A survey of pork quality in relation to pre-slaughter conditions, slaughterhouse facilities, and quality assurance

A survey at five pigs' slaughterhouses was performed to investigate the effect of a quality assurance system, pre-slaughter conditions and slaughterhouse facilities on pork quality. Totally, 2246 pigs were included over four transports per slaughterhouse, i.e. two transports were produced according to a quality assurance system and the other two were conventional pigs. Meat quality was measured on 446 pigs. The pH in the longissimus dorsi muscle and the electrical conductivity in the semimembranosus muscle were measured 30min post-mortem. Twenty-four hours later pH and electrical conductivity in both the longissimus dorsi and the semimembranosus muscle were measured. Pigs managed according to a chain quality protocol showed an overall higher potential for improved meat quality. Differences in meat quality between the different slaughterhouses were also found, however they were dependent on muscle type and time of measuring. Influencing factors on pork quality seemed to be stocking density during transport, the handling during offloading the pigs from the truck, stocking density, and air temperature during lairage.     

Predictive value of slaughterhouse measurements of ultimate pork quality in seven halothane negative Yorkshire populations

An experiment with 1969 pigs, belonging to Yorkshire sire lines, was set up in cooperation with seven Dutch breeding organizations. The pigs, which were claimed to be halothane negative, were slaughtered in weekly batches. Light reflectance was determined with the Hennessy Grading Probe (HGP) and Fibre Optic Probe (FOP), in addition to pH(1) and rigor mortis at 45 min post mortem (p.m.). Further meat quality determinations were performed either in the slaughterhouse at 20 h p.m., or in the laboratory at 24 h p.m.. At first sight, both the scatter of light (HGP-PSE, FOP) and pH, measured at 45 min p.m., appeared to be indicative of the ultimate meat quality score. More accurate analyses, however, showed that the value of reflectance values is limited and less suitable in comparison to pH(1), especially with reference to the prediction of ultimate quality characteristics of water holding capacity. The correlations for pH(1) with drip loss were rather consistent, ranging from -0·34 to -0·52 per breeding population. In contrast, HGP-reflectance values ranged from -0·27 to 0·34, while those based on FOP(1) had a range from nearly zero (0·02) to 0·20. The proportion of variation (R(2) × 100%) in drip loss, explained by a set of slaughterline measurements, ranged from 13 to about 28% per breeding population. The use of measurements carried out at 20 h p.m. improved the R(2) × 100% for drip loss to a range from 50 to 62%.     

Effects of dry-ageing on pork quality characteristics in different genotypes

Presumably, dry-ageing enhances flavour attributes of meat by surface desiccation to increase and modify fatty acid content and other organoleptic molecules. However information regarding dry-ageing of fresh pork is limited. To examine the effects of dry-ageing on pork quality, Large White (LW, n = 24) and Large White × Duroc (Duroc, n = 24) barrows were slaughtered and three longissimus thoracis et lumborum sections from each side of the carcass were wet or dry-aged for 2, 7 or 14 d. Dry-aged meat had lower (P < 0.001) moisture and higher (P < 0.001) protein content due to higher purge losses (P < 0.001) when compared with wet aged meat. However no dry-ageing effect (P > 0.05) was observed on sensory characteristics. The increase in the duration of ageing decreased moisture content and drip loss and increased (P < 0.001) protein content, purge loss and L*, chroma and hue values. These changes were more accentuated in dry-aged meat (P < 0.01). Days of ageing dependent increases (P < 0.001) were observed for instrumental and sensory tenderness and juiciness in both ageing types. Moreover, meat from Duroc barrows had lower (P < 0.001) moisture and protein content, and higher (P < 0.01) fat content, L* and hue values. Instrumental and sensory tenderness, juiciness and flavour were higher (P < 0.01) in meat from Duroc than LW barrows. Increases (P < 0.01) in flavour intensity and decreases in off-flavour of meat from LW barrows were greater (P < 0.05) in d 7 than in d 14. Therefore the duration of ageing affected most quality and sensory characteristics, while the changes to quality attributes of dry versus wet-aged pork were attributable to the differences in shrink losses in the present study.     

