CO2 stunning procedure on Manchego light lambs: Effect on meat quality

This study examined the effect of different gas stunning methods (concentration of CO₂/time of exposure (G1: 80%90s; G2: 90%90s; G3: 90%60s; G4: 80%60s) on the initial meat quality of Manchego breed light lambs (25 kg live weight) and at 7 days post-mortem, assessed by pH, colour coordinates, water holding capacity (WHC), cooking loss (CL), drip loss (DL) shear force (SF) and lipid oxidation. An electrically stunned control group (G5) was used. Stunning method had a significant effect on pH values (P < 0.001) as well as on pH decline (P < 0.01). The lowest pH was found at 24 h post-slaughter in G1 and the highest one on G5. The greatest drop in pH (pH₀–pH₂₄) was found in G1 and G5 while the smallest in G3. In general values of colour coordinates, WHC and DL were similar in all groups. Stunning method affected CL (P < 0.001) at 7 days post-slaughter, with the lowest values being found in G1. Significant differences among groups were found (P < 0.05) in SF values at both post-mortem times, with less tender meat in groups stunned with 80% CO₂, especially in G1. A significant effect (P < 0.001) due to the type of stunning was found at 24 h on lipid oxidation, with the highest value in G5. After ageing this parameter was lowest (P < 0.05) in G1 and G4.     

Effect of electrical stunning on meat quality of lamb

The effects of stunning on both initial and up to 2 weeks post mortem storage meat quality of Spanish Manchega breed lamb were studied. Twenty-four lambs were distributed into two groups. The first group (US; n =12) were slaughtered without previous stunning. In the second group (ES; n =12) animals were electrically stunned. Meat quality was assessed by examining pH, colour as L*, a*, b* values, water holding capacity (WHC) and shear force (SF). Stunning did not affect any parameter studied in the first 24 h post mortem. There were increasing differences between groups in pH (P<0.001) from 5 days onwards. In general stunning did not have an effect on WHC, SF and colour parameters. Ageing of meat affected SF in the ES group but not in the US one; however, there were no significant differences between treatments at any of the ageing times.     

EFFECT OF LOW VOLTAGE ELECTRICAL STIMULATION ON THE CARCASS AND SHELF-LIFE CHARACTERISTICS OF SPECIAL FED VEAL

Special fed veal calves (N = 75) were slaughtered in study 1 and assigned to the following treatments; control (C), electrical stimulation (ES) immediately postmortem for 20 s (ES20–IP) or 40 s (ES40–IP), and ES 10 min postmortem for 20 s (ES20–10) or 40 s (ES40–10) using a Jarvis BV 80 electrical stimulator. Temperature, pH and 24 h carcass traits were evaluated. ES durations of 40 s produced more desirable carcass traits. In study 2, 40 calves were slaughtered and assigned to C or ES40–IP treatments. Temperature, pH, carcass characteristics, purge loss, percent free water, color stability, Warner-Bratzler shear force and palatability of biceps femoris slices were evaluated. ES reduced (P < 0.05) pH (at 45 min, 3 h and 24 h) and decreased (P < 0.05) percentage free water, but did not affect color stability, palatability or shear force values of veal from study 2. Low voltage ES enhanced postmortem pH decline in both studies (especially in study 1) and improved the 24 h (postmortem) longissimus characteristics of veal in study 1.     

THE EFFECTS OF DELAYED PICKING AND HIGH-TEMPERATURE CONDITIONING ON THE TEXTURE OF HOT- AND COLD-BONED BROILER BREAST MEAT

Four trials were conducted to evaluate the effects of delayed picking for 30 min versus normal picking, high temperature conditioning at 32°C versus low temperature conditioning at 0°C, and hot boning versus cold boning on broiler breast meat tenderness, pH, sarcomere length and R-values. None of the treatments affected cold-boned shear values. Within the hot-boned group, delayed picking significantly increased shear value (14.5 kg) compared with normally picked samples (12.5 kg). Conditioning at 32°C significantly lowered shear values (12.5 kg) compared with 0°C (14.6 kg). High-temperature conditioning lowered muscle pH immediately after evisceration, but delayed picking had no effect. Following 24 h aging, treatments had no effect on muscle pH or R-value. These results indicate that 32°C conditioning temperature and early picking significantly reduced meat toughness, but not to a commercially practical degree.     

