Muscle glycogen level and meat quality in pigs of different halothane genotypes

The halothane genotype of 22 Polish landrace pigs was determined using halothane test and blood typing. Eight homozygous normal (NN), eight hetero-zygotes (Nn) and six homozygous recessive (nn) were identified. The levels of glycogen and lactate were measured in biopsy samples taken from the longissimus lumborum using a shot biopsy technique. pH (pH(1)) and IMP/ATP ratio (R) were determined at 30 min after slaughter, while pH, meat colour and water holding capacity were determined on the day after slaughter. The halothane genotype did not affect intra vitam glycogen level. The nn pigs had a higher R value and lower pH(1) than both Nn and NN animals. Heterozygous animals were intermediate between both homo-zygotes for biopsy lactate level and meat colour. The lactate content of biopsy samples was significantly correlated with pH(1) (r = -0·68; P < 0·01), R (r = 0·68; P < 0·01), meat colour (r = 0·57; P < 0·01) and water holding capacity (r = 0·45; P · 0·05).     

Influence of PSE pork on the quality and economics of cooked, cured ham and fermented dry sausage manufacture

PSE pork (pH(1) ≤ 5·8) and non-PSE pork (5·8 < pH(1) ≤ 6·4) were used for cooked, cured ham production and, with beef, in a 48 52 mixture for fermented dry sausage manufacture. Technological yields of PSE and non-PSE hams were, respectively, 94·0 and 105·9% which corresponded to 5·0 FMK/kg loss for the PSE ham compared to the non-PSE ham. In addition, cooked PSE ham had a poorer organoleptic quality compared to non-PSE ham. However, PSE meat could be mixed with normal meat for the production of fermented dry sausage without quality defects.     

响应面法优化低钠盐水火腿加工工艺

为研究一种低钠盐水火腿的加工工艺,选取复合磷酸盐添加量、盐水注射量、滚揉时间和低钠盐替代比为考察因素,通过单因素实验探究对低钠盐水火腿得率、保水性、质构和异味(仅低钠盐替代比需测定)的影响,利用响应面法,以得率和保水性作为响应值进行优化,并根据实际可操作性调整,得到低钠盐水火腿的加工工艺。结果表明,低钠盐水火腿的最优加工工艺为:复合磷酸盐添加量0.39%,盐水注射量15%,滚揉时间15 h,低钠盐替代比53%。在此条件下,低钠盐水火腿的得率为(93.88%±2.05%),保水性为(87.37%±1.82%),与预测值非常接近。在该工艺下,得到的低钠盐水火腿具有良好的得率、保水性和质构,并且无异味;此外,与普通盐水火腿相比,钠含量降低了27%,为低钠盐水火腿的加工提供了技术支撑。     

Bovine Longissimus dorsi muscle glycogen and color response as affected by dietary regimen and post-mortem electrical stimulation in young bulls

Eighty bulls were assigned to one of two groups and fed a dietary regimen to defer or accelerate growth until slaughter. Bulls fed at an accelerated rate of growth (or high energy regimen) had higher post-mortem pH, and lower muscle glycogen stores, with darker lean color, and improved shear and palatability traits compared to deferred fed animals. Bulls fed at an accelerated rate of growth also had a higher degree of marbling and USDA quality grade. Electrical stimulation did not affect (P > 0·05) ultimate pH, but reduced (P < 0·05) glycogen values at 0 and 2 h post mortem. Electrical stimulation also improved muscle color, lowered cooking losses and improved the palatability of cooked longissimus dorsi steaks.     

A note on the relationships between cured-cooked and dry-cured ham processing yields

Right and left hams from 353 pigs slaughtered at around 100 kg body weight were processed into cured-cooked hams and dry-cured hams, respectively. Weights and yields at various stages of each process, carcass lean content and fresh meat quality traits were registered. Technological yield of cured-cooked processing (saleable cooked ham weight/defatted–deboned fresh ham weight) was more closely correlated to ultimate pH (r = 0.51, p < 0.001) than to carcass leanness (r = −0.13, p < 0.05) whereas the reverse situation – r = 0.15 (p < 0.01) and r = −0.62 (p < 0.001), respectively – was found for technological yield of dry-cured processing (saleable dry ham weight/trimmed fresh ham weight). The correlation between the two technological yields was significantly positive but of fairly moderate magnitude (r = 0.36). The correlation between the overall yields (saleable processed ham weight/entire fresh ham weight) of the two processes revealed to be very close to zero (r = −0.01).     

