牛乳中乳清蛋白质的功能活性研究进展

近年来,牛乳的营养功能备受关注,牛乳乳清中的活性蛋白在其中发挥重要的作用。随着对其研究的深入,乳品加工技术的升级与创新,对牛乳乳清中的活性蛋白认知逐渐明晰。本文重点介绍牛乳乳清中α-乳白蛋白、β-乳球蛋白、乳铁蛋白、免疫球蛋白的功能活性的研究进展,阐述牛乳加工灭菌过程对上述牛乳乳清蛋白活性的影响,旨在为我国牛乳乳清蛋白的功能活性基础研究以及乳功能基料的产业化提出新思路,为乳品行业技术创新指明方向。     

乳清蛋白对脱脂发酵乳的流变特性及贮存稳定性的影响

研究了乳清蛋白对脱脂发酵乳流变学特性及贮存稳定性的影响，在VAYC-370为发酵剂的情况下，分别以质量分数为10％，20％，30％和40％的乳清蛋白替代脱脂奶粉进行发酵，结果表明，乳清蛋白会降低发酵乳凝胶的硬度、提高发酵乳的内聚性，同时发现乳清蛋白可提高搅拌型发酵乳的贮存稳定性．表明发酵乳凝胶的内聚性与贮存稳定性呈正相关关系。     

热处理对牛乳蛋白还原性的影响

借鉴AOAC的蛋白-还原物质（PRS）测定法,对不同受热处理的牛乳以及酪蛋白、乳清的还原性进行了检测研究。通过比较、分析不同热处理牛乳PRS,得到了区分巴氏乳与其它热处理牛乳PRS,同时得出乳清蛋白与酪蛋白之间的热反应性是影响牛乳蛋白还原性的主要原因,为进一步研究乳清蛋白的热变性以及乳清蛋白与酪蛋白之间的热反应奠定了基础。     

热处理对液态乳中乳清蛋白的影响研究进展

牛乳中的乳清蛋白主要包括β-乳球蛋白、α-乳白蛋白、牛血清白蛋白和免疫球蛋白。在牛乳加工过程中,热处理会使乳中乳清蛋白发生变性,影响了乳清蛋白的结构和活性,进而降低了牛乳的营养价值。本文对乳业发达国家液态乳的主要加工方式以及热处理过程对4种乳清蛋白的影响进行了综述。     

不同热处理方式对牛奶乳清蛋白的影响

目的：比较不同热处理方式对牛奶中乳清活性蛋白的影响。方法：以奶场牛乳、巴氏杀菌乳、超高温瞬时灭菌(UHT)乳和蒸汽侵入式直接杀菌(INF)乳4种不同热处理方式的牛奶作为研究对象，观察4种牛奶活性蛋白含量及热处理后牛奶中美拉德反应产物含量等的变化情况；采用SEM、FTIR、荧光光谱分析仪和Malvern纳米粒度仪分析微观结构。结果：4种热处理牛奶中，奶场牛乳的乳清蛋白含量最高，INF杀菌乳与巴氏杀菌乳中乳清蛋白含量和美拉德反应产物含量相当；UHT灭菌乳的粒径及其乳清蛋白极性环境均显著增加；4种牛奶乳清蛋白二级结构中无规则卷曲逐渐增加，乳清蛋白结构从有序向无序转化。结论：蒸汽侵入式直接杀菌对乳清活性蛋白的损伤程度小于超高温瞬时灭菌，与巴氏杀菌相当，且此方法处理的牛乳保存期高于巴氏杀菌乳。     

不同巴氏杀菌处理对绵羊乳总蛋白及乳清蛋白二级结构的影响

目的: 分析不同巴氏杀菌处理下绵羊乳蛋白的结构变化,同时以牛乳为对照,比较二者差异性。 方法 :分别以低温长时巴氏杀菌（65 ℃ 30 min）、高温短时巴氏杀菌（85 ℃ 15 s）和超巴氏杀菌（121 ℃ 5 s）对绵羊乳、牛乳进行杀菌处理,探究巴氏杀菌处理对绵羊乳和牛乳总蛋白及乳清蛋白二级结构的影响。 结果: 3种巴氏杀菌处理均会影响绵羊乳总蛋白和乳清蛋白二级结构,改变乳蛋白原空间结构;相比总蛋白,乳清蛋白二级结构稳定性受热处理影响更大（P＜0.05,超巴氏杀菌处理对绵羊乳总蛋白与乳清蛋白二级结构影响最大,乳清蛋白变性程度最大。绵羊乳与牛乳在3种巴氏杀菌处理方式下蛋白二级结构的变化规律略有差异。 结论: 3种巴氏杀菌处理下低温长时巴氏杀菌绵羊乳蛋白结构及组成变化最小,且绵羊乳总蛋白与乳清蛋白二级结构的变化规律与牛乳略有不同,在绵羊乳液态奶加工时应引起足够重视。     

