Application of high pressure processing to improve the functional properties of pale, soft, and exudative (PSE)-like turkey meat

Improvement of functional and rheological properties of turkey breast meat proteins with different ultimate pHs at 24 h post-mortem (pH₂₄) was attempted using high pressure processing (up to 200 MPa for 5 min at 4 °C). Pressures of 50 and 100 MPa were found to increase the water holding capacity of low pH meat. At these pressures, higher protein surface hydrophobicity and greater exposure of sulfhydryl groups were evident. These elements may have contributed to improved water retention properties of the treated protein. The formation of a better gel network was also evident at 50 and 100 MPa as revealed by the dynamic viscoelastic behavior. Application of high pressure significantly (P < 0.05) increased total protein solubility in both low and normal pH meats. Aggregation of myofibrillar proteins increased in low pH meat at higher pressure (200 MPa) as revealed by SDS-PAGE profile.

Industrial relevance

A major concern in the poultry industry is reduced meat functionality, such as low water holding capacity (WHC) in low pH poultry meat leading to reduced yield causing economic loss in the production of further processed products. An alternative technology to reduce salt and improve water retention properties is by the application of high pressure processing (HPP) to produce healthier food products.     

Physicochemical and structural properties of myofibrillar proteins isolated from pale,soft, exudative (PSE)-like chicken breast meat: Effects of pulsed electric field (PEF)

The present study was performed to clarify the effects of pulsed electric field (PEF) on the physicochemical properties and conformations of myofibrillar proteins (MPs) extracted from pale, soft, exudative (PSE)-like chicken breast meat. Various PEF parameters, including the electric field intensity (0–28 kV/cm) and pulse frequency (0–1000 Hz), were varied. The results showed that as the PEF intensity increased, the solubility, surface hydrophobicity and sulfhydryl group content of the MPs were significantly improved. However, when the intensity exceeded 18 kV/cm, these properties declined, which was possibly due to protein aggregation caused by functional group interactions. Additionally, the PEF treatment altered the rheological properties of PSE-like MPs and induced the formation of low-elasticity MPs. However, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the primary structure of the MPs was not altered after the PEF treatment. According to the circular dichroism (CD) spectroscopy results, the α-helix contents of the PEF-treated samples were increased but the β-turn and random coil contents were reduced.Industrial relevanceThe occurrence of PSE-like chicken meat is one of the most serious quality issues worldwide and can decrease the consumer's purchasing desire and result in extensive economic losses for the poultry processing industry. MPs play a vital role in the qualitative characteristics of chicken products. As a potential novel processing technology, PEF has potential applications for improving the functionality of PSE-like chicken protein to expand its application in the food industry.     

不同冻藏条件对鸡胸肉品质特性的影响

为研究不同冻藏条件对鸡胸肉品质特性的影响,本实验以新鲜鸡胸肉为原料,于-16、-26和-36 ℃分别冻藏1、2、3、4、5、6个月,分析比较不同冻藏温度和时间对鸡胸肉的系水力、色泽、蛋白质变性程度、嫩度、脂肪酸败及新鲜度的影响情况。结果表明,随着冻藏温度的升高及冻藏时间的延长,pH呈现先降低后升高的趋势,鸡胸肉的解冻损失率、蒸煮损失率、剪切力以及b*值也逐渐增加,L*值、总蛋白及肌原纤维蛋白溶解度显著降低(p<0.05),但对肌浆蛋白的溶解度无显著影响(p<0.05);a*值则在冻藏前1个月显著增加(p<0.05),但随后逐渐降低,且随着冻藏温度升高而减小(p<0.05)。衡量系水力指标的解冻损失和蒸煮损失结果,衡量色差的L*、a*和b*值以及衡量蛋白变性指标的三大蛋白溶解度和TBARS值与TVB-N值均表明,鸡胸肉在冻藏温度为-36~-26 ℃及冻藏时间为5个月内能有效维持较好的鸡胸肉食用品质。此外,各指标间的相关性分析表明,不同冻藏条件下解冻损失率、蒸煮损失率、剪切力、TVB-N值、TBARS值、a*值、b*值、蛋白溶解度与新鲜鸡胸肉呈现显著的差异(p<0.05),而pH、L*值与新鲜鸡胸肉差异不明显(p>0.05)。本文为快速发展的冷冻禽肉的加工及贮藏环境提供了理论依据。     

Can calcium chloride injection facilitate the ageing-derived improvement in the quality of meat from culled dairy cows?

