Effect of pressure and holding time on colour,protein and lipid oxidation of sliced dry-cured Iberian ham and loin during refrigerated storage

The effect of high pressure (HP) treatments (200 MPa 15 min, 200 MPa 30 min, 300 MPa 15 min, 300 MPa 30 min) on colour, lipid and protein oxidation in sliced vacuum-packed dry-cured Iberian ham and loin during refrigerated storage (90 days, + 4 °C) was evaluated. Pressure level and holding time increased the extent of lipid oxidation in both products. Dry-cured ham showed a higher susceptibility to lipid oxidation than dry-cured loin since HP treatment increased TBA-RS values in dry-cured ham samples while HP treatment decreased TBA-RS values in dry-cured loin samples. However, HP treatment did not affect protein oxidation in both meat products. On the other hand, HP treatment affected instrumental colour since non-pressurized dry-cured meat products showed higher redness than pressurized ones. Regarding changes under storage, after 90 days of refrigerated storage lipid and protein oxidation increased while redness decreased in both HP treated and non-treated dry-cured meat products. Changes induced by HP were only noticeable after HP treatment, as storage reduced the initial differences between HP treated and non-treated samples. Therefore, the lack of differences in long stored dry-cured ham and loin HP treated and non-treated indicates that the application of HP (200–300 MPa/15–30 min) could not affect the quality of dry-cured meat products.Industrial relevanceDry-cured meat products are the meat-based products with the highest sensory quality in Spain and have a high projection in exterior markets. High pressure processing is effective in controlling pathogen and spoilage microorganisms in meat and meat products although it can promote color and oxidation changes that modify sensory characteristics. The study aimed the evaluation of pressure and holding time on color changes and protein and lipid oxidation at vacuum packed slices of Iberian dry-cured ham and loin during subsequent extended chilled storage. High pressure treatment of dry-cured Iberian ham and loin induce changes after treatment although initial differences are not maintained along refrigerated storage.     

类PSE禽肉的品质特征探讨及研究进展

类苍白、柔软、汁液易流失(pale,soft and exudative,PSE)禽肉现象是禽肉屠宰加工中长期存在的问题,给禽肉工业带来了严重的经济损失。本文简述了类PSE禽肉历史,然后探讨类PSE禽肉的品质特征(颜色、p H值、质构特性、保水性)和分类标准,论述类PSE禽肉蛋白质功能特性包括蛋白质溶解性和凝胶特性劣变机制,最后分析类PSE禽肉蛋白质功能特性改善的方法和发展方向,以期为禽肉工业中解决类PSE禽肉蛋白质功能特性劣变问题提供理论依据和技术支持。     

High pressure induced changes in beef muscle proteome: Correlation with quality parameters

The relationship between pressure induced changes on individual proteins and selected quality parameters in bovine longissimus thoracis et lumborum (LTL) muscle was studied. Pressures ranging from 200 to 600 MPa at 20 °C were used. High pressure processing (HPP) at pressures above 200 MPa induced strong modifications of protein solubility, meat colour and water holding capacity (WHC). The protein profiles of non-treated and pressure treated meat were observed using two dimensional electrophoresis. Proteins showing significant differences in abundance among treatments were identified by mass spectrometry. Pressure levels above 200 MPa strongly modified bovine LTL proteome with main effects being insolubilisation of sarcoplasmic proteins and solubilisation of myofibrillar proteins. Sarcoplasmic proteins were more susceptible to HPP effects than myofibrillar. Individual protein changes were significantly correlated with protein solubility, L*, b* and WHC, providing further insights into the mechanistic processes underlying HPP influence on quality and providing the basis for the future development of protein markers to assess the quality of processed meats.     

