麦胚球蛋白的分离制备及理化性质研究

采用Osborne分级分离的方法制备得到麦胚球蛋白，获得的球蛋白的蛋白质含量为87．3％（干基），得率为5．8g／100g脱脂麦胚粉，其在脱脂麦胚粉蛋白中的构成比例为15．6％。氨基酸分析表明，除蛋氨酸略低于FAO／WHO的推荐值外，其它七种必需氨基酸都高于或接近FAO／WHO的推荐值；另外，谷氨酸、精氨酸、天冬氨酸和丙氨酸的含量十分丰富，而胱氨酸和半胱氨酸的含量最低。还原的十二烷基硫酸钠-聚丙烯酰胺电泳（SDS—PAGE）表明，麦胚球蛋白主要有六备谱带，其分子量依次为57．8kDa、41．8kDa、38．7kDa、24．1kDa、16．5kDa和14．3kDa。差示扫描量热仪（DSC）分析表明麦胚球蛋白干粉和稀溶液的变性温度分别为98．2℃和83．8℃。     

牛羊乳蛋白组分比较研究

羊乳被国际营养学界誉为"奶中之王",逐渐被人们列为日常生活的营养保健佳品。该文对羊乳和牛乳的蛋白组分(主要是酪蛋白和乳清蛋白)含量、氨基酸组成及变异体等方面的差异进行了综述,并且对两者酪蛋白胶束的差异进行了比较,为羊乳检验和加工提供理论依据。     

牛乳中蛋白质的电泳分析技术研究

运用十二烷基硫酸钠聚丙烯酰胺凝胶电泳(SDSPAGE)法分析牛乳蛋白质,以脱脂牛乳为对照,分析牛乳中掺入不同比例大豆蛋白粉和乳清蛋白粉的样品,经凝胶图像分析系统分析得这2种蛋白粉掺入牛乳的最低检出限分别为:0.79%和4.4%(m/m),应用该法对5种市售婴幼儿奶粉进行鉴定,表明该法能较快速准确地表征乳蛋白组成,为乳及乳品质量的监控提供了一种直观有效的手段.     

荔枝汁中谷蛋白结构及特性

采用Osborne分级法制备荔枝汁中的谷蛋白,并采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）、差示扫描量热仪、红外光谱等方法分析荔枝汁中谷蛋白的分子质量分布、热稳定性以及二级结构等。结果表明：荔枝谷蛋白分子质量较大,主要集中在50?kDa及以上,而且成分复杂,约有10?个条带,经还原后,少量大分子质量条带消失,出现新的较小分子质量条带,其分子质量集中在50?kDa左右;用蛋白样品结合SDS的能力表征蛋白质的表面疏水特性,得出1?mg的荔枝谷蛋白样品结合（74.25±5.26）μg?SDS;游离巯基含量为（29.83±1.72）μmol/g,总巯基含量为（40.59±2.04）μmol/g,二硫键含量为（5.38±0.18）μmol/g;荔枝谷蛋白的变性峰值为105.24?℃;β-折叠和β-转角为荔枝汁谷蛋白主要结构,所占百分比分别为33.92%和64.7%。因此,可初步推断荔枝谷蛋白组分复杂,分子质量较大,具有较强的表面疏水性,二硫键含量较少,对热较稳定。     

超高压处理对乳清分离蛋白结构及致敏蛋白含量的影响

以乳清分离蛋白为研究对象,通过测定圆二色性光谱、巯基含量以及内源性荧光光谱等研究了不同超高压水平(100、200、400和600 MPa)对其二级、三级结构的影响,并采用水解度测定、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳以及2个标志性致敏蛋白(β-乳球蛋白和 α-乳白蛋白)含量的检测来解析超高压对乳清分离蛋白致敏性的影响....     

牦牛乳酪蛋白肽制备及乙酰化脱苦

采用碱性蛋白酶对牦牛乳酪蛋白进行水解,得到牦牛乳酪蛋白肽.以醋酸酐为酰化试剂,利用结构修饰的方法对牦牛乳酪蛋白肽进行脱苦研究,探讨醋酸酐添加量、pH对牦牛乳酪蛋白肽酰化度及苦味的影响.结果显示,碱性蛋白酶最佳水解条件为,温度55℃,pH7.0,酶添加量1.25％,反应3h.维持酰化反应pH7以上,产物乙酰化程度最高,醋酸酐的添加量与脱苦效果呈正比,当醋酸酐添加量为40％时,牦牛乳酪蛋白肽酰化产物的苦味基本消失.     

