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.     

Recommended terminology for the muscle commonly designated 'longissimus dorsi'

Musculus longissimus of the erector spinae is frequently used by meat scientists because of its relative mass, its commercial importance and its variability in quality. Its designation has fluctuated considerably due to confusion over interpretation of accepted anatomical guidelines, some of which have been altered to improve precision. We recommend that meat and muscle scientists refer to the part of the whole muscle they generally use as the Longissimus thoracis et lumborum (LTL) or to either of its two parts, Longissimus thoracis (LT) or longissimus lumborum (LL), depending on which is referenced. The word dorsi should be omitted, the word musculus (or its abbreviation M.) preceding all muscles in Latin should not be used in English, and the longissimus atlantis, capitis and cervicis should not be included except when they are actually used.     

Halothane genotype, pre-slaughter handling and stunning method all influence pork quality

Seventy-six Landrace and four Large White × Landrace pigs (n=80) of 90-134 kg liveweight were randomly allocated to a 2×2×2 factorial experiment to determine the effect of halothane genotype [heterozygous for the halothane gene (Nn) and homozygous dominant (NN)], pre-slaughter handling (minimal and negative) and stunning method (CO(2) stunning and electrical) on pork quality. The rate of muscle pH decline post-slaughter of the m. longissimus thoracis et lumborum (LTL) muscle was faster in Nn pigs compared with NN pigs (0.86 and 0.30 pH units/h, respectively). Pork from Nn pigs was also paler in colour, had higher percentage drip loss and purge and lower sarcoplasmic and myofibrillar protein solubility compared with NN pigs. Pork from CO(2) stunned pigs had a lower drip loss compared to pork from electrically stunned pigs (5.80 and 7.28%, respectively?- means of both genotypes combined). Tenderness of pork assessed at 24 h post-slaughter was not influenced by genotype, pre-slaughter handling or stunning method. However, pork from Nn pigs aged for 5 days post-slaughter was less tender than NN pigs (5.84 and 4.84 kg, respectively). Pale, soft and exudative pork was produced in all negatively handled Nn pigs, regardless of stunning method. The average amount of ecchymosis-affected muscle trimmed from carcasses of electrically stunned pigs was higher compared to pigs stunned with CO(2) (65 and 0.7 g, respectively). These data indicate that although halothane status was the most important factor influencing pork quality, pre-slaughter handling and stunning method also influenced meat and carcass quality.     

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。     

Improving pork quality by electricalstimulation or pelvic suspension ofcarcasses

This investigation compared the separate and combined effects on meat quality of electrical stimulation (ES) and pelvic suspension of pig carcasses chilled rapidly or conventionally. Sides from 80 pigs, 80–90 kg live weight, were allocated to one of four treatments followed by either conventional chilling (1°C for 24 h) or rapid chilling (-20°C for 2–3 h, before 1°C until 24 h post-slaughter). The four treatments were: Achilles suspended, with and without high voltage ES, and pelvic suspended, with and without ES.

The quality attributes: pH, colour and opacity, drip loss, instrumental and sensory texture were measured in M. longissimus thoracis et lumborum, at 10 days post-slaughter. Rapid chilling reduced the evaporative weight loss by 0·5% There were no significant effects of treatment on colour or opacity, although ES samples were slightly paler. Drip loss was also slightly greater with ES, particularly when combined with pelvic suspension, but in no case was the meat classified as PSE. Instrumental measurements of 'texture showed improved tenderness from both ES and pelvic suspension, even after 10 days ageing. The improvement was less pronounced when ES and pelvic suspension were combined Taste panelling confirmed that samples treated by ES or pelvic suspension, separately or combined, were significantly more tender than samples from non-ES, Achilles hung sides. ES and pelvic suspension were equally effective in improving the tenderness of pork loin. Pelvic suspension did not suffer the disadvantage of increased drip loss that occurred with ES in this study.     

