冻藏条件下高白鲑肌肉蛋白质的生化特性

以肌肉基本营养成分、蛋白质组成、肌原纤维蛋白Ca~(2+)-ATPase活性、总巯基含量、羰基含量及表面疏水性作为测定指标,考察高白鲑在冻藏过程中的肌肉蛋白质的变化规律。结果显示:高白鲑蛋白质含量为(18.95±0.12)%;随着冻藏时间的延长,肌原纤维蛋白、肌浆蛋白及肌基质蛋白含量均逐渐减少,其中肌原纤维蛋白含量变化最大,由初始值35.86%下降至4.13%,而碱溶性蛋白含量逐渐增加,由初始值19.14%增加至23.74%;肌原纤维蛋白Ca~(2+)-ATPase活性随冻藏时间的增加而降低,冻藏结束时,Ca~(2+)-ATPase活性为0.075μmol Pi/mg protein/min,比冻藏开始时降低了72.8%;总巯基含量随冻藏时间延长逐渐减少,整个冻藏周期呈现两段式下降,冻藏前期下降迅速,后期下降缓慢;羰基含量随冻藏时间的延长不断增加,前2周增加迅速,由初始的4.17 nmol/mg protein增加至4.93 nmol/mg protein;随着冻藏时间的延长,高白鲑肌原纤维蛋白表面疏水性逐渐增大。综合各指标的变化情况,表明随着冻藏时间的延长,高白鲑肌肉蛋白质变性加剧。为研究鱼肉蛋白质在冻藏过程中变化规律提供理论参考。     

菊粉对冻藏鲢鱼鱼糜肌原纤维蛋白抗冻性的影响

研究菊粉对冻藏鲢鱼鱼糜肌原纤维蛋白抗冻性的影响,对鲢鱼鱼糜盐溶性蛋白含量、肌原纤维蛋白的Ca2＋-ATPase活性、总巯基含量、活性巯基含量、表面疏水性进行分析。结果表明,在－18 ℃条件下冻藏5 周后,菊粉可以抑制鲢鱼糜肌原纤维蛋白的冷冻变性,盐溶性蛋白含量、肌原纤维蛋白的Ca2＋-ATPase活性、总巯基含量、活性巯基含量的下降趋势和表面疏水性的增加趋势均得到抑制,其中1.5%菊粉的抗冻效果优于其他实验组且与商业抗冻剂接近。研究结果为开发热量和甜度较低的抗冻剂提供一定的理论依据。     

海藻糖对防止鲤鱼鱼糜蛋白质冷冻变性的研究

以冻藏鱼糜盐溶性蛋白含量、巯基含量及肌原纤维蛋白Ca2+-ATP 酶活性为指标, 探讨冷冻鲤鱼鱼糜在冻藏过程中添加海藻糖对蛋白质变性作用的影响。结果表明：5%海藻糖溶液浸渍处理组,冻藏7周后,盐溶性蛋白含量、巯基含量分别比空白组高16.16%和8.8%;5%海藻糖溶液浸渍处理组,冻藏30d后,肌原纤维蛋白Ca2+-ATP 酶活力的下降率比空白组低29.6%。可见添加海藻糖能有效地防止蛋白质变性,提高冷冻鲤鱼鱼糜的品质。     

卡拉胶寡糖对秘鲁鱿鱼肌原纤维蛋白功能特性的影响

为探讨卡拉胶寡糖对冻藏鱿鱼肌肉品质特性的影响,以0、0.2%、0.4%和0.6%(w/v)卡拉胶寡糖与鱿鱼肌原纤维蛋白溶液进行混合,在120d冻藏过程中,分析测定肌原纤维蛋白浊度、乳化能力、Ca~(2+)-ATPase活性、羰基含量、总巯基含量及表面疏水性等变化情况。结果表明,经冻藏120d后,空白组鱿鱼肌原纤维蛋白浊度、羰基含量和表面疏水性显著增加至0.623m~2/g、6.47nmol/mg和38.12μg,而其乳化活性指数(EAI)、乳化稳定性(ESI)、Ca~(2+)-ATPase活性和总巯基含量则显著下降至8.31m~2/g、9.39%、0.131U/mg和16.46μmol/mg(P<0.05)。相比于空白组,0.6%卡拉胶寡糖处理鱿鱼肌原纤维蛋白的浊度、羰基含量和表面疏水性增加至0.562m~2/g、5.05nmol/mg和32.05μg,而其EAI、ESI、Ca~(2+)-ATPase活性和总巯基含量则维持在9.18m~2/g、10.18%、0.163U/mg和21.03μmol/mg,对鱿鱼肌原纤维蛋白功能特性的保护作用显著优于空白组(P<0.05)。由上,较高浓度的卡拉胶寡糖对冻藏鱿鱼肌原纤维蛋白冷冻氧化变性的抑制作用较好,其可为冻藏鱿鱼的品质保障技术提供一定的理论依据。     