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 different carbon dioxide concentrations and exposure times in stunning of slaughter pigs: Impact on animal welfare and meat quality

The objective of this study was to determine the impact of different slaughter procedures on animal welfare and meat quality. Before slaughter in a dip-lift, one-gondola system, 460 pigs were exposed to an atmosphere containing either 80% or 90% CO(2) for 70 or 100s, and at the longer exposure time with stun-to-stick intervals of either 25-35 or 40-50s. Clinical parameters (reflexes, catecholamines and lactate) showed deficiencies in animal welfare after stunning with 80% CO(2) for 70 and 100s, with an interval of 40-50s, and with 90% CO(2) for 70s. Stunning with 80% CO(2) for 70 or 100s always induced stress, as indicated by higher lactate levels, and reduced meat quality as indicated by low pH(24) values (5.4 in Musculus longissimus and 5.5 in Musculus semimembranosus) and low impedance (Py(24)) values, especially in combination with the longer stun-to-stick interval (40-50s). Stunning with 80% or 90% CO(2) in a dip-lift system was found to be acceptable for animal welfare (percentage of clinical reflexes) only in combination with the longer exposure time of 100s and the shorter stun-to-stick times of 25-35s. When 90% CO(2) was used, the longer stun-to-stick interval of 40-50s also gave results acceptable with regard to animal welfare. Generally, in comparison to 80% CO(2) stunning meat quality was superior (higher pH(24) and Py(24) values) after stunning with 90% CO(2).     

The interaction between pH and temperature decline early postmortem on the calpain system and objective tenderness in electrically stimulated beef longissimus dorsi muscle

The study investigated the effects of pH and temperature decline early postmortem (pm) on calpains and calpastatin activities and objective tenderness in M. longissimus thoracis et lumborum. A total of 40 sides were used to generate a range of pH and temperature declines, by different stimulation treatments (i.e. low voltage stimulation applied for either 10 or 40 s 3 min pm), and chilling treatments (fast or slow). Both rapid glycolysis, or a slow chilling regime significantly reduced μ-calpain level at 4 h pm (P< 0.001 and P< 0.05, respectively). There were significant interactions between pH and temperature at 1.5 h pm on μ-calpain and calpastatin activities at 24 h pm (P< 0.05). Rapid glycolysis resulted in lower shear force and compression measurements at day 1, although because of low ageing rates, an intermediate pH decline (i.e. pH 5.9-6.2 at 1.5 h pm) resulted in the most tender meat after 14 days ageing. Higher shear forces in the slow glycolysing sides appeared to be associated with the later activation of tenderising process, as well as physical shortening. The optimum pH decline early pm varied with days ageing, with an intermediate pH decline resulting in the lower shear forces for meat aged for 14 days.     

禁食对僵直前后鸡肉加工特性的影响

三黄鸡分别禁食0、8、16h和24h,采用三管齐断法宰杀,于宰后僵直前(0h)、僵直阶段(3h)和僵直后(24h)分别制成鸡肉糜,测定新鲜肌肉的pH值,鸡肉肠的蒸煮损失、加压损失、剪切力值、肉色和质构等指标,观察不同禁食时间对僵直前后鸡肉糜制品品质的影响。结果表明：随着禁食时间延长,pH值先升高后降低(P＜0.05),蒸煮损失和加压损失都有增加的趋势,剪切力值有降低的趋势,未禁食组僵直前鸡肉肠的硬度、弹性、黏聚性、胶黏性和咀嚼性最高,禁食16h组僵直和僵直前的质构特性优于禁食8h和24h组。随着宰后时间延长,pH值显著降低,持水力显著下降,僵直后鸡肉肠的质构特性劣于僵直和僵直前鸡肉肠的质构特性。     

Pre-slaughter stress arising from on-farm handling and its interactions with electrical stimulation on tenderness of lambs