Carcass characteristics and meat quality of halothane negative and halothane positive pietrain pigs

One hundred and seventy-six Pietrain pigs were tested for halothane sensitivity by means of a 5-min halothane anaesthesia in two experiments. One hundred and twenty were halothane negative (HN) and 56 were halothane positive (HP). In one experiment pigs were slaughtered under commercial (stress) conditions; in the other experiment pigs were killed under minimal stress conditions.

The carcasses of HP pigs were meatier and shorter and contained 2·2% more muscle than the carcasses of HN pigs.

Halothane positive pigs gave a meat of poorer quality, as assessed in the fresh state. When the pigs were slaughtered under commercial conditions, hams from HP pigs were not inferior in curing ability and had a higher total processing yield of Paris ham due to their higher trimming yield. When the pigs were killed under minimal stress conditions, there was no difference in the total processing yield betwen HN and HP pigs, because the technological yield was markedly reduced in HP pigs. However, in both cases, HP pigs produced more cooked ham per pig.

It is suggested that different physiological mechanisms may account for either PSE (pale soft exudative) or DFD (dark firm dry) meat. The former is the consequence of an excessively high rate of post mortem glycolysis which is clearly manifest in HP pigs when they are killed under minimal stress conditions and the latter appears to be unrelated to halothane sensitivity as the ultimate pH of HP and HN pigs is similar when the animals are slaughtered under stress conditions.     

Muscle glycogen: Comparison of iodine binding and enzyme digestion assays and application to meat samples

A rapid assay for tissue glycogen is described. Bovine liver and muscle glycogen were solubilized with perchloric acid (7-10%) and incubated with an iodine (I(2)-KI) solution containing saturated CaCl(2). The optical density of the amber-brown color was determined at 460 nm. Color development was immediate, stable for up to 2 h, and was linear with respect to glycogen concentrations up to 600 μg glycogen/ml. The iodine assay was applied to fresh, frozen, and aged bovine muscle samples and was compared to enzymic (amyloglucosidase) digestion of glycogen followed by glucose determination. The correlation between the iodine and enzyme methods was linear over the range of 0-1400 g glycogen/g tissue (corr = 0·875; P < 0·01; n = 172). The iodine binding assay can be employed with confidence as an indicator of tissue [glycogen] and is faster and more reliable than the enzyme assay. Comparison of the iodine enzyme assays on aged meat samples revealed marked decreases in muscle glycogen during the first 48 h post slaughter. The decreases were identical whether determined by iodine binding or enzyme assay. Regardless of assay method, post-mortem concentrations of glycogen in bovine sternomandibularis muscle were more variable than in longissimus dorsi samples.     

不同贮藏温度西式火腿切片品质变化规律研究

为研究市场上低温火腿切片的质量和安全性,对不同贮藏温度的真空包装火腿切片的品质变化进行动态跟踪,分析产品在0～4、7～11℃条件下,其感官品质、菌落总数、大肠菌群、色泽、pH值、水分含量、保水性和质构特性的动态变化。结果表明：两种产品品质变化的规律大致相同。0～4℃贮藏比7～11℃产品的菌落总数增长相对缓慢,pH值、水分含量,保水性和质构特性的变化更加稳定。低温更有利于保持产品品质的稳定性和安全性,延长肉品的货架期。     