This study investigated whether the positive effects of ageing on tenderness of meat from culled dairy cows can be facilitated by CaCl₂. Injections of 250 mM CaCl₂ solution (10% wt/wt) were performed on Longissimus dorsi samples from 32 7-yrs old cows. Samples were vacuum packaged and aged for 0, 1, 3, 5 and 7 days. Ageing alone produced lighter and less red meat with lower shear force, higher myofibrillar fragmentation and tenderness scores but also elevated lipid oxidation. For most traits investigated, CaCl₂-injected meat exhibited similar ageing effects, but drip loss increased with age. The CaCl₂-injected meat had a lower shear force and myofibrillar fragmentation increased more rapidly, but drip loss, off-flavour scores, colour stability and oxidative stability were inferior to untreated meat. Overall, it was found possible to accelerate tenderisation of such meat with CaCl₂, but only at the cost of adverse effects in some other quality traits.     

Effect of chloride salts on protein extraction and interfacial protein film formation in meat batters

Six comminuted chicken breast meat mixes and six meat batters were made with isoionic NaCl (25 g kg^?1), MgCl₂, CaCl₂, KCl, LiCl (IS = 0.43) and 15 g kg^?1 NaCl (IS = 0.26). The quantity and type of proteins extracted and used for interfacial protein film (IPF) formation was determined and related to batter stability. The monovalent salts produced IPF which differed in individual protein content between salts but which all contained significantly larger amounts of protein (P < 0.01) than those using divalent salts. MgCl₂ extracted more protein than CaCl₂ and produced a different protein profile in the IPF. However, MgCl₂ formed unstable raw batters whereas CaCl₂ did not. In addition, a simple, rapid method for extracting and quantifying proteins from meat batters was developed to assist in direct determination of the actual soluble protein uptake by the fat phase during comminution.     

Combination treatment of high-pressure and CaCl2 for the reduction of sodium content in chicken meat batters: effects on physicochemical properties and sensory characteristics

A combination of high-pressure processing (HPP, 200 MPa, 10 min) and CaCl₂ (0.2%, w/w) on the cooking loss (CL), expressible moisture (EM), textural properties (hardness, springiness, cohesiveness, chewiness and firmness) and sensory attributes of reduced-sodium (1.25% NaCl) chicken meat batters (RCMB) was investigated. The results revealed that combining HPP with CaCl₂ significantly decreased EM, elevated sensory properties and acted synergistically in reducing CL and improving hardness, chewiness and firmness, which enabled RCMB to obtain quality characteristics similar to those with high salt (2.5% NaCl) content. These changes brought about by combined HPP and CaCl₂ could be attributed to increased apparent viscosity and proportion of immobilised water, enhanced rheological (elastic) properties and a denser, homogeneous protein gel network with evenly dispersed small fat globules. It is interesting to take advantage of the synergy between moderate HPP and low concentrations of CaCl₂ to develop meat products with reduced sodium content.     

Improved gelation functionalities of myofibrillar protein from pale,soft and exudative chicken breast meat by nonenzymatic glycation with glucosamine

The potential of nonenzymatic glycation of myofibrillar proteins (MPs) to improve the gelation functionalities of pale, soft and exudative (PSE‐like) chicken breast meat was investigated. MP suspensions (4 mg mL^?1) obtained from both normal and PSE‐like chicken breast meat were mixed with glucosamine at a ratio of 1:6 (protein : glucosamine) in phosphate‐buffered saline (0.6 m KCl, 20 mm K₂HPO₄/KH₂PO₄, 0.02% NaN₃ and pH 7.5) and incubated at 37 °C for 12 h. Untreated normal and PSE‐like MP suspensions maintained at 4 °C were used as positive and negative controls, respectively. The glycation treatment increased the surface hydrophobicity but decreased the reactive sulfhydryl contents compared to those of the control (P < 0.05), indicating that the tertiary conformation of the protein changed. Correspondingly, these glycated samples also exhibited significant improvements in gel strength and the water‐holding capacity (P < 0.05). Conclusively, nonenzymatic glycation is a potential technique to improve the properties and offer a means for effective use of PSE‐like meat.     