Gelation of chicken batters during heating under high pressure

The gelling process of chicken meat batters, which were heated (75 °C) under atmospheric pressure or high pressure (200/400 MPa), was investigated by determining the hardness of batter, residual denaturation enthalpy, microstructure, and protein secondary structure. The results showed that meat batters heated at 200 MPa showed a similar increase in hardness to heat-only samples, but meat batters heated at 400 MPa showed a texture decreasing tendency after a limited increase. High pressure disrupted the myofibrils, promoted protein denaturation and aggregation in the first stage of heating under pressure treatment. In the second stage of treatment, heating was the main driving force for protein gelation, which was disturbed by hindering the structural transformation of proteins in the presence of high pressure during heating. The effect of 200 MPa on muscle proteins was relatively gentle and had a less negative effect. Excessive high pressure should be avoided when applying heating under pressure for gel-type meat products processing.Industry relevanceHigh-pressure processing is increasingly applied in the meat industry. By combining high pressure with heating, their effects on texture improvement and microbial inactivation can be maximized. In this study, the influence of high pressure on the texture of meat products was analyzed, which showed that excessive pressure would significantly interfere with the thermal denaturation of the protein, thus adversely affecting the formation of the gel structure. High pressure at 400 MPa and above should be avoided when applying heating under pressure for gel-type meat products processing.     

High-Pressure Pretreatment to Improve the Water Retention of Sodium-Reduced Frozen Chicken Breast Gels with Two Organic Anion Types of Potassium Salts

The effect of high-pressure pretreatment (HPP, 100–300 MPa) before heating on the water holding capacity (WHC) and cooking loss (CL) of sodium-reduced (1.35% NaCl) frozen chicken breast gels with the organic anion types potassium lactate (KL-gel) and potassium citrate (KC-gel) was investigated. The results showed that 100–300 MPa could significantly decrease the CL of both gels, and 200 MPa increased the WHC of the KC-gel (P?<?0.05). HPP could decrease the storage modulus (G′) of meat batters, increase the thermal stability of their proteins, facilitate gelation with a dense and uniform microstructure, and immobilize free water, thus improving the gel’s water retention. The water retention of the pressurized sodium-reduced gel varied with the organic anion types of salts. The water retention was better with pressurized KC-gel than with KL-gel, resulting from higher pH and thermal stability of the batters. These results indicate that proper HPP could improve the water retention of sodium-reduced meat gels with organic potassium salts, thus increasing the economic benefit and properties of sodium-reduced products from frozen meat.     

高压和食盐对鸡肉肠品质特性的影响

在不同压强条件（0.1、200、400 MPa）下对不同食盐添加量（质量分数0%、1%、2%）的生鸡肉肠加热（60 ℃）处理30 min,测定处理后鸡肉肠的持水力、水分分布、质构特性和微观结构,分析高压和食盐对鸡肉肠热诱导凝胶特性的影响。结果发现：常压下,减少食盐添加量会降低鸡肉肠的保水性和质构特性,但高压处理能降低食盐对鸡肉肠的影响。相比常压组,200 MPa高压处理能显著提高产品的保水性和质构特性（P＜0.05）,而400 MPa的高压处理则显著降低产品的保水性和质构特性（P＜0.05）。高压能促进肉糜中的肌纤维分解,使不易流动水的比例升高,自由水比例下降;200 MPa下能形成致密的凝胶网络,而400 MPa则阻碍凝胶网络的形成。高压结合加热处理可用于提高低盐鸡肉肠的品质特性。     

超高压处理对僵直前獭兔肉品质及微观结构的影响

以僵直前獭兔肉为原料,在室温（25 ℃）条件下,分别用100、200、400 MPa超高压处理15 min,－8 ℃贮存24 h,然后对兔肉进行品质分析和超微结构研究。结果表明：随着压力的升高,兔肉亮度（L*）值升高,红度（a*）值降低,兔肉颜色由浅红色逐渐变为灰白;随着压力的升高兔肉蒸煮损失率、滴水损失率呈现先下降后上升的趋势,在200 MPa时兔肉的蒸煮损失率、滴水损失率最低,分别为31.54%和2.61%;超高压对兔肉嫩度影响显著（P＜0.05）,在0.1～200 MPa之间,剪切力随压力增大而降低,而400 MPa处理时,兔肉剪切力急剧升高并显著高于对照组（0.1 MPa）;100 MPa压力处理,兔肉组织结构与对照组相比变化不大,而400 MPa时兔肌肉显微组织结构变化明显：肌节收缩,肌纤维歪曲、片段化,蛋白质发生解聚、三级结构遭到破坏。可见,不同的超高压对僵直前獭兔肉的品质和微观结构有显著影响,且200 MPa是最适于僵直前兔肉处理的超高压条件。     

