Combination of high pressure and heat on the gelation of chicken myofibrillar proteins

The effects of combinations of high pressure and heat on chicken myofibrillar gels were investigated. High pressure was either applied simultaneously with heating (heating under pressure, HUP), before heating (PBH) or no high pressure with heat-only (HT). PBH treatment induced many similar properties in gels as did by HT treatment, except that PBH treatment promoted secondary structure transformation and formed more covalent bonds. HUP treatment resulted in less heat denaturation of the protein, induced fewer hydrophobic interactions and covalent bonds, hindered secondary and tertiary structural transformation, and formed a gel with a more porous microstructure. The gels induced by HUP treatment had softer texture and higher water holding capacity than gels induced by PBH or HT treatments. These findings suggest that high pressure with HUP treatment changes gel properties by resisting the heat-induced denaturation and gelation of myofibrillar proteins, while high pressure with PBH treatment alters gel properties by promoting denaturation of myofibrillar proteins.Industrial relevanceThe main constituents in meat are myofibrillar proteins, which are responsible for the functional properties of processed meat products. The gelation of myofibrillar proteins differs according to the sequence in which pressure/temperature combinations are applied. The pressure-modified protein interactions should be considered when adopting high pressure in meat product processing since the microstructure of the meat gel is affected by pressure, which would further affect water holding capacity and textural properties. HUP treatment showed its advantages in forming a fine microstructure and improving water-holding capacity.     

高压均质对肌原纤维蛋白乳化特性及结构的影响

探讨高压均质对猪肉肌原纤维蛋白(myofibrillar protein,MP)乳化特性的改善效果。以不同均质压力(20 MPa和40 MPa)分别处理肌原纤维蛋白1次和2次,测定肌原纤维蛋白的乳化特性和结构特性。均质处理能够改善肌原纤维蛋白的溶解性、乳化活性和乳化稳定性,提高乳化液的电位以及降低蛋白的粒径,其中以40MPa均质处理1次,效果最为显著。随着均质压力的增加,总巯基含量降低而活性巯基含量先升高后降低,同时表面疏水性表现出上升趋势。红外光谱表明均质处理能够改变肌原纤维蛋白的二级结构,α-螺旋和β-折叠含量减少,β-转角和无规卷曲含量增加。高压均质能够改善MP的乳化特性,为高压均质应用于肌原纤维蛋白的实际生产及改善肉类制品的品质提供了理论依据。     

l‐histidine improves water retention of heat‐induced gel of chicken breast myofibrillar proteins in low ionic strength solution

The effects of 5 mm l ‐histidine (l ‐His) on water‐binding capacity, gel strength, thermal gelling properties of chicken breast myofibrillar proteins (MPs) in 1 mm NaCl or 0.6 m NaCl solutions (pH 7.0) were investigated. l ‐His could significantly increase the solubility and thermal gelling ability of MPs in 1 mm NaCl. l ‐His at 1 mm NaCl shortened the water relaxation time and decreased the water mobility of MPs gel. l ‐His promoted the formation of MPs gel structure with small pores and thin strands at 1 mm NaCl. These resulted in the enhanced water retention and weak gel strength of MPs in low ionic strength solution. The water‐binding capacity of MPs gels formed in 1 mm NaCl containing 5 mm l ‐His was equivalent to that with 0.6 m NaCl. The information could offer certain theoretical foundation to apply l ‐His as sodium salt substitute for developing low‐salt meat gelling product with high yield.     

Mass transfer dynamics during high pressure brining of chicken breast

The objectives of this study were to investigate the changes in mass transfer, textural properties and water holding capacity of chicken breast when brine treated under different pressures. Chicken breasts were treated for up to 20 min in 4% sodium chloride solution under five pressures: 50, 100, 150, 200, and 300 MPa at 25 ± 1 °C. The results indicated that the total weight and water uptake of the chicken breast increased with increasing pressure up to 150 MPa, and then decreased with further pressure increase up to 300 MPa. Chicken breast samples brined at 150 MPa, with a sodium chloride effective diffusivity value of 2.96 × 10⁻⁸ m²/s, exhibited minimum hardness and maximum water holding capacity. In general, pressure treatment at 150 MPa was found to be the most suitable level for curing based on its higher yield, effective diffusivity and improved texture and water holding capacity.     