Chicken breast quality – normal,pale, soft and exudative (PSE) and woody – influences the functional properties of meat batters

Three classes (normal, PSE‐like and woody, thirty for per class) of fresh chicken breast meats were selected from a Chinese processing plant. Then, three classes of chicken breast meats were used to prepare meat batters and meatballs. This study investigated the effects of three classes of chicken breast meat on the physicochemical properties, water distribution, protein secondary structures and microstructures of meatballs. PSE‐like and woody meatballs both had lower water holding capacity and textural properties than normal meatballs. Furthermore, the free water mobility and proportion in PSE‐like and woody meatballs were increased (P < 0.05). According to near‐infrared spectroscopy results, the intensity of the 1940‐nm bands of PSE‐like and woody classes both increased. Both PSE‐like and woody meatballs formed more aggregated gel matrices than normal class. PSE‐like and woody classes had higher α‐helix and lower β‐structure contents (P < 0.05). Overall, compared with normal meatballs, PSE‐like and woody meatballs showed inferior functional properties.     

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.     

基于低场核磁共振探究解冻过程中肌原纤维水对鸡肉食用品质的影响

本研究旨在基于低场核磁共振横向弛豫时间T2分析解冻过程中肌原纤维水的分布及流动性与鸡肉食用品质间的关联性。以冷鲜鸡胸肉（宰后32 h）为对照,采用冷藏解冻、微波解冻（微波-1、微波-2）与超声解冻（180、200 W）5 种不同方式解冻中心温度为－20 ℃的冻结鸡胸肉,测定肉样T2、品质特性指标并分析它们之间的相关性。结果显示：解冻过程中肉样的T2水分分布情况发生明显变化,与对照组相比,除微波-2解冻外,其余4 组解冻肉样均发生不易流动水T22（40～50 ms）向自由水T23（100～250 ms）迁移;同时,微波-2解冻与200 W超声解冻出现强结合水水分群T20（0～0.1 ms）;相关性分析表明,T20、T21和T22峰比例与肉样的持水能力、嫩度和多汁性呈极显著正相关（P＜0.01）,与解冻损失率、蒸煮损失率呈显著（P＜0.05）或极显著（P＜0.01）负相关;剪切力与T20峰比例呈显著负相关（P＜0.05）,与T22峰比例呈极显著负相关（P＜0.01）。解冻方式对肉样的外观和风味无显著影响（P＞0.05）,微波-2解冻肉样的质地与多汁性评分最接近于对照组,整体可接受性更高;冷藏解冻与超声解冻肉样的质地与多汁性更差,整体可接受性也更低。因此,本项研究结果表明在解冻过程中肌原纤维水的迁移情况对鸡肉品质具有显著影响,并且微波-2解冻程序能够更好地抑制解冻过程中肉品质的下降。     

The interaction of pulsed electric fields and texturizing ‐ antifreezing agents in quality retention of defrosted potato strips

The combination of pulsed electric fields (PEF) and texturizing and antifreeze agents on quality retention of defrosted potato strips were studied. Potato strips (10 mm thickness, 100 g) were placed in different solutions (1% w/v) of CaCl₂, glycerol, trehalose as well as NaCl and sucrose, treated with PEF (0.5 kV cm^?1, 100 pulses, 4 Hz). Then, all the samples were soaked in the same solutions for 10 min. After draining, samples were packed into polypropylene pouches and stored at ?18 °C for 12 h. Samples were thawed out at room temperature (20 °C) in 3 h. Untreated controls and PEF treated control samples were also frozen and thawed in similar conditions. To assess the potato strip quality, the thawed samples were analysed for moisture content, weight loss, firmness and colour attributes. The results indicate that PEF treatment by itself is not a suitable pre‐treatment method for frozen potato strips and should be assisted by CaCl₂ and trehalose treatment to prevent softening after defrosting. Firmness analyses determined that application of PEF alone results in 2.38 N. However, PEF in combination with CaCl₂ and trehalose result in 2.97 N and 2.99 N, respectively, which are both significantly firmer than the samples solely treated with PEF. CaCl₂ and trehalose were effective in not only maintaining the structural integrity of the cells, but also retaining colour attributes. The L* value was found to be higher (P < 0.05) in CaCl₂ and trehalose treated samples (58.95 and 57.21, respectively), as compared to PEF treated samples (53.97) denoting a darker colour. Application of CaCl₂ and trehalsoe in combination with PEF also resulted in significantly less weight loss after thawing.     