超高压对低盐海藻鸡肉糜品质的影响

为探究超高压对低盐海藻鸡胸肉糜的影响,考察了不同压力（0.1～500 MPa/10 min）和保压时间 （0～25 min/300 MPa）时肉糜的色泽、盐溶蛋白溶解度、蒸煮损失率、持水性、冻融损失率、质构以及流变特 性的变化规律。结果表明：随着压力的升高,肉糜亮度（L*）和白度（W）先降低后增加,在200 MPa时最低, 红度（a*）逐渐上升;100～300 MPa超高压处理对盐溶蛋白溶解度无显著影响（P＞0.05）,压力大于300 MPa 时盐溶蛋白溶解度显著降低（P＜0.05）;蒸煮损失率和冻融损失率随压力的升高呈先降低后增加趋势,在压力 为300 MPa时达到最低值;与0.1 MPa处理组相比,100～500 MPa压力处理使肉糜持水性显著升高（P＜0.05）; 硬度和弹性随着压力的增加先升高后降低,在200～300 MPa时达最大值,200、300 MPa处理组间无显著差异 （P＞0.05）;与0.1 MPa处理组相比,超高压处理能够改善海藻鸡胸肉糜的储能模量（G’）和相位角正切值 （tan δ）。保压时间对低盐海藻鸡胸肉糜色泽、盐溶蛋白溶解度、蒸煮损失率无显著影响（P＞0.05）;随着保压 时间的延长,肉糜的持水性、G’、tan δ值和质构得到改善,但保压时间过长（25 min）可破坏肉糜的硬度和弹性。 本研究表明超高压处理能够改善低盐海藻鸡胸肉糜的品质,为新型肉制品的开发提供了理论依据。     

Effects of high pressure, subzero temperature, and pH on survival of Listeria monocytogenes in buffer and smoked salmon

High pressure processing is a novel food preservation technology, applied for over 15 years in the food industry to inactivate spoilage and pathogenic microorganisms. Many studies have shown the differential resistance of bacterial cells to high pressure. Listeria monocytogenes is a bacterium able to grow at refrigerated temperature and to survive for a long time in minimally processed foods such as raw smoked fish. The freezing process does not cause significant decline of L. monocytogenes. The phase diagram of water under pressure permits a pressure treatment under subzero temperature, without the disadvantages of freezing for food quality. The aim of this study was to estimate if combined effects of pressure and subzero temperature could increase the destruction of L. monocytogenes in buffer and in smoked salmon. We investigated effects of high pressure processing (100, 150, and 200 MPa) combined with subzero temperatures (-10, -14, and -18 degrees C) and pH (7.0 and 4.5). Results showed that the most effective high-pressure treatment to inactivate L. monocytogenes was 200 MPa, -18 degrees C, and pH 4.5. The relevance of pressure holding time and the synergistic effect of pressure coupled with the subzero temperature to inactivate bacteria are highlighted. Modifications of physical properties (color and texture) were a lightening of color and an increase of toughness, which might be accepted by consumers, since safety is increased.     

超高压处理对大豆拉丝蛋白特性的影响

本文研究了超高压处理对大豆拉丝蛋白特性的影响，以达到改善其再加工特性的目的。实验利用不同超高压处理条件（200～600 MPa,10～30 min）对大豆拉丝蛋白进行处理，采用傅里叶变换红外光谱、紫外吸收光谱和内源荧光光谱分析超高压对大豆拉丝蛋白结构的影响，并通过持水力、表面相对疏水性、游离巯基含量的变化研究超高压对大豆拉丝蛋白功能特性的影响。结果表明：随着压力和时间的增加，β-折叠、无规则卷曲相对含量上升，大豆拉丝蛋白的二级结构向着无序化方向进行；同时蛋白质三级结构伸展，内部疏水基团暴露量增多，但过大的压力和过长的时间则会使得疏水基团重新包埋。400 MPa、10 min时，大豆拉丝蛋白的持水力、游离巯基含量以及表面相对疏水性达到最大值，分别比对照组高32.87%、41.57%、15.66%。综上，适当条件的超高压处理有利于提高大豆拉丝蛋白再加工特性，这为超高压技术应用于大豆拉丝蛋白的生产提供参考。     