发酵型乳清饮料的加工工艺

针对乳清营养丰富但利用状况不佳的现状,本文旨在以乳清为原料,经乳酸菌发酵,开发发酵型乳清饮料。首先探讨了乳清的制备。确定乳清制备中各个环节的工艺参数,保证乳清营养成分稳定不变。然后在乳清发酵特性和乳清饮料稳定性研究的基础上,拟定了纯牛乳乳清饮料和混合乳乳清饮料的工艺流程,并讨论了操作要点,从而生产出口味纯正、酸甜可口、低乳糖且含有一定量乳清蛋白的高营养饮料。     

发酵型乳清饮料的加工工艺

针对乳清营养丰富但利用状况不佳的现状,本文旨在以乳清为原料,经乳酸菌发酵,开发发酵型乳清饮料。首先探讨了乳清的制备。确定乳清制备中各个环节的工艺参数,保证乳清营养成分稳定不变。然后在乳清发酵特性和乳清饮料稳定性研究的基础上,拟定了纯牛乳乳清饮料和混合乳乳清饮料的工艺流程,并讨论了操作要点,从而生产出口味纯正、酸甜可口、低乳糖且含有一定量乳清蛋白的高营养饮料。      

乳清蛋白的特性及应用

乳清蛋白具有一定的功能特性和生物学活性,在食品行业中应用越来越广泛。通过改性,可以显著改善乳清蛋白的功能特性,如热稳定性、热凝胶特性、乳化特性等。蛋白变性影响乳清蛋白的特性,本文论述了乳中成分和环境条件对变性的影响。乳清蛋白在食用膜、乳品检测、蛋白提纯等方面的综合利用充分体现了其在食品行业中良好的市场前景。     

α-乳白蛋白提取工艺研究及副产物功能性质评价

研究了热附聚法结合凝乳酶处理从牛乳中直接提取α-乳白蛋白的工艺,得到富含α-乳白蛋白的乳清和副产物——附聚β-乳清蛋白的凝乳酶干酪素。富含α-乳白蛋白的乳清中α-乳白蛋白与β-乳球蛋白的浓度比达到3.03,达到了商业化产品的水平。副产物——附聚β-乳清蛋白的凝乳酶干酪素与市售凝乳酶干酪素在溶解性、持水性和乳化性方面存在的差异较小,将附聚β-乳清蛋白的凝乳酶干酪素作为原料应用于仿真干酪中,质构测定结果未显示出在质构方面与普通凝乳酶干酪素对照样品存在明显差异。     

乳清蛋白及与其它乳成分的热聚合作用机制研究进展

乳蛋白决定奶类品质,而热加工会影响乳清蛋白尤其是β-乳球蛋白的稳定性。热处理时,乳清蛋白不仅自身发生不同程度的聚合,而且通过巯基-二硫键分别与酪蛋白胶束和乳脂球膜蛋白发生结合。乳清蛋白亦可与其它乳成分如乳糖、钙盐、乳脂发生热聚合作用。本文根据乳品受热温度的不同,针对乳清蛋白间及其与其它乳成分的相互作用途径进行分析,阐明热聚合作用过程及机理,对改善乳制品的热稳定性、凝胶性等功能性质具有重要的理论意义,拓宽乳清蛋白作为配料在相关食品体系中的应用。     

Stability of Whey Proteins during Thermal Processing: A Review

Whey proteins have many benefits due to their high nutritional value and their various applications in food products. A drawback of whey proteins is their instability to thermal processing, which leads to their denaturation, aggregation, and, under some conditions, gelation. As thermal processing is a major treatment in the processing of milk and milk products, its influence on whey proteins has been extensively studied. Understanding the mechanisms involved during each stage of denaturation and aggregation of whey proteins is critical to devising ways of improving their stability. These aspects are reviewed in this paper. Also covered are approaches to preventing or reducing heat‐induced aggregation of whey proteins. Inhibition of aggregate formation has considerable potential for alleviating the problems that arise from the instability of whey proteins.     

