离体牛肉排酸时间对嫩度的影响

屠宰试验测定８头海黑杂种牛的牛肉嫩度，表明离体牛肉随排酸时间的延长其嫩度值发生明显的变化，在室温１２℃～１５℃下排酸４８ｈ肌肉嫩度从开始（屠宰后４ｈ）的１１．３３ｋｇ下降到３．９８ｋｇ，差异非常显著，采用排酸方法可提高牛肉嫩度。     

不同储藏温度和时间对长白猪肌肉pH、失水率及脂质氧化的影响

研究测定了长白猪屠宰后12h肌肉pH的下降速度、极限值和肌间脂肪氧化速度,及不同储藏温度和时间对肌肉pH值、失水率及脂质氧化的影响。结果表明:屠宰后0～5h长白猪肌肉pH值下降速度较快,9～12hTBA值变化速度较快。4℃条件下,储存时间对长白猪肌肉pH影响不显著,对滴水损失影响极显著,TBA值影响显著;-20℃冷冻条件下,储存时间对长白猪肌肉pH、TBA影响显著,对解冻失水率影响不显著。温度对pH值和TBA值的影响不明显,对滴水损失和解冻失水率有极显著的影响。通过回归分析,长白猪肌肉滴水损失和解冻失水率随pH升高而降低;-20℃条件下TBA值随pH升高而升高。     

热应激影响鸡肉品质的研究进展

热应激是家禽业最主要的环境应激源之一.急性或慢性热应激均可引起肉鸡生长速度降低、饲料转化效率下降、免疫系统受损、肠道菌群紊乱及肉质下降.影响肉质方面,主要涉及3种机制:(1)屠宰应激和屠宰后,糖原转化导致乳酸积累增加,特别是在肌肉温度较高时,pH值迅速下降,引起肌浆蛋白变性,导致肌肉持水能力降低;(2)热应激加速肉鸡呼...     

美国肉牛、肉羊业现状与前景

一、牛与牛肉生产继1990年牛肉生产下降1.5%后,1991年预计可恢复到1989年的水平。由于1990年母牛屠宰数下降,以及饲料牛肉(fed beed)生产比预期的少,使牛肉供应较少,牛和牛肉价格达到最高纪录。从加拿大和墨西哥进口肥育牛(feeder cattle)和供屠宰肉用牛(slaughter cattle)数量急剧增加。     

屠宰致晕法对肉仔鸡肌肉品质的影响

选择6周龄健康AA肉仔公鸡50只,研究屠宰致晕方法对其肌肉品质的影响。结果表明经过麻醉(二氧化碳、电)处理后屠宰的肌肉的pH1和pH24;ORP1值和ORP24相差较小,其ORP1值和ORP24值也均低于其他处理,剪切力也显著低于未经麻醉直接屠宰的处理,对滴水损失没有太大影响。致晕屠宰法对肉质有一定的影响,相对于直接屠宰,致晕后屠宰可以改善肉质。     

冷却排酸期间牛胴体温度与pH的变化及其对牛肉汁液渗出性的影响

为研究牛胴体温度与pH变化规律对牛肉汁液渗出性的影响,本研究对100头秦川牛胴体的前部(脖肉)、中部(外脊)、后部(臀肉)在屠宰后冷却排酸过程中温度与pH随屠宰后时间的变化进行了同步跟踪测定,并对冷却排酸后相应部位肉表面的汁液渗出性加以分析。结果表明,中部胴体温度下降速率最高,分别是前部和后部的1.75和1.45倍。前部胴体pH下降速率最小,中部和后部胴体下降速率分别是前部胴体的6.56和4.88倍,最终pH为前部胴体>中部胴体>后部胴体。而pH下降至6时的温度与汁液渗出性之间具有极好的正相关性,其线性回归方程拟合度R2均达到0.8以上。pH为6时的温度均对汁液渗出性有明显影响。结果提示,胴体温度与pH的相对变化会对肉的持水力产生明显影响。     

屠宰日龄对矮脚黄鸡胸肌品质的影响

以矮脚黄鸡为研究对象,系统地分析了屠宰日龄对胸肌屠宰肉质性状的影响.结果显示,屠宰日龄对胸肌肌肉pH值的影响很小,对肉质的影响主要表现为随日龄增加,肌内脂肪含量增加,肌纤维直径变粗,肌纤维密度下降.为保证肌肉品质的一致,应保持恒定的上市日龄.     

