包装方式和宰后不同时间包装对羊肉品质的影响

为探究包装方式和宰后不同时间包装对羊肉贮藏品质的影响,本研究对宰后1 h热分割羊肉和冷却成熟24 h后的分割羊肉分别进行热收缩包装、真空包装、贴体包装、50%（体积分数,下同）O2＋50% CO2气调包装,测定其在（2±2）℃贮藏过程中pH值、色泽、贮藏损失率、蒸煮损失率、离心损失率、剪切力、挥发性气味的变化。结果表明：与宰后24 h包装相比,宰后1 h包装羊肉pH值在贮藏14 d时更高,但其贮藏期间色泽较好,色泽稳定性更高,贮藏损失率更低。从整体来看,3 种真空处理（热收缩包装、真空包装、贴体包装）羊肉嫩度均优于气调包装羊肉,且宰后1 h包装时真空条件处理对羊肉嫩化效果最好,宰后24 h羊肉在贮藏前期气调包装对羊肉嫩化效果较好;而无论何时包装,热收缩包装和气调包装羊肉贮藏损失率均显著小于其他处理组（P＜0.05）,在贮藏前期色泽及稳定性较好,但贮藏后期色泽稳定性下降明显,气调包装羊肉在14 d时已部分发绿,贮藏21 d时挥发性气味变化显著。综上,宰后1 h包装有利于提高羊肉贮藏期间色泽及持水力,改善真空处理羊肉嫩度,宰后24 h包装可提高50% O2＋50% CO2气调包装羊肉贮藏前期的嫩度;其中热收缩包装和气调包装羊肉持水力高,贮藏前期色泽及稳定性好,真空包装、贴体包装羊肉品质变化相对稳定,适宜长期贮藏。     

宰后电刺激对新疆多浪羊肉品质的影响

以新疆地方品种多浪羊为研究对象,探讨电刺激对其宰后羊肉品质的影响。结果表明：电刺激显著加快多浪羊宰后肌肉pH值的下降速率（P＜0.05）,显著降低多浪羊肉贮藏损失和宰后1?d的蒸煮损失率（P＜0.05）;电刺激组肌原纤维小片化指数显著高于对照组（0?s）（P＜0.05）,宰后1?d多浪羊肉剪切力显著低于对照组（P＜0.05）。电刺激可以显著降低宰后3?d羊肉的L*值和b*值（P＜0.05）;电刺激能够显著加快宰后初期（14?h内）肌肉无氧糖酵解速率,糖原、三磷酸腺苷和二磷酸腺苷降解速率以及乳酸、一磷酸腺苷和肌苷酸生成速率（P＜0.05）。综合分析3?个不同电刺激时间处理组（30、60、90?s）,其中电刺激60?s对多浪羊肉品质改善效果最佳,可以将电压70?V、频率50?Hz、60?s的电刺激处理作为新疆多浪羊宰后电刺激的参数推广应用。     

Apoptosis during postmortem conditioning and its relationship to duck meat quality

The aim of this work was to examine the relationship of skeletal muscle apoptosis and postmortem development of meat quality. Colour, cooking loss, myofibril fragmentation index (MFI) and shear force of duck breast and thigh meat postmortem were measured, and changes of positive nuclei were assessed with Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphophate nick end-labelling method (TUNEL). Correlation analysis revealed that apoptosis were positively correlated with colour (L^∗, a^∗ and b^∗), cooking loss and MFI (P < 0.05), while it is negatively correlated with shear force (P < 0.05). Our results indicate the growing level of duck skeletal muscle cell apoptosis was associated with the postmortem development of meat quality traits such as meat colour, water holding capacity and tenderness.     

Changes in Shear Parameters,Protein Degradation and Ultrastructure of Pork Following Water Bath and Ohmic Cooking

The objective of this study was to investigate the effects of ohmic (OH) and water bath (WB) cooking on shear parameters, protein degradation and ultrastructure changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range, 20–100 °C). The cooking loss and Warner–Bratzler shear force of the OH-cooked meat were significantly lower (P?<?0.05) while protein solubility, pH and endothermic transition temperature were higher than those obtained by WB cooking at the same EPTs (range, 20–80 °C). Sodium dodecyl sulphate polyacrylamide gel electrophoresis analysis showed that during OH cooking, the meat had slightly fainter protein bands than that of WB-cooked ones. Less obvious shrinkage of the sarcomere and loss in the structure of Z discs were detected especially in OH-cooked meat at EPTs (100 °C). Strong correlations among pH, cooking loss, Warner–Bratzler shear force, sarcoplasmic protein solubility, T _max2, and T _max3 were observed in meat following OH cooking.     

