高温处理对牛肉蛋白质化学作用力及肌原纤维蛋白结构的影响

以牛背最长肌为研究对象,对其进行高温处理（110、115、121 ℃分别加热3、6、9、12、15 min）,通过分析蛋白质化学键、傅里叶变换红外光谱、紫外光谱、内源荧光光谱以及蛋白质片段大小等结构信息变化,探讨高温处理对牛肉蛋白质化学作用力及肌原纤维蛋白结构的影响。结果表明,随着处理温度的升高和加热时间的延长,牛肉蛋白中离子键和氢键含量显著下降（P＜0.05）,疏水相互作用和二硫键含量显著升高（P＜0.05）。肌原纤维蛋白二级结构发生重排,N—H和C—N伸缩振动以及N—H弯曲振动较为明显。高温处理促使芳香族氨基酸残基暴露于分子表面,并改变了肌原纤维蛋白质疏水区域的局部结构和蛋白质的三级结构。此外,在高温处理下肌原纤维蛋白发生了明显的降解聚集,并形成了大量小分子质量的蛋白片段。可见,高温处理能够显著改变牛肉蛋白质的化学作用力及肌原纤维蛋白的结构,本研究为高温处理下牛肉蛋白质变化机制的研究提供参考。     

广式腊肠加工及贮藏过程中蛋白质降解动态研究

本文以总氮、非蛋白氮、游离氨基酸、氨基态氮及挥发性盐基氮为指标,通过对比方法,系统研究了广式腊肠日照自然干燥脱水和人工加热烘烤脱水加工工艺和不同的贮藏条件下蛋白质降解的动态变化。研究结果表明,人工加热烘烤脱水腊肠非蛋白氮、游离氨基酸的含量均高于日照自然干燥脱水腊肠,而氨基态氮含量则低于日照自然干燥脱水腊肠。在贮藏过程中,干燥脱水方法、包装形式及贮藏温度对于腊肠的非蛋白氮含量及氨基态氮含量有显著性影响(p<0.05)。长期高温贮存(30℃、100d)腊肠挥发性盐基氮含量尽管有所上升但对腊肠风味的影响不大。     

猪背最长肌蛋白质在冷冻贮藏过程中的变化

为研究冻藏时间对猪背最长肌蛋白质特性的影响,本文主要采用凝胶电泳、差示量热扫描技术分析了猪背最长肌在-18 ℃冻藏0 d和1、3、6、9、12、15月后,其蛋白质的疏水性、巯基含量、降解情况、热稳定性的变化。结果表明:随冻藏时间的延长,蛋白质溶解度显著降低(p<0.05),肌原纤维蛋白(MPI)的表面疏水性和巯基含量升高,发生降解的MPI主要集中在67 kDa和20~29 kDa;肌球蛋白和肌浆蛋白的变性温度和焓值呈现逐渐降低的趋势,表明这两类蛋白的热稳定性降低。在冻藏的前3个月内,猪背最长肌的各项指标维持在较好的水平,从第6个月开始,所有指标的变化幅值增加,变化速率加快。研究发现,冻藏6个月以后,猪背最长肌蛋白质品质开始加速下降。     

羊肉火腿加工过程中蛋白质的降解

对羊肉火腿加工过程中蛋白质的降解变化进行了研究。结果表明,总氮的含量在加工过程中先降低后升高,非蛋白氮含量和蛋白质水解指数在加工过程中持续增加;通过SDS-PAGE图谱分析,肌浆蛋白和肌原纤维蛋白均发生了降解,其中肌浆蛋白的降解主要发生在腌制期和发酵中期,肌原纤维蛋白则是在腌制期和发酵初期;各种游离氨基酸含量随着加工工艺的进行呈现不同程度增加,其中大部分游离氨基酸含量变化最显著的时期是在发酵初期和中期。     

温度对风干罗非鱼块品质的影响

以腌制后的罗非鱼块为原料,研究30、40、55、70℃四个干燥温度对风干罗非鱼块脂肪氧化、蛋白质分解及感官品质的影响.结果表明:热泵干燥温度对风干罗非鱼块非蛋白氮、氨基态氮、挥发性盐基氮、酸价、POV和TBA有显著性影响(p＜0.05),四种干燥温度干制罗非鱼块的非蛋白氮和蛋白质水解指数的顺序为:30℃＞40℃＞70℃＞55℃,且低温有利于蛋白质水解为氨基态含氮化合物.30℃和40℃干燥的风干鱼块脂肪氧化程度大于55℃和70℃干燥样品,虽然低温干燥下样品过氧化值和酸价高于高温干燥样品,但其过氧化值和酸价均未超过国家相关标准.研究结果表明,低温干燥风干罗非鱼块的组织状态、色泽、气味、鲜味和咀嚼度较好,样品可接受性高;低温有利于产品形成饱满的风味,且脂肪适度氧化及蛋白质的水解有利于促进产品风味的形成.     