牛肉质性状及其影响因素北大核心CSCD

肉质性状指标包括pH、色泽、嫩度、系水力、肌内脂肪含量和脂肪酸组成等,这些性状受到包括牛的品种、年龄、性别和基因型等遗传因素以及饲养管理和屠宰工艺等环境因素的共同影响。同一品种牛,屠宰月龄较小的母牛或阉牛,其肉品质较好;不同品种或群体的牛,会因钙蛋白酶抑制素、钙蛋白酶、二酰甘油酰基转移酶1、脂肪酸结合蛋白4及硬脂酰辅酶A去饱和酶等基因的多态性而产生肉质性状差异。屠宰前的应激反应和屠宰后的排酸方式因影响肉的极限pH而改变肉品质。肌肉生长抑制素基因突变促进产肉性能的同时,可能对肉品质有一定影响。本文就影响牛肉品质的若干因素研究进展作一综述。     

不同生长阶段早胜牛公牛的肉品质分析

为研究不同生长阶段早胜牛公牛的牛肉品质差异,本试验选取6、12、18、24月龄早胜牛公牛各3头,屠宰后取背最长肌并检测各物理指标、常规养分组成、氨基酸含量。结果表明:随着生长年龄增大,早胜牛公牛肌肉的蒸煮损失、滴水损失显著减小,剪切力、系水力显著增大,6月龄牛肉最嫩;24月龄牛肌肉肉色最深;18月龄肌肉粗蛋白质含量显著高于其他阶段,8、24月龄牛肌肉粗脂肪含量显著高于其他阶段;12月龄以上早胜牛公牛肌肉的氨基酸组成较为均衡,必需氨基酸、鲜味氨基酸含量较高,24月龄牛肉营养价值最高。可见,6月龄公牛牛肉较嫩,但从营养价值方面考虑,推荐食用18月龄以上早胜牛公牛牛肉。     

不同性别和加镁日粮在肉牛生产中的应用研究

将72头小母牛和72头小公牛分成4组,4个日粮组分别添加0、0.25%、0.50%和0.75%的MgO,试验时间是育成期的最后14d,即屠宰前2周。本试验旨在研究镁（Mg）和性别对牛的应激和牛背最长肌（LM）质量的影响。结果显示,公牛和母牛对应激的反应差异显著,母牛在屠宰前所表现的应激要远远高于公牛,主要表现在母牛的肾上腺皮质（HPA）轴和交感——肾上腺轴的激活更为明显。另外,公牛相对母牛在屠宰前的应激相对较低,屠宰后48h背最长肌pH值较高（LMpH,P=0.042）,同时母牛的LM相对公牛的嫩度要好（P=0.008）。本试验中,母牛和公牛的第48h背最长肌pH值和背最长肌平均剪切力（LMWBSF）之间有一定的线性关系。在屠宰后第3d和第7d,pH值对LM剪切力的影响是非常大的（P〈0.05）,但在牛屠宰后第21d,pH值对LM剪切力的影响已经不再明显（P〉0.05）。牛在屠宰后,牛肉的LM的最终pH值高于5.65时,LM牛肉的嫩度相对较差,但当LM切块放置至少18d或更长时间,肉质将会有所好转。牛日粮中添加Mg除了可增加牛血清中Mg的含量（P=0.011）外,对牛的生理应激和LM质量却没有任何影响（P〉0.05）。目前关于Mg的添加对减少屠宰前牛的应激和牛肉质量方面没有太多的报道。     

