山羊乳蛋白质及其组学分析

为探索山羊乳蛋白质的基本组成,利用蛋白质组学技术——功能强大的分离技术,结合高分辨率的质谱分析,以获得极其重要的乳蛋白信息。采用毛细管电泳法解析山羊乳中的宏量蛋白质,采用蛋白质组学技术分析山羊乳中乳清蛋白和乳脂肪球膜蛋白的种类和功能分布,以及乳粉加工工艺对山羊乳蛋白质组成的影响,并以牛乳蛋白质作比较。结果发现,通过蛋白质组学技术鉴定出山羊乳乳清蛋白103种,乳脂肪球膜蛋白121种;在热处理和均质过程中,乳清蛋白是首先变性的蛋白质,尤其是β-乳球蛋白,而乳脂肪球膜蛋白含量降低的同时会引起其中的β-乳球蛋白、β-酪蛋白及α-酪蛋白的含量显著增加。综上所述,蛋白质组学技术为山羊乳蛋白质的进一步研究奠定了基础,为研究加工过程中乳蛋白组分的变化提供了机会。     

基于陶瓷膜技术的羊乳酪蛋白和其他组分的高效分级分离

为量化0.05 μm陶瓷膜脱除羊乳中乳清蛋白、乳糖、灰分、钙和磷的能力,在50 ℃条件下,脱脂乳进行3 倍浓缩,之后2 次间歇补水至原体积进行清洗过滤,最终得到1 份截留液、3 份透过液,并计算各组分总脱除率。结果表明：乳清蛋白脱除率为96.17%,乳糖脱除率为86.42%,灰分脱除率为73.39%,钙脱除率为34.90%,磷脱除率为55%。稀释过滤完毕后膜的纯水膜通量衰减系数为55.57%,使用质量分数为2%氢氧化钠和1%的硝酸溶液进行清洗,膜通量的恢复系数为99.21%。0.05 μm陶瓷膜可以实现羊乳酪蛋白和其他组分的有效分离,该技术适合在没有干酪乳清的条件下,以生鲜乳为原料加工酪蛋白胶束粉、乳清蛋白粉、乳糖等乳基配料产品。     

超滤膜分离技术回收乳清蛋白工艺研究

研究利用超滤膜分离技术,从干酪素乳清废弃液中回收乳清蛋白,通过对不同超滤膜性能的比较,选择最佳的超滤膜材料、工艺流程以及运行参数,并测得分离效果。结果表明:采用PW2540型聚醚砜卷式超滤膜较好,其最佳工艺参数为操作温度35℃,操作压力0.5MPa,且超滤膜透液通量较高,运行稳定。乳清蛋白粉中蛋白质含量72.40%,灰分3.85%。经红外光谱检测证明乳清蛋白粉品质得到较大程度的提高。每吨乳清废弃液中可回收乳清蛋白粉5.13kg,具有较好的经济效益及减排环保效益。     

高蛋白饮用型长保质期酸奶产品的研究

对高蛋白酸奶的加工方法及稳定体系和工艺进行了研究。通过添加乳清蛋白和膜浓缩2种不同方式提高产品蛋白含量;通过稳定性观察、感官测试和稳定性检测综合评价产品稳定体系。试验结果表明,采用反渗透膜过滤方式提高蛋白含量,杀菌温度118℃,发酵温度43℃;稳定体系琼脂添加量0.05%,果胶添加量0.19%,此条件下产品的感官、持水性和稳定性最佳。     

希腊式酸羊奶的研制

以新鲜羊奶为主要原料,添加羊乳清粉,研究了希腊式酸羊奶的工艺条件。 通过单因素试验和正交试验,以感官评分及酸度 为评价指标,确定希腊式酸羊奶的最佳发酵工艺条件。 结果表明,希腊式酸羊奶的最佳发酵工艺条件为羊乳清粉添加量1.0%,接种 量6%,发酵温度42 ℃,发酵时间8 h。 在此最佳条件下,感官评分达到87分,酸度为97 °T。 希腊式酸羊奶质地均匀,口感细腻浓郁,酸甜 适中,发酵乳香味明显,羊膻味不明显,其理化及微生物指标均符合相关国家标准。     

微波技术在鉴别豆浆中豆浆伴侣的应用试验

利用微波加热,使豆浆脱水。研究了相同量的豆浆及其豆浆伴侣脱水前后豆浆液滴直径的变化。纯豆浆和含有不同量豆浆伴侣的豆浆脱水后液滴直径变化不同,以此为根据判断豆浆中是否有豆浆伴侣的存在。该方法现象明显、易于判断、操作简单、检测成本低、速度快,便于推广,为广大消费者提供一种自我判断豆浆中是否含有豆浆伴侣的简便快速的鉴别方法。     

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。     

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.     