牦牛乳酪蛋白肽制备及乙酰化脱苦

采用碱性蛋白酶对牦牛乳酪蛋白进行水解,得到牦牛乳酪蛋白肽。以醋酸酐为酰化试剂,利用结构修饰的方法对牦牛乳酪蛋白肽进行脱苦研究,探讨醋酸酐添加量、pH对牦牛乳酪蛋白肽酰化度及苦味的影响。结果显示,碱性蛋白酶最佳水解条件为,温度55℃,pH7.0,酶添加量1.25%,反应3h。维持酰化反应pH7以上,产物乙酰化程度最高,醋酸酐的添加量与脱苦效果呈正比,当醋酸酐添加量为40%时,牦牛乳酪蛋白肽酰化产物的苦味基本消失。      

辣木叶渣中非水溶性蛋白及酶解效果研究

以碱提蛋白后的辣木叶渣为原料,选择酶种类、酶用量、酶解温度、时间为自变量,利用响应面分析法建立蛋白提取率二次回归模型,并采用SDS-PAGE分析酶解后总蛋白电泳图谱的变化。结果表明,酶解后辣木叶渣蛋白仍有(34.92±1.42)mg/g的残留蛋白,其中酶解条件为碱性蛋白酶添加量1.8%,酶解温度为55℃,酶解时间70 min,电泳图谱显示谷蛋白、醇溶蛋白为25 KD~100 KD高分子亚基,叶渣中非水溶蛋白为酶解后形成的15 KD以下小分子蛋白,疏水作用和二硫键是导致溶解性降低的主要原因。     

生物解离大豆过程中形成的乳状液结构

以不同酶解时间（1、2、3?h）、不同酶添加量（1%、2%）生物解离大豆过程中形成的乳状液为研究对象,探究乳状液中乳滴聚集机制、结构特征及分子间相互作用。通过乳状液中蛋白水解度、显微镜观察、Zeta电位、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE）、荧光色谱等指标的测定发现：经过蛋白酶酶解,乳状液中蛋白水解度在7%左右;生物解离使乳状液蛋白被酶解成分子质量较小的肽段,乳状液油脂与蛋白之间的亲和力降低,乳滴出现聚集,Zeta电位绝对值减小;SDS-PAGE条带上出现了由二硫键引起的大分子质量的蛋白聚集体;另外,乳状液荧光光谱中,乳状液相对于相同酶解条件下大豆分离蛋白荧光强度明显减弱,可能是由磷脂的存在、蛋白质-油脂之间的相互作用及蛋白质聚集体导致。     

燕麦麸蛋白的组成及功能性质研究

以燕麦麸为原料制备了燕麦麸浓缩蛋白（OBPC）。同时，也按照Osborne蛋白分级提取方法对燕麦麸蛋白进行了精细的分类，分别得到了燕麦麸清蛋白、球蛋白、醇溶蛋白和谷蛋白。球蛋白和谷蛋白是燕麦麸蛋白的主要组分。清蛋白提取液中含有高含量的可溶性碳水化合物，可以通过（NH4）2S04分级沉淀的方法将其纯度由6．5％提高到67．2％。SDS-PAGE的结果表明OBPC及各蛋白组分有不同的分子组成。OBPC及各蛋白组分的功能性质，包括溶解性、持水持油性、乳化活性、泡沫性质也分别进行了测定，以评价燕麦蛋白作为一种潜在的配料在食品中的应用价值。     

山羊奶与牛奶和人奶营养成分的比较

对山羊奶、牛奶和人奶中蛋白质、脂肪、维生素、矿物质等主要营养成分进行了比较,分析了3种奶中主要营养成分的差别。通过比较发现,山羊奶在总体营养成分方面优于牛奶,更接近人奶。但山羊奶存在铁、叶酸和维生素B12含量较低以及羊奶膻味的问题,应在营养上对这方面加以重视。     

Evaluation of the allergenicity of goat milk, cow milk, and their lactosera in a guinea pig model

