冷却鸡肉保水性评定指标标准化及其与肉色、嫩度和pH24 h相关性研究

对鸡肉不同保水性测定指标（蒸煮损失、滴水损失和压榨损失）的处理条件和操作规程进行统一标准化,同时探讨保水性各指标之间及与肉色、宰后24 h pH值（pH24 h）的相关关系。结果表明：滴水时间对滴水损失有显著影响（P＜0.05）;压力大小和加压时间对压榨损失有显著影响（P＜0.05）;水浴温度和中心温度对蒸煮损失影响显著（P＜0.05）。根据实验结果以及实际工艺的要求各指标测定条件推荐为：滴水损失肉块大小为2 cm×2 cm×2 cm、滴水时间为48 h;压榨损失压力大小为35 kg、加压时间为5 min;蒸煮损失水浴温度为75 ℃、肉样中心温度为70 ℃。相关性分析结果表明：剪切力值与蒸煮损失呈显著正相关（P＜0.05）;pH24 h值与亮度（L*）值呈极显著负相关（P＜0.01）,与压榨损失和滴水损失呈显著负相关（P＜0.05）;滴水损失与其他保水性指标之间均存在显著相关性。pH24 h值在一定程度上影响肉色和保水性,滴水损失可作为保水性的最佳指示参数。     

宰后不同时间冻结对猪肉保水性和组织结构的影响

采用配对试验设计方法研究了宰后45 min和宰后4 h冻结肉样在冻结损失、解冻汁液流失、蒸煮损失、加压失水率、蛋白溶解度、pH、剪切力和组织结构变化等方面的差异,结果显示:(1)宰后45 min冻结的肉在总的冻结和解冻损失、解冻汁液流失和蒸煮损失方面均显著小于宰后4h冻结的肉样(P<0.05)。宰后45 min冻结肉样在加压失水率和冻结损失方面无显著差异(P>0.05)。(2)肌浆蛋白溶解度宰后45 min冻结的肉显著高于宰后4 h冻结的肉(P<0.01)。而总蛋白溶解度和肌原纤维蛋白溶解度则都是宰后45 min冻结的肉低于宰后4 h冻结的肉。(3)宰后45 min冻结肉样的pH显著高于宰后4 h冻结的肉样(P<0.01)。(4)随着宰后时间的延长,未冻结肉样的肌细胞外空隙面积明显增大。(5)宰后45 min冻结的肉样比宰后4 h冻结的肉样的冰晶分布更均匀,相对来说其冰晶也较小一些。     

宰后猪背最长肌踝蛋白降解与汁液流失率的关系

本文采用蛋白质印迹技术(Western blot)对猪宰后正常肉(RFN肉)与PSE (Pale,Soft,Exudative)肉的踝蛋白(Talin)的变化进行测定,并且分析宰后两种肉样的pH、温度以及踝蛋白变化与持水性的关系。结果表明:宰后正常组的pH高于PSE组,但温度低于PSE组。宰后45 min与24 h的pH与汁液流失率之间呈显著负相关(p < 0.05),宰后45 min与3 h的温度与汁液流失率之间呈显著正相关(p < 0.05),说明宰后早期低pH是导致PSE肉的产生的重要因素。宰后两组肉样的踝蛋白都随时间的延长而逐渐降解,宰后9 h,正常肉样与PSE肉样的踝蛋白相对光密度值差异显著(p < 0.05),而在其余的测定时间点(45 min、3、12、24 h)两种肉样的踝蛋白相对光密度值无显著差异(p > 0.05)。宰后各时间点(45 min、3、9、12 h)踝蛋白的相对光密度值与汁液流失率呈不显著正相关(p > 0.05)。研究表明:正常组的踝蛋白降解程度低于PSE组的踝蛋白降解程度。     

磷脂酶活性对冷却肉持水性的影响

对正常肉和PSE肉样的肉质特性和磷脂酶活性进行了测定和分析。宰后PSE肉的pH1h和pH24h低于正常肉,而L值(宰后1h、24h)、脂肪氧化程度、汁液流失率、贮藏损失、蒸煮损失和磷脂酶A2总活性明显高于正常肉。冷却肉的汁液流失率与pH1h和pH24h呈强负相关,与T1h、磷脂酶A2总活性和非钙依赖型磷脂酶A2呈显著正相关。结果说明,宰后的低pH、宰后早期肌肉高温和磷脂酶A2活性对冷却肉汁液流失有重要作用。     

生猪宰前不同静养时间和屠宰方式对背长肌肌肉pH值和滴水损失的影响

两个不同的屠宰场分别随机选取50头待宰的商品猪分为两组,分别进行屠宰前禁食6h和12h处理,测定背最长肌pH值和滴水损失率.结果表明,6h和12h不同的静养时间对肌肉滴水损失率没有显著差异,但是升高了屠宰后24h肌肉pH值,表明宰前较长时间的静养有利于提高肌肉品质性能.另外对电击致晕屠宰和活体屠宰方式相比,前者滴水损失率明显低于后者,表明电击致晕的屠宰方式对提升肉品质量来讲是一种更适宜推广的方式.     