Variations in meat quality in live halothane heterozygotes identified by biopsy samples of M. longissimus dorsi

The meat quality of halothane heterozygotes (Nn) was investigated using British Landrace (n = 18) and Landrace × Large White pigs (n = 67). Normal and PSE meat were identified in both breeds using M. longissimus dorsi (LD). In Landrace × Large White Nn pigs, the potential meat quality identified using small biopsy LD samples (500 mg) showed a wide spectrum in water-holding capacity (WHC), ranging from normal (43%) to PSE (57%). Predictions of meat quality in live pigs were confirmed from post-mortem assessments of LD samples based on pH(1) and fibre optic probe measurements. Our results show that Nn pigs have the propensity to produce a higher proportion of PSE than normal carcasses. The predictive meat quality test performed on small biopsy LD samples offers an opportunity not currently available to the pig industry, to select Nn pigs with the potential to produce pork of superior WHC.     

Effect of dietary supplementation of vitamin E on pig meat quality

The effect of vitamin E on pig meat quality was investigated using British Landrace (NN and nn), Landrace × Large White (NN and Nn) and Pietrain (nn) pigs. Daily dietary supplementation of 500 mg vitamin E/kg diet for 46 days could reduce drip loss in unfrozen longissimus thoracis (LT) by 45% and 54% in Nn and NN pigs, respectively. In PSE-prone Landrace × Large White Nn pigs, daily supplementation of 1000 mg vitamin E/kg diet for the same period could significantly (P < 0.001) reduce excess release of Ca(2+) and prevent the formation of PSE carcasses, evaluated from both biopsy and post- mortem LT samples. Experimental evidence from erythrocyte fragility and water-holding capacity of biopsy LT samples suggested that vitamin E improved pig meat quality by its ability to stabilize membranes. Stabilization of membrane integrity in isolated mitochondria of LT by vitamin E was associated with inhibition of phospholipase A(2) activity.     

Lightness of the color measured by computer image analysis as a factor for assessing the quality of pork meat

The aim of this study was an attempt to use computer image analysis (CIA) to detect PSE (pale, soft, exudative) defect in pork meat. Material for the study was 50 slices obtained from pork longissimus muscles (m. longissimus) from 50 different animals. Based on measurements of pH, electrical conductivity, color lightness (L*), sixteen of the slices were classified as PSE meat. Another sixteen slices showed features of a normal meat. Photos of tested meat slices were taken and analyzed with computer image analysis. The article presents the data in three color models: RGB, HSV/HSB and HSL. Obtained results demonstrate the possibility of using V/B values (HSV/HSB model), L (HSL model) and the R, G, B values with the RGB model to detect PSE defect in pork meat.     

Effect of dietary vitamin E supplementation on pork quality

The purpose of this experiment was to examine the effect of dietary vitamin E supplementation on pork quality, and in particular on colour stability. Crossbred pigs (n = 72) at a mean weight of 44 kg were assigned to one of two treatments. One group received, during a period of 84 days prior to slaughter, a tapioca based diet, which contained 8 mg vitamin E per kg feed. The other group received during this period the same diet, except it was supplemented with 200 mg vitamin E per kg feed. Muscle samples of longissimus thoracis and lumborum (LL) and psoas (PM) were collected at 24 hr post mortem and meat quality was assessed: pH, drip and cooking loss, shear force and intramuscular fat content. Colour stability was evaluated in fresh muscle (LL and PM) and after freezing (LL only) by measuring redness (a(?)-values) during 6 days of storage at 7 °C. TBA-values and microbiological counts were also determined during storage. Results showed that extra dietary vitamin E had no effect on pig performance (daily gain, feed efficiency, lean meat percentage) nor on meat quality traits. The vitamin E levels were five times higher in the muscles of the treated group than the control group. In comparison with fresh LL muscle, colour stability was lower in PM and after freezing. In both muscles, the vitamin E treatment reduced TBA-values, in particular after frozen storage. No effect was found on microbiological counts. Colour stability was improved in LL after 6 days of storage, but not in PM. The effect in LL is too late to be of practical significance, since pork is usually sold well before that time in The Netherlands. It is suggested that variation in feedstuff composition of the diet may possibly explain part of the variable results reported in literature for the effect of vitamin E supplementation on colour stability of pork.     