Comparison of different dietary magnesium supplements on pork quality

Forty-eight crossbred (Large White×Landrace) boars were used to compare the effect of dietary magnesium aspartate (MgAsp), magnesium sulphate (MgSO(4)) and magnesium chloride (MgCl(2)) on muscle glycogenolysis and pork quality. The pigs were fed finisher feed supplemented with either MgAsp, MgSO(4) and MgCl(2) for 5 days prior to slaughter. At the abattoir, all pigs received 15 electric shocks from an electric goad 5min prior to slaughter. Pigs fed the diet supplemented with MgSO(4) had the highest plasma Mg concentrations at slaughter in comparison with pigs fed the MgAsp and MgCl(2) supplemented diets. There were no differences in plasma adrenaline and noradrenaline concentrations at slaughter between the different diets. Pigs fed the Mg diets had higher muscle glycogen concentrations in the Longissimus thoracis (LT) muscle at 5min and at 40min (except MgCl(2)) post-slaughter compared to pigs fed the control diet. Also pigs fed the Mg diets had lower muscle lactic acid concentrations in the LT at 5min post-slaughter and lower drip loss at 24hr post-slaughter compared to pigs fed the control diet. These results indicate that cheaper magnesium sources, MgSO(4) and MgCl(2), are as efficacious as MgAsp in reducing drip loss and improving pork quality.     

Shelf life of pork from five different quality classes

A total of 117 loins were selected on the cutting line at 24 h post-mortem to study the long term shelf life (35 days, 4 °C) of vacuum packaged pork from five different quality classes (PSE: pale, soft, exudative; PFN: pale, firm, non-exudative; RSE: red, soft, exudative; RFN: red, firm, non-exudative; and DFD: dark, firm, dry). The microbial load at 0 d was not significantly different (P > 0.05) among the pork quality classes, indicating that the initial microflora was influenced by the dressing conditions at the plant, not by the meat quality class. But after 35 d of storage, total aerobic mesophilic and presumptive lactic acid bacteria counts were higher (P < 0.05) in DFD pork due to its higher ultimate pH. RSE was the second quality class most susceptible to spoilage, whereas PFN, RFN and PSE pork had similar microbial loads. Further research is needed to elucidate the causes of the shorter shelf life in RSE pork.     

不同电击昏方式对猪肉品质的影响

研究了不同电击昏方式对猪肉色泽、系水力的影响及其与PSE肉发生率之间的关系。对48头猪分3个组分别进行不电击昏（对照）,手工头部电击昏和自动头胸电击昏3种处理。结果表明电击昏使宰后pH下降较快,肉色明亮度和红色度增大,肌肉系水力下降,断骨率增多,PSE肉发生率增大;采用手工头部电击昏系统和自动头胸电击昏系统处理的猪其PSE肉发生率分别为25％和12．5％,断骨率分别为8．33％和2．67％。自动头胸电击昏系统显著提高了猪肉的品质。     

不同真空解冻条件对猪肉品质的影响

该研究以猪前腿肉为研究对象,通过测定猪肉真空解冻的解冻和空气自然解冻速率以及解冻后猪肉的保水性、pH值和猪肉的质地等指标,研究真空解冻在真空度分别为100、500、1000、2000 Pa条件下对冷冻猪肉解冻效果的影响.结果 表明,与空气自然解冻相比,真空解冻的解冻速率明显快于空气解冻,同时能更好地保持解冻后猪肉的品质...     

Majorcan Black Pig as a traditional pork production system: Improvements in slaughterhouse procedures and elaboration of pork carpaccio as an alternative product

The Majorcan Black Pig (MBP) was used as a model of differentiated traditional system within the Q-PorkChains project. The MBP farms were taken as an example of traditional system using a local breed which claims for high meat quality products. Welfare Quality® protocol was applied at the slaughterhouse and improvement strategies related to ante-mortem conditions and technological meat quality were defined. Pork carpaccio from MBP was elaborated to evaluate its sensory properties as an alternative to the existing MBP products. MBP tenderloins were better suited than those from pigs from a commercial breed to elaborate this product.     

不同淀粉对猪肉丸品质的影响

实验主要研究马铃薯淀粉、小麦淀粉、绿豆淀粉和木薯变性淀粉在加工温度为70、80、90℃和100℃对猪肉丸品质的影响。通过感官评定、测定色差、蒸煮损失、质构来比较猪肉丸品质的差异。实验结果得出:木薯变性淀粉做出来的猪肉丸在感官评价、蒸煮损失率、硬度、弹性和咀嚼性比其它三组淀粉表现出的效果好,加工温度为90℃时猪肉丸的感官评价、硬度、弹性和咀嚼性最大。     

不同致晕方式宰后猪肉品质的差异分析

选用电击致晕、CO2致晕及不致晕三种方式,对150头商品猪进行屠宰试验,测定其肌肉pH值及24h滴水损失率.结果表明:不致晕屠宰比致晕后屠宰肌肉pH值偏低,且致晕后屠宰肌肉的滴水损失率明显低于不致晕屠宰.相比于致晕后屠宰,不致晕直接屠宰产生的PSE肉等劣质肉的风险较高,且从动物福利的角度考虑,也应先对动物致晕后再实施屠宰.     