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.     

不同排酸方式对巴美肉羊肉品质的影响

随机选择相同饲养条件下的巴美肉羊,以非吊挂排酸和吊挂排酸两种方式进行对比实验,分别测定其不同部位0.5～48h pH值的变化规律和24～72h剪切力的变化规律。结果显示：非吊挂排酸羊股二头肌、背最长肌、臂三头肌均在宰后6h或8h的pH值显著小于吊挂排酸羊（P〈0.05）。非吊挂排酸羊在不同时间pH值没出现显著下降,吊挂排酸羊在不同时间pH值易出现显著下降。通过对巴美肉羊宰后24～72h时间内指定部位肌肉剪切力变化规律得出吊挂排酸羊3个指定部位剪切力总体要比非吊挂排酸羊剪切力低。在吊挂排酸方式下背最长肌剪切力最易出现显著变化。     

不同电压电击昏对猪肉品质的影响

30头品种、年龄、性别相同的杂交猪(体重120 kg±5 kg)随机分成3组,每组10头,分别用215、150、100V的电压在头部进行电击昏后屠宰.取背长肌测定各项肉质指标.结果显示:宰后45 min采用215 V电压电击昏组的猪肉pH值与150 V电压组差异显著(P<0.05),其它时间点差异不显著;215 V电压组与100 V电压组相比在45 min、1.5、2.5、24 h差异显著(P<0.05).150 V电压组与100 V电压组相比在1.5、2.5 h差异显著(P<0.05).击昏电压对宰后背长肌的色泽(L*和a*值)、滴水损失、蒸煮损失、嫩度、没有显著影响(P<0.05);宰后24 h 215 V组的细胞间空隙面积明显高于其它两个组.生产操作中建议击昏电压采用150 V电压.     

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。     

不同宰后时间冷冻对肉糜质量的影响

将宰后4、12、24和48h的分割猪后腿肉进行常规冷冻,经0～4℃解冻后制成肉糜,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冻结对肉糜品质指标的影响规律。结果显示:采用不同宰后冷冻时间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值显著升高。这说明长时间存放对于肉糜品质的保持不利。通过对同一存放时间不同宰后时间冷冻的比较来看,采用宰后4h和12h冷冻的原料肉生产的肉糜其蒸煮损失显著低于宰后24h和48h冷冻的原料肉所生产的肉糜。存放试验进行过程中宰后12h冻结肉样生产的肉糜系水力始终保持较大。这提示宰后12h冻结的原料肉可能更适合进行肉糜生产。     

Prediction of pork quality attributes from near infrared reflectance spectra

Near infrared spectroscopy (NIRS) is one of the most promising techniques for large-scale meat quality evaluation. We investigated the potential of NIRS-based models to predict drip loss and shear force of pork samples. Near infrared reflectance spectra (1000-2500 nm), water-holding capacity, shear force, ultimate pH, and colour (L(?), a(?), b(?)-value) of 96 pork longissimus muscles were recorded at 2 days post mortem. Stepwise multiple linear regression (SMLR) and partial least squares regression (PLSR) analyses were used to formulate models for drip loss and shear force. Prediction models for drip loss correlated moderately strong with measured drip loss (R=0.71-0.74), which is similar to the correlation obtained using a combination of ultimate pH, filter paper test, and L(?)-value (R=0.74). The current results indicate that NIRS enables the classification of pork longissimus muscles with a superior or inferior water-holding capacity as having a drip loss lower than 5% or higher than 7%. No useful models could be constructed for shear force.     