Effect of castration on meat quality in Piemontese cattle

The effect of early (5 month) or late castration (13 month) on meat quality of hypertrophied Piemontese cattle was investigated. Twenty four animals, equally divided into three groups (early castrated, EC; late castrated, LC; intact males, IM) were reared under the same experimental conditions and slaughtered at the same age. Twenty four hours after slaughter the pH was measured on the longissimus thoracis of the right side. After 11 days of ageing the following analyses were performed on the longissimus thoracis et lumborum: water, protein and ether extract contents, hydroxyproline content and collagen solubility, colour (L, a(L), b(L), hue and chroma), drip and cooking losses, Warner-Bratzler shear values and sensory analysis (appearance of the raw meat and eating qualities of the cooked meat). Compared with intact males, the castrates had lower water and hydroxyproline contents and higher contents of protein and ether extract. No significant differences were observed between early and late castration, except for cooking losses.     

The effect of time and type of electrical stimulation on the calpain system and meat tenderness in beef longissimus dorsi muscle

Effects of type and time of electrical stimulation on the calpain system, sensory and objective meat quality in the M. longissimus thoracis et lumborum from 38 pasture-fed carcasses, were investigated under conventional chilling conditions. High voltage stimulation was applied to whole carcasses at 3 min post-mortem (pm) and to sides at either 40 or 60 min pm, whilst low voltage stimulation was applied to whole carcasses at 3 min pm and to sides at 40 min pm. Unstimulated sides served as controls. The levels of extractable μ-calpain and calpastatin decreased during stimulation by 28-44% and 8-17%, respectively. Shear force and adjusted tenderness score showed that stimulation at 3 min, irrespective of type of stimulation, resulted in significantly tougher meat (P<0.05) which was associated with an rapid rate of pH decline, compared to stimulation at 40 min. Higher calpastatin levels soon after stimulation at 3 min (P < 0.05) and lower μ-calpain level at 24 h pm for high voltage stimulation at 3 min (P<0.05) coincided with the tougher meat. On the other hand, high voltage stimulation at 40 and 60 min resulted in similar tenderness and levels of μ-calpain and calpastatin post-stimulation and 24 h pm. Significantly tougher meat from the control sides, with a higher μ-calpain levels at 24 h pm and similar sarcomere length, compared to those from low voltage stimulation at 40 min (P<0.001), appeared to be linked to the later activation of the calpain system. Results from the current study suggest that early application of stimulation may be associated with a very rapid decline in pH and consequently a reduction in meat quality.     

Is colour brightness (L-value) a reliable indicator of water-holding capacity in porcine muscle?

A total of 265 pork carcasses representing a broad variation in quality was used to examine the relationship between colour (L-value) and water-holding capacity (WHC) in the longissimus thoracis et lumborum. Thirty-four samples appeared to possess 'normal' reddish pink colour (L-value 52·0-58·0) but had 'unacceptable' WHC (>5·0% drip loss). Conversely, 25 samples were pale in colour (L-value >58·0) but were 'acceptable' in WHC. When muscles were dark (L-value 52·0) the WHC was always acceptable. Some samples were subjected to further analysis. Variations in iron content, haematin content, sarcomere length and degree of soluble protein denaturation failed to explain why brightness and WHC were not more closely related. When L-value and WHC were compared to pH(45) (pH, 45 min post mortem), WHC exhibited a biphasic relationship to pH(45) whereas L-value did not. These results indicate that WHC and brightness are determined by independent pre-rigor biological phenomena, strengthening the argument that brightness is not necessarily a reliable predictor of WHC. Researchers selecting pork for specific investigations, or commercial companies using fresh pork for either further processing or for retail, should not rely on colour brightness alone to insure that other quality properties such as WHC and firmness will also be acceptable.     