羊乳乳清蛋白组成和功能及其与人乳、牛乳的对比分析

本研究将羊乳、牛乳、人乳中乳清蛋白进行分离并结合液质联用技术鉴定,在羊乳、牛乳、人乳乳清蛋白中分别鉴定出156、278、454种蛋白质。与牛乳与人乳乳清蛋白对比显示,羊乳含有99种特异性表达蛋白质,与牛乳和人乳分别有31种和15种相同表达蛋白质。通过分析基因本体(gene ontology,GO)功能注释发现,羊乳乳清蛋白在生物过程中主要发挥生物调节作用;在分子功能上,主要体现在结合作用方面;在细胞组成上,参与的细胞组成主要为细胞器区和胞外区。羊乳乳清蛋白在以上三种功能上与人乳有较大差距,但与牛乳相近。通过分析京都基因与基因组百科全书系统(Kyoto Encyclopedia of Genes and Genomes,KEGG)代谢通路可知,羊乳主要参与补体和凝血级联反应以及吞噬作用,对人体免疫能力有积极影响。对羊乳与人乳、牛乳乳清蛋白组成及功能区别的研究,为羊乳的进一步研究和开发提供一定的理论参考。     

不同泌乳期羊乳和牛乳的高通量定量乳清蛋白质组学

利用高分辨质谱技术获取牛初乳、牛常乳、羊初乳和羊常乳的乳清蛋白组轮廓,基于其非标记定量强度建立偏最小二乘判别分析模型。结果发现牛初乳和牛常乳在蛋白质组成方面较羊初乳和羊常乳更相似,同时筛选出羊乳中丰度较高的9 种蛋白用作标志物区分这4 组乳样。生物信息学分析发现羊乳中的高丰度蛋白大部分与免疫应答和代谢过程有关,说明羊乳更有助于新生儿建立抗微生物感染的免疫系统。该研究可加深对羊乳蛋白的认识,对牛乳及其制品的营养改良和母乳替代品的生产具有重要意义。     

膜技术在乳品工业中的应用

综述膜的设计及结构,以及膜技术在乳品工业中应用的研究进展。随着膜技术的发展以及人们对乳成分知识的深入了解,膜技术在液态乳的除菌、乳蛋白的分离、干酪的加工、乳清的处理、初乳的处理,乃至干酪盐水及废水处理与纯化等方面的应用日益广泛。膜技术将为提高乳制品质量、新产品开发、提高生产效率及增加产品利润提供新的途径,成为在不破坏乳成分的前提下保证乳制品安全的强有力的加工手段。     

Fatty Acids Profiles of Fresh Milk,Yogurt and Concentrated Yogurt from Peranakan Etawah Goat Milk

The objective of the study was to characterize the fatty acids profiles of goat milk and its fermented products i.e. yogurt and concentrated yogurt. Fresh milk from Peranakan Etawah goats was collected directly from local goat farmers, and processed into stirred-type fresh yogurt. The yogurt was then further processed into concentrated yogurt using Berge method. A total of 26 fatty acids were detected in milk, yogurt and concentrated yogurt, comprised of both saturated and unsaturated fatty acids. The oleic acid, stearic acid and palmitic acid were the major fatty acids found in fresh milk, yogurt and concentrated yogurt. There were changes in the profiles of individual fatty acids during processing of fresh goat milk into yogurt and concentrated yogurt.     

Evaluation of commercially available, wide-pore ultrafiltration membranes for production of α-lactalbumin-enriched whey protein concentrate

Commercially available, wide-pore ultrafiltration membranes were evaluated for production of α-lactalbumin (α-LA)-enriched whey protein concentrate (WPC). In this study microfiltration was used to produce a prepurified feed that was devoid of casein fines, lipid materials, and aggregated proteins. This prepurified feed was subsequently subjected to a wide-pore ultrafiltration process that produced an α-LA-enriched fraction in the permeate. We evaluated the performance of 3 membrane types and a range of transmembrane pressures. We determined that the optimal process used a polyvinylidene fluoride membrane (molecular weight cut-off of 50 kDa) operated at transmembrane pressure (TMP) of 207 kPa. This membrane type and operating pressure resulted in α-LA purity of 0.63, α-LA:β-LG ratio of 1.41, α-LA yield of 21.27%, and overall flux of 49.46 L/m²·h. The manufacturing cost of the process for a hypothetical plant indicated that α-LA-enriched WPC 80 (i.e., with 80% protein) could be produced at $17.92/kg when the price of whey was considered as an input cost. This price came down to $16.46/kg when the price of whey was not considered as an input cost. The results of this study indicate that production of a commercially viable α-LA-enriched WPC is possible and the process developed can be used to meet worldwide demand for α-LA-enriched whey protein.     

冷冻的蓝靛果山羊酸奶工艺条件优化

以蓝靛果、山羊奶为试材,采用单因素试验及L9(34)正交试验确定其复合酸奶产品的最优发酵工艺条件,比对其在冷冻与冷藏条件下产品质量稳定性,形成冷冻的蓝靛果山羊酸奶酿造工艺。试验结果表明:最优发酵工艺为蓝靛果果酱6%、蔗糖7%、接种量4%、发酵时间4.5 h、发酵温度43℃,按此参数生产的蓝靛果山羊酸奶感官评分达98分,理化指标与卫生指标均达到GB 19302-2010《食品安全国家标准发酵乳》要求,具有蓝靛果和酸奶特有的风味。产品在-18℃~-20℃条件下冷冻贮藏,比0℃~4℃条件下冷藏,其质量更稳定。制成冷冻的蓝靛果山羊酸奶可显著改善山羊奶膻味、实现营养与保健功效互补,提高产品附加值。