海藻糖在冷冻罗非鱼鱼糜中的抗冻作用研究

以盐溶性蛋白的溶解度、肌原纤维蛋白Ca2+-ATPase活性以及凝胶性能的变化为指标,初步探讨了海藻糖在罗非鱼鱼糜的冷冻加工及冻藏过程中对蛋白质变性的影响。结果表明,冷藏8周后,添加5%和10%海藻糖组鱼糜的盐溶性蛋白含量分别比对照组高出28.02%和33.31%;Ca2+-ATPase的活性保持分别比对照高出26%和22%;凝胶强度分别比对照高37.75%和42.82%。结论:添加5%以上的海藻糖能有效地抑制冷冻罗非鱼鱼糜冻藏过程中的蛋白质变性,减缓凝胶强度的降低,提高鱼糜制品的品质。     

海藻糖、乳酸钠对冻藏鳙鱼鱼糜蛋白抗冻效果的影响

以凝胶强度、盐溶性蛋白含量、Ca~(2+)-ATPase活性、总巯基、表面疏水性为指标并结合DSC分析(差示扫描量热分析),研究了海藻糖、乳酸钠在8%(w/w)水平上对鳙鱼鱼糜蛋白在-18℃冻藏24周的抗冻效果,并将其抗冻效果与传统商业抗冻剂(4%蔗糖+4%山梨糖醇)进行了对比。结果表明,海藻糖、乳酸钠的加入能较好地抑制冻藏鳙鱼鱼糜蛋白的冷冻变性,表现在这2种物质加入后,冻藏鳙鱼鱼糜的凝胶能力得到较好的维持,盐溶性蛋白含量、Ca~(2+)-ATPase活性和巯基含量的下降及表面疏水性的增加也得到很好的抑制,2种物质的抗冻效果比传统商业抗冻剂具有明显的优势。DSC分析表明,抗冻剂的添加可能改变了鳙鱼鱼糜肌球蛋白的结构,使其变得更稳定,从而表现出较好的冻藏稳定性。海藻糖、乳酸钠都属于低甜度、低热值物质,因此在鱼糜加工业中有望成为传统商业抗冻剂的替代物。     

海藻糖对罗非鱼糜及蛋白抗冻作用的研究

以罗非鱼为原料,提取肌原纤维蛋白,添加10%海藻糖。在不同的冷冻时间下对其蛋白盐溶性,ATPase活性及巯基含量为指标,与未添加海藻糖对比研究肌原纤维蛋白的变性程度。制作罗非鱼糜,添加10%海藻糖作为对比,与蛋白变性过程同步,研究鱼糜的凝胶强度、保水性、弹性、咀嚼性等指标。结果表明,随着冻藏时间的延长,鱼糜蛋白盐溶性ATPase活性及巯基含量均呈下降趋势,鱼糜的保水性、弹性凝胶强度等也同步下降。而添加海藻糖对该趋势有抑制作用。     

两种抗冻剂对罗非鱼鱼糜的凝胶性及抗冻性的影响

以凝胶性能、盐溶性蛋白含量及肌原纤维蛋白Ca2+-ATPase活性的变化为指标,研究了商业抗冻剂(蔗糖/山梨醇)和海藻糖在罗非鱼鱼糜冻藏过程中对蛋白质变性的影响。结果表明,冷藏20周后,添加8%商业抗冻剂和8%海藻糖组鱼糜的破断强度分别比对照高出39.14%和601.11%,凹陷强度分别比对照高出34.14%和39.85%,凝胶强度分别比对照高出36.03%和41.05%,盐溶性蛋白含量分别比对照高出30.00%和38.86%,肌原纤维蛋白Ca2+-ATPase活性分别为下降了67.12%和57.89%,而对照的肌原纤维蛋白Ca2+-ATPase没有活性。结论:添加8%海藻糖比8%商业抗冻剂更能有效抑制罗非鱼鱼糜在冻藏过程中的蛋白质变性,减缓凝胶强度的降低,提高鱼糜制品的质量。     

