Tenderness of pre- and post rigor lamb longissimus muscle

Lamb longissimus muscle (n=6) sections were cooked at different times post mortem (prerigor, at rigor, 1dayp.m., and 7 days p.m.) using two cooking methods. Using a boiling waterbath, samples were either cooked to a core temperature of 70 °C or boiled for 3h. The latter method was meant to reflect the traditional cooking method employed in countries where preparation of prerigor meat is practiced. The time postmortem at which the meat was prepared had a large effect on the tenderness (shear force) of the meat (P<0.01). Cooking prerigor and at rigor meat to 70 °C resulted in higher shear force values than their post rigor counterparts at 1 and 7 days p.m. (9.4 and 9.6 vs. 7.2 and 3.7 kg, respectively). The differences in tenderness between the treatment groups could be largely explained by a difference in contraction status of the meat after cooking and the effect of ageing on tenderness. Cooking pre and at rigor meat resulted in severe muscle contraction as evidenced by the differences in sarcomere length of the cooked samples. Mean sarcomere lengths in the pre and at rigor samples ranged from 1.05 to 1.20 μm. The mean sarcomere length in the post rigor samples was 1.44 μm. Cooking for 3 h at 100 °C did improve the tenderness of pre and at rigor prepared meat as compared to cooking to 70 °C, but not to the extent that ageing did. It is concluded that additional intervention methods are needed to improve the tenderness of prerigor cooked meat.     

Microstructural and mechanical properties of camel longissimus dorsi muscle during roasting,braising and microwave heating

This study was conducted to investigate the effects of various heating methods, including roasting, braising and microwave heating, on mechanical properties and microstructure of longissimus dorsi (LD) muscle of the camel. Shear value and compression force increased during microwave heating more than roasting and braising. Results obtained from scanning electron microscopy (SEM) showed more damage from roasting than in either braising or microwave heating. Granulation and fragmentation were clear in muscle fibers after roasting. The perimysium membrane of connective tissue was damaged during braising, while roasting left the perimysium membrane largely intact. The mechanical properties and microstructure of muscle can be affected by changes in water content during cooking.     

Changes in colour of beef m. longissimus dorsi muscle during ageing

The effects of vacuum packaging, chilling rate (slow or fast), and fat cover thickness (?4 mm or 7-8 mm) on the colour parameters of beef m. longissimus dorsi muscle were assessed during ageing. The m. longissimus dorsi muscle was aged on the carcass or in vacuum packaging. Muscle samples for analysis were taken on days 0 (24 hr post mortem), 2, 4, 8, 12 and 16 to ascertain the parameters. Ageing time influenced all colour parameters, while chilling rate affected lightness ('L'), yellowness ('b'), and hue angle difference (HD), and fat cover thickness influenced 'L' and 'b' only.     

Influence of hydrocortisone acetate of the longissimus dorsi muscle during gestation of rats

The evolution in detail of the N retention during gestation was studied, dividing it in short periods of time, and how that retention affects Longissimus dorsi muscle. Simultaneously, the same study in pregnant rats treated with hydrocortisone acetate was done. During gestation N balance maintains high values that tend to increase at days 18 to 21. The greatest metabolic utilization of the N dietary corresponds to this period in which the percentage of the N retained in relation to the N absorbed is markedly higher than in previous days of gestation. In spite of the excellent quality and adequate concentration of protein in the diet, the administration of 4 mg/100 g weight and day of hydrocortisone acetate maintains the pregnant rat in a negative balance until day 18, as a consequence of the decrease in food intake and faecal and urinary N losses. From day 18 to day 21 of gestation the balance of N increases and the metabolic utilization of the dietary N is similar between pregnant rats injected with NaCl 0.9% and pregnant rats injected with hydrocortisone acetate. The Longissimus dorsi normal growth pattern (in relation to weight and N content) in young adult rats is not modified by gestation. The catabolic effects of hydrocortisone acetate on Longissimus dorsi muscle in pregnant rats can be observed from day 9 of treatment. The longer the treatment the higher the effect is.     