Prediction of pork quality with near infrared spectroscopy (NIRS): 1. Feasibility and robustness of NIRS measurements at laboratory scale

The objective was to study prediction of pork quality by near infrared spectroscopy (NIRS) technology in the laboratory. A total of 131 commercial pork loin samples were measured with NIRS. Predictive equations were developed for drip loss %, colour L*, a*, b* and pH ultimate (pHu). Equations with R(2)>0.70 and residual prediction deviation (RPD)≥1.9 were considered as applicable to predict pork quality. For drip loss% the prediction equation was developed (R(2) 0.73, RPD 1.9) and 76% of those grouped superior and inferior samples were predicted within the groups. For colour L*, test-set samples were predicted with R(2) 0.75, RPD 2.0, colour a* R(2) 0.51, RPD 1.4, colour b* R(2) 0.55, RPD 1.5 and pHu R(2) 0.36, RPD 1.3. It is concluded that NIRS prediction equations could be developed to predict drip loss% and L*, of pork samples. NIRS equations for colour a*, b* and pHu were not applicable for the prediction of pork quality on commercially slaughtered pigs.     

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。     

宰后猪肉pH值、骨架蛋白表达水平和持水性之间的关系

以20 头猪的背最长肌为材料,分别于宰后45 min和3、9、12、24 h测定猪背最长肌的pH值和整联蛋白、黏着斑蛋白、踝蛋白表达水平,并测定汁液流失率,探讨它们之间的关系。结果显示：高pH组（pH45 min≥6.00,n＝6）的汁液流失率和踝蛋白表达水平低于低pH组（pH45 min≤5.78,n＝14）,整联蛋白和黏着斑蛋白表达水平高于低pH组。pH值和整联蛋白、黏着斑蛋白表达水平与汁液流失率呈负相关,踝蛋白与之相反。pH值和整联蛋白、黏着斑蛋白、踝蛋白表达水平分别解释了汁液流失率变异的77%、41%、44%和34%。上述结果表明：pH值和骨架蛋白变化都会对猪肉持水性产生影响,但pH值的降低对猪肉持水性的影响比骨架蛋白降解影响更大。pH值会通过影响细胞骨架完整性,进而影响最终产品的持水性。宰后45 min的pH值可以用于预测宰后猪肉的汁液流失率。     

Effects of PSE on the quality of cooked hams

Meat quality comparisons were carried out on hams produced from pork legs showing evidence of PSE and normal pork legs. Quality measurements included drip loss, sliceability, cooking loss, TBARS analysis and colour evaluation (Hunter L, a, b). A total of 40 pork legs were selected from a commercial slaughtering plant, 20 from carcasses showing PSE and 20 from normal carcasses based on L, a, b, and pH values. Carcass pH taken between the third/fourth rib was measured 45 min, 90 min, and 24 h after slaughter. Using a Minolta colorimeter (Hunter L, a, b,), colour of the Longissimus dorsi muscle was measured 24 h after slaughter. PSE had an adverse effect on cooked hams in comparison to normal cooked hams with respect to driploss (P<0.01), cooking loss (P<0.01), sliceability (P<0.01), colour (P<0.05) and lipid oxidation (P<0.05). Cooked hams manufactured from severe PSE pork in this study had an estimated financial loss of 50% (IRL￡4.90) in comparison to those manufactured from normal pork (IRL￡9.80).     

梅山猪与三元杂交猪肉宰后成熟过程品质变化比较

目的：比较梅山猪与三元杂交猪的肉品质以及影响两个猪种持水力的因素,为梅山猪肉质性状的选择提供一定的参考。方法：选取6 头梅山猪和6 头三元杂交猪,在宰后45 min取胴体左侧背最长肌,采用低场核磁共振技术测定肌肉中水分分布情况以及酪蛋白酶原分析法测定钙蛋白酶的活性,在成熟过程中的1、3、7 d测定肌肉的持水力。结果：梅山猪肉色的L*值和a*值与三元杂交猪差异显著（P＜0.05）。梅山猪宰后成熟1、3 d的贮藏损失率和宰后1 d的蒸煮损失率显著低于三元杂交猪（P＜0.05）,说明梅山猪肉具有较高的保水性。梅山猪宰后45 min的pH值显著高于三元杂交猪（P＜0.05）。低场核磁共振T2弛豫测定结果表明,梅山猪肉中结合水含量显著高于三元杂交猪,自由水含量显著低于三元杂交猪（P＜0.05）。肌肉水分分布的差异在一定程度上解释了两种猪肉的持水力的变化。梅山猪与三元杂交猪肉中的钙蛋白酶活性在成熟第1天差异显著（P＜0.05）,成熟第3天和第7天差异不显著。结论：钙蛋白酶活性对这两个猪种的保水性影响不大,肌肉的水分分布及宰后45 min、pH值的差异解释了梅山猪具有较高的保水性。     

Muscle pH(60), colour (L, a, b) and water-holding capacity and the influence of post-mortem meat temperature