水酶法提取大豆油与其他不同种大豆油品质差异研究

通过对大豆油的感官指标、理化指标及部分功能性成分的比较,研究不同种大豆油(水酶法提取大豆油、一级大豆油、三级大豆油、压榨大豆油、溶剂浸提大豆油)的品质差异。结果表明,水酶法大豆油的外观品质介于一级油与三级油之间;色泽处于二级油与三级油之间,折光率最高,密度处于一级油和三级油之间;水分及挥发物的含量和p-茴香值最高,碘价最低,酸价、过氧化值介于一级油和二级油之间;水酶法大豆油的亚麻酸未检出,其饱和脂肪酸含量最低,总不饱和脂肪酸含量最高,磷脂含量介于一级大豆油和三级大豆油之间。     

添加发酵剂对猪肉脯品质的影响

分别利用戊糖片球菌,植物乳杆菌,肉糖葡萄球菌单一菌种和复合菌种对原料肉进行发酵,生产发酵型猪肉脯,分析了成品质构、水分活度、肌原纤维小片化指数(MFI)和感官品质等指标的变化。结果表明:与对照组相比,发酵可以明显改善产品的质构和感官品质。其中经肉糖葡萄球菌和戊糖片球菌复配发酵的产品剪切力可降低39.8%,MFI由对照组42.87提高到84.73。各发酵组的水分活度(Aw)和水分含量无显著区别,但与对照组相比有显著下降(p<0.05)。添加肉糖葡萄球菌发酵组和三组复配发酵组猪肉脯感官评分显著高于对照组(p<0.05)。      

不同注水比例对猪肉营养品质的影响

目的探讨不同注水比例对猪肉的营养流失情况。方法以猪背最长肌为原料,分别注入10%、20%、30%和40%的去离子水,分析了猪肉注水后其流失液的透光率、色差值、灰分含量、蛋白含量、游离氨基酸含量和矿物质含量。结果随着注水比例的增加,猪肉的汁液特性发生显著变化,其中汁液流失率、汁液的透光率、L*值随注水比例增大而逐渐增大,a~*、b~*值随着注水比例的增加而显著降低(P0.05);而且注水会大大降低猪肉的营养价值,随着注水比例的增加,猪肉中蛋白质和矿物质元素的流失量显著增加(P0.05),其中矿物质元素流失量的大小依次为K、P、Na、Mg、Ca、Zn、Cu,同时也造成了17种游离氨基酸的大量流失,包括必需氨基酸苏氨酸、缬氨酸、异亮氨酸、亮氨酸、苯丙氨酸和赖氨酸。结论从猪肉的营养价值而言,为注水猪肉的判别提供理论参考依据。     

不同注水量对猪肉食用品质的影响

通过研究不同注水量(0、10%、20%、30%、40%)对猪肉色泽、pH、剪切力、滴水损失、蒸煮损失、压榨损失、离心损失、贮藏损失、拿破率的影响,比较分析正常猪肉与不同比例注水猪肉食用品质的差异。结果表明:随着注水量的增加,L^*、b^*、滴水损失、蒸煮损失、压榨损失、离心损失、贮藏损失显著增大(p<0.05),a^*、剪切力随着注水量的增加显著减小(p<0.05);当注水量小于20%时,注水猪肉的L^*、压榨损失、贮藏损失、离心损失与正常猪肉差异显著(p<0.05),而当注水量大于等于20%时,注水猪肉的L^*、a^*、压榨损失、贮藏损失、离心损失、剪切力值、蒸煮损失、滴水损失均与正常猪肉存在显著性差异(p<0.05)。与正常猪肉相比,注水后的猪肉亮度增加,保水性变差,嫩度有所增加。相关性分析表明,注水后肉块保水性的变化影响色泽的改变,同时也会影响嫩度的变化。     