Quality and Nutritional Minerals in Chicken Breast Muscle Treated with Low and High Pulsed Electric Fields

The present research investigated the effects of pulsed electric fields (PEF), low PEF (LPEF, 2.5 kV, 200 Hz and 20 μs) and high PEF (HPEF, 10 kV, 200 Hz and 20 μs), on the quality of chicken breast at 1 and 4 days post-treatment and on the concentrations of minerals (phosphorus, iron, zinc and potassium) in raw and cooked samples. HPEF increased (P < 0.001) the temperature of the chicken breasts. The shear force of chicken breasts was not affected by treatment and post-treatment storage time and their interaction (P > 0.05). The concentrations of P, K, and Zn were decreased by cooking (P < 0.001) only. The concentration of Fe was not affected by treatment, storage time, or cooking. Both LPEF and HPEF treatments did not have negative effects on the quality of chicken breast, indicating that PEF processing of chicken breast does not have a negative impact on the quality.     

高强度超声对鹅胸肉嫩度及品质的影响

为了解超声技术对鹅胸肉品质的影响,采用高强度超声（超声功率800 W,超声总时间42 min,工作时间 2 s、停歇时间3 s）对鹅胸肉进行处理。测定未超声和超声处理的鹅胸肉于4 ℃下放置不同时间（0、6、12、24、 36、48 h）的pH值、肌原纤维小片化指数、蒸煮损失率、剪切力、表面微观结构、肌原纤维蛋白降解情况、肉品 的热力学性质等指标。结果显示：与未经超声处理的鹅胸肉相比,超声处理后随着放置时间的延长,肉品pH值升 高,肌原纤维小片化指数显著增大,蒸煮损失率和剪切力显著减小（P＜0.05）;表面微观结构发生明显变化,肌 动蛋白和肌球蛋白热敏性增大,导致更多肌原纤维蛋白降解,游离肌动蛋白含量显著增加（P＜0.05）,从而显著 改善鹅胸肉的嫩度。因此,超声处理可破坏鹅胸肉肌原纤维的完整结构,缩短宰后肉品成熟所需时间,进一步提高 鹅胸肉的品质。     

不同电刺激处理时间对宰后马肉成熟过程中嫩度的影响

采用不同电刺激处理时间对宰后马肉进行处理,对马肉成熟过程中的蒸煮损失率、剪切力、可溶性蛋白浓度(soluble protein concentration,SPC)、肌原纤维小片化指数(myofibrillar fragmentation index,MFI)、胶原蛋白溶解性及微观结构进行研究。结果表明:不同电刺激处理时间对宰后马肉成熟过程中的蒸煮损失率没有显著影响(P0.05);在一定电刺激处理时间范围内,马肉成熟过程中剪切力下降,SPC上升,MFI上升,胶原蛋白溶解性上升。实验条件下电刺激60 s对改善马肉的嫩度具有较好的效果,进一步延长电刺激处理时间对嫩度的改善效果不明显。电刺激60 s、成熟14 d时,马肉剪切力较对照组下降了13.8%,SPC与MFI分别是对照组的1.16倍与1.28倍,电刺激破坏了马肉的肌纤维结构。适当的电刺激处理能够促进宰后马肉的成熟,使较为粗糙的马肉得到有效的嫩化。本研究为马肉电刺激嫩化机理及产品开发提供了一定的理论依据。     