高压均质在液态食品杀菌中的研究进展

高压均质是一种非热加工技术,随着高压技术和设备的发展和革新,现今高压均质的压力可以达到400 MPa,为食品杀菌提供了新思路。相关研究认为高压均质通过剪切、碰撞、空穴、湍流、涡旋、加热等结合效应对食品中的致病菌和腐败微生物产生破坏作用。本文介绍了高压均质的作用原理,结合微生物、食品物料的理化特性、均质条件等因素讨论该技术在食品杀菌中的研究进展,并分析了该技术的应用前景。      

Contribution of sarcoplasmic proteins to myofibrillar proteins gelation

Surimi, a refined protein extract, is produced by solubilizing myofibrillar proteins during the comminuting and salting stages of manufacturing. The resulting paste gels on heating to produce kamaboko or a range of analog shellfish such as crab claw, filament sticks, fish mushroom, and so on. The myosin molecule is the major myofibrillar protein in gelation. It is believed that washing steps during the traditional surimi process play an important role in enhancing the gel properties of the resultant kamaboko by removing water-soluble (sarcoplasmic, Sp-P) proteins. By contrast, some researchers claim that retaining Sp-P or adding it into the surimi gel network not only does not interfere with the action of myofibrillar proteins during the sol-gel transition step but also improves the gel characteristics of the resultant kamaboko. It seems that retention of Sp-P or their addition into raw surimi does enhance the textural properties of kamaboko gel perhaps by functioning as a proteinase inhibitor, particularly against trypsin and trypsin-like proteinases but this depends on the type of applied surimi process. Among different types of Sp-P, it has been claimed that some proteins such as endogenous transglutaminase (TGase) play a more important role than other Sp-P in bond formation, by catalyzing the cross-linking of myosin heavy chain (MHC) molecules during low-temperature setting of surimi, resulting a more elastic kamaboko gel.     

Preliminary study on the effect of caspase-6 and calpain inhibitors on postmortem proteolysis of myofibrillar proteins in chicken breast muscle

The objective was to determine the effect of three different protease inhibitors, caspase-6 specific inhibitor VEID-CHO (N-Acetyl-Val-Glu-Ile-Asp-al), calpain inhibitor leupeptin or calpain inhibitor EGTA on protein degradation, ultrastructure of myofibrils and calpain activity during postmortem (PM) aging of chicken muscle. Results showed that proteolysis of nebulin, troponin-T and desmin during 14-days postmortem storage were inhibited significantly by leupeptin. Inhibitive effects of VEID-CHO and EGTA on these protein degradations were significant only during 1-day postmortem storage. The activities of calpains were inhibited noticeably by leupeptin and EGTA, but not by VEID-CHO. Samples treated with VEID-CHO, leupeptin and EGTA retarded structural disruption of chicken muscle fibers. These results demonstrate that calpain is a major contributor to PM tenderization; while caspase-6 plays, if any, a minimal role in the conversion of chicken muscle to meat.     

高压均质对大米蛋白功能特性及物化特性的影响

试验研究了不同均质压力(0~120 MPa)对浓度4%的大米蛋白功能特性和物化特性的影响。结果表明:随着压力的增加,大米蛋白的溶解性显著增加(P0.01),且在120 MPa下达到最大,为82.09μg/mL;乳化活性指数先增大后降低,在80 MPa下达到最大,为14.82 m~2/g;乳化稳定性指数降低。在压力的作用下,大米蛋白的粒径减小;离子键变化不显著(P0.05);氢键、疏水相互作用、巯基及二硫键的含量均发生显著性变化(P0.05),表明高压均质对大米蛋白的三维结构产生一定的影响。     

Use of low-field nuclear magnetic resonance to characterize water properties in frozen chicken breasts thawed under high pressure

The state of water in high-pressure-thawed and conventionally water bath-thawed chicken breasts was analyzed using low-field nuclear magnetic resonance. The influence of high-pressure thawing on water holding capacity, including thawing loss, cooking loss and expressible fluid, was evaluated. Thawing loss was significantly reduced (p < 0.05) compared to the conventional thawing method but neither cooking loss nor total expressible fluid changed significantly (p > 0.05). Higher thawing pressures lead to the T₂₁ relaxation time being increased from 39.9 to 55.9 ms, and P₂₁ increased from 89.5 to 94.9 %. Significant negative correlations (p < 0.01) were observed between the thawing loss and T₂₁, T₂₂, P₂₁. These results indicate that high thawing pressures can transform the water from the loosely bound water fraction (T₂₂) to a more tightly bound (T₂₁) water fraction with the increase in water relaxation time.     