Collagen cross-linking in porcine m. longissimus lumborum: Absence of a relationship with variation in texture at pork weight

The determination of all currently known intermolecular cross-links present in intramuscular collagen of porcine m. longissimus lumborum is described in relation to the texture of the meat as determined both objectively by instrumentation and subjectively by sensory panel. The variation in texture observed in the m. longissimus lumborum of pork weight pigs has been shown to be unrelated to the total collagen content or to the nature of the collagen intermolecular cross-links. We have also demonstrated a considerable error in the colorimetric method for quantitation of hydroxyproline when determining the very low values of collagen present in pig meat. During this study we have established a sound protocol for the determination of all the known cross-links in intramuscular collagen of meat from any meat animal species.     

HALOTHANE GENOTYPE, CHILLING AND LOCATION WITHIN MUSCLE: EFFECTS ON PORK QUALITY

Intact sides were subjected to accelerated chill (AC: −30C for 2.5 h, 4C for 20–22 h) or conventional chill (CC: 4C for 22–24 h). Color, drip loss, and pH were evaluated 24 h postmonem at three sites (inner, mid, and outer) in the Semimembranosus (SM) and Biceps femoris (BF) with the inner site closest to the femur. Zle Longissimus thoracis (LT) and the Longissimus lumborum (LL) were also evaluated. Accelerated chill improved color and drip loss of the Longissimus muscle. Accelerated chill had no fleet on the quality measurements of the ham, although site differences occurred. The fleets of genotype on color, drip loss, and pH in the loin and ham muscles were not consistent in the muscle groups studied. Compared to CC, AC has beneficial fleets on fresh pork quality of the Longissimus muscle, but not the ham muscles.     

Perspective of NIRS measurements early post mortem for prediction of pork quality

The potential of near-infrared spectroscopy (NIRS) measurements early post mortem was investigated to predict ultimate drip loss, colour, tenderness and intra-muscular fat of pork. Three locations (M. longissimus thoracis, M. longissimus lumborum and M. semimembranosus) in 102 pig carcasses were tested at the end of the slaughter line. A priori variation in pork quality was introduced using an experimental design covering: genotype, lairage time, pre-slaughter handling and day of slaughter. At 1 h post mortem a diode array VIS/NIR instrument (Zeiss MCS 511/522, 380-1700 nm) equipped with a surface fibre optic probe was used and at 1 day post mortem ultimate pH, drip loss, colour and shear force was measured on similar locations. Results indicated that it was possible to predict intra-muscular fat content (correlation (R(2) of 0.35 with multiple linear regression), standard error of prediction (SEP)=3.6 g/kg), but the configuration has to be refined for on-line application (bigger aperture). For drip loss no correlation was achieved with the PLS method. Even extremes (low drip loss (<2.5%) or high drip loss (>4.5%)) in drip loss were not discriminated. Predicting drip loss with NIRS early post mortem is not successful, although NIRS in the slaughter line has potential as a fast predictor of intra-muscular fat. Possibilities for using the NIRS technique to get to know more about muscle metabolism and post mortem changes are promising.     

Application of constant current, low voltage electrical stimulation systems to pig carcasses and its effects on pork quality

This study examined the effectiveness of a constant current, low voltage electrical stimulation system on improving pork quality when applied to pigs at 2 min post-exsanguination. A total of 48 female Duroc×Large White/Landrace pigs of 85–90 kg liveweight were randomly allocated immediately prior to slaughter to one of four constant current electrical stimulation treatments: control (no electrical stimulation), 50, 200 and 400 mA. Stimulation was applied to pig carcasses at 2 min post-exsanguination for 30 s. No differences (P>0.05) in WB shear force values, muscle lightness or PSE incidence of pork M. longissimus lumborum (LL) was found due to electrical stimulation treatment. Muscle pH of the LL muscle was lower (P<0.001) in carcasses in the 200 and 400 mA treatments compared to those from carcasses in both the 50 mA and control treatment groups, when measured at the various time points from 40 min to 8 h post-slaughter. Although carcasses stimulated with 200 and 400 mA had higher percentage drip loss (P<0.05) and purge (P<0.001), this was not found to impact WB shear force values, muscle lightness or PSE incidence.     

