阿魏酸在大豆分离蛋白制备可食性膜中的应用

在大豆分离蛋白成膜液中添加0.5mmol/100ml的阿魏酸能增加膜的机械强度,降低膜对水蒸气、氧气、二氧化碳和氮气的透性,同时,采用阿魏酸处理较易制备大豆分离蛋白与花生油或玉米淀粉组成的复合膜。阿魏酸能改善大豆分离蛋白成膜特性的可能机理是因为它增加了蛋白分子之间的交联。     

阿魏酸-米渣蛋白复合膜的结构及性能

通过测定膜的机械性能、水蒸气透过率、水溶性研究了阿魏酸对米渣蛋白膜性能的影响,通过傅里叶红外光谱、差示扫描量热法、X-射线衍射、扫描电子显微镜表征了膜的结构特征。结果表明,当阿魏酸添加量为0.1%(W/V)时,与对照组相比,膜的抗拉强度提高20.33%,水蒸气透过率降低20.58%,水溶性降低23.88%。傅利叶红外光谱(FTIR)显示,添加阿魏酸后酰胺带吸收峰发生红移,β-折叠转变为易变的随机螺旋分子结构,蛋白质的二级结构发生改变;差示扫描量热法(DSC)分析表明阿魏酸增强了分子间的相互作用,提高了膜的玻璃化转变温度,使膜具有更好的热稳定性;X-射线衍射(XRD)分析表明阿魏酸与蛋白质分子间发生共价交联,膜的结晶度提高;扫描电镜(SEM)结果显示复配阿魏酸后的米渣蛋白膜的表面结构更均匀平整。因此,阿魏酸的添加使米渣蛋白膜具有更优的性能和更稳定的空间结构。     

明胶添加量对兔皮明胶膜特性与结构的影响

从兔皮中提取明胶制备明胶膜,通过测定不同明胶添加量下膜的机械性能、水蒸气透过率、亚基组成和结构,探究明胶添加量对明胶膜特性与结构的影响。结果表明随着明胶添加量的增加,明胶膜体系内网络空间结构变大,从而膜的厚度增加。力学结果显示,明胶添加量为4 g/100 m L(w/v)时,明胶膜抗拉强度最高(p0.05);明胶添加量为6 g/100 m L(w/v)时,明胶膜断裂伸长率最低(p0.05)。水蒸气透过率结果表明随着明胶添加量的增加,水蒸气透过率呈现上升趋势。凝胶电泳结果显示,明胶添加量为4 g/100 m L(w/v)时,低分子量的蛋白组分产生更多交联,形成蛋白质-蛋白质交联的结构,此浓度下明胶膜的抗拉强度最大。FT-IR分析表明:当明胶添加量增加至4 g/100 m L(w/v)时,酰胺A带向高波数移动,说明肽链上的N-H基团并没有与甘油的-OH基团相互反应,而是明胶分子的官能团之间产生更强的相互作用,形成独特的网络结构。同时,酰胺Ⅰ带曲线拟合结果也表明当明胶添加量为4 g/100 m L时,膜内稳定结构较多,明胶分子之间的相互反应达到最大化,明胶膜的稳定性和成膜性能较优。     

不同pH下阿魏酸对大豆分离蛋白膜性能的影响

本文报道了阿魏酸、pH及碱液等对大豆分离膜的的影响。以大豆分离蛋白为主要基质的成膜溶液调pH、热处理后铺板干燥，揭膜，在相对湿度为52％的室温环境下平衡48h后测定膜的抗拉强度、断裂伸长率、水蒸气透性、颜色等。结果表明，大豆蛋白膜的断裂伸长率随pH的升高而增加，抗拉强度在中性pH以上时也是随pH升高而增加；阿魏酸的添加可显著增加膜的拉伸张力和断裂伸长率，但也使膜的颜色变深；阿魏酸还使我们可以在成膜溶液pH为中性时制备具有较强抗拉强度的膜：加阿魏酸100、200、300mg(此用量分别相当于大豆分离蛋白的2％、4％、6％)将成膜溶液pH调为7．0,与对照相比，可使断裂伸长率提高24．2％～54．4％，抗拉强度提高62．5％～94．3％。     