Effect of high pressure treatments combined with various levels of κ-carrageenan on cold-set binding in restructured pork

This study investigated the effects of high pressure processing and κ-carrageenan on cold-set binding in restructured pork meat. High pressure (>200 MPa) combined with carrageenan level higher than 1.5% caused increased breaking force and tensile strength ( P  < 0.05). Increasing the pressure level caused a continuous κ-carrageenan network in the junctions between meat particles, as confirmed by scanning electron microscopy imaging. With regard to the water binding properties, all treatments showed moisture content ranging between 74% and 76%. Increases in pressure levels and holding times tended to improve the water-holding capacity (WHC) of restructured pork; however, the κ-carrageenan concentration showed no relation with WHC. Cooking loss decreased significantly ( P  < 0.05) with increases in both pressure level and κ-carrageenan concentration. By increasing pressure levels, both the L ^*- and a ^*-values increased, but the b ^*-value showed no significant difference ( P  > 0.05) among the treatments, with the exception of 100 MPa for 30 min. The addition of κ-carrageenan had no effect on colour ( P  > 0.05). Therefore, the results indicate that pressure above 200 MPa and addition of 1.5% carrageenan has potential use in cold-set meat restructuring.     

Effect of high-pressure treatment on the quality of prepared chicken breast

In this study, the effect of high-pressure processing (HPP) on the physico-chemical properties and microstructure of prepared chicken breast meat products was investigated. The result showed that the pH and TBARS values of the prepared chicken breast gradually increased, while the total volatile basic nitrogen value constantly decreased with the increase of pressure (0.1–500 MPa). In addition, the colour attributes (L* and a* values) and texture indexes (hardness and chewiness) significantly improved as the pressure increased. The results of low-field nuclear magnetic resonance demonstrated that the peak area of immobilised water (T₂₂) first enhanced and then declined with the increase of pressure, reaching the maximum value at 200 MPa. Moreover, the integrity of microstructure and protein secondary structure of prepared chicken breast were also disrupted. These findings could serve as a theoretical basis for a better application of HPP in prepared chicken breast meat products.     

超高压对鲤鱼肉糜-MgCl2凝胶特性的影响

为研究超高压对低盐鲤鱼肉糜凝胶品质的影响,本文在低盐条件下（2% NaCl）,探讨了不同压力超高压处理（100~400 MPa）对含有0.3%氯化镁（MgCl₂）鲤鱼肉糜凝胶的蒸煮得率、保水性、色泽、质构、凝胶强度和流变学特性的改善作用。结果表明:适当的压力处理结合MgCl₂可以显著提高鲤鱼肉糜的凝胶品质。当处理压力为200 MPa时,鲤鱼肉糜凝胶的蒸煮得率、保水性、硬度、凝胶强度均达到最大值,分别为93.14%、95.24%、3327.25 g、3277 g。与对照组相比,适当的压力处理可以显著改善鲤鱼肉糜-MgCl₂凝胶的储能模量（G'）,同时对产品的色泽影响较小。因此,超高压结合氯化镁可以改善低盐鲤鱼鱼糜凝胶的品质,为低盐淡水鱼糜制品的开发提供理论依据。     