The effect of electrical stimulation of lamb carcasses (n=269) or its absence (n=257) on shear force of m. longissimus thoracis et lumborum (LT) was monitored during ageing in pasture-fed merino lambs (n=526). The lambs were slaughtered on four different days allowing durations of between one to 10 days of recovery from pre-slaughter handling (yarding, weighing and crutching) that affected ultimate pH (pH(u)). The right LT was removed 20-40min post-slaughter, tightly-wrapped in cling film (prevents the muscle cross-section increasing and thus minimising shortening) and rapidly cooled to 15°C to enter rigor mortis and age. At 0, 4, 24 and 72h post-slaughter, pH measurements and samples for shear force measurement were taken. Pre-slaughter handling had a significant negative effect on pH(u) and several days recovery were required for pH(u) to reach values associated with optimal meat quality as reflected by pH(u). Lambs with one and three days recovery (no significant difference between them) had a pH(u)>5.7 in 50% of the muscles and 19.4%>pH(u) 5.8. Whereas, in lambs with 8-10 days recovery (no significant difference between them), only 8% had a pH(u)>5.7 and 3.1%>pH(u) 5.8. Within each slaughter day electrically stimulated lambs were always more tender than non-stimulated lambs. For non-stimulated muscles at 72h, shear force values >40N occurred for 11.2% of the muscles: for electrically stimulated muscles at 72h, shear force values >40N occurred for 1.9% of the muscles. The rates of tenderisation were slower for intermediate pH(u) values resulting in higher shear force values at all ageing durations. With ageing at 72h for intermediate pH(u), non-stimulated muscles (n=38) 17.64% were >40N and for stimulated muscles (n=34), 7.9% were >40N.     

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。     

Difference in tenderness and pH decline between water buffalo meat and beef during postmortem aging

The objective of this research was to determine the difference in tenderness and some characteristics of water buffalo meat and beef during postmortem aging. Five female crossbred water-buffalo (Philippine Carabao×Bulgarian Murrah) and five female crossbred cattle (Brahman×Philippine Native), were finished on the same diet for 6 months and slaughtered at 30 months of age. The muscle pH was measured at 40min, 3h, 7h, 24h, and 48h postmortem. Longissimus thoracis (LT) and semimembranosus (SM) muscles were excised at 2d postmortem, and shear force was measured at 2, 4, 7, and 14d postmortem. Glycogen and lactate concentrations were determined from 0, 2, and 4d LT samples, and myosin heavy chain type of buffalo and cattle LT was determined by ELISA methods. Myofibrillar protein degradation was also observed by SDS-PAGE and Western blotting of fast-type troponin T. Results showed that the buffalo meat had significantly lower shear force values compared to beef for LT and SM muscles, which was supported by a difference in troponin T degradation. Postmortem pH decline of buffalo meat was significantly slower than that of beef, which was confirmed by lactic acid concentrations, but was not explained by glycogen content. In addition, there was no significant difference in the ratio of slow to fast type muscle fibers in buffalo and cattle, indicating that myosin heavy chain type was not responsible for the difference in pH decline and tenderness between the buffalo meat and beef. This study demonstrated that the tenderness of water buffalo meat was superior to that of Brahman beef, which may have been due to the difference in pH decline and the subsequent effect on muscle protease activity.     

Meat quality in suckling lambs: effect of pre-slaughter handling

Thirty-three suckling lambs of the Manchega breed were used to compare the effects of pre-slaughter handling (PSH) on initial meat quality and at 7 days post-mortem. Lambs were distributed into three groups: electrically stunned (ESL; n=15), stunned using CO(2) (GSL; n=10) and slaughtered without previous stunning (USL; n=8). Meat quality was evaluated by examining pH, colour (L*, a*, b* values), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24 h post-mortem, the highest pH corresponded to the USL group (P<0.05) whereas the lowest pH decline (pH(0)-pH(24)) corresponded to the GSL group (P<0.05). Differences in pH among groups disappeared after 7 days post-mortem. In general, PSH did not affect values of WHC, CL and colour parameters. After 7 days post-mortem, there were significant differences between groups in DL, this being lowest (P<0.05) in stunned animals. GSL resulted in more tender meat (lower SF value) than ESL and USL (P<0.05). Moreover, there was no blood splash in any of the carcasses of the GSL group.     

Effect of electrical stunning on meat and carcass quality in lambs

The effect on meat quality and the presence of haemorrhages were assessed in head-only electrically stunned and non-stunned lambs. Colour (L?, a?, b?), muscle ultimate pH (pHu), chilling losses and carcass weight at 45 min and 24 h were not significantly different between treatments. However, the amount of blood lost relative to live body weight and the killing-out were significantly higher (P<0.05) in electrically stunned lambs compared with non-stunned lambs. No carcasses with petechiae, ecchymosis, haematomas and bone fractures were found in either treatment. On the other hand, the incidence of hearts with petechiae was significantly (P<0.05) higher in electrically stunned lambs compared with lambs slaughtered without prior stunning. It is concluded that meat quality and the incidence of haemorrhages are unaffected by head-only electrical stunning for 3 s at a constant voltage of 250 V.     

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...     