不同冻结和解冻方式对猪肉品质的影响

为探究冻结和解冻方式对猪肉品质的影响,以解冻汁液流失率,p H,脂类氧化（TBARS）值,蛋白质溶解度,滋味及微观结构的变化作为猪肉品质的评定指标。采用-18、-27、-70℃三种冻结温度进行冻结,冻结后-18℃冻藏3 d,每个冻结组解冻时均分别采用4℃低温空气、25℃静水、25℃空气三种方式进行解冻。结果表明:冻结方式与解冻方式对猪肉品质均有不同程度的影响。通过多因素方差分析可以得出,解冻汁液流失、蛋白质溶解度同时受冻结、解冻方式影响显著（p<0.05）。p H受冻结、解冻方式影响不显著（p>0.05）;TBARS受解冻方式影响显著（p<0.05）,受冻结方式影响不显著（p>0.05）;解冻方式是影响滋味变化主要因素;-70℃冻结和4℃低温解冻能够较好地保持猪肉品质。      

猪肉肉质和风味的提高与改善

介绍了影响猪肉肉质的因素和改善肉质的方法,主要有营养调控和管理方式的改善。     

不同冷冻方式对调理猪肉贮藏期品质影响的对比研究

本文以猪肉为主要原料,添加适量的调味料或辅料,经适当加工,使预冷12h后,中心温度约为10℃的调理猪肉通过风冷冷冻和浸渍式冷冻两种方式对其进行处理,将其中心温度分别降至-5、-18℃,然后把-5、-18℃的肉块放入相应温度的冰箱保藏,并对四种保藏处理下的调理猪肉在一定贮藏期内(24周)的保水性、滴水损失、蒸煮损失、质构特性、TVB-N、菌落总数、p H、色泽(L*a*b*)进行了对比研究。研究表明:四种冷冻处理下,-18℃组肉样的色差、TVB-N、TBA要显著低于-5℃组(p0.05),而巯基含量则显著高于-5℃组;其中浸-18℃组的菌落总数要显著低于其他组。且浸渍式冷冻工艺要优于风冷冷冻工艺,除保水性外,浸渍式冷冻组在色泽、菌落总数、挥发性盐基氮(TVB-N)、硫代巴比妥酸值(TBA)、质构特性等其他各项指标要优于风冷冷冻组。     

Effect of different electrical stimulation and chilling treatments on pork quality

The effect of different chilling and electrical stimulation (ES) treatments on the carcass and eating quality of pork has been examined. Preliminary trials (Study I), with a variety of ES treatments, indicated that, on the basis of pH fall, drip loss and tenderness, the most effective was that using 700 V peak at 12·5 Hz for 90 s applied at 20 min post-slaughter. These ES parameters were used throughout the main study (II) using 80 pigs, one side of which was stimulated and the other not, before being chilled rapidly (10°C in deep loin within 2–3 h of slaughter) or conventionally (10°C in deep loin within 5 h of slaughter).

Changes in pH and temperature during chilling were observed and, after chilling, quality assessments on LD and Sm muscles included drip loss, muscle opacity and instrumental toughness at 3 days post-slaughter.

Electrical stimulation, 20 min post-slaughter, improved tenderness of the LD and, to a lesser extent, the Sm of rapidly chilled pig sides. This advantage was gained without producing PSE pork. In fact, drip loss from the LD was consistently less from the sides which had been stimulated.     

不同包装方式对冷鲜猪肉的保鲜效果

研究了普通托盘包装、真空包装、高氧气调包装(70%O2+30%CO2)和一氧化碳气调包装(0.4%CO+30%CO2+69.6%N2)对冷鲜猪肉的保鲜效果。通过对不同包装方式下冷鲜猪肉在贮藏期的色泽、汁液流失、挥发性盐基氮和微生物的分析,发现真空包装、高氧气调包装和一氧化碳气调包装均显著抑制了冷却肉中微生物的生长,提高了贮藏期间的色泽品质,但是真空包装汁液流失严重,且抑菌效果不如2种气调包装;高氧气调包装虽然有较好的护色效果和抑菌效果,但易使肉后期色泽变暗;一氧化碳包装既能维持贮藏期内较好的肉色,又能起到较好的抑菌效果,对冷却猪肉具有较理想的保鲜效果。     

基于市场调查对安全优质猪肉生产的几点建议

猪肉是我国最主要的消费肉类产品,随着猪肉需求由数量需求向质量需求转变,无残留、无污染、无公害、品质好的安全优质猪肉成为人们的追求目标。为了解北京市海淀区安全优质猪肉市场情况,对该地区生鲜猪肉品牌、猪品种、价格、认证方式等进行了初步调查分析,指出了安全优质猪肉生产中存在的问题并提出了几点建议,以期对安全优质猪肉的生产提供参考。