The use of the pH(60) and colour parameters (L, a, b) as chilled pork drip loss predictors 24 h post-mortem as well as the influence on this meat characteristic of an early blast cooling regime (90 min post-mortem) were investigated. Despite the best correlation found with pH(60) (-0·647), both indicators were found to be poor for this purpose, it being impossible to use them alone for pork quality classification (PSE/DFD status). Comparing the evolution between the drip losses on chilled and early deep frozen (-60°C) longissimus dorsi pork cuts, the results indicate that both the thawing regime and the time the samples stay in refrigeration, influence the observed trends significantly. The general drip loss enhancement seen after thawing as well as the increasing meat toughness, judged subjectively, must be due to cold-shortening and/or thaw rigor phenomena.     

Use of electrical conductivity to predict water-holding capacity in post-rigor pork

This study was designed to re-examine the interrelationships among ultimate pH (pH_u), electrical conductivity (EC) and water-holding capacity (WHC), and to test if EC, using one of two EC instruments, and pH_u can be used to predict WHC. The % drip (PD) was used as measure of WHC. Forty-seven pork loins were classified either as PSE (pale, soft, exudative), RSE (reddish-pink, soft, exudative), RFN (reddish-pink, firm, non-exudative) or DFD (dark, firm, dry), based on L* values, PD and pH_u. The measurement of EC, conducted using the instrument developed at the University of Wisconsin-Madison (UW-EC) was highly correlated to PD at 24 h post mortem (CD=66%), but the pH (NWK) measure of EC was not as highly related to WHC as UW-EC. The predictive value of pH_u and EC for WHC were similar. When 47 samples were divided into three different groups, such as low (< 2% drip), medium (2–6% drip) and high (> 6% drip) drip loss, UW-EC alone grouped 80% of the samples correctly. Thus, EC seemed to be an accurate predictor of WHC in pork muscle when measured at 24 h post mortem. It is conceivable that EC can be used independently, or with even better success in combination with pH_u, to classify WHC of pork carcasses.     

紫外照射结合乳酸处理对冷冻藏猪肉品质的影响

研究紫外辐照结合乳酸处理对冷冻藏猪肉品质的影响,明确该方法对藏猪肉冷冻贮藏的可行性。测定指标包括冷冻藏猪肉的肉色、质构、pH、TVB-N值。结果显示,在贮藏期内与对照组比,处理组L^*值基本呈下降的趋势,a^*值也低于对照组,且呈先升高后降低的趋势,与对照组差异显著(p<0.05);pH显著增加(p<0.05);处理组与对照组的滴水损失逐步增加;TVB-N值较对照组显著降低(p<0.05);试验后期,处理组与对照组在硬度和弹性方面出现显著差别(p<0.05)。结果表明:紫外照射结合乳酸处理对藏猪肉冷冻品质具有显著的影响,在工厂中使用时具有简便易行、提升品质的潜在作用。     

Prediction of technological quality (cooking loss and Napole Yield) of pork based on fresh meat characteristics

In order to investigate if cooking loss and Napole Yield can be predicted from various fresh meat characteristics, pH (1, 15, 30, 60, 120 min and 24 h post mortem), temperature (1, 15, 30, 60, 120 min and 24 h post mortem), water-holding capacity (Honikel's drip loss method and centrifugation loss), and NMR T2 relaxation 24 h post mortem were measured in fresh porcine M. longissimus dorsi from 102 Hampshire crossbreeds of known RN(-) genotype. Subsequently, cooking loss and Napole Yield were determined on cooked and cured, cooked samples, respectively, and partial least squares regression (PLS) was carried out to investigate possible intercorrelations between the physico-chemical measurements performed on the fresh meat and cooking loss/Napole Yield. Significant correlations were found between NMR T2 relaxation measured in fresh pork 24 h post mortem and the cooking loss (R=0.64) and Napole Yield (R=0.58), whereas no correlations were found between traditionally applied methods such as pH measurements, Honikel's method and centrifugation, and the cooking loss/Napole Yield. Consequently, it is concluded that NMR T2 relaxation characteristics of fresh pork in contrast to traditional fresh meat characteristics contain information about factors of importance for cooking loss/Napole Yield from cooked uncured/cured pork. The result implies that low-field (LF) NMR data from fresh meat reflects information about water compartmentalisation and mobility that is partly decisive for subsequent heat-induced changes of importance for the distribution of water within the cooked meat. In addition, the obtained results show that LF NMR data measured on fresh meat also seems to contain information about the inherent water of importance for the technological characteristics of the meat even when the meat is cured before cooking.