羊乳酒在发酵过程中主要参数变化的研究

以新鲜羊奶为原料,采用乳酸菌和酵母菌共发酵方法,在29 ℃条件下振荡发酵羊乳,以pH值、酒精度、总氮及非蛋白氮含量为评价指标,通过凯氏定氮法、十二烷基硫酸钠-聚丙烯酰氨凝胶电泳法（SDS-PAGE）,对羊乳酒在发酵过程的不同时期蛋白质降解的动态变化进行了研究。研究结果表明,羊乳酒在发酵的过程中的pH值呈现先降低后升高再降至稳定的趋势;酒精度呈现缓慢增长的趋势;总氮含量变化不大;非蛋白氮含量随着乳酒发酵的进行缓慢升高;SDS-PAGE结果显示,羊乳酒中蛋白质发生了不同程度的降解,小分子蛋白增多,蛋白分子质量主要分布在17～35 kDa。     

黑龙江市售乳制品蛋白质质量评价

为评价黑龙江省市售乳制品中蛋白质的质量,采用凯氏定氮法和三氯乙酸沉淀法测定黑龙江市售不同厂家生产的全脂加糖乳粉、纯酸牛乳、配制型乳饮料和灭菌纯牛乳中的蛋白质和非蛋白氮含量,计算各乳制品的蛋白氮指数和非蛋白氮指数。结果表明, 利用蛋白氮指数和非蛋白氮指数评价乳制品中蛋白质质量是可行的,并建立了4种乳制品的蛋白氮指数和非蛋白氮指数模型。黑龙江市售合格的全脂加糖乳粉、纯酸牛乳、配制型乳饮料和灭菌纯牛乳的蛋白氮指数范围分别为0.990～0.995、0.870～0.956、0.402～0.633和0.929～0.943,其非蛋白氮指数范围分别为0.005～0.010、0.084～0.130、0.367～0.598和0.069～0.071。总体来说,黑龙江市售乳制品蛋白质含量大多数符合国家标准规定,但部分乳制品的蛋白质质量有待提高。     

高温处理对牛肉脂肪酸及脂肪氧化的影响

对新鲜牛背最长肌进行高温处理(110,115,121℃),并分别保持5,10,15,20min,采用气相色谱法研究高温对牛背最长肌肌内脂肪酸组成和脂肪氧化的影响。结果表明,121℃高温处理时,肌内脂肪氧化速度显著大于110,115℃的(P0.05);饱和脂肪酸(SFA)含量明显增加(P0.05),不饱和脂肪酸(UFA)含量降低(P0.05);SFA受处理温度(110,115℃)影响不显著(P0.05),受处理时间影响显著(P0.05),而热处理温度和时间对UFA含量均有显著影响(P0.05);长链饱和脂肪酸出现一定程度的断裂和降解,短链及中链脂肪酸含量显著上升(P0.05)。     

风干肠加工和贮藏过程中蛋白质的降解规律

以总氮、非蛋白氮、氨基酸态氮、挥发性盐基氮、游离氨基酸以及不同种类蛋白质（肌浆蛋白、肌原纤维蛋白、碱溶蛋白和碱不溶蛋白）为指标,分析研究风干肠加工和贮藏过程中蛋白质的降解规律。结果表明：风干肠加工和贮藏过程中总氮含量没有显著变化;非蛋白氮含量持续升高,从原料肉的469.4 mg/100 g增加到成品肠的786.4 mg/100 g,贮藏240 d后增加至1 256.1 mg/100 g;多肽氮和氨基酸态氮含量在加工和贮藏过程中均持续增加,挥发性盐基氮含量在风干过程中没有显著变化,在贮藏180 d后迅速增加;大部分游离氨基酸含量经过加工和贮藏均有所提高,只有半胱氨酸含量明显降低;在加工过程中,肌浆蛋白和肌原纤维蛋白含量均因降解而减少,基质蛋白含量明显增加;在贮藏过程中,肌浆蛋白含量持续降低,肌原纤维蛋白含量在贮藏前180 d无明显变化,贮藏至240 d明显减少,基质蛋白含量没有显著变化。     