Comparison of reduction in foodborne viral surrogates by high pressure homogenization

With the increasing global spread of human noroviral infections and the emergence of highly virulent noroviral strains, novel inactivation methods are needed to control foodborne outbreaks. High pressure homogenization (HPH) is a novel method that can be applied for foodborne virus reduction in fluids being continuously processed. Our objective in the present study was to compare the titer reduction by HPH between feline calicivirus strain F9 (FCV-F9) and murine norovirus 1 (MNV-1) as surrogates for human noroviruses, and MS2 (single-stranded F-RNA coliphage) and somatic coliphage φX174 (single-stranded DNA) as indicators of fecal contamination. Duplicate experiments with each virus in phosphate-buffered saline were carried out with homogenization pressures of 0, 100, 200, 250, and 300 MPa, with exposure temperatures of 24, 46, 63, 70, and 75°C, respectively, for <2 s. FCV-F9 was found highly susceptible to HPH treatment pressures of 300 MPa, with a reduction of >4.95 log PFU/ml. Lower pressures of 250, 200, and 100 MPa resulted in reductions of 1.61, 0.60, and 0.18 log PFU/ml of FCV-F9, respectively, while MNV-1 was not reduced at these lower pressures. Coliphage φX174 showed no significant reduction at 300 MPa or lower homogenization pressures in comparison with MS2, which did show 3.3-log PFU/ml reduction at 300 MPa. Future studies using juices for industrial application of HPH to determine microbial inactivation with simultaneous retention of sensory and nutritional value of foods are needed.     

高压均质压力对烟用料液中致香物质含量的影响

  目的  研究高压均质压力对烟用料液中主要致香物质含量的影响,为该技术在烟用料液生产加工中的应用提供数据支撑。  方法  分别设定不同的均质压力（0 MPa、60 MPa、90 MPa、120 MPa、150 MPa）对同一批次烟用料液进行高压均质处理,检测均质后料液中的致香物质,并利用单因素方差分析、回归分析和聚类分析研究不同均质压力条件下料液中致香物质含量的差异性及变化趋势。  结果  (1) 当均质压力从0 MPa升高至150 MPa,对所检测到的22种主要致香物质含量均产生了显著性影响,其中有18种致香物质含量呈逐渐增加的趋势。(2)在实验范围内,随着均质压力的升高,料液中的各类致香物质含量及其总量呈逐渐增加的抛物线型变化趋势,且回归方程的拟合度均较高（R2≥0.8778）。(3)几个不同均质压力处理后的料液样品可以分为中低压（60 MPa和90 MPa）和高压（120 MPa和150 MPa）两类,说明当均质压力由90 MPa升高至120 MPa后,对料液中的整体致香物质含量产生了非常显著的影响。  结论  高压均质技术可以有效提升烟用料液中的小分子致香物质含量。验证实验结果表明,高压均质技术主要通过促进料液中大分子物质的降解或水解反应,从而增加了小分子物质的含量。      

高压均质技术提高烟用料液稳定性

  目的  为改善烟用料液的均一性,避免分层、沉淀产生,运用高压均质技术提高料液的稳定性。  方法  通过选取不同的均质压力、均质次数探讨高压均质对料液稳定系数、离心沉淀率、颗粒粒径、烟草提取物粘度及颗粒沉降速率的影响。  结果  :（1）随着均质压力的升高,料液的稳定系数先增加后下降,离心沉淀率减小后又增大,均质压力120 MPa时料液稳定性较好;（2）随着均质次数的增加,料液的稳定系数增加,离心沉淀率下降后上升,根据回归分析的结果,均质次数7次时料液稳定性较好;（3）增大均质压力至150 MPa,料液颗粒粒径显著减小（均质前:1.02 μm;均质后:0.4 μm,P < 0.01）,增加均质次数对料液颗粒粒径无显著影响;（4）均质次数较均质压力对料液烟草提取物粘度的影响更为显著;（5）增加均质压力至120 MPa,颗粒在料液中的沉降速率减小约45%（均质前:1.98 μm/s;均质后1.07 μm/s,P < 0.05）。  结论  高压均质技术可有效提高烟用料液均一、稳定性。      

