添加猪肉蛋白对米酒乳杆菌蛋白质代谢相关基因表达的影响

米酒乳杆菌是常见的异型发酵乳酸菌,常常用于肉类工业发酵剂。为了了解其在肉类环境中对氮源的代谢机制,用定量PCR对米酒乳杆菌La22在添加肌浆蛋白和肌原纤维蛋白的培养基中生长时蛋白质代谢相关基因的表达量进行分析。结果显示,La22在添加猪肉蛋白的2种培养基中生长时,有6个与天冬氨酸和谷氨酸代谢相关的基因表达量发生了明显变化,在S-CDM培养基中生长时,基因asnA2明显上调,基因pyrB、purA和glnA明显下调;在M-CDM培养基中生长时,pyrB、asnA1和purF明显上调,而purA和glnA明显下调;胞外蛋白酶仅有clpL基因在2种培养基中均表现为明显上调。在S-CDM培养基中hslV基因明显下调,而在M-CDM中,基因prtM、hslU和clpE均表现为明显下调。在添加猪肉蛋白的CDM培养基中生长时,编码Opp系统的5个基因中,只有oppB和oppC表达量明显上调,而dtpT基因则明显下调;基因puopT在M-CDM培养基中明显上调,而在S-CDM中上调不明显。有7种编码米酒乳杆菌肽酶的基因在2种猪肉蛋白培养基中表达量上调。结果表明米酒乳杆菌能通过蛋白质代谢基因表达调节来适应含猪肉蛋白的培养环境。     

植物乳杆菌对猪肌肉蛋白提取物分解能力的研究

初步探讨了植物乳杆菌6003的全细胞、细胞提取液(CE)、两种物质的组合对肌肉的肌浆蛋白和肌原纤维蛋白提取物的蛋白水解活性,用生物培养法、SDS-PAGE电泳、游离氨基酸变化来分析反应产生的复合物。结果表明,发酵96h后,植物乳杆菌全细胞中蛋白酶引发肌浆蛋白的明显水解;添加细胞提取液(CE)加强了水解作用;两种酶源组合物的活性增加了肌原纤维蛋白中Lys、Arg、Leu的含量,而只增加了肌浆蛋白中Ala的含量。     

米酒乳杆菌对风鸭肌肉蛋白质降解的影响

以米酒乳杆菌(Lactobacillus sake)为发酵剂加工风鸭,研究其在风鸭加工过程中对肌肉蛋白降解的影响。用SDS-PAGE电泳分析蛋白质的降解规律,同时比较加工初期及末期游离氨基酸的变化,并以不接菌样品为对照。结果表明,与对照样相比,米酒乳杆菌促进了肌浆蛋白与肌原纤维蛋白的降解,显著增加了游离氨基酸的总量;产鲜氨基酸、苦味氨基酸的总量和比例均显著增加;必须氨基酸总量显著增加,比例未发生显著变化;甜味氨基酸的总量未发生显著变化,比例显著下降。总之,米酒乳杆菌是一种优良的发酵剂。     

氮源对保加利亚乳杆菌关键蛋白酶基因表达的影响

选择6株保加利亚乳杆菌(KLDS 1.0207,1.0501,1.1007,1.9201,1.9203,1.0208)进行脱脂乳发酵。应用RT-PCR技术,在mRNA转录水平上,探讨不同氮源对保加利亚乳杆菌的蛋白水解体系中关键蛋白酶基因(prtB,oppD,pepC,pepF,pepQ,pepX,pepT)表达的影响。结果表明:在12%脱脂乳中培养12 h,6株保加利亚乳杆菌菌株间的蛋白水解活力存在显著差异(P0.05);在脱脂乳体系中,添加大豆蛋白胨可以显著下调prt B基因表达(P0.05),添加酪蛋白胨显著下调6株菌pepC,pepF,pepQ,pepX,pepT基因表达(P0.05);opp D在不同菌株中的基因表达量趋势不完全相同。添加酵母浸提物,基因的表达量整体呈上调趋势,只有菌株KLDS 1.0208的各目的基因表达量显著下调(P0.05)。6株菌的蛋白酶基因表达量受培养基质中氮源影响,各基因表达依赖肽供给。     