禁食时间对宰后早期鸡肉持水力和嫩度的影响

三黄鸡分别禁食0、8、16h和24h,三管齐断法宰杀,于宰后5h内分别测定滴水损失、蒸煮损失、加压损失、蛋白溶解性、剪切力值、糖原、乳酸和pH值等指标,观察禁食对宰后早期鸡肉持水力和嫩度的影响。结果表明：随着禁食时间延长,宰后糖原含量(P＜0.05)和pH值均降低;随着宰后时间延长,糖原含量和pH值变化趋势与宰后时间正相关,而乳酸含量变化趋势与宰后时间负相关。宰后早期,pH值对肌肉持水力有显著影响(P＜0.05),而蛋白溶解度对持水力变化贡献不大。禁食使得宰后早期肌肉剪切力值有增大趋势,但处理组之间差异不显著。与未禁食鸡相比,禁食8h和禁食16h能够提高宰后肌肉持水力。     

Effect of cooking temperature and time on the physico-chemical, histological and sensory properties of female carabeef (buffalo) meat

The effect of cooking temperature (80-100°C) and time (30-60min) on collagen solubility of Semimembranosus muscle in carabeef were investigated. The pH, cooking loss, shear force value, collagen content, collagen solubility, sensory evaluation and histological observations of water bath cooked and pressure cooked Semimembranosus meat samples were measured. Increase in pH, cooking loss, collagen solubility and tenderness scores with decrease in shear force value and collagen content was observed with increases in cooking temperature and time. However, no statistical difference was observed for shear force values, collagen solubility values and tenderness scores in pressure cooked meat and meat cooked in a water bath at 100°C for 45min, inferring that cooking of buffalo meat at 100°C for 45min improved collagen solubility and tenderness to the same extent as that due to pressure cooking.     

The Effects of Marination and Cooking Regimes on the Waterbinding Properties and Tenderness of Beef and Bison Top Round Roasts

ABSTRACT: The combined effect of marination and different cooking regimes on the cooking yield and palat-ability of bison and beef top round roasts was investigated. Semimembranosus (SM) muscles from beef and bison top rounds were injected with a marinade to achieve 20% extension by weight and 0.5% sodium chloride and 0.3% sodium tripolyphosphate levels and then subdivided into 4 roasts and cooked by following 4 cooking regimes: cooking at a constant temperature of 75°C (control; C); similar to the control treatment except that roasts were held at an internal temperature of 55°C for 45 min (Hold45) or 90 min (Hold90) prior to final cooking at 75°C; initial cooking at 55°C with a 5°C increase in oven temperature every hour (Step-up) until the 71°C internal temperature was achieved. Cooking yield, expressible moisture, purge, and shear force of processed roasts were determined. Marination by injection improved the yield and tenderness of beef and bison SM roasts. The cooking yield for injected samples (78%) was significantly (P < 0.05) higher compared with noninjected controls (68%). Injected SM roasts from bison had lower cooking losses than those from beef, whereas control samples from these 2 species did not differ in their cooking yields. Injected beef SM was more tender than bison SM; however, marination significantly reduced the shear force values of SM roasts for both species (i.e., shear force values of 82 N in control samples was reduced to 63 N in injected ones). The cooking regimes, Hold45, Hold90, and Step-up (which allowed a longer time at 55 to 60°C), gave products with lower ( P < 0.05) shear force values than those of the controls. Based on the cooking yield and time involved, the Hold 45 treatment performed the best.     

Influence of cooking conditions on cooking loss and tenderness of raw and marinated chicken breast meat

The influence of different cooking treatments on tenderness and cooking loss, as main quality characteristics of chicken breast meat, was investigated. Industrial skinless chicken breast meat samples were designated as raw and marinated and cooked in the oven by hot air and hot air-steam mixture at 130, 150 and 170 °C, for 4, 8 and 12 min. Cooking losses were evaluated by weight changes before and after cooking, and tenderness changes were determined on cooked samples by measuring shear force using instrumental texture analysis. Results showed that marination, followed by air-steam cooking is the best combination to obtain the most tender chicken breast slices. The time and temperature of cooking showed similar effects on cooking loss and tenderness: short cooking time (4 min) and temperatures of 130–150 °C resulted in lower cooking losses and best meat tenderness, in both not marinated and marinated meat. Statistically significant correlations between tenderness and cooking loss indicated that the cooking loss correlated better with cooking time than with cooking temperature. An opposite phenomenon was observed for meat tenderness.     