(31)P NMR study of post mortem changes in pig muscle

The rate and the extent of post mortem pH changes in pig muscle largely determine pork quality. Fast pH fall combined with low ultimate pH leads to pale soft exudative (PSE) meat; high ultimate pH leads to dark firm dry (DFD) meat. Post mortem metabolism was studied in pig muscle using(31)P NMR. Fifteen pigs, i.e. 7 Large White pigs and 8 Pietrain pigs, were used. Five pigs of each breed were slaughtered, taking care to minimize preslaughter stress. The other pigs (3 Large Whites and 2 Pietrains) were injected with 0·1 mg adrenaline per kg liveweight before slaughter, in order to increase meat ultimate pH. All the animals were killed by electronarcosis and exsanguination. Three of the adrenaline-treated pigs (1 Large White and 2 Pietrains) gave meat with ultimate pH above 6 (DFD meat). The pigs with normal muscle ultimate pH, i.e. 6 Large Whites and 6 Pietrains, had very variable rates of post mortem muscle metabolism (pH at 30 min after slaughter: 6·17-6·85 in Large Whites; 6·04-6·23 in Pietrains). The relationships between pH and ATP changes were similar in all pigs showing normal muscle ultimate pH, whereas ATP disappeared at a high pH value (on average pH 6·4) in pigs with high ultimate pH. The course of post mortem biochemical changes in a given animal could be predicted rather well by examination of a single(31)P NMR spectrum obtained around 30 min after death. At this time, muscle with a low rate of metabolism simultaneously showed medium to high pH, high ATP content (4-6·8 μmol/g) and rather low Pi content (6-14 μmol/g); muscle with a fast rate of metabolism (PSE-prone muscle) had low pH, low to medium ATP content (1·1-4 μmol/g) and generally high phosphomonoester (PME) content (9-23 μmol/g); muscle with high ultimate pH (DFD-prone muscle) had high pH, low PME content (4-8 μmol/g) and high Pi content (22-27 μmol/g).     

Effect of time between adrenaline injection and slaughter on the rate and extent of post-mortem metabolism in porcine skeletal muscle

The aim of this work was to study the effect of time between adrenaline injection and slaughter on the rate and extent of post-mortem metabolism in pig muscle. Five pigs were subcutaneously injected with adrenaline (0·3 mg/kg) or with a saline solution 4 h, 1 h or 15 min prior to slaughter. pH(1), pH(u) and FOP(u) were measured in Longissimus dorsi (LD) and Biceps femoris (BF) muscles. m.LD samples were taken 20 days before slaughter using biopsy sampling, immediately after bleeding and 45 min post mortem for biochemical analysis. m.LD glycolytic potential (very close to glycogen content) was decreased by the injection of adrenaline 4 h and 1 h prior to slaughter, when comparing values at rest (20 days before slaughter) and values determined immediately after bleeding. The depletion was greater fro the injection performed 4 h before slaughter. In this group pH(u) was higher foe adrenaline-injected pigs (5·69 versus 5·47 for pigs injected with saline solution) but the difference was not significant. Pigs injected with adrenaline 1 h prior to slaughter exhibited higher glucose, glucose-6-phosphate and lactate levels immediately after slaughter, lower pH(1) and higher FOP values in m.LD than control pigs. Since the differences in pH(1) were not explained by differences in the rate of build-up of lactate, it was hypothesized that pigs injected with adrenaline 1 h prior to slaughter had lower muscle pH at slaughter. It was concluded that the rate or the extent of post mortem metabolism in pig muscle may be affected independently, by manipulating the time between adrenaline injection and slaughter.     

The effect of temperature and ultimate pH on the increase in meat toughness resulting from restraint during cooking

Samples of stretched muscle cooked at 50, 60, 70 or 80°C, while restrained at either their original pre-cooking length or further tensioned at about 130% of their original pre-cooking length, had significantly (P < 0·001) greater Warner-Bratzler (WB) peak shear force values for all temperatures than similar samples cooked without restraint except for those restrained at their original length and cooked at 50°C. Restraint during cooking at 80°C increased the peak shear force values of stretched sheep muscles with ultimate pH values in the range 5·5-7·0. This increase, which has been related to connective tissue strength, was not significantly related to ultimate pH. Both initial yield and peak force values, for samples cooked either restrained or unrestrained, decreased significantly (P < 0·001) and at similar (not significantly different) rates with increase in ultimate pH.     

Muscle glycogen depletion pattern in halothane-gene-free pigs at slaughter and its relation to meat quality

Muscle fibre type composition and glycogen depletion pattern at slaughter as related to meat quality, were studied in M. longissimus dorsi of halothane-gene-free Swedish Yorkshire pigs fed a high (n=19; 10 entire males and 9 gilts) or a low (n=18; 10 entire males and 8 gilts) protein diet. The muscle consisted of, on average, 8% type I, 9% type IIA and 83% type IIB fibres. Muscle fibre areas were significantly smaller in entire male pigs than in gilts irrespective of fibre type. There were no marked differences in muscle characteristics between pigs fed the low and high protein diets. Low glycogen concentrations were found in most type I and type IIA muscle fibres, while a greater variation in glycogen content was evident in type IIB fibres. The pigs were divided into two groups according to the proportion of glycogen depleted IIB fibres (more or less than 30% depleted IIB fibres). In the group where 30% or more of the type IIB fibres were glycogen depleted, a tendency toward DFD meat (dry, firm, dark) was seen, as the meat had higher ultimate pH (5·62 vs 5·52; p=0·02), lower drip loss (2·7% vs 4·4%; p=0·007) and lower reflectance value (darker meat; 16·5 vs 20·6 EEL units; p=0·0005), compared with the group with less than 30% depleted IIB fibres. No difference in total glycogen content was found between these two groups. This indicates that the distribution of glycogen in different fibre types seems to be of importance for the ultimate meat quality.     