不同初始pH值对保加利亚乳杆菌关键蛋白酶基因表达的影响

由于保加利亚乳杆菌自身不能直接利用外源蛋白,其必须通过蛋白水解体系外源蛋白质,生成供菌体正常生长需要的短肽和游离氨基酸。选择具有高蛋白水解活力的6株保加利亚乳杆菌作为供试菌种。将菌株接种于不同初始pH值的灭菌脱脂乳中,在m RNA转录水平上,应用实时荧光定量PCR技术,探讨保加利亚乳杆菌的蛋白水解体系中关键蛋白酶基因表达情况。结果表明:在脱脂乳体系中,初始pH值对保加利亚乳杆菌蛋白水解关键酶基因的表达存在显著影响,随着初始pH值的升高菌株KLDS 1.0501,1.9201,1.9203和1.0208的各基因表达量均上调,在pH=6.5时,部分基因表达量继续上调,且各菌株间蛋白基因表达有较大差异。     

干酪乳杆菌6033蛋白酶降解肌肉蛋白质的作用研究

本试验将干酪乳杆菌(Lactobacillus casei，Lc)6033蛋白酶液按5％的比例分别加入肌浆蛋白和肌原纤维蛋白提取液，然后设定不同的pH值，于15℃培养7d，定时取样，测定反应后的pH值、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测蛋白质的变化。结果发现：不同设定的肌浆蛋白和肌原纤维蛋白试验组在反应初期pH值均稍稍降低，随着反应进程，各试验组的pH值呈现出逐步升高的趋势；其中，肌浆蛋白以pH5．0、4．5组的变化较为明显，肌原纤维蛋白则以pH6．0、5．0、4．5组的变化较为明显。经7d振荡培养后，电泳检测发现，各试验组肌浆蛋白均表现出分解现象，尤其以pH5．0组和pH4．5组更为明显；而肌原纤维蛋白也都表现出了明显的分解现象，尤以pH5．0组肌原纤维蛋白分解最明显。     

乳酸菌发酵对草鱼肉理化特性和蛋白质降解变化的影响

研究了乳酸片球菌、乳杆菌-Lo3、乳杆菌-B5407和清酒乳杆菌4种不同乳酸菌在发酵草鱼肉时鱼肉理化特性及蛋白质降解变化的规律和特征。结果表明:添加乳酸菌后,鱼肉pH值迅速由最初的6.25降至2d时的5.06～5.40,对照组则为5.98;接种发酵剂的草鱼肉的TBA和TVB-N值的上升较缓慢,整个发酵过程中显著低于对照组(P<0.05);腌制草鱼肉的蛋白质在发酵期发生了轻微的降解,游离氨基酸略有增加;贮藏期间游离氨基酸量显著增加,肌浆蛋白和肌原纤维蛋白均发生了强烈的水解,接菌组的蛋白降解显著多于对照组,其中,接种乳酸片球菌和乳杆菌-B5407组降解程度最大。     

波纹巴非蛤蛋白分离及其性质研究

为了充分利用波纹巴非蛤蛋白质资源,对波纹巴非蛤蛋白质组成进行了分离,得到肌浆蛋白、肌原纤维蛋白、基质蛋白3种蛋白组分,并对其分子量分布和功能特性进行检测和分析。研究结果表明:肌浆蛋白组分占原料粗蛋白的31.2%,肌原纤维蛋白组分占45.42%,基质蛋白占20.69%,非蛋白氮占1.67%。SDS-PAGE电泳分析显示:肌浆蛋白组分亚基分子质量分布比较广泛,在200～29.0 kDa;肌原纤维蛋白组分分子质量大多介于66.4～200 kDa和29.0～38.0 kDa之间;基质蛋白组分在190 kDa、97 kDa、44 kDa、29 kDa附近有明显的条带。相同浓度下,温度升高肌浆蛋白和肌原纤维蛋白溶液浊度都上升,溶解度下降,变化趋势相似;pH对肌浆蛋白的浊度和溶解度影响不显著,在pH3.5～9.5,其溶解度均在71%以上,但肌原纤维蛋白浊度和溶解度受pH影响较大,当pH为4.5时,肌原纤维蛋白的溶解度降到最低,浊度达到最大;离子强度下降,肌原纤维蛋白溶液的浊度上升,溶解度下降。     