Effect of Quillaja saponaria dietary administration on colour, oxidative stability and volatile profile of muscle longissimus dorsi of Barbarine lamb

Eighteen Barbarine lambs were assigned during 77days to three dietary treatments (n=6): control, oat hay ad libitum and 400g of concentrate; QS60 and the QS90 control diet supplemented with 60mg and 90mg Quillaja saponaria (QS) bark extract/kg dry matter, respectively. The analysis of pre-frozen longissimus dorsi muscle showed that the QS90 treatment reduced meat redness (a*) and saturation (C*) measured after 2h of blooming. It also reduced the rate of decrease in a* values (P=0.02) during 14days of refrigerated storage. Supplementation with QS extended meat colour stability by reducing (P<0.05) the rate of increase in hue angle (H*) values. Neither the rate of metmyoglobin accumulation at the meat surface nor lipid peroxidation over storage duration differed between treatments. The overall meat volatile compound profile was similar between the groups. We conclude that supplementing QS affects meat colour development at the meat surface and extends its stability without producing detrimental effects on meat volatile compounds.     

The influence of temperature on shortening and rigor onset in beef muscle

At sufficient ATP concentration and temperatures below about 15°C, pre-rigor beef muscles (neck muscles) contract; this phenomenon is known as cold shortening. There is also a contracture at higher temperatures occurring just before rigor onset which is called rigor shortening. While rigor shortening starts in neck muscles at pH around 6·3–6·0 and at about 2 μMol ATP/g muscle, cold shortening can begin at pH around 7·0 and the full ATP concentration (4 μMol ATP/g) in the muscle. Shortening can take place as long as there is no irreversible formation of the actomyosin complex in the muscle, i.e. before rigor onset occurs, which can be measured by intermittent loading of the muscle. The degree of extensibility which follows starts to decrease at the moment of rigor onset. This irreversible loss of extensibility at temperatures between the freezing point (?1°C) and physiological temperatures (38°C) starts at various pH values and ATP concentrations in the muscle. At 38°C the rigor onset occurs at pH 6·25 and about 2 μMol ATP/g muscle, dropping at 15°C to pH 5·75 and 1 μMol ATP/g muscle. At 0°C, as at all temperatures below 10°C, the loss of extensibility at medium loads (about 250 g/cm²) begins shortly after cold shortening. This loss of extensibility is reversible by increasing the load or raising the temperature. The irreversible loss, or rigor onset, however, occurs at 0°C with pH of 6·1–6·2 and 1·8–2·0 μMol ATP/g muscle. Thus, the onset of rigor is influenced by more than one factor. Temperature, pH and ATP concentration each play a rôle.Maximum loss of extensibility or completion of rigor is reached between 10°C and 38°C at pH 5·5–5·6 and less than 0·5 μMol ATP/g muscle. At 0°C the completion of rigor takes place at pH 6·0, but still at 0·5 μMol ATP/g muscle. The latter fact shows that the completion of rigor is solely dependent on the ATP concentration in the muscle; nevertheless, the pH of rigor completion is higher in the extreme cold shortening range. This is apparently due to a different pH/ATP relationship in muscles at low temperatures.The results are discussed in terms of changes in the concentration of Ca²⁺ ions and ATP.The results are of particular interest for the handling of hot-boned meat; that is, for both the cooling of pre-rigor muscle and the use of hot-boned meat for processing.     

Tenderising in M. longissimus dorsi of beef, veal, rabbit, lamb and pork

The decrease in toughness of M. longissimus dorsi with storage time at 1°C was effectively described by an exponential decay equation. The average rate constant for beef, veal and rabbit was 0·17 whilst that for lamb was 0·21 and that for pork, 0·40 days(-1). However, the rate constants were not significantly different due to variations both within muscles and between animals. On average, 50% of the tenderising occurred in 2 days for pork and in 4·2 days for beef, veal and rabbit, and 80% in 4·9 and 9·5 days, respectively. At the completion of tenderising, beef and rabbit were the toughest and pork the most tender, whilst the greatest tenderising occurred in beef and lamb.     