饲粮中金针菇菌渣水平对山羊屠宰性能及肉品质的影响

本试验旨在研究饲粮中金针菇菌渣水平对山羊屠宰性能及肉品质的影响。试验选用28只体重为(23.35±2.45)kg的波杂羊(波尔山羊×徐淮山羊),随机分成4组(每组7只),分别饲喂含0(A组,作为对照组)、15%(B组)、25%(C组)、40%金针菇菌渣(D组)的试验饲粮。试验羊单独饲喂,在试验结束时(饲喂45 d后)进行屠宰,分别测定山羊的屠宰率、眼肌面积以及背最长肌的pH、色度、剪切力、蒸煮损失率和滴水损失率。结果表明:1)C组的屠宰率与B组差异不显著(P0.05),但显著高于A和D组(P0.05);C组的屠宰率分别比A、B和D组提高了2.46%、1.35%和8.32%。B和C组的眼肌面积与A组差异不显著(P0.05),但显著高于D组(P0.05)。2)C组山羊的背最长肌的滴水损失率与B和D组差异不显著(P0.05),但显著低于A组(P0.05);与A、B和D组相比,C组山羊的背最长肌的蒸煮损失率显著降低(P0.05);B、C和D组的剪切力差异不显著(P0.05),但均显著低于A组(P0.05)。饲粮中添加不同水平的金针菇菌渣对山羊背最长肌宰后45 min pH(pH_(45 min))、宰后24 h pH(pH_(24 h))、红度(a~*)值和黄度(b~*)值无显著影响(P0.05),但能显著降低背最长肌亮度(L~*)值。由此可见,饲粮中添加不同水平的金针菇菌渣对山羊的屠宰性能以及肉品质产生不同程度的影响,饲粮中金针菇菌渣水平为25%时对提高山羊的屠宰性能以及改善肉品质方面具有较好的效果。     

Effects of genetic and environmental factors on muscle glycogen content in Japanese Black cattle

Monosaccharides such as glucose contribute to the development of meat flavor upon heating via the Maillard reaction; therefore, monosaccharide content is related to beef palatability. Here, we analyzed the effects of genetic and environmental factors on the content of glycogen, one of the precursors of monosaccharides, in the muscles of 958 fattened Japanese Black cattle from Yamagata Prefecture. Analysis of variance showed that muscle glycogen content was affected by the farm and postmortem periods, but not by sex, slaughter age, slaughter month or number of days detained at the slaughter yard. Additionally, consumption of digestible brown rice feed elevated muscle glycogen levels. Glycogen heritability was estimated to be 0.34, and genetic correlations between glycogen and carcass weight (CW) or beef marbling standard (BMS) were weak. The predicted breeding values varied among paternal lines. These results demonstrated that genetic factors might improve muscle glycogen content and therefore beef palatability, but do not influence CW or BMS.     

肉牛宰前体表温度和牛肉pH值间关系的研究

用红外成像仪对60头肉牛屠宰前的体表温度进行测量,并对新鲜牛肉样品的肌糖元含量进行分析,将测试结果与排酸后的pH进行比较,结果表明:产生高pH肉的肉牛在屠宰前体温明显偏高(χ2χ20.05),而肌糖元含量偏低,但未达到统计学显著水平(P0.05)。     

Bruising and muscle pH with mixing groups of cattle pre-transport.

The effects on bruising and muscle pH of mixing cows and steers at loading, and 96 hours before loading, for transport to slaughter were examined. A second experiment investigated the effect on bruising of mixing two strange groups of steers at loading, 24 and 96 hours before loading. All cattle were hornless Bos indicus crossbreds from the same property in north Queensland. The bruise score, bruise trim weight and muscle pH of mixed cows and steers did not differ significantly from that of those transported separately. Mixing of two strange groups of steers did not significantly affect bruising. Time of mixing had no noteworthy effect on bruising. Cows bruised significantly (P less than 0.01) more than steers. These results have important implications for low cost beef management.     

蛋白质水平对肉牛屠宰指标的影响

[目的]探讨不同蛋白质水平对肉牛屠宰指标的影响。[方法]选用5个营养水平的精料补充料配方,分别饲喂5个试验组肉牛,并与对照组进行比较。[结果]饲喂粗蛋白水平较高的精料补充料有利于胴体脂肪的沉积和眼肌面积的增大,有利于肉牛的胴体测量指标的提高。蛋白质水平对脏器重量的影响主要集中在头、皮、肝、肾、胆囊、膀胱和横膈膜,对消化器官重、心重、肺重、脾重的影响没有发现规律性。[结论]提高肉牛屠宰指标可以通过补充蛋白质来实现。     