乳清蛋白-茁霉多糖-阿魏酸复合可食性膜的研制

以乳清浓缩蛋白、茁霉多糖、阿魏酸为成膜材料,制备乳清浓缩蛋白-茁霉多糖-阿魏酸复合膜。分别对复合膜的厚度、刺穿强度、拉伸强度、水蒸气透过系数、含水量和溶解性等性能进行测试,研究成膜材料添加量和成膜条件与复合膜性能的关系。结果表明:乳清浓缩蛋白中添加茁霉多糖和阿魏酸作为增强剂,可明显提高膜的性能。最优工艺条件为成膜温度80℃,pH9.0,阿魏酸添加量200 mg/100 mL,茁霉多糖添加量150 mg/100 mL。     

pH为中性的大豆分离蛋白膜的制备及特性

以大豆分离蛋白、甘油、阿魏酸为组成成分的成膜溶液调pH为中性,热处理后铺板干燥,揭膜,在相对湿度为52%的环境下平衡48h后测定膜的抗拉强度、断裂伸长率、颜色等。结果表明,阿魏酸的添加方法和添加量对膜的这些特性都有显著影响;阿魏酸的添加可显著增加膜的拉伸张力(20.2%～34.5%)和断裂伸长率(62.5%～94.3%),但也使膜的颜色变深;阿魏酸使pH为中性的大豆分离膜的机械性能可与通常在pH9或以上制备的这类膜相媲美,这使大豆分离蛋白膜有了更广泛的潜在应用前景。     

小麦水溶性戊聚糖对面筋形成及品质影响的研究

着重研究变性及未变性小麦水溶性戊聚糖对面筋形成及品质的影响。结果表明：同小麦不溶性戊聚糖，添加小麦水溶性戊聚糖也导致面筋产率及延伸性降低、抗延伸阻力增加。采用木聚糖酶对小麦水溶性戊聚糖变性并不能消除其对面筋产率及品质的负作用，但添加游离阿魏酸可克服其负作用。同时添加变性及未变性小麦水溶性戊聚糖及游离阿魏酸较单独添加变性及未变性戊聚糖面筋产率提高，延伸性增大。根据研究结果推断：小麦水溶性阿拉伯木聚糖结合的阿魏酸对戊聚糖与面筋蛋白质的交互作用起到了关键作用。     

碱解麦麸制备阿魏酸的研究

将麦麸脱脂、去蛋白质后采用正交实验,确定了碱解麦麸释放阿魏酸的最佳工艺为:氢氧化钠浓度0.5%,提取温度85℃,提取时间6h。提取液中添加100mg/L的亚硫酸钠能增加释放出的阿魏酸的保留率,并可通过增加碱浓度而缩短提取时间。碱降解后剩余的残渣较之原麦麸更易被盐酸和黑曲霉分泌的多糖水解酶降解,显示残渣可作为制备低聚糖的基料。     

大豆分离蛋白在成膜后的营养特性变化

采用胃蛋白酶和2，4，6-三硝基苯磺酸分别测定大豆分离蛋白膜的消化率和赖氨酸有效性。结果表明，蛋白质的消化率和赖氨酸有效性随成膜溶液的pH升高而下降，并因一些增加蛋白交联的物质如单宁、阿魏酸和过氧化氢的添加而降低。蛋白膜的机械性与膜蛋白消化率和赖氨酸有效性存在一定负相关，即机械性能较强的膜，其消化率和赖氨酸有效性较低。不过，玉米淀粉似乎是个例外，它在改善机械特性的同时，也保持了大豆蛋白膜的营养。由于大豆分离蛋白制备成膜后，其消化率和赖氨酸有效性下降，因此将大豆蛋白膜称为生物可降解膜似乎比称作可食性膜更科学。     