The object of this study was to determine the allergenicity of goat milk (GM) and cow milk (CM) and that of their respective lactosera (GML and CML), by in vivo and in vitro assays. Two systemic tests for anaphylaxis were carried out in guinea pigs, the animals being sensitized orally with the 2 types of milk and lactosera. Sera were taken from the orbital sinus of the experimental animals at 0 and 22 d of the experiment to perform the serological study and the passive cutaneous anaphylaxis test. For the latter, the guinea pigs were sensitized passively with antibodies against the 4 antigen solutions. Enzyme-linked immunosorbent assay and Western blot were used to determine the specific antibodies of the isotypes immunoglobulin G1 and immunoglobulin G(Fc) developed against the same 4 antigen solutions. From these anaphylaxis and antibody-production tests, it was concluded that GM is hypoallergenic when compared with CM. The lactosera produced more closely grouped results, with values always below those of the corresponding milk. None of the proteins in the 4 immunizing solutions were identified as being their main allergen. These results show the hypoallergenicity of GM versus CM, and also that both casein and lactoserum proteins may be responsible for allergy in each case. To analyze the possibility of producing an innocuous food for those allergic to milk proteins, it would be of interest to identify the epitope(s) responsible for such allergenicity.     

掺假羊乳及其制品中牛乳的检测技术研究进展

羊乳具有营养价值高、蛋白质组成更接近人乳、脂肪球直径小及致敏性低等优点,更利于人体消化吸收,受到消费者和乳品企业的青睐.近年来我国羊乳产业发展迅速且潜力巨大,但由于受羊乳产量和养殖规模的限制,羊乳价格昂贵,市场中存在羊乳及其制品掺假牛乳的现象,且掺假手段多样,难以辨别.为了保证消费者的健康和权益,保障羊乳市场良性发展,...     

羊乳与牛乳理化特性比较

以莎能奶山羊羊乳为样品,利用乳样自动分析仪,氨基酸自动分析仪、等离子发射光谱、色谱分析对其基本成分、氨基酸组成及含量进行了分析和检测,并与牛乳理化特性进行比较,为科学合理地利用羊乳,生产具有独特功能的羊乳制品提供了理论依据。     

Physicochemical and functional properties of goat milk whey protein and casein obtained during different lactation stages

During lactation, goat milk contains colostrum, transitional milk, mature milk, and end milk. The protein present in goat milk during different lactation periods has different characteristics. This study aimed to characterize the protein profile of goat milk samples obtained at different lactation stages and to identify changes in the physicochemical and functional properties of whey protein and casein from goat milk collected at 1, 3, 15, 100, and 200 d after calving. The results demonstrated that the lactation period had a great influence on the physicochemical and functional properties of goat milk whey protein and casein, especially the protein properties of colostrum on the first day after delivery. The denaturation temperature, hydrophobicity, and turbidity of whey protein were significantly higher on the first day postpartum than at other lactation periods. Correspondingly, the colostrum whey protein also had better functional properties, such as emulsification, oil holding capacity, and foaming properties on the first day postpartum than at other lactation periods. For casein, the turbidity, particle size, water holding capacity, and foaming properties on the first day after delivery were significantly higher than those at other lactation periods, whereas the denaturation temperature, oil holding capacity, and emulsification followed the opposite trend. For both whey protein and casein, the 2 indicators of emulsifying properties, namely, emulsifying activity index and the emulsion stability, also followed an opposite trend relative to lactation stage, whereas the changes in foaming capacity with the lactation period were completely consistent with the change of foaming stability. These findings could provide useful information for the use of goat milk whey protein and casein obtained during different lactation stages in the dairy industry.     

Comparative study on the microstructure and functional properties of casein in goat milk processed by different methods

This work compared the thermal stability, microstructure and functional properties of casein (CN) in goat milk processed by different methods, including homogenisation, low-temperature long-time (LTLT), high-temperature short-time (HTST), ultrapasteurisation (UP) and ultrahigh temperature (UHT) treatment. The greatest development of CN-whey protein complexes was observed in LTLT goat milk and the least in HTST goat milk. The CN micelles in LTLT, UP and UHT milk were more obviously changed than the CN micelles in HTST milk, and the random coil content increased significantly after the homogenisation, UP and UHT treatments. The homogenisation had a significant effect on the functional properties of CN. In addition, the most obvious changes in the properties of CN were observed in LTLT and UHT goat milk. The results suggested that homogenisation, pasteurisation and UHT can cause effective changes in the functional properties of CN in goat milk that facilitate its application in the milk industry.     