拴系与散栏饲养方式对肉牛屠宰性能及肉品质的影响

本研究从动物福利的角度出发,探索拴系式饲养与散栏饲养对肉牛屠宰性能及肉品质量的影响。选择体重接近(220±9.78)kg、(9±0.57)月龄、健康无病的16头西门塔尔杂交改良育肥公牛随机分为2组,每组8头牛。拴系式饲养为对照组,散栏饲养为试验组。预试期为7 d,正试期84 d。结果表明:散养组眼肌面积、熟肉率及肉样超氧化物歧化酶(SOD)含量显著高于拴系组(P<0.05),而宰后1 h pH值以及肾脂和大网膜脂肪重均显著低于拴系组(P<0.05),其他屠宰性能及肉品质指标未出现显著差异(P<0.05)。     

Comparison of carcass and meat characteristics of Brahman grade cattle (Bos indicus) and crossbred water buffalo (Bubalus bubalis)

This study was conducted to determine and compare the live traits, carcass yield and the physical, chemical, processing and sensory properties of meat from 20 Brahman grade cattle (crossbred cattle) and crossbred water buffalo (Philippine carabao × Murrah, Bulgarian or Indian) with an average age and weight of 29 months and 434 kg, respectively. The animals were fed a similar diet for 180 days before slaughter. A survey was performed to establish consumer meat preference between the two species. Live weights before slaughter of the two species were found to be different (P < 0.05) with the crossbred water buffalo showing higher bodyweight. However, the crossbred water buffalo had a lower (P < 0.05) dressing yield based on hot carcass weight and chilled carcass weight. The lower dressing yield of crossbred water buffalo can be attributed to its higher (P < 0.05) weights of edible and non‐edible slaughter by‐products. The chilled carcass yield of the forequarters and hindquarters from crossbred cattle and crossbred water buffalo were comparable when expressed as percent of live weight and chilled carcass weight. The estimated lean yield was higher in crossbred cattle than crossbred water buffalo. Crude protein, ash, fat, cholesterol, myofibrillar, sarcoplasmic and insoluble protein contents of the beef and carabao meat were all similar. Water holding capacity, pH, muscle fiber diameter, tenderness, firmness and marbling score in carabeef were all comparable to the beef. Redness was found to be higher (P < 0.05) in carabeef than the beef as measured with a color meter. The consumer meat preference survey showed that 55.9% selected the beef while 44.1% preferred carabeef. The color and amount of fat on the outside of the beef sample were primary in buyer selection.     

Effects of dietary supplementation with vitamin E and organic selenium on the oxidative stability of beef.

The effects of supplementation of beef cattle diets with organic Se (0.3 mg/kg) and vitamin E (300 I.U. alpha-tocopheryl acetate/kg feed), for 55 d preceding slaughter, on the antioxidant status and oxidative stability of muscle was examined. Dietary vitamin E supplementation led to an increase (P < 0.05) in plasma, and longissimus muscle alpha-tocopherol levels. In minced longissimus muscle stored in 80% 02:20% CO2, lipid and oxymyoglobin oxidation were lower (P < 0.05) in muscle from vitamin E-supplemented animals compared with unsupplemented animals. Dietary Se supplementation did not significantly affect muscle Se levels, glutathione peroxidase activity, or susceptibility to lipid and oxymyoglobin oxidation in the presence or absence of vitamin E. Covariance analysis indicated that, in addition to muscle alpha-tocopherol, differences in muscle glutathione peroxidase activity, and pH could account for variation in the susceptibility of muscle to lipid and oxymyoglobin oxidation.     

Effect of preslaughter experience on behaviour, plasma cortisol and muscle pH in farmed red deer

Three groups of farmed red deer were shot in the field, three groups were slaughtered on the farm and three groups were transported to commercial slaughterhouses. The behaviour of the animals was observed and peripheral plasma cortisol concentrations were measured immediately after slaughter and neck muscle pH was measured 24 hours after slaughter. The deer could be handled and herded without agitation when only one unhindered direction was open to them and nothing in the environment caused alarm. Shallow angled loading ramps were preferable. Deer shot in the field and deer penned without handling had low average plasma cortisol concentrations (less than 7 ng/ml) and a muscle pH less than 5.74 whereas deer which had been herded on the farm, or transported to a slaughterhouse, had high cortisol concentrations (greater than 20 ng/ml) and a muscle pH above 5.74. However, only four of 66 male deer transported to a slaughterhouse had a muscle pH above 6.0, the pH associated with dark cutting meat in red deer.