B, and BI at 240 d were 0.40, 0.32, 1.11, 0.73, and 0, 0.35, 0.30, and 0.87% of DM, respectively. Buffer-soluble CP in HMC increased from 1.5 to 2.0% of DM at 0 d to >4.0% of DM at 240 d. Inoculation had no effect on buffer-soluble CP but increased NH₃-N content of HMC. Corn A contained more isopropanol-soluble CP than did corn B and peak areas for 6 α, and all γ and δ zein regions were greater for corn A. Ensiling (0 vs. 240 d) decreased all zein subunits with the exception of 2 α and 1 δ subunit. Ensiling decreased (42.2-73.2%) γ zeins, which are primarily responsible for cross-linking in the starch-protein matrix. Despite altering lactate and acetate contents, inoculation had no effect on degrading hydrophobic zein proteins in HMC. Data suggest that hydrophobic zein proteins in the starch-protein matrix of HMC are degraded by proteolytic activity over an extended ensiling time.     

玉米黄粉中淀粉含量对热处理效果的影响

以5批淀粉含量不同的玉米黄粉为原料,以水解度为检测指标,研究玉米黄粉中淀粉含量对热处理效果的影响,结果表明:在温度121℃、时间30min的热处理条件下,热处理可将玉米黄粉中的淀粉全部去除。热处理的效果受玉米黄粉中淀粉含量的影响,当淀粉含量大于17.07%时,热处理才对酶解效率有促进作用,但仅使玉米黄粉的水解度提高了1.73%。用反相色谱方法研究了热处理对玉米黄粉中醇溶蛋白结构变化的影响,图谱表明,热处理可以使醇溶蛋白各组分的疏水性能和相对提取率增加。     

Technical note: quantification of zeins from corn, high-moisture corn, and corn silage using a turbidimetric method: comparative efficiencies of isopropyl and tert-butyl alcohols

Zeins are corn endosperm storage proteins that encapsulate starch granules into a protein matrix, which can act as a barrier to starch accessibility and digestion. Laboratory methods to quantify zein are seldom used because they are considered arduous and time-consuming. A recently published rapid turbidimetric method (mTM) was reinvestigated by changing the solution originally used for the zein solubilization step. In particular, the aim was to explore whether, and to what extent, the use of tert-butyl alcohol (t-BuOH-mTM) in lieu of isopropyl alcohol (i-PrOH-mTM) was able to improve the quantification of zeins from dry corn, high-moisture corn, and corn silage samples. The nature of the alcohol influenced the zein extraction values, and t-BuOH-mTM gave higher zein values in corn (3.6 vs. 3.3 g/100 g of dry matter) and corn silage samples (1.2 vs. 0.9 g/100 g of dry matter) compared with i-PrOH-mTM. In contrast, similar zein extraction values were obtained for high-moisture corn (2.1 vs. 1.9 g/100 g of dry matter, respectively). Sodium dodecyl sulfate-PAGE analysis revealed no contamination by nonzein proteins with the use of tert-butyl alcohol. Overall, these findings indicated that tert-butyl alcohol has a greater ability to solubilize zein compared with isopropyl alcohol and thus the t-BuOH-mTM allowed greater extraction of zeins. Considering the growing interest of animal nutritionists in zein proteins, such results should provide useful information for routine laboratory analysis.