Quantitative Detection of Poultry in Cooked Meat Products

ABSTRACT: There is a growing awareness of perceived harm from meat species adulteration, both intentional and accidental. The present study developed a monoclonal antibody (Mab)-based enzyme-linked immunosorbent assay (ELISA) for the quantitative detection of chicken and turkey meat adulterated in cooked (100 °C, 15 min) mammalian meat. The specificity of Mab 5D2 to different species (pork, beef, lamb, deer, horse, duck, chicken, and turkey) and tissues (serum, gizzard, heart, and liver) was studied by noncompetitive ELISA. The detection of cooked chicken in beef, and turkey in pork was accomplished by competitive and noncompetitive ELISAs. Both ELISAs were optimized to quantify cooked poultry in red meats. The new Mab-based ELISAs enabled the detection of cooked poultry in red meats at levels as low as 1% (v/v) or better. The correlation ( r > 0.994) between chicken or turkey concentrations and ELISA signals permitted the quantification of poultry adulterants in cooked non-poultry meats.     

基于宰后蛋白质磷酸化研究L-组氨酸和L-赖氨酸对鸡胸肉加工特性的影响

为研究低盐（1% NaCl）条件下添加L-组氨酸（L-histidine，L-His）及L-赖氨酸（L-lysine，L-Lys）调节宰后鸡胸肉肌原纤维蛋白磷酸化的变化规律及其对鸡胸肉加工特性（蒸煮损失、质构、蛋白溶解度、流变特性）的影响，提取腌制后鸡胸肉肌原纤维蛋白，进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳，再通过荧光染色和液相色谱-串联质谱鉴定。结果表明：L-His和L-Lys的添加不影响肌原纤维蛋白的整体磷酸化水平，但是可以改变单个蛋白质的磷酸化水平；相比于1% NaCl处理组，1% NaCl＋0.06% L-His/L-Lys处理组硬度和蛋白溶解度均有显著提高，蛋白流变特性改善，蒸煮损失无显著变化；相关性分析得出，多个蛋白质磷酸化水平与肉的蒸煮损失及蛋白溶解度等加工特性呈显著正相关或负相关，且单个蛋白质的磷酸化水平还会受到其他蛋白质磷酸化水平的影响；将11 条磷酸化水平差异显著的条带进行质谱鉴定后，发现大多是与肌肉收缩或糖酵解有关的酶，表明L-His、L-Lys的添加可能通过对肌原纤维蛋白磷酸化水平产生正面效应影响宰后僵直成熟过程，进而影响肉品品质。     

Influence of pulsed electric fields (PEF) with calcium addition on the texture profile of cooked black beans (Phaseolus vulgaris) and their particle breakdown during in vivo oral processing

This study investigated the use of pulsed electric fields/PEF (electric field strengths 1–2 kV/cm, specific energy 9–127 kJ/kg) to facilitate calcium uptake into black beans in preserving their hardness from thermal degradation during subsequent cooking (1 h, 70–90 °C). Increasing specific energy reduced CaCl₂ concentration in PEF processing media to 100 ppm to improve the hardness of cooked black beans. Those pre-treated at lower energy required min. 300 ppm CaCl₂. Cooked black beans with PEF-pretreatment shared similar hardness as without PEF but unexpectedly chewier (18–43% more energy to disintegrate the beans). In vivo mastication study showed particle size at 18 and 24 s of mastication was significantly different (p < 0.05) wherein “PEF without CaCl₂” had the smallest particles compared to “No PEF with CaCl₂” and “PEF with CaCl₂”. The outer seed coats of PEF-pretreated beans were easily masticated to smaller and consistent particles. This implies that PEF improved particle breakdown during mastication.     

Effects of Agaricus bisporus on gel properties of chicken myofibrillar protein

The gel-forming ability of myofibrillar protein (MP) is highly correlated with the characteristics of emulsified meat products. Incorporation of Agaricus bisporus (Ab) powder into MP gels may enhance its gel properties to facilitate the development of a novel and safe meat product. Therefore, this study investigated the effects of Ab powder on gel strength, water holding capacity (WHC), texture, rheological behaviour, LF-NMR spin–spin relaxation (T₂), microstructure and protein secondary structure of the MP gel system. The results indicated that the gel strength, WHC, G' value and G" value were significantly improved when the addition of Ab powder increased from 0% to 6% (P < 0.05). Meanwhile, the T₂ relaxation time was shortened, and free water was transformed into immobilised water. The texture of the gel was improved when 1%–4% Ab powder was added compared to the control. Furthermore, Ab filled in the gel network and promoted the unfolding of MP α-helix and the formation of MP β-sheet during the thermal denaturation of MP, leading to a dense aggregated network structure. The study suggested that Ab could be a promising ingredient in improving chicken MP's gel properties and developing fat-reduced meat products.     