不同生长阶段保加利亚乳杆菌关键蛋白酶基因表达变化规律

乳酸菌自身不能直接利用外源蛋白质,必须通过蛋白水解体系水解外源蛋白质,生成供菌体正常生长需要的短肽和游离氨基酸。该研究选择6株保加利亚乳杆菌(KLDS1.0207、1.0501、1.1007、1.9201、1.9203、1.0208)进行脱脂乳发酵,在mRNA转录水平上,应用实时荧光定量PCR技术,探讨保加利亚乳杆菌的蛋白水解体系中关键蛋白酶基因(prtB、oppD、pepC、pepF、pepQ、pepX、pepT)在菌体不同生长阶段表达的动态变化。结果表明,所有菌株生长曲线均呈S型。随着菌体在脱脂乳中的不断生长,蛋白水解活力极显著增强(P<0.01),7个目的基因相对表达量呈现总体上调。6株菌的prtB和oppD基因在对数期的相对表达量极显著高于对照组(4h)(P<0.01)。对数期的胞内肽酶基因(pepC、pepF、pepQ、pepX、pepT)的表达量与对照组(4 h)相比,呈极显著上调(P<0.01),但菌株KLDS 1.0207的pepQ基因在对数期下调,而稳定期上调。由此可见,蛋白水解活力较高的菌株,其生长和产酸特性也较高;发现在脱脂乳中培养保加利亚乳杆菌,其关键蛋白酶基因的表达量呈时间依赖性,且菌株间各蛋白酶基因表达量有较大差异。     

植物乳杆菌分子伴侣蛋白基因在盐胁迫下的表达分析

以一株分离筛选自东北自然发酵大酱中的耐盐植物乳杆菌FS5-5为实验对象,通过实时荧光定量聚合酶链式反应技术,在转录水平上对其分子伴侣蛋白的相应基因在盐胁迫下的表达进行研究。结果表明：在菌体对数生长期,分子伴侣蛋白调控系统中,基因groEL、groES、dnaK、dnaJ、hsp1、hsp2、usp均受MRS培养基中NaCl的诱导而表达上调,并且NaCl的质量浓度越高,基因受诱导表达上调越显著,而hsp3虽受MRS培养基中NaCl的诱导表达有所上调,但其受诱导表达上调显著程度与NaCl质量浓度不呈正相关。     

真空滚揉腌制对伊拉兔肉品质特性的影响

本实验研究了真空滚揉腌制前后伊拉兔肉食用品质特性、质构特性、肌浆蛋白、肌原纤维蛋白、总蛋白溶解度和游离氨基酸含量的变化。结果表明：真空滚揉腌制可以显著改善兔肉的食用品质,提高兔肉的pH值,改善兔肉的色泽,降低兔肉的蒸煮损失和压榨损失,提高保水性,改善兔肉嫩度和质构特性;真空滚揉腌制会导致肌原纤维蛋白分解、肌浆蛋白溶出、游离氨基酸含量下降,引起兔肉品质特性的变化。     

Protein Degradation by Lactobacillus plantarum and Lactobacillus casei in a Sausage Model System

ABSTRACT: :
The proteolytic activity of a starter culture involving Lactobacillus plantarum and Lactobacillus casei towards meat sarcoplasmic and myofibrillar proteins during the fermentation of a sausage-like system was studied. After 96 h of incubation the proteolytic system of L. plantarum CRL681 caused a degradation of both sarcoplasmic and myofibrillar proteins, whereas L. casei CRL705 showed a different affinity to meat proteins. The inoculation of both strains showed a higher activity toward sarcoplasmic fraction. These results correlated with a high rate of sarcoplasmic protein degradation observed in SDS-PAGE analysis. The generation of free amino acids as well as the pH drop at the end of the incubation period was maximal in presence of the mixed starter culture, thereby demonstrating the suitability of these strains to be used in the fermentation of meat products.     