猪肉宰后成熟时间对肉松成松品质的影响

以猪后腿肉为对象,研究宰后成熟时间对肉松成松品质的影响。将宰后猪肉置于0～4 ℃条件下成熟,分别于0、3、6、9、12、24、36、48 h取样,测定其pH值、剪切力和肌原纤维小片化指数（myofibrillar framgmentation index,MFI）,并加工成肉松,通过含松率、蓬松度、净蓬松度和绒松度等指标对成松品质进行综合评价。结果表明：猪肉宰后成熟6h pH值为6.01±0.07,剪切力为（51.09±2.60） N,MFI为58.021±1.635,加工成肉松的含松率为（72.27±2.90）%,蓬松度为（6.88±0.11） cm3/g,净蓬松度为（7.68±0.46） cm3/g,绒松度为（2.44±0.27） cm3/g,综合评分为0.084 2;猪肉宰后成熟12 h pH值为5.63±0.04,剪切力为（61.54±3.81） N,MFI为64.41±2.03,进入最大僵直期,此时加工成肉松的含松率为（61.57±2.45）%,蓬松度为（6.25±0.13） cm3/g,净蓬松度为（7.08±0.14） cm3/g,绒松度为（1.60±0.09） cm3/g,综合评分为0.305 0;宰后成熟24、36、48h（处于解僵后期）的猪肉加工成肉松成松品质综合评分相对于6 h内的猪肉较高;综合评分越低,肉松的成松品质越好,因此,宰后成熟6 h之内的猪肉成松品质较好,成熟6 h以后不再适合加工成肉松。     

致昏电压对兔肉品质的影响研究

采用100、75、65、55V和人工致昏(对照组)的宰杀方式,研究其对兔肉品质的影响,结果表明:不同致昏电压对兔肉pH值的影响差异不显著(p>0.05),只有75V致昏组与100V致昏组间宰后1h的背最长肌pH值差异显著(p<0.05);宰后1h,不同致昏电压对兔背最长肌的肉色亮度L*值、红度a*值、黄度b*值和后腿肉的L*值、a*值的影响差异不显著(p>0.05);宰后24h,75V致昏组的肌肉颜色鲜红,而人工致昏组和100V致昏组的肌肉颜色较苍白;100V致昏组的滴水损失最大,为3.738%,而75V致昏组的最小,为2.420%;蒸煮损失最大的为100V致昏组,最小的为55V致昏组,其次是75V组;肌肉嫩度最好的是75V致昏组,最差的是人工致昏组。     

包装对羊肉冷藏过程中热休克蛋白表达及羊肉品质的影响

为探究不同包装方式下羊肉冷藏过程中热休克蛋白27(heat shock protein 27,Hsp27)、Hsp70表达量的变化及其与羊肉品质间的关系,以宰后1?h羊背最长肌为研究对象,进行托盘、真空、高氧气调(O2、CO2体积比75:25)和低氧气调(O2、CO2体积比50:50)包装,分析Hsp27和Hsp70表...     

不同宰后时间切碎对肉糜质量的影响

将宰后4、12、24、48h 的分割猪后腿肉制成肉糜,于0～4℃存放1w,测定蒸煮损失、系水力、pH值等指标随贮藏时间的变化状况,以确定不同宰后时间切碎对肉糜品质指标的影响规律。结果显示：采用不同宰后时间切碎肉样所生产的肉糜在1w 的存放过程中,总体来说蒸煮损失显著上升,系水力显著下降,pH 值有所升高。这说明长时间存放对肉糜品质的保持不利。通过对同一存放时间不同宰后时间切碎的比较来看,采用宰后12h的原料肉生产的肉糜其蒸煮损失显著低于宰后4、24、48h 冷冻的原料肉所生产的肉糜。存放实验进行过程中宰后4h 和12h 肉样生产的肉糜系水力始终保持较大,宰后4h 最大。这提示可能宰后12h 以前的新鲜原料肉更适合进行肉糜生产。     

Effect of Freezing of Beef on Subsequent Postmortem Aging and Shear Force

Seventy-two steaks were used to determine effects of freezing postrigor muscle on aging of meat and shear force. Steaks were removed from each carcass 24 hr postmortem and aged at 2°C for 2 or 6 days; or frozen at ? 30°C for 27 days, thawed 24 hr and aged 2 or 6 days at 2°C. After aging, steaks were cooked and shear force determinations made. Aging of meat reduced shear force values; however, meat aged after freezing had lower (P < 0.03) shear force values than meat aged before freezing. Meat cooked after freezing had greater (P < 0.05) cooking losses. Freezing enhances the aging process and improves shear values of meat.