大豆分离蛋白/纳米纤维素/阿魏酸复合膜的制备及其包装性能

在大豆分离蛋白中添加纳米纤维素和阿魏酸,制备不同组分的大豆蛋白复合膜,研究纳米纤维素和阿魏酸的添加对复合膜的拉伸强度、断裂伸长率、水蒸气透过率、氧气透过率、吸湿性、透光率、接触角及抑菌率的影响。结果表明:当纳米纤维素添加量为20.0 g、阿魏酸添加量为0.4 g时,复合膜的性能最佳,与纯大豆分离蛋白膜相比,其拉伸强度和接触角分别提高116.19%和127.21%,吸湿性也有所提升,而断裂伸长率、水蒸气透过率以及氧气透过率分别降低59.76%、90.91%和77.55%,透光率也显著下降(P0.05)。通过扫描电子显微镜、傅里叶变换红外光谱和X射线衍射分析可知,阿魏酸的交联作用使蛋白质分子结构变得致密,并使纳米纤维素分子与蛋白质分子间作用力加强,使其表面变得光滑,横截面变得平整,而阿魏酸的添加也使复合膜具有了一定的抑菌作用。本实验为大豆蛋白复合膜的进一步研究提供了技术参考,拓宽了大豆蛋白复合膜的应用范围。     

Ferulic acid and its position among the phenolic compounds of wheat

Ferulic acid (3-methoxy-4-hydroxycinnamic acid) is the main phenolic acid occurring in cell walls of monocotyledones. Due to its blue-and-white fluorescence it is easily identified and is located in the cereal grain morphological parts. Its 40-fold greater concentration was found in the cells walls of the seed coat and aleuronic layer than in the cells walls of endosperm. Most often, it is linked by ester bonds with hemicellulose chains, mainly with arabinose residues and it also polymerizes with lignin through ether bonds. However, ferulic acid in the pentosane molecules forms specific complexes with proteins through chemical bonds with amino acids. It is interesting to mention the theory of the pentosane gel formation in which a great role is assigned to ferulic acid. An oxidized form of ferulic acid-diferulic acid-produces gel formation by linking two pentosane or protein molecules. The blue-and-white fluorescence of ferulic acid can be applied to determine flour contamination with grain coat particles and its ability to form complexes with pentosanes and proteins is important in the formation of dough texture with its semi-elastic properties.     

Effect of ferulic acid and α-tocopherol antioxidants on properties of sodium caseinate edible films

Edible films, based on sodium caseinate containing three different concentrations of ferulic acid or α-tocopherol (20, 40 and 60 mg/g sodium caseinate), were obtained in order to evaluate the effect of these compounds on properties of the caseinate matrices. Special emphasis was placed on their effect on the films’ oxygen barrier properties, which are decisive in the prevention of the oxidation of foods containing lipids. Films were characterized as to their tensile, optical and surface properties as well as their barrier properties to water vapor, oxygen and aroma compounds (n-hexanal and n-hexanol). Ferulic acid was more efficient at reducing oxygen and n-hexanal permeability than α-tocopherol. Although ferulic acid slightly increased the stiffness of films at low concentration, in general, both antioxidants slightly reduce mechanical resistance, water vapor permeability, gloss and transparency of the films.     

Determination of sulfur-containing amino acids in food products

To define the most accurate method for determination of sulfur-containing amino acids in foods, the possibility was tried of using a method suggested by Moore. The method is based on preliminary oxidation of cystine and methionine by performic acid and transformation of these substances to acid hydrolysis resistant cysteic acid and methionine sulphone. Model experiments and use of foods (wheat flour, grade II, and protein part of chicken egg) demonstrated that exposure of proteins to performic acid brings about oxidation of sulfur-containing amino acids to the hydrolysis-resistant forms which may be defined by chromatography with a greater accuracy. Experiments without preliminary oxidation by performic acid showed that foods experience an appreciable destruction (by 30-60%) of cystine and methionine. Therefore, it is advisable that during studies into amino acids contained by proteins, additional hydrolysis may be performed with preliminary oxidation of the samples by performic acid, which enables the determination of the content of methionine and cystine with a greater accuracy.     