壳聚糖的高压均质降解动力学研究

采用高压均质技术(piston-gap型高压均质机)降解壳聚糖,考察循环次数及原料相对分子质量对其降解效果的影响,研究高压均质降解动力学,探讨其降解产物相对分子质量与循环次数之间的关系。结果表明:高压均质降解效果随循环次数的增加及原料相对分子质量的增大而提高;壳聚糖的高压均质降解过程遵循一级反应动力学;壳聚糖降解产物的相对分子质量与循环次数之间存在函数关系。     

微射流均质机的超微粉碎机理分析

根据微射流均质机的工作原理,将物料的粉碎过程分成3个阶段:进入阀孔段、经过和离开阀孔段和靶板撞击段,结合Griffith的强度理论和流体动力学的数值模拟,对各段的超微粉碎作用形式和效果进行分析.结果表明,在液流加速进入阀孔阶段,压力梯度、空化效应是料液中的悬浮物破碎的关键机制;经网孔喷出段的湍流碰撞与摩擦加剧了颗粒的剪切破碎;靶板撞击段强化了破碎效果.     

Fate of Staphylococcus aureus in cheese treated by ultrahigh pressure homogenization and high hydrostatic pressure

We evaluated the influence of ultrahigh pressure homogenization (UHPH) treatment applied to milk containing Staphylococcus aureus CECT 976 before cheese making, and the benefit of applying a further high hydrostatic pressure (HHP) treatment to cheese. The evolution of Staph. aureus counts during 30 d of storage at 8°C and the formation of staphylococcal enterotoxins were also assessed. Milk containing approximately 7.3 log₁₀ cfu/mL of Staph. aureus was pressurized using a 2-valve UHPH machine, applying 330 and 30 MPa at the primary and the secondary homogenizing valves, respectively. Milk inlet temperatures (T_in) of 6 and 20°C were assayed. Milk was used to elaborate soft-curd cheeses (UHPH cheese), some of which were additionally submitted to 10-min HHP treatments of 400 MPa at 20°C (UHPH+HHP cheese). Counts of Staph. aureus were measured on d 1 (24 h after manufacture or immediately after HHP treatment) and after 2, 15, and 30 d of ripening at 8°C. Counts of control cheeses not pressure-treated were approximately 8.5 log₁₀ cfu/g showing no significant decreases during storage. In cheeses made from UHPH treated milk at T_in of 6°C, counts of Staph. aureus were 5.0 ± 0.3 log₁₀ cfu/g at d 1; they decreased significantly to 2.8 ± 0.2 log₁₀ cfu/g on d 15, and were below the detection limit (1 log₁₀ cfu/g) after 30 d of storage. The use of an additional HHP treatment had a synergistic effect, increasing reductions up to 7.0 ± 0.3 log₁₀ cfu/g from d 1. However, for both UHPH and UHPH+HHP cheeses in the 6°C T_in samples, viable Staph. aureus cells were still recovered. For samples of the 20°C T_in group, complete inactivation of Staph. aureus was reached after 15 d of storage for both UHPH and UHPH+HHP cheese. Staphylococcal enterotoxins were found in controls but not in UHPH or UHPH+HHP treated samples. This study shows a new approach for significantly improving cheese safety by means of using UHPH or its combination with HHP.     

鸡肉肌原纤维蛋白静态流变特性的研究

利用流变仪研究了肌原纤维蛋白(MP)浓度、温度、pH和离子强度四个因素对肌原纤维蛋白静态流变特性的影响.运用幂率定律计算出K(粘度系数)和n(流变指数).结果表明:MP样品的剪切应力均随着MP浓度和离子强度的增大而上升,而随着温度和pH的上升先增大后减小;K和n与肌原纤维蛋白浓度,温度,pH和离子强度有关;肌原纤维蛋白溶液的n值最大为0.463,当MP溶液浓度为30mg/mL,pH6.0,离子强度0.6时,n值最小为0.162,且n值随MP浓度和离子强度的增加而降低,说明流体假塑性随MP浓度和离子强度的增加而增加.     