西门塔尔杂交牛不同部位肉间的差异性

测定雄性西门塔尔杂交牛（西门塔尔牛♀×南阳黄牛♂）的肩肉、霖肉、黄瓜条、臀肉、牛腱和牛腩6 个部位肉的蛋白质、脂肪、水分及胶原蛋白含量、pH值、色差、质构、剪切力以及凝胶乳化特性指标。结果表明：西门塔尔杂交牛的牛腩具有高蛋白、高脂肪、低水分含量等特点,且剪切力较高、蒸煮损失较低;霖肉含高蛋白、低胶原蛋白和低水分含量,保水性与凝胶特性较好,但其脂肪含量较低;臀肉具有较高的弹性、咀嚼性和保水性,但凝胶特性和乳化特性较差;肩肉的硬度、弹性和咀嚼性均适中,保水性较差;牛腱的蛋白含量、脂肪含量、解冻损失较低,凝胶弹性和乳化稳定性好;黄瓜条弹性、嫩度、凝胶保水性和乳化性均较好,但解冻损失较大。上述结果表明,西门塔尔杂交牛不同部位肉的特性有显著差异,不同特性的部位肉适宜的加工方式不同。     

超高压处理对牦牛肉贮藏性能的影响

牦牛肉分别经200、400、600 MPa超高压处理480 s，测定4°C条件下贮藏0、4、8、12、16 d后感官、pH、微生物、色泽、蛋白质与脂质氧化情况，以探讨超高压处理对牦牛肉贮藏期内品质的影响。结果表明：超高压处理可以显著降低贮藏期内牦牛肉的菌落总数、总挥发性盐基氮含量（total volatile basic nitrogen, TVB-N）(P<0.05)，延长保质期，且经贮藏4～8 d后能良好保持牦牛肉的感官品质。经超高压处理后牦牛肉L*值、b*值显著增大（P<0.05）,a*值在400 MPa时显著增大（P<0.05）并在贮藏期内维持在最高水平，且400 MPa组各类肌红蛋白（Myoglobin, Mb）含量也表现出良好的肉色稳定性，但a*值在其他压力处理后显著减小（P<0.05）。但经超高压处理后牦牛肉肌原纤维蛋白（Myofibrillar Protein, MP）羰基含量与表面疏水性增高、巯基含量降低，TBARS值升高。Pearson相关性分析结果也表示超高压处理后牦牛肉品质的变化与压力、蛋白质氧化、脂质氧化和微生物相关（P<0.05...     

Physicochemical and functional properties of cowpea protein isolates treated with temperature or high hydrostatic pressure

The effect of thermal (TT, 70 and 90 °C) and high hydrostatic pressure (HHPTs, 200, 400 and 600 MPa) treatments on physicochemical and functional properties of cowpea protein isolates (CPIs) extracted at pH 8.0 (A8) and pH 10.0 (A10) was analyzed. The pH of protein extraction affected some physicochemical properties (surface hydrophobicity (Ho) and denaturation temperature), without affecting the functional properties. Treatments led to the formation of soluble protein aggregates stabilized by disulfide bonds, especially with TT at 90 °C. TT and HHPTs shifted the wavelengths of maximum emission to red and to blue, respectively. All treatments induced unfolding and denaturation. HHPTs was more efficient than TT to enhance gelation and water holding capacities. Interestingly, treated and untreated CPIs exhibited high values of solubility (72–97%). TT and HHPT induced greater changes in physicochemical and functional properties of A8 than in those of A10. Remarkably, functional properties were improved from the less energetic treatments (70 °C, 200 MPa).Industrial relevanceThe comparison between treatments (one traditional and one corresponding to an emerging technology) gives information about the possibility of obtaining modified proteins for different functional purposes. The modified cowpea protein isolates may be used in beverages because of high solubility, in desserts because of gel formation capacity and/or as additives in other foodstuff because of improved water holding capacity. This knowledge would increase the added value of a local production currently marketed without processing.     