A Comparison of the Effect of Meat Formulation on the Heat Resistance of Free or Encapsulated Cultures of Lactobacillus sakei

ABSTRACT: The protective culture, Lactobacillus sakei Bactoferm-B2, is not particularly resistant to commercial cooking conditions of meat products. Encapsulation in lyophilized alginate beads supplemented with glycerol was tested as a means to protect L. sakei against heat treatment in broth culture, and in an acidified chicken meat model (pH 5.0). Significantly enhanced ( p < 0.05) cell protection by encapsulation was observed in liquid media acidified to pH 5.0 and 5.7, but not in the meat model. Indeed, unencapsulated freezedried cells were significantly more resistant ( p < 0.05) in meat. Meat model constituents, such as the binders and meat itself, provided protection to the free cells.     

Contribution of starter cultures to the proteolytic process of a fermented non-dried whole muscle ham product

Porcine longissimus dorsi muscles were cured by brine injection. Curing brine containing 15% (w/v) NaCl, 1.33% (w/v) glucose, 750 ppm sodium nitrite, and appropriate levels of either Lactobacillus sakei LAD, L. sakei LAD plus Kocuria varians FT4 (formally Micrococcus varians), L. sakei LAD plus papain and GDL (glucono-delta-lactone) plus K. varians FT4, was injected to the muscle at a pumping rate 15% w/v. The effect of these treatments on the proteolysis in the ham system was compared to a control ham, produced without starter culture and containing GDL acidulant to control pH and antibiotics to reduce the contribution of background microflora. Hydrolysis of sarcoplasmic and myofibrillar protein fractions was evaluated by SDS-PAGE and reverse phase-HPLC. Hams with different treatments were also investigated for differences in amino acid profile, protein and non-protein nitrogen level, colour, pH, water activity and moisture and microbiological evolution. There was no significant difference in the gross compositional analysis of any of the treatments compared to the control. There was no significant difference (p>0.05) in the protein content, non-protein nitrogen level, SDS-PAGE and free amino acid analysis between the control ham and ham inoculated with proteolytic starter culture. However, it was observed that hams containing starter cultures exhibited decreases in certain peptide fractions and corresponding increases in some free amino acids compared to the uninoculated control. It can be concluded that, while the principle mechanisms resulting in the proteolysis of this non-dried ham product involve the activity of endogeneous cathepsins, the addition of proteolytic starter cultures influence the amino acid profile thereby potentially enhancing the sensorial attributes of the ham.     

No Effect of Hydrodynamic Shock Wave on Protein Functionality of Beef Muscle

ABSTRACT: The protein functionality of meat proteins after treatment with hydrodynamic shock wave was determined. Frankfurters (cooked to 71 °C) were evaluated for cooking yield, CIE L*a*b*, nitrosylhemochrome, Texture Profile Analysis (hardness, cohesiveness), and stress and strain (torsion testing). Compared to the control samples, the hydrodynamic shock waves (HSW) did not affect ( P < 0.05) myofibrillar or sarcoplasmic protein solubility, cooking yield, or color. Textural properties and gel strength of the frankfurters were not affected ( P < 0.05) by HSW. These results suggested that beef trim obtained from HSW-processed meat could be used interchangeably with normal meat trim in the production of further processed meats since the functionality of meat protein was not affected significantly by the HSW process.     

Apparent Specific Heat of Chicken Breast Patties and their Constituent Proteins by Differential Scanning Calorimetry

Chicken breast meat yielded three endothermic transitions, with peak transition temperatures of 53,70, and 79°C. Comparison with the purified protein fractions indicated that these transitions corresponded to denaturation of myofibrillar (53°C) and sarcoplasmic (70 and 79°C) proteins. The apparent specific heat profile of chicken breast meat was successfully modeled as a weighted average of the apparent specific heat of the constituent proteins. The specific heats of sarcoplasmic protein, myofibrillar protein, and chicken breast meat were strongly influenced by temperature; however, the specific heat of stromal protein was nearly constant across the temperature range considered (i.e., 10 to 100°C).     