Potential of high pressure homogenization in the control and enhancement of proteolytic and fermentative activities of some Lactobacillus species

Different species of Lactobacillus involved in dairy product fermentation and ripening were considered in order to study the effect of high pressure homogenization (HPH) on: (i) fermentation kinetics of HPH treated cells inoculated in milk; (ii) metabolic profiles; (iii) release of intracellular proteolytic enzymes; and (iv) enhance of the activity of extracellular or cellular wall located proteolytic enzymes. The HPH treatments applied were 50, 100, 150 MPa, 2 cycles at 50 and at 100 MPa. The viability loss did not exceed 1.3 log cfu/ml after the higher treatments applied. The electrophoretic profiles of α- or β-casein incubated with the different cell free filtrates shown that HPH positively affected the proteolytic activity of some strains. Moreover, HPH affected the acidification rates of the milk inoculated with the processed cells and the primary metabolism of some strains. Regarding volatile compounds, ethanol, acetoin and 2-methyl butyric acid were subjected to the major changes when the inoculum had been processed.     

鸡肉肌原纤维蛋白静态流变特性的研究

利用流变仪研究了肌原纤维蛋白(MP)浓度、温度、pH和离子强度四个因素对肌原纤维蛋白静态流变特性的影响。运用幂率定律计算出K(粘度系数)和n(流变指数)。结果表明:MP样品的剪切应力均随着MP浓度和离子强度的增大而上升,而随着温度和pH的上升先增大后减小;K和n与肌原纤维蛋白浓度,温度,pH和离子强度有关;肌原纤维蛋白溶液的n值最大为0.463,当MP溶液浓度为30mg/mL,pH6.0,离子强度0.6时,n值最小为0.162,且n值随MP浓度和离子强度的增加而降低,说明流体假塑性随MP浓度和离子强度的增加而增加。      

响应面法优化鸡胸肉肌原纤维蛋白酶法水解工艺条件

以鸡胸肉为原料,提取肌原纤维蛋白,测定其蛋白质浓度及氨基酸组成;以水解度为测定指标,利用响应面法优化该肌原纤维蛋白酶解工艺条件,并考察其产物肽分子量分布。结果表明:提取的肌原纤维蛋白浓度为59.27%;该蛋白氨基酸种类齐全,组成比例均衡,必需氨基酸含量高达40.90%;碱性蛋白酶是肌原纤维蛋白酶解的最佳用酶;在单因素实验基础上,经Box-Behnken实验优化得到碱性蛋白酶水解肌原纤维蛋白最佳工艺条件为:加酶量3500 U/g、p H7.8、温度44℃,此条件下经6 h酶解,水解度达33.17%;肽分子量分布分析知,最佳水解条件下酶解液中<1000 u的小肽含量高达61.5%,说明碱性蛋白酶能较高程度的水解肌原纤维蛋白。      

响应面法优化鸡胸肉肌原纤维蛋白酶法水解工艺条件

以鸡胸肉为原料,提取肌原纤维蛋白,测定其蛋白质浓度及氨基酸组成;以水解度为测定指标,利用响应面法优化该肌原纤维蛋白酶解工艺条件,并考察其产物肽分子量分布。结果表明:提取的肌原纤维蛋白浓度为59.27%;该蛋白氨基酸种类齐全,组成比例均衡,必需氨基酸含量高达40.90%;碱性蛋白酶是肌原纤维蛋白酶解的最佳用酶;在单因素实验基础上,经Box-Behnken实验优化得到碱性蛋白酶水解肌原纤维蛋白最佳工艺条件为:加酶量3500 U/g、p H7.8、温度44℃,此条件下经6 h酶解,水解度达33.17%;肽分子量分布分析知,最佳水解条件下酶解液中1000 u的小肽含量高达61.5%,说明碱性蛋白酶能较高程度的水解肌原纤维蛋白。