Improving water retention of chicken breast meats by CaCl2 combined with pulsed electric fields

Frozen poultry meat is the most widely consumed animal-based food. However, water loss often leads to quality loss of poultry meat. Therefore, the present study sought to investigate the combined effect of calcium chloride (CaCl₂) and pulsed electric fields (PEF) treatment on chicken breast meats and the mechanisms underlying protein degradation. The results showed that the synergistic effect was superior to the single treatment. Compared with the untreated group, the combination of CaCl₂ and PEF increased water holding capacity of chicken breast meats by 16.61% and decreased cooking loss by 28.93%. Low-field nuclear magnetic resonance (LF-NMR) results indicated that the synergistic treatment promoted water molecules' binding capacity in myofibrils of poultry meat, which exhibited higher immobilised water. Additionally, the combination of CaCl₂ and PEF led to increased degradation of proteins of high-molecular weight and surface hydrophobicity of myofibrillar protein. Furthermore, the extension of the protein molecule and microenvironmental changes promoted interaction between protein and water. In conclusion, the synergistic treatment of CaCl₂ and PEF enhanced water retention and improved physicochemical properties of the myofibrillar protein in chicken breast meats.     

Influence of the season on the relationships between NMR transverse relaxation data and water‐holding capacity of turkey breast meat

In the last few years the poultry industry has seen a significant deterioration in meat quality properties during the summer season. The objective of this study was to evaluate the seasonal effect (summer and winter) on turkey meat quality assessed by both conventional and low‐resolution nuclear magnetic resonance (LR‐NMR) analysis. Eighty‐eight breast muscle samples (35 winter and 53 summer) from BUT‐Big 6 turkeys belonging to 16 different flocks, were randomly collected from a commercial processing plant. The samples were analysed for transverse relaxation times (T₂) by LR‐NMR and for initial pH (15 min post mortem), ultimate pH (24 h post mortem) and pH after cooking, temperature at 15 min post mortem, water‐holding capacity (WHC, drip loss, filter paper press wetness and cooking loss) at 24 h post mortem, colour of raw and cooked meat and chemical composition (moisture, lipids and proteins). The results indicate that, during the summer season, turkey breast meat undergoes a relevant WHC decrease. Cluster analysis of the raw LR‐NMR data evidenced the presence of two groups corresponding to samples harvested in each different season. Correlations between the LR‐NMR signal and the conventional parameters measuring WHC were obtained by a recently proposed type of principal component regression (PCR) termed relative standard deviation PCR. Copyright © 2004 Society of Chemical Industry     

Effects of high pressure and ohmic heating on shell loosening,thermal and structural properties of shrimp (Pandalus borealis)

This study aimed at understanding the effects of high pressure (HP) and ohmic heating (OH) on the peelability, the underlying mechanisms of HP- and OH-induced shell tightening, the thermal and structural properties of shrimp parts. HP improved the peelability of shrimp at low pressure level (<350 MPa) and short holding time (≤3 min) and the optimum condition for peeling was at 100 MPa for 3 min at 5 °C. However, a higher pressure level (>350 MPa) led to a decrease in the peelability. High pressure at 600 MPa stabilized cuticular and epidermal collagen and formed new collagen-like structures by new linkages, which strengthened the muscle-shell connection and reduced the peelability. Shrimp meat induced from HP at 100 MPa and 600 MPa had minorly denatured myofibrillar proteins. OH as a blanching method did not significantly improve the peelability of shrimp at most of the studied conditions. Some extreme conditions (e.g. at 50 °C) caused a markedly low peelability due to occurrence of collagen gelatinization. The gel formation from collagen-gelatin transformation under heating added strength to adherence of shell to epidermis and muscle, as a consequence, a difficult peeling was experienced. OH also denatured proteins in shrimp meat and caused loss of astaxanthin.Industrial relevance.The industrial processing of ready-to-eat shrimp involves the on-ice or in-brine maturation process which loosens the shrimp's shell from its meat, and therefore enable the mechanical peeling. However, the traditional maturation is time consuming (up to several days), inevitably leads to reduced quality of shrimp meat. This study shows the possibility of the application of HP at mild pressure levels to promote the shell loosening at short HP processing time (≤3 min). However, at more severe HP conditions could lead to the shell tightening which was caused by HP-induced stabilization of collagen in shell and epidermis. The study also shows that ohmic heating (<5 min) might not be a significant blanching method to support the maturation since OH had minor positive effect on shell loosening at some OH conditions (e.g. 2 or 10% NaCl, 92 V, and 30 or 35 °C), but had a counter effect at most OH conditions especially at high temperature.