Importance of casein micelle size and milk composition for milk gelation

The economic output of the dairy industry is to a great extent dependent on the processing of milk into other milk-based products such as cheese. The yield and quality of cheese are dependent on both the composition and technological properties of milk. The objective of this study was to evaluate the importance and effects of casein (CN) micelle size and milk composition on milk gelation characteristics in order to evaluate the possibilities for enhancing gelation properties through breeding. Milk was collected on 4 sampling occasions at the farm level in winter and summer from dairy cows with high genetic merit, classified as elite dairy cows, of the Swedish Red and Swedish Holstein breeds. Comparisons were made with milk from a Swedish Red herd, a Swedish Holstein herd, and a Swedish dairy processor. Properties of CN micelles, such as their native and rennet-induced CN micelle size and their ζ-potential, were analyzed by photon correlation spectroscopy, and rennet-induced gelation characteristics, including gel strength, gelation time, and frequency sweeps, were determined. Milk parameters of the protein, lipid, and carbohydrate profiles as well as minerals were used to obtain correlations with native CN micelle size and gelation characteristics. Milk pH and protein, CN, and lactose contents were found to affect milk gelation. Smaller native CN micelles were shown to form stronger gels when poorly coagulating milk was excluded from the correlation analysis. In addition, milk pH correlated positively, whereas Mg and K correlated negatively with native CN micellar size. The milk from the elite dairy cows was shown to have good gelation characteristics. Furthermore, genetic progress in relation to CN micelle size was found for these cows as a correlated response to selection for the Swedish breeding objective if optimizing for milk gelation characteristics. The results indicate that selection for smaller native CN micelles and lower milk pH through breeding would enhance gelation properties and may thus improve the initial step in the processing of cheese.     

Developmental changes in proteins of casein micelles in goat milk using data-independent acquisition-based proteomics methods during the lactation cycle

Casein micelles (CM) play an important role in milk secretion, stability, and processing. The composition and content of milk proteins are affected by physiological factors, which have been widely investigated. However, the variation in CM proteins in goat milk throughout the lactation cycle has yet to be fully clarified. In the current study, milk samples were collected at d 1, 3, 30, 90, 150, and 240 of lactation from 15 dairy goats. The size of CM was determined using laser light scattering, and CM proteins were separated, digested, and identified using data-independent acquisition (DIA) and data-dependent acquisition (DDA)-based proteomics approaches. According to clustering and principal component analysis, protein profiles identified using DIA were similar to those identified using the DDA approach. Significant differences in the abundance of 115 proteins during the lactation cycle were identified using the DIA approach. Developmental changes in the CM proteome corresponding to lactation stages were revealed: levels of lecithin cholesterol acyltransferase, folate receptor α, and prominin 2 increased from 1 to 240 d, whereas levels of growth/differentiation factor 8, peptidoglycan-recognition protein, and 45 kDa calcium-binding protein decreased in the same period. In addition, lipoprotein lipase, glycoprotein IIIb, and α-lactalbumin levels increased from 1 to 90 d and then decreased to 240 d, which is consistent with the change in CM size. Protein–protein interaction analysis showed that fibronectin, albumin, and apolipoprotein E interacted more with other proteins at the central node. These findings indicate that changes in the CM proteome during lactation could be related to requirements of newborn development, as well as mammary gland development, and may thus contribute to elucidating the physical and chemical properties of CM.     

超高效液相色谱-四级杆-飞行时间质谱法与代谢组学技术分析牛乳与羊乳差异性

目的采用超高效液相色谱-四级杆-飞行时间质谱仪(ultra-performanceliquidchromatographyquadrupole time-of-flight mass spectrometry, UPLC-Q-TOF)高分辨质谱和代谢组学技术分析牛乳与羊乳差异。方法以小分子化学物质(分子量MW1000u)为研究对象,采用主成分分析、正交偏最小二乘法-判别式分析等多元统计分析手段,借助ProgenesisQI软件和数据库分析差异。结果初步鉴定出128种物质,其中在牛乳中含量高的物质有38种,在羊乳中含量高的物质90种。牛乳和羊乳在小分子代谢物上有明显差异(P0.05),主要为脂质、有机酸、糖类等,并剖析了伏马毒素B1、牛磺鹅去氧胆酸和乳清酸等典型的潜在生物标志物。结论本方法简单、便捷、且灵敏度高,为牛羊乳的真假鉴别以及牛羊乳差异性的进一步分析提供了理论支持。