Process optimisation of pulsed electric fields pre-treatment to reduce the sous vide processing time of beef briskets

This study used multiple regression to model the effect of pulsed electric field (electric field strengths 0.7, 1.0 or 1.5 kV cm⁻¹) and sous vide (60 °C for either 12, 18 or 24 h) processing on the quality parameters (tenderness, cooking loss, colour, lipid stability) of beef brisket. Pulsed electric fields (PEF) at 0.7 kV cm⁻¹ and 1.5 kV cm⁻¹ followed by sous vide processing for 12–20.2 and 20.8–23.7 h, respectively gave the lowest values for hardness (<20.2 N), shear force (100.5 N mm⁻¹ s⁻¹) and cooking loss (<17.4%). PEF treatment prior to sous vide processing had no significant effect on lipid oxidation, colour stability, cooking loss or in vitro protein digestibility of sous vide-processed brisket. Increasing the electric field strength and/or prolonging the sous vide time significantly increased collagen solubilisation in the sous vide brisket. This study demonstrated that a PEF pre-treatment can reduce sous vide processing time while enhancing the tenderness of tough meat cuts.     

延迟冷却对牛肉品质影响的研究

研究了常规冷却和延迟冷却对中国杂交黄牛(鲁西黄牛×西门塔尔)宰后冷却过程中牛胴体pH、温度的变化、胴体冷却失重、背最长肌汁液损失、蒸煮损失、保水性、肉色及成熟过程中剪切力值的变化。结果表明:延迟冷却减缓了牛胴体温度的降低速率(P<0.05),加快了牛胴体pH的降低(P<0.05);延迟冷却提高了牛背最长肌的嫩化速度,改善了肉色(P<0.05),但增加了汁液损失和蒸煮损失,降低了保水性(P<0.05)。因此,优化延迟冷却程序是必要的。     

Tenderness of pre- and post rigor lamb longissimus muscle

Lamb longissimus muscle (n=6) sections were cooked at different times post mortem (prerigor, at rigor, 1dayp.m., and 7 days p.m.) using two cooking methods. Using a boiling waterbath, samples were either cooked to a core temperature of 70 °C or boiled for 3h. The latter method was meant to reflect the traditional cooking method employed in countries where preparation of prerigor meat is practiced. The time postmortem at which the meat was prepared had a large effect on the tenderness (shear force) of the meat (P<0.01). Cooking prerigor and at rigor meat to 70 °C resulted in higher shear force values than their post rigor counterparts at 1 and 7 days p.m. (9.4 and 9.6 vs. 7.2 and 3.7 kg, respectively). The differences in tenderness between the treatment groups could be largely explained by a difference in contraction status of the meat after cooking and the effect of ageing on tenderness. Cooking pre and at rigor meat resulted in severe muscle contraction as evidenced by the differences in sarcomere length of the cooked samples. Mean sarcomere lengths in the pre and at rigor samples ranged from 1.05 to 1.20 μm. The mean sarcomere length in the post rigor samples was 1.44 μm. Cooking for 3 h at 100 °C did improve the tenderness of pre and at rigor prepared meat as compared to cooking to 70 °C, but not to the extent that ageing did. It is concluded that additional intervention methods are needed to improve the tenderness of prerigor cooked meat.     

Optimisation of Sous Vide Processing Parameters for Pulsed Electric Fields Treated Beef Briskets

The goal of this research was to optimise sous vide processing parameters for beef briskets, previously treated with pulsed electric fields (PEF), to enhance meat tenderness while maintaining other quality attributes such as water holding capacity, colour, and collagen solubility. PEF-treated briskets (electric field strength 1.5 kV/cm; specific energy of 90–100 kJ/kg) were subjected to various sous vide temperature and time combinations for the process optimisation using response surface methodology. Sous vide temperature was found to significantly reduce the shear force of PEF-treated meat while time significantly reduced its hardness. In addition, beef briskets processed by PEF prior to sous vide processing showed less variation owing to a reduction in the effect of biological variation on the parameters tested. According to the response optimiser prediction, sous vide processing at 60 °C for 24 h resulted in optimal quality and tenderness. Scanning electron microscopy (SEM) revealed that PEF-treated meat showed evidence of pore formation in connective tissue and polarised-sensitive optical coherence topography (PS-OCT) revealed that the collagen matrix of PEF-treated meat had a reduced birefringence capacity compared to non-PEF-treated meat, which indicated a breakdown of the collagen.     