不同食品中阿魏酸含量的分析

为比较不同食品中阿魏酸含量,采用高效液相色谱法测定米类、面类、玉米类三类食品共26份试样中的阿魏酸含量。结果表明,三类食品中玉米类食品阿魏酸含量最高,其中冷冻玉米棒阿魏酸含量高达318.4 mg/100 g(以干物质计);阿魏酸含量与食品加工精度和加工方法有关,未经加工的食品和加工精度较低的食品阿魏酸含量较高,加工精度越高,阿魏酸含量越低;一般湿法加工的食品阿魏酸含量要高于干法加工的食品。     

反复卤煮对老汤品质的影响研究

传统酱卤肉制品因老汤的使用而深受消费者喜爱,卤汤在连续的使用过程中不断积累较多的可溶性滋味物质,使其本身具有鲜醇浓厚独特的美味,进而赋予卤煮制品特有的滋味。本研究以白羽肉鸡鸡腿为原料,对传统卤煮工艺不同卤制次数卤汤中的营养物质如蛋白质、游离氨基酸、呈味核苷酸、味精当量等和有害物质中的杂环胺的变化进行研究。结果表明:与对照组第0锅卤汤相比,当卤制次数达到第9锅时,卤汤中蛋白质含量由0.09%增加至3.86%,总游离氨基酸含量由68.57 mg/100g上升至601.92 mg/100 g,呈味核苷酸含量由0.78 mg/100 g达到了22.97 mg/100 g,味精当量(EUC)值由0.0068 g MSG/100 g升高至1.32 g MSG/100 g,但有害物质中杂环胺含量由12.29 ng/g上升至28.64 ng/g。因此,传统卤煮工艺中随着卤制次数的增加,卤汤中营养物质的含量呈不断上升的趋势,同时有害物质中杂环胺的含量也不断富集。     

添加多酚对鲤鱼肌原纤维蛋白结构及膜性能的影响

研究不同添加量（1%、2%、3%、4%、5%）多酚化合物（阿魏酸、鞣酸、迷迭香酸和丁香酸）对鲤鱼肌原纤维蛋白结构和膜特性的影响。结果表明,与丁香酸、迷迭香酸和阿魏酸相比,添加鞣酸的蛋白成膜液中自由氨基和巯基含量最低,表明鞣酸具有较高的蛋白交联能力（P＜0.05）。随着多酚添加量的增加,膜的弹性和拉伸强度逐渐增强,断裂伸长率逐渐降低（P＜0.05）,表明添加多酚化合物提高了膜的硬度和强度。在相同质量分数条件下,添加鞣酸的鲤鱼肌原纤维蛋白膜具有最高的弹性和拉伸强度。添加多酚化合物有效降低了鲤鱼肌原纤维蛋白膜的紫外和可见光透过率,降低程度取决于多酚的种类和浓度。添加多酚化合物的鲤鱼肌原纤维蛋白膜可用于高脂食品的内包装,防止食品脂质氧化、延长货架期。     

红花苗营养成分的分析与评价

为阐明红花苗的营养价值,分析了国内外30种红花苗的蛋白质、粗纤维、抗坏血酸、可溶性糖、氨基酸、矿质元素等主要营养成分,通过与油菜、白菜等6中常见蔬菜对比及氨基酸比值系数法,综合评价红花苗蛋白质的营养价值。红花苗的蛋白质、抗坏血酸含量均明显高于6中常见蔬菜,属于高钾高钙低钠食品。红花苗中含有18种氨基酸和人体必需的8种氨基酸,氨基酸总量、必需氨基酸含量和非必需氨基酸的平均含量范围分别为17.49 g/100 g~20.03 g/100 g、6.650%~7.613%和10.483%~12.413%,变异系数分别为5.23%、6.40%和6.05%。30个参试品种必需氨基酸占氨基酸总量的比值（E/T）大多在36%~39%之间,略低于FAO/WHO理想蛋白标准;必需氨基酸与非必需氨基酸的比值（E/N）大多在58%~62%之间,接近并略高于FAO/WHO理想蛋白标准。氨基酸比值系数分60.25~76.40,蛋白质相对于鸡蛋标准蛋白的贴近度为0.90~0.93。必需氨基酸指数EAAI值均接近1。属于优质蛋白源。His、Ala、Arg、Asp、Glu、Phe这6种氨基酸使得红花苗呈现出不同的风味。参试红花苗均具有较高的营养价值,为可食用的优质蛋白源。     