UHT乳贮存中常见问题及其原因分析

UHT乳作为“营养全价”食品倍受消费者喜爱。但是UHT乳在贮藏中容易出现一些质量问题,常见的有：脂肪上浮、形成沉淀和凝胶、乳清析出、酸包和胀包及色香味的改变等。针对以上问题进行了论述,并探讨了产生的原因及相应的预防措施。     

Technological optimization of manufacture of probiotic whey cheese matrices

In attempts to optimize their manufacture, whey cheese matrices obtained via thermal processing of whey (leading to protein precipitation) and inoculated with probiotic cultures were tested. A central composite, face-centered design was followed, so a total of 16 experiments were run using fractional addition of bovine milk to feedstock whey, homogenization time, and storage time of whey cheese as processing parameters. Probiotic whey cheese matrices were inoculated with Lactobacillus casei LAFTIL26 at 10% (v/v), whereas control whey cheese matrices were added with skim milk previously acidified with lactic acid to the same level. All whey cheeses were stored at 7 °C up to 14 d. Chemical and sensory analyses were carried out for all samples, as well as rheological characterization by oscillatory viscometry and textural profiling. As expected, differences were found between control and probiotic matrices: fractional addition of milk and storage time were the factors accounting for the most important effects. Estimation of the best operating parameters was via response surface analysis: milk addition at a rate of 10% to 15% (v/v), and homogenization for 5 min led to the best probiotic whey cheeses in terms of texture and organoleptic properties, whereas the best time for consumption was found to be by 9 d of storage following manufacture.     

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。     

LONG-TERM STORAGE OF ASEPTICALLY PROCESSED AND PACKAGED DAIRY FLUIDS1

Aseptically processed and packaged dairy fluids were investigated for stability during long-term storage. Model solutions of whey and sodium caseinates, and combinations of them with milk fat were used. Sedimentation in whey protein solutions was extensive. No significant sedimentation was observed in casein solutions even after 500 days of storage. Addition of milk fat retarded sedimentation in whey protein solutions initially. Very little fat separation was observed in whey-fat solutions. Larger amounts of fat separation were observed in casein-fat or casein-whey-fat solutions. Casein-whey-fat sediments were in the form of a gel. Sporadic gelation was observed in casein solutions. Sedimentation rates from cheese whey alone are similar to gelation rates for milk for similar thermal treatments. Reactivated enzymes may be responsible for both phenomena.     

Effect of transglutaminase on the heat stability of milk: a possible mechanism

Treatment of milk with transglutaminase (TGase) affects its heat stability, but the manner in which it does so depends on whether or not the milk had been preheated before incubation and on the temperature of preheating. In raw milk, it appears that cross-link formation between the individual caseins is responsible for preventing the dissociation of kappa-casein from the micelles at pH values in the region of minimum stability. In milks preheated before incubation with TGase, denaturation of whey protein may have allowed the formation of cross-links by TGase between denatured whey proteins and the individual caseins which, in combination with cross-linking of the caseins, contributed to greatly improved heat stability at pH > 6.5. It appears from the results of this study that TGase has potential commercial applications as a food-grade additive capable of improving the heat stability of milk.     

Freezing Qualities of Raw Ovine Milk for Further Processing

Raw whole ovine (sheep) milk was frozen at −15°C and −27°C and microbiological and physico-chemical properties were evaluated periodically. Total bacteria decreased at a faster rate in milk stored at −15 than at −27°C. Acid degree values for milk stored at −15°C were significantly higher than that stored at _27°C. Samples stored at −15°C exhibited protein destabilization after 6 mo of storage, while those stored at −27°C were stable throughout the 12-mo storage period.Frozen ovine milk was evaluated in several products including cheese, yogurt, and whey protein concentrates. Products produced from milk frozen at −27°C exhibited good sensory and functional characteristics. Ovine whey showed a higher proportion of β-lactoglobulin, about the same proportion of α-lactalbumin and lower proportions of serum albumin and immunoglobulin than bovine whey. Ovine whey protein concentrate showed significantly better foam overrun, foam stability, and gel strength than bovine or caprine whey protein concentrates.     

硬质发酵干酪加工设备简述

在简要说明我国发展干酪生产必要性的基础上,以切达干酪加工生产为例,从原奶的预处理、凝块的形成和加工、乳清排放以及质构化和盐化、灌装和压榨、包装和储存等5个方面详细介绍了国内外硬质干酪产品加工设备类型和使用情况,以期推动我国干酪加工设备的国产化进程。