海藻糖、山梨糖醇、柠檬酸钠对大黄花鱼肌原蛋白抗冷冻变性的影响

以大黄花鱼为实验材料,将海藻糖、山梨糖醇、柠檬酸钠组成不同的混合抗冻剂,比较添加不同抗冻剂时冻藏各阶段的大黄花鱼肉的硬度和持水性以及大黄花鱼肌原蛋白盐溶性、Ca~(2+)-ATPase活性、巯基含量、总巯基含量、表面疏水性的变化规律,并在冻藏35 d后进行SDS-PAGE凝胶电泳,分析不同抗冻剂下鱼糜蛋白的变性程度。结果表明,不同抗冻剂均能抑制大黄花鱼蛋白的冷冻变性,海藻糖、山梨糖醇、柠檬酸钠三者的混合对大黄花鱼肌原蛋白抗冷冻变性效果优于山梨糖醇、柠檬酸钠混合抗冻剂和海藻糖的单独使用。加入海藻糖、山梨糖醇、柠檬酸钠混合抗冻剂的鱼肉品质下降较慢,肌原蛋白理化特性较稳定且其鱼肉蛋白结构变化缓慢。     

添加剂对南美白对虾冻藏期间蛋白质变性的影响

以南美白对虾为研究对象,在虾肉中分别加入10%海藻糖、10%菊糖和5%麦芽糊精,将虾肉置于-18℃下冻藏2个月,每隔15 d测定虾肉肌原纤维蛋白的Ca2+-ATPase活性、盐溶性蛋白含量、活性巯基含量和肌原纤维蛋白表面疏水性,探讨糖类添加剂对虾肉冻藏期间蛋白质变性的影响。结果表明:海藻糖、菊糖和麦芽糊精均抑制了冻藏过程中虾肉肌原纤维蛋白Ca2+-ATPase活性、盐溶性蛋白含量、活性巯基含量的降低和表面疏水性升高的程度,延缓了南美白对虾肉冻藏期间蛋白质的冷冻变性。3种添加剂中,抗冻效果高低顺序依次为:海藻糖、菊糖、麦芽糊精,其中添加海藻糖与菊糖处理间无显著差异(P0.05),但两者的抗冷冻变性效果均显著高于添加麦芽糊精处理组(P0.05)。基于玻璃化转变理论,阐明了3种添加剂对虾肉抗冻效果的机制,为水产品抗冷冻变性剂的筛选提供理论依据。     

Short communication: Muscle protein synthetic response to microparticulated whey protein in middle-aged men

Whey protein concentrate (WPC) is a high-quality dairy ingredient that is often included in formulated food products designed to stimulate muscle anabolism. Whey protein concentrate can be affected by UHT processing, and its sensory properties are not compatible with some formulated food products. Microparticulated WPC (mWPC) is a novel ingredient that is resistant to heat treatment and has enhanced sensory properties. When 16 healthy middle-aged men consumed 20 g of either WPC or mWPC, both proteins increased plasma essential AA and leucine concentrations with no detectable difference in curve kinetics. Myofibrillar protein synthesis was increased in both groups for 90 min after ingestion with no difference between groups. Ingestion of mWPC resulted in a muscle anabolic response that was equivalent to that of WPC over the full 210-min measurement period. Formulated products incorporating mWPC or standard WPC would provoke equivalent anabolic responses.     

Co-precipitation of whey and pea protein – indication of interactions

The aim was to optimise the yield of co-precipitation of whey protein isolate (WPI) and pea protein isolate (PPI) and compare co-precipitates and protein blends with respect to solubility. The yield of co-precipitates was tested with different protein ratios of WPI and PPI in combination with different temperatures and acid precipitation (pH 4.6). The highest precipitation yield was obtained at protein ratios WPI < PPI, high temperature and alkaline protein solvation. The solubility was measured by an instability index and absorption spectroscopy of re-suspended precipitated proteins at pH 3, 7 and 11.5. Co-precipitates had significantly lower solubility than protein blends. Protein ratios WPI > PPI, low precipitation temperature and high pH showed the highest solubility. Differences in protein composition between co-precipitates and protein blends were observed with SDS-PAGE and matrix-assisted laser desorption ionisation time-of-flight, and indicated different protein–protein interaction in samples, which needs further investigations.     