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).     

Textural properties and microstructure of low-fat and sodium-reduced meat batters formulated with gellan gum and dicationic salts

Instrumental texture characteristics of low-fat, reduced-sodium meat batters formulated with other salts (KCl and MgCl₂ or CaCl₂) with gellan gum were evaluated. Fat and sodium reduction through incorporation of gellan gum and either of the dicationic salts produced less rigid, more ductile structures. Inclusion of magnesium chloride resulted in better performance, whereas addition of calcium chloride resulted in less desirable properties. The dicationic salts level used probably inhibited the gellan gum thermoreversible properties, affecting its water holding properties. Microstructural differences between the dicationic salt treatments were apparently due to the effect of dicationic salt concentration on myofibrillar protein extraction and solubilization, and gellan gum gelation properties. Use of magnesium chloride in tandem with gellan gum in the studied low-fat, reduced-sodium meat batters effectively compensated for the structural differences caused by fat and sodium reduction.     

Water holding capacity of sodium-reduced chicken breast myofibrillar protein gel as affected by combined CaCl2 and high-pressure processing

The water holding capacity (WHC) of sodium-reduced (0.3 m sodium chloride, corresponding to the salt percentage (w/v) of 1.755%) myofibrillar protein (MP) gel in response to combined calcium chloride (CaCl₂, 20, 60, 100 mm ) and high-pressure processing (HPP, 200 MPa, 10 min) was investigated. The results showed that 200 MPa + 20 mm CaCl₂ synergistically increased the WHC of MP gel via reducing particle size of MP solutions, strengthening hydrogen-bonding and disulphide-bonding, promoting formation of β-sheet and uncoiling of α-helix, exposing tryptophan residues, enhancing hydrophobic interactions of aliphatic residues and forming a compact and continuous networked gel structure. However, high concentrations (≥60 mm ) of CaCl₂ could attenuate the enhancing effects of HPP on the WHC by inducing decreased hydrogen bonds, fewer tryptophan residues exposed and coarser and aggregated gel structures with large cavities. Therefore, a combined moderate HPP and low concentration of CaCl₂ is a potential alternative for developing sodium-reduced meat products.     

The effect of active caspase-3 on degradation of chicken myofibrillar proteins and structure of myofibrils

The objective of this study was to investigate the potential contribution of caspase-3 to meat postmortem tenderisation by examining the role of caspase-3 in the degradation of myofibrillar proteins and disruption of myofibril structure in vitro. Myofibrillar protein prepared from chicken muscle was incubated with EDTA or EDTA plus caspase-3 at 25 °C for 16 h and used for detecting muscle protein degradation and ultrastructure of myofibril. Results revealed that caspase-3 reproduced the degradation patterns of titin, nebulin and α-actinin during postmortem storage of meat, but caused little proteolysis of desmin and no appearance of 28–30 kDa peptides. Meanwhile, caspase-3 also induced the weakening in the I band adjacent to Z-lines, which occurred during meat postmortem ageing. Therefore, caspase-3 could account only for a part of the myofibrillar protein degradation observed in naturally aged meat and is likely involved in postmortem tenderisation of meat together with other endogenous proteases.     

Effect of pulsed electric field on calpain activity and proteolysis of venison

The present study evaluated the effect of pulsed electric field (PEF) on the calpain activity, proteolytic pattern and myofibrillar protein profile of cold-boned Longissimus dorsi obtained from red deer (Cervus elaphus). PEF treated samples, T₁ (2.5 kV, 50 Hz) and T₂ (10 kV, 90 Hz) and a non-treated control were aged for 21 days at 4 ± 1 °C. The samples were analysed for shear force (N), myofibrillar fragmentation index (MFI), calpain activity, proteolysis of desmin and troponin-T and myofibrillar protein profile (SDS-PAGE). No significant impact of PEF was observed on the shear force and MFI. A slight increase was recorded in the calpain activity and proteolysis of troponin-T, suggesting a tendency of PEF to improve the tenderization process. Collectively, the results from casein zymography, Western blotting and myofibrillar protein profile suggest that PEF did not produce any significant impact on the tenderization process of venison.