SmartStretch™ technology VI. The impact of SmartStretch™ technology on the meat quality of hot-boned beef striploin (m. longissimus lumborum)

The impact of SmartStretch™ technology and ageing (0 or 14 days ageing) on the meat quality traits of m. longissimus lumborum hot-boned from adult cull cattle was assessed. Tenderness, as reflected in reduced shear force measurement, was significantly (P < 0.05) improved in 0 day aged stretched samples over the non stretched samples. After 14 days ageing there was no longer any difference in the tenderness between stretched and non stretched samples and the aged meat was significantly tenderer than either the SmartStretch™ treated or non stretched meat aged for 0 days. Sarcomere length was unchanged by stretching. Presentation traits such as purge loss and fresh colour were unaffected by the stretch treatment, whilst cooking loss was significantly (P < 0.05) increased by stretching and ageing for 14 days.     

低压静电场辅助冷藏对牛肉品质的影响

为研究低压静电场辅助冷藏对牛肉品质的影响,采用牛背最长肌作为实验材料,探究其在静电场（实验组）和非静电场环境下（对照组）冷藏过程中的品质变化。对比分析了肉样在贮藏期间菌落总数、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、色泽、贮藏损失率、蒸煮损失率和剪切力的变化,并通过扫描电子显微镜、透射电子显微镜分别观察肌肉的微观结构和超微结构。结果表明：与静电板隔距10、30 cm和50 cm处肉样在贮藏第7天时菌落总数分别为5.11、5.54、5.27（lg（CFU/g））,显著低于对照组（6.41（lg（CFU/g）））（P＜0.05）。贮藏期内,实验组肉样维持了较高的新鲜度,其TVB-N含量均显著低于对照组（P＜0.05）。此外,贮藏期内与对照组相比,实验组肉样贮藏损失率更低,且剪切力显著下降（P＜0.05）,L*值、a*值显著升高（P＜0.05）,肉样的持水力、嫩度较高,色泽更亮。扫描电子显微镜、透射电子显微镜观察结果显示,实验组肉样贮藏期间肌纤维束排列相对紧密,较好地维持了肌肉微观结构。综上,低压静电场辅助冷藏可有效延长牛肉贮藏期,缓解其在贮藏期间的品质劣变,肉样与静电板的有效隔距为10～50 cm。     

延迟冷却对牛肉品质及超微结构影响的研究

本文研究了常规冷却与延迟冷却对中国杂交黄牛(鲁西黄牛×西门塔尔)宰后冷却过程中牛胴体pH值、温度变化、胴体冷却失重、肉色及成熟过程中剪切力值、背最长肌汁液损失、蒸煮损失、保水性、肌原纤维结构变化的影响.结果表明延迟冷却能减缓牛胴体温度的下降速率(P＜0.05),加快牛胴体pH值的降低(P＜0.05),提高牛背最长肌的嫩化速率,改善肉色(P＜0.05),但加剧了汁液损失、蒸煮损失,降低了保水性(P＜0.05).延迟冷却对成熟0d、3d时的肌原纤维结构影响显著(P＜0.05),延迟冷却组的肌节长度明显长于对照组的肌节长度.     

SmartStretch™ technology. IV. The impact on the meat quality of hot-boned beef rostbiff (m. gluteus medius)

The impacts on traits of the m. gluteus medius hot-boned from young cattle were assessed after stretching (SmartStretch™) and ageing (0 or 8 days ageing). Tenderness, as reflected in reduced shear force measurement, was significantly (P < 0.05) improved in 0 day aged stretched samples over the un-stretched control. After 8 days ageing there was no longer a difference in the tenderness between stretch treatments. Meat aged for 8 days was significantly more tender than 0 day aged meat irrespective of treatment. Sarcomere length was significantly (P < 0.05) increased by stretching. There was a significant (P < 0.05) negative relationship between sarcomere length and shear force. Presentation traits, such as purge loss and fresh colour, were unaffected by the stretch treatment, while cooking loss was significantly (P < 0.05) reduced by stretching in the 0 day aged samples.