大豆蛋白溶解性研究

该文概述大豆蛋白溶解特性及其与一般物质溶解差异,介绍提高大豆蛋白溶解性改性方法及研究现状,对比不同改性增溶方法优、缺点,并提出今后大豆蛋白改性研究方向。     

细菌中蛋白质样品制备方法研究进展

细菌在生长繁殖时,细菌蛋白的表达受到环境影响而存在较大差异,使得细菌蛋白表达具有复杂性.在食品生产加工过程中可能会受到致病菌污染,细菌产生的内毒素和外毒素均会对人体健康构成威胁,因此需要高灵敏度和高特异性的检测方法来定量分析和鉴定食品中的细菌毒素.蛋白组学方法可以揭示细菌蛋白组成及其潜在的生物学功能,感染过程中菌体蛋白...     

The structures and functions of ice crystal-controlling proteins from bacteria

Many organisms have evolved into unique mechanisms which minimize freezing injury due to extracellular ice formation. Specifically, certain bacteria have produced a few proteins each with different functions. For example, the ice nucleation protein acts as a template for ice formation, which is responsible for imparting ice nucleating activity. The anti-nucleating protein inhibits the fluctuation of ice nucleus formation by a foreign particle in the water drop. Also, the antifreeze proteins depress the freezing temperature, modify or suppress ice crystal growth, inhibit ice recrystallization, and protect the cell membrane from cold-induced damage. In this article, a review on the current knowledge of the structure and the function of these three types of proteins, which are capable of interacting with ice itself or its nuclei from bacteria.     

酶制剂在蛋白质加工行业的应用

蛋白质的加工是食品行业中发展最快的领域之一，蛋白质加工的主要用酶是蛋白质水解酶，以蛋白质加工和研究的几个热点领域，如大豆分离蛋白、米蛋白、谷朊蛋白等为例，对酶制剂在蛋白质加工中的应用进展情况进行了回顾并对未来发展进行了展望。     

Effects of silage protein degradability and fermentation acids on metabolizable protein concentration: A meta-analysis of dairy cow production experiments

A meta-analysis was conducted using data from dairy cow production studies to evaluate silage metabolizable protein (MP) concentrations. The data consisted of 397 treatment means in 130 comparisons, in which the effects of silage factors (e.g., date of harvest, wilting, silage additives) were investigated. Within a comparison, a fixed amount of the same concentrate was fed. A prerequisite of data to be included in the analysis was that silage dry matter (DM), crude protein (CP), ammonia N, lactic acid (LA), and total acid (TA) concentrations and digestibility were determined. A smaller data set (n = 248) comprised studies in which silage water-soluble N concentration was also analyzed. The supply of MP was estimated as amino acids absorbed from the small intestine using a model with constant values for ruminal effective protein degradability (EPD) and intestinal digestibility of rumen undegraded protein. Microbial protein was calculated on the basis of digestible carbohydrates and rumen degradable protein (RDP). Alternative models were used to estimate microbial protein formation, assuming the energy values of RDP and TA to be equivalent to 1.00, 0.75, 0.50, 0.25, and 0 times that of digestible carbohydrates. Because EPD values are seldom determined in production trials, they were derived using empirical models that estimate them from other feed components. The goodness of fit of models was compared on the basis of root mean squared error (RMSE) of milk protein yield (MPY) predicted from MP supply (adjusted for random study effect) and Akaike's information criterion. Metabolizable protein supply calculated from basal assumptions predicted MPY precisely within a study (RMSE = 16.2 g/d). Variable contribution of RDP to the energy supply for microbial synthesis influenced the precision of MPY prediction very little, but RMSE for MPY increased markedly when the energy supply of rumen microbes was corrected for TA concentration. Using predicted rather than constant EPD values also increased RMSE of MPY prediction. These observations do not mean that the supply of MP from undegraded feed protein is constant. However, it suggests that our current methods overestimate the range in EPD values and that the techniques have so many inherent technical problems that they can mask the true differences between the feeds. Including new elements in feed protein evaluation models may not improve the precision of production response predictions unless the consequent effects on the supply of other nutrients are taken into account.     

大豆蛋白生产与应用现状

该文综述大豆蛋白制品—大豆蛋白粉、大豆分离蛋白、大豆浓缩蛋白、大豆组织蛋白生产现状、存在问题及大豆蛋白在面制品、肉制品、乳制品、饮料制品等中应用现状。     

几种新型花生蛋白产品的生产

本文从花生蛋白质利用的角度介绍了几种新型花生蛋白产品的加工工艺，针对我国人民膳食结构中蛋白质的摄入水平较低的实际情况，论述了花生蛋白开发利用的必要性，展望了花生蛋白开发利用的广阔前景。