Purification and Use of Glycomacropeptide for Nutritional Management of Phenylketonuria

ABSTRACT:  Individuals with phenylketonuria (PKU) cannot metabolize phenylalanine (Phe) and must adhere to a low-Phe diet in which most dietary protein is provided by a Phe-free amino acid formula. Glycomacropeptide (GMP) is the only naturally occurring protein that does not contain Phe, and is of interest as a source of protein for dietary management of PKU. However, commercially available GMP contains too much Phe from residual whey proteins and does not contain adequate levels of all the indispensable amino acids to provide a nutritionally complete protein. The aim of this study was to increase purity of GMP and develop a mass balance calculation for indispensable amino acid supplementation of GMP foods. Cation exchange chromatography, ultrafiltration/diafiltration, and lyophilization were used at the pilot plant scale to decrease Phe. Enough purified GMP (5 kg) was manufactured to provide 15 PKU subjects with a 4-d diet in which the majority of protein was from GMP foods. A mass balance was used to supplement GMP foods so that all indispensable amino acids met or exceeded the daily recommended intake. GMP foods were tested in a human clinical trial as a replacement for the traditional amino acid formula. Nutritionally complete GMP foods created with high purity GMP provide individuals with PKU with more options to manage PKU, which may lead to improved compliance and quality of life.     

Responses to amino acid imbalances and deficiencies in lactating dairy cows

Lactating cows were exposed to large amino acid imbalances and deficiencies by i.v. infusion to characterize responses in milk production and plasma concentrations of metabolites and hormones. Six cows in early lactation were fed a basal diet of 9% CP and infused continuously for 6 d with saline (negative control), 1.1 kg/d of a complete amino acid mix (positive control), or the equivalent mix lacking Met, Lys, His, or all 3 branched-chain amino acids. All cows received all treatments in 6 successive periods in a Latin square design. Infusion of the complete amino acid mix resulted in an increase in the plasma concentrations of several essential amino acids, insulin, and glucagon. Milk protein production was stimulated by 19%, which accounted for 10% of the infused amino acid. Plasma urea, acetate, and β-hydroxybutyrate concentrations were increased. Compared with saline, the amino acid mixtures lacking Met, Lys, or His increased essential amino acids, glucose, insulin, and glucagon concentrations in plasma, and decreased growth hormone. Plasma concentration of the essential amino acid absent from the infusate fell 2-fold but milk protein yield remained within 12% of its basal value. Dry matter intakes were depressed 35% over the first 2 d of infusion of imbalanced mixtures but recovered thereafter. Milk fat yields were increased 258 and 320 g/d by mixtures devoid of Lys and His, respectively. Correction of a Met, Lys, or His deficiency did not affect hormone concentrations in plasma and milk protein yield increased 27% due entirely to increased concentration of the single amino acid in plasma. Although imbalance and deficiency generated similar amino acid profiles in plasma, it was concluded that endocrine responses to total amino acid supply during imbalance can override imperfections in the circulating amino acid profile to maintain milk protein yield at higher levels than expected from deficiency states. Both imbalance and deficiency were characterized by a low protein:fat ratio in milk. Infusion of a mix of amino acids lacking Val, Ile, and Leu, despite a decrease in plasma Leu to 58% of its basal value, increased milk protein and fat yields to the same extent as the complete amino acid mix.