超声波辅助酶法水解寻氏肌蛤蛋白

采用超声波辅助中性蛋白酶水解寻氏肌蛤,以-氨基态氮含量为检测指标。首先采用单因素和正交优化试验L9(34)确定酶法水解薄壳肉蛋白的最适条件.研究结果为:pH6.5,水解时间5 h,温度55℃,酶浓度2.0%,料液比1∶2,水解液的α-氨基态氮含量为0.372 6 g/100 mL。在此基础上,研究功率300 W的超声波预处理对酶解效果的影响,综合考虑,采用超声波预处理10 min,α-氨基态氮含量提高到0.394 1 g/100 mL。     

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。     

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.     

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...     

大豆分离蛋白改性对其功能性质影响

大豆分离蛋白是大豆蛋白最为精制形式,广泛应用于食品工业,并在不同产品中表现出不同功能。该文综述近年来大豆分离蛋白物理、化学、酶法及基因工程改性对其功能性质影响,经不同方式改性可产生合适功能性质,从而拓宽大豆分离蛋白在食品工业中应用。     

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。     

Physicochemical and Functional Properties of Soy Protein Substrates Modified by Low Levels of Protease Hydrolysis

ABSTRACT: Endo-protease treatments achieving low degrees of hydrolysis (DH 2% and 4%) were used to improve functional properties of hexane-extracted soy flour (HESF), extruded-expelled partially defatted soy flour (EESF), ethanol-washed soy protein concentrate (SPC), and soy protein isolate (SPI). These substrates had protein dispersibility indices ranging from 11% to 89%. Functional properties, including solubility profile (pH 3 to 7), emul-sification capacity and stability, foaming capacity and stability, and apparent viscosity were determined and related to surface hydrophobicity and peptide profiles of the hydrolysates. Protein solubilities of all substrates increased as DH increased. Emulsification capacity and hydrophobicity values of the enzyme-modified HESF and EESF decreased after hydrolysis, whereas these values increased for SPC and SPI. Emulsion stability was improved for all 4% DH hydrolysates. Hydrolyzed SPC had lower foaming capacity and stability. For substrates other than SPC, foaming properties were different depending on DH. Hydrolysis significantly decreased the apparent viscosities regardless of substrate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated differences in the molecular weight profiles of the hydrolysates. HESF and EESF, which had high proportions of native-state proteins, showed minor changes in the peptide profile due to hydrolysis compared with SPC and SPI.     

Formulation,process conditions,and biological evaluation of dairy mixed gels containing fava bean and milk proteins: Effect on protein retention in growing young rats

Food formulation and process conditions can indirectly influence AA digestibility and bioavailability. Here we investigated the effects of formulation and process conditions used in the manufacture of novel blended dairy gels (called “mixed gels” here) containing fava bean (Vicia faba) globular proteins on both protein composition and metabolism when given to young rats. Three mixed dairy gels containing casein micelles and fava bean proteins were produced either by chemical acidification (A) with glucono-δ-lactone (GDL) or by lactic acid fermentation. Fermented gels containing casein and fava bean proteins were produced without (F) or with (FW) whey proteins. The AA composition of mixed gels was evaluated. The electrophoretic patterns of mixed protein gels analyzed by densitometry evidenced heat denaturation and aggregation via disulfide bonds of fava bean 11S legumin that could aggregate upon heating of the mixtures before gelation. Moreover, fermented gels showed no particular protein proteolysis compared with gel obtained by GDL-induced acidification. Kinetics of acidification were also evaluated. The pH decreased rapidly during gelation of GDL-induced acid gel compared with fermented gel. Freeze-dried F, A, and FW mixed gels were then fed to 30 young (1 mo old) male Wistar rats for 21 d (n = 10/diet). Fermented mixed gels significantly increased protein efficiency ratio (+58%) and lean mass (+26%), particularly muscle mass (+9%), and muscle protein content (+15%) compared with GDL-induced acid gel. Furthermore, F and FW formulas led to significantly higher apparent digestibility and true digestibility (+7%) than A formula. Blending fava bean, casein, and whey proteins in the fermented gel FW resulted in 10% higher leucine content and significantly higher protein retention in young rats (+7% and +28%) than the F and A mixed gels, respectively. Based on protein gain in young rats, the fermented fava bean, casein, and whey mixed proteins gel was the most promising candidate for further development of mixed protein gels with enhanced nutritional benefits.