Effect of dietary Vitamin E on the stability of raw and cooked pork

Experiments were designed to investigate the effects of dietary α-tocopherol supplementation for 2 weeks prior to slaughter on plasma and muscle α-tocopherol levels and on the oxidative stability of raw and cooked pig muscle during refrigerated storage at 4°C. Plasma and muscle α-tocopherol levels of the pigs on the α-tocopherol supplemented diet (200 mg α-tocopherol acetate/kg feed) were ～2·5-fold higher than those of the pigs on the control diet (30 mg α-tocopherol acetate/kg feed). Dietary supplementation with α-tocopherol significantly (p < 0·01) improved the oxidative stability of both raw and cooked muscle after storage at 4°C for up to 8 days. α-Tocopherol stabilized the membrane-bound lipids against metmyoglobin/H(2)O(2)-initiated oxidation and also significantly (p < 0·05) improved the oxidative stability of rendered fat.     

不同月龄和部位乌珠穆沁羊AMPK活性与肉品质的关系

为研究乌珠穆沁羊不同生长阶段、不同骨骼肌一磷酸腺苷激活蛋白激酶（adenosine monophosphate-activated proteinkinase,AMPK）活性、糖酵解相关指标和肉质相关指标的内在变化规律,选取3、6、9月龄乌珠穆沁羊背最长肌、股二头肌和腰大肌,分别测定其AMPK活性、肌糖原含量、乳酸含量、己糖激酶（hexokinase,HK）活性、pH值、剪切力和色泽等指标。结果表明：AMPK活性升高时pH24 h值、红度值（a*）明显下降,并呈显著负相关（P<0.05）;剪切力随着月龄增大而降低（P<0.05）,腰大肌黄度值（b*）最大,背最长肌b*最小,腰大肌a*变化规律与b*相同,股二头肌与背最长肌a*变化规律与b*相反;同一部位肌糖原含量与月龄呈显著正相关（P<0.05）,背最长肌最大,股二头肌最小（P<0.05）,乳酸含量变化规律与肌糖原含量总体相同;HK活性与月龄呈正相关（P<0.05）,腰大肌最大,股二头肌最小（P<0.05）,AMPK活性随着b*、肌糖原总体含量、6月龄与9月龄乳酸和HK活性升高呈现显著上升趋势（P&l...     

Influence of repeated restraint and isolation stress and electrolyte administration on carcass quality and muscle electrolyte content of sheep

Crossbred lambs were assigned, within weight blocks, to one of four treatments applied in a 2 × 2 factorial design (n = 6 per treatment). Treatment main effects included no stress (NS) or three consecutive days of restraint and isolation stress (RIS) and treatment with either water (W) or electrolytes (E). The experimental design resulted in four treatments, namely NS-lambs given W, NS-lambs given E, RIS-lambs given W, and RIS-lambs given E. Stress treatment consisted of moving each lamb from its home stanchion to a separate location and isolation from visual and tactile contact with other lambs for 6 hours daily for 3 days before slaughter. All lambs received a 320 ml oral drench of either W or E on each day after the stress treatment. Stress treatment reduced (P < 0·05) semitendinosus (ST) muscle glycogen by 4·8-fold. At 24 h post mortem, muscle pH for semimembranosus (SM), biceps femoris (BF) and infraspinatus (IF) was higher (P < 0·05) in RIS-lambs that in NS-lambs. Hunter L(?)a(?)b(?) values, measured on muscle cross-section, revealed a lighter (P < 0·05) BF; more (P < 0·05) red BF, ST, and longissimus dorsi (LD); and more (P < 0·05) yellow ST, SM, BF, and LD for NS-than for RIS-lambs. Muscle from RIS-lambs contained less (P < 0·05) potassium than that from NS-lambs. Restraint and isolation stress of lambs resulted in a reduction in muscle glycogen, but only slight increases in ultimate pH and minimal influences on muscle color. Administration of electrolytes had no effect on lamb carcass quality.     