Effect of acid- and alkaline-aided extractions on functional and rheological properties of proteins recovered from mechanically separated turkey meat (MSTM)

Functional and rheological characteristics of acid- and alkali-extracted proteins from mechanically separated turkey meat (MSTM) have been investigated. Extractions were carried out at 4 pH values (2.5, 3.5, 10.5, and 11.5). The study demonstrated that alkali and acid extractions resulted in significant (P < 0.0001) decreases of cooking and water loss compared to raw MSTM; however, the cooking loss was found to be similar (P = 0.5699) among the different protein isolates. Proteins extracted at pH 10.5 showed the lowest (P = 0.0249) water loss. Emulsion and foaming properties were found to be slightly higher in alkali-extracted proteins compared to those for acid extractions. The myofibrillar protein fraction showed better ability to form and stabilize emulsions compared to sarcoplasmic proteins. Myofibrillar proteins also showed better foam expansion; however, foam volume stability was similar for both myofibrillar and sarcoplasmic protein fractions. Textural characteristics (hardness, chewiness, springiness, and cohesiveness) of recovered proteins were found to be unaffected (P > 0.05) by different extraction pH. The protein extracted at pH 3.5 formed a highly viscoelastic gel network as evidenced by storage modulus (G') values, whereas the gel formed from proteins extracted at pH 10.5 was found to be the weakest. The work also revealed that acid treatments were more effective for removal of total heme pigments from MSTM. Color characteristics of protein isolates were markedly improved compared to the initial material and tended to be better when subjected to acid extractions. PRACTICAL APPLICATION: Mechanically separated meat is one of the cheapest sources of protein obtained by grinding meat and bones together and forcing the mixture through a perforated drum. The use of mechanically separated turkey meat (MSTM) for the production of further processed poultry products is limited due to its undesirable color and textural properties. Recovery of proteins from MSTM using pH shifting process will help the poultry processors to get better returns and also create opportunity to produce functional food ingredients.     

Effects of rice bran fiber on heat-induced gel prepared with pork salt-soluble meat proteins in model system

The technological effects of rice bran fiber on pork salt-soluble meat proteins in a model system were investigated. Rice bran fiber at levels of 0% (control), 0.1%, 0.5%, 1%, and 2% was added at the same time as salt-soluble meat protein to maintain similar moisture levels in all samples. Samples with increasing amounts of added rice bran fiber had higher pH, yellowness, sarcoplasmic and total protein solubilities. The moisture content, myofibrillar protein solubility and water holding capacity were the highest in the treatments containing with 1% rice bran fiber. However, the lightness and redness, textural properties decreased with increasing rice bran fiber levels. SDS gel electrophoresis did not reveal any changes in proteins regardless different rice bran fiber levels. The apparent viscosity indicated that improvements in water holding capacity and decreased texture due to added rice bran fiber.     

IDENTIFICATION OF PROTEOLYTIC PRODUCTS AS INDICATORS OF QUALITY IN GROUND AND WHOLE MEAT

This study was devoted to the identification of specific peptides and proteins which can serve as indicators of spoilage in meat. Samples of ground and whole meat were subjected to storage at 4C; at intervals of 0, 2, 4, 8, 12 and 16 days, samples were analyzed for pH and microbial populations and subjected to extraction and separation of individual sarcoplasmic and myofibrillar peptides and proteins by SDS (sodium dodecyl sulfate) and native electrophoresis and by RP-HPLC. Sarcoplasmic protein and peptide fractions from RP-HPLC were collected and identified by (electrospray ionization mass spectrometry) ESI-MS. The results demonstrated substantial differences in microbial population and pH between ground and whole meat during storage. Separation by SDS-electrophoresis showed substantial changes in myofibrillar protein of ground meat after 12 days and of whole meat after 16 days of storage. Separation and identification of sarcoplasmic proteins by SDS-electrophoresis and by RP-HPLC followed by ESI-MS revealed the disappearance of a protein fraction band of MW 36 kDa after 8 days of storage in ground and whole meat.     

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。