THE RELATIONSHIP BETWEEN COLOR AND WATER-HOLDING CAPACITY IN POSTRIGOR PORCINE LONGISSIMUS MUSCLE

A total 264 pork loins were selected to represent a wide range of pork quality of the longissimus thoracis et lumborum. CIE L*C*h color space showed a closer relationship to the subjective color score than L*a*b*color space. Lightness (L*) was the best measure to predict water-holding capacity (WHC). There were highly significant (p < 0.001) correlations between the measures of color and WHC, and curvilinear relationships between either WHC and color or pHu were observed. In normal muscle color range (reddish-pink), there was considerable variation in WHC. Within the RSE + RFN groups of muscles, less variation of WHC could be accounted for by variations in color measurements. Color and WHC were not closely related and suggest that the RSE (reddish-pink, soft, exudative) condition should be classified as a separate quality category of pork muscle.     

Distribution of intramuscular lipid throughout M. longissimus thoracis et lumborum in Japanese Black, Japanese Shorthorn, Holstein and Japanese Black crossbreds

Intramuscular lipid content of M. longissimus thoracis et lumborum was determined at five locations within the ribeye muscle from 267 Japanese Black, Japanese Shorthorn, Holstein and Japanese Black crossbred steers and heifers or cows in order to investigate the distribution of marbling. Breed was a highly significant (P < 0·001) source of variation for amount of marbling at each of the locations measured. Percentage of lipid was higher at the extremities of the muscle than in the middle part and was not affected by sex at any location except for opposite the 6th rib (P > 0·05). Regression equations were derived which relate the percentage of lipid at various locations within M. longissimus thoracis et lumborum to that opposite the 6th rib. A substantial portion of the variation in marbling observed at the other locations could be accounted for by marbling at the 6th rib (R(2) = 0·73-0·90). These data confirm that marbling varies within the ribeye muscle but suggest that it is rather consistent in the distribution pattern exhibited by Japanese Black cattle and their crosses.     

Meat quality of cryptorchid lambs grazing either dryland or irrigated perennial pasture with some silage supplementation

The meat quality of lambs grazed on perennial pasture (ryegrass Lolium perenne, cocksfoot, Dactylis glomerata and white clover Trifolium repens) was examined in three treatments; group 1 (S) lambs were grazed on dryland pasture for 30 days and then offered a supplement of pasture silage ad libitum until slaughter, 30 days later (n = 21). Lambs in group 2 (P) were grazed on dryland pasture throughout (n = 28) and those in group 3 (IP) on irrigated pasture (n = 28). Lambs in group IP had a significantly (p < 0.001) heavier pre-slaughter liveweight and hot carcass weight than lambs in the other two groups. There was no significant difference (p < 0.05) infatscore between groups or in GR when adjusted to a common carcass weight. For cold carcass weight (reduced sample) IP lambs were still significantly heavier than those from group P, but no different to those from group S (n = 15, 15 and 10, respectively). There was no significant difference between groups for measures of fatness or for m. longissimus thoracis et lumborum (LL) area when adjusted to a common carcass weight of 23.6 kg. There was a significant difference between (p < 0.001) treatments for pH, group P carcasses having higher pH values for the LL muscle, with no treatment effect on m. semimembranosus (SM) pH. Differences between groups for meat colour values (L (?), a (?), b (?)) showed no consistent trend and there was no significant difference (p > 0.05) between groups in tenderness of the LL and SM muscles as indicated by shear force values. Aroma of the loin meat from pasture-fed lambs (P) was considered significantly (p < 0.05) stronger than from lambs in groups S and IP (n = 6, all groups) and the flavour of samples from lambs in group P was significantly (p < 0.05) stronger than from lambs in group IP. Overall there was no significant (p < 0.05) difference in acceptability between groups. The results indicate that consumers would be unlikely to detect the differences identified by the panel and that pasture silage will not have an adverse effect on lamb eating quality.     

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.