The effect of oestrus behaviour on muscle glycogen concentration and dark-cutting in beef heifers

Preliminary observations at an abattoir showed an association between oestrus behaviour and dark-cutting in beef. Two follow-up experiments examined the relationship between oestrus behaviour and muscle glycogen content, carcass bruising and meat ultimate pH. In the first experiment heifers in oestrus were compared with controls in mid-cycle. Oestrus was associated with a loss of glycogen in M. longissimus dorsi. Also plasma creatine kinase activity increased, reflecting bruising or strenuous muscle activity. In the second experiment heifers were slaughtered during oestrus. On the basis of pre-slaughter behaviour they were assigned to active or inactive groups, which subsequently yielded 39% and zero dark-cutting carcasses, respectively. Loss of muscle glycogen was accounted for by the number of times an animal mounted (r = -0·85). Likewise, variation in meat ultimate pH was associated with mounting activity (P < 0·001). Carcass bruising was higher in the active group (P < 0·0.001) and the main cause of bruising was being mounted (r = 0·74). It was concluded that single penning of oestrus heifers to eliminate mounting activity would reduce the incidence of dark-cutting.     

Effectson carcass weight and meat quality of pigs dehaired by scalding or singering post-mortem

Two experiments were designed to compare the effects of two pig dehairing techniques. In the first experiment, 120 pigs were slaughtered in the same abattoir in five weekly sereis. One half of each series was dehaired by singeing (the usual technique in this abattoir), while the other half was dehaired in a scalding-dehairing combination. In the second experiment, 48 pigs were slaughtered in two series, one-half of each series in an abattoir practising singeing, the other half in an abattoir practising scalding. Temperature and pH were measured 30 min after slaughter in the longissimus lumborum. Meat quality was assessed the day after slaughter in various muscles. One ham was cured and cooked, while the other one was processed by dry-curing. In both experiments, carcass weights and yields were noticeably higher after singeing. Hams were heavier in singed carcasses, but their proportions in the carcasses were little or not at all affected by the dehairing technique. Proportions of loins, shoulders and bellies were similar with both dehairing techniques. The dehairing technique affected neither temperature nor rate of post-mortem pH fall. Meat quality as assessed on fresh meat was slightly better in singed carcasses. Weights of cooked ham and dry ham per side were higher in singed carcasses, due to the higher initial ham weight, but processing yields were not affected by the dehairing technique.     

Cold-batter mincing of hot-boned and crust-freeze-air-chilled ham muscle reduced fat content in protein gels

The purpose of this study was to generate low-fat hot dog using a combination of hot-boning/crust-freeze-air-chilling (HB-CFAC) and cold-batter mincing technologies. After slaughter, pork hams were subjected to hot boning (HB)/CFACor chill-boning (CB)/CFAC prior to 9 min mincing including 3 min pre-mincing. Control gels were prepared with ham, back fat and common ingredients while low-fat gels were prepared with ham, water and common ingredients. The pH values of HB muscle and cooked gels were significantly higher than those of CB muscle and cooked gels. The fat and moisture contents of control gels were higher and lower, respectively, than those of low-fat gels, regardless of HB or CB. The protein functionality and gel-forming ability of HB muscle were superior to those of the CB muscle. These results indicate that fat can be reduced with no textural quality loss when HB-CFAC muscle was cold-batter minced presumably due to improved protein functionality and gel-forming ability.     

Variation of residual glycogen-glucose concentration at ultimate pH values below 5.75

The aim of this study was to investigate the relationship between residual carbohydrate (glycogen-glucose) concentration and ultimate pH of beef. Ultimate pH of longissimus dorsi (LTL), gluteus medius (GM) and semimembranosus (SM) muscles was determined from the left side of 133 Ayrshire bull carcasses. Corresponding muscle samples (about 3 g) were obtained from the sites of the pH measurements. The relationship was curvelinear. At low pH values the total range of residual glucose concentration was up to 73 mmol/kg, maximum being 83 and minimum 10 mmol/kg. The concept of medium-stress beef, where the combination of low ultimate pH and low residual glycogen is an indication of diminished glycogen content at the time of slaughter, is introduced. The potential negative effects of low residual glycogen concentration on the shelf-life of ground beef is discussed.