不同品种猪背最长肌肌苷酸含量及相关基因表达的比较

以安徽地方品种圩猪、安庆六白猪以及国外瘦肉型品种长白猪为研究对象,采用高效液相色谱法测定3种猪背最长肌肌苷酸(IMP)含量。利用家畜或家禽中已鉴定的影响肉质性状的QTLs信息与猪的基因组比对,得到可能与猪肉质相关的目的基因:ADSL与GARS-AIRS-GART基因。定量PCR法比较影响肌苷酸含量的ADSL与GARS-AIRS-GART基因mRNA在肝脏、心脏和背最长肌组织中的表达水平,并研究2种基因在不同猪种中的表达量与IMP含量的相关性。结果表明:长白猪的背最长肌肌苷酸含量高于圩猪和六白猪。ADSL mRNA在3种猪的表达模式均表现为背最长肌中最高,心脏次之,肝脏最低的趋势。而GARS-AIRS-GART mRNA的表达模式为背最长肌最高,肝脏次之,心脏最低的趋势。ADSL mRNA在长白猪肝脏的表达量,GARS-AIRS-GART mRNA在圩猪肝脏和六白猪心脏的表达量均与IMP含量显著负相关。     

Factors affecting the colour of lamb meat from the longissimus muscle during display: The influence of muscle weight and muscle oxidative capacity

Spectrophotometric measures were used to determine the redness:browness (R630/R580) of 4238 lamb longissimus muscle after 3 days under simulated display. The results were analysed using linear mixed effects models. Environmental factors represented by effects such as kill group and site of production produced the greatest variation of up to 2.76 units in R630/R580. Isocitrate dehydrogenase activity, reflecting muscle oxidative capacity, reduced R630/R580 by 0.5 units. Selection for high muscling sires increased R630/R580 by 0.27 units, likely due to changes in muscle oxidative capacity. Lamb carcass weight also increased R630/R580 by 0.5 units. Analysis of genotypic factors influencing lamb size and growth rate such as sire type and dam breed further supported that increased growth rate improves meat R630/R580. Our findings suggest that breeding for increased growth rate and increased muscle weight could result in Australian lamb meat retaining its red colour for extended periods whilst on display.     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged.     

Effect of frozen storage on lipids and lipolytic activities in the longissimus dorsi muscle of the pig

 Samples of longissimus dorsi muscle from pigs were vacuum-packed and stored at –18  °C for a 6-month period. The quantity of total lipids, non-polar lipids, phospholipids and cholesterol remained unchanged during storage. However, there was a decrease (1.4%) in the polyunsaturated fatty acid percentage of the phospholipid fraction after 6 months of frozen storage, mainly due to the decrease in linoleic fatty acid. Nevertheless, there was no change in fatty acid composition of the non-polar lipid fraction. Phosphatidylethanolamine was the phospholipid most affected during the frozen storage, with a significant decrease from an intial percentage of 26.6% to 23.0% after 6 months of storage. Important activities of muscle lipolytic enzymes were still recovered after the storage, which explains the continuous release of free fatty acids reported during the process, with a net increase of 50.6 mg/100 g dry matter. The highest release of free fatty acids was reported during the 1st month of frozen storage. At the 6th month of frozen storage the compositions of both the free fatty acid and phospholipid fractions were similar. With respect to oxidation, the thiobarbituric acid test number showed a slight increase during the process while the peroxide value remained unchanged. Received: 16 March 1998 / Revised version: 17 June 1998     

Effects of muscle shortening and proteolysis on Warner-Bratzler shear force in beef longissimus and semitendinosus

The effect of the addition of the fungal protease EPg222 on the sensory characteristics of dry fermented sausage "salchichón" ripened with commercial starter cultures was investigated. Sausages were prepared with purified EPg222 and Staphylococcus carnosus, Staphylococcus xylosus, and Lactobacillus sakei as starter cultures, ripened for 145 days and compared with a control batch only inoculated with the starter cultures. Dry fermented sausages ripened with EPg222 and starter cultures showed higher amount of NPN and volatile compounds derived from amino acid catabolism, than control ripened only with starter cultures. Several branched aldehydes, acids and alcohols such as 2- and 3-methylbutanoic acid and 2-methylpropanol were detected only in enzyme treated samples. Sensory analysis reflected higher values for aroma intensity of sausages treated with EPg222 and lower values of hardness than control. The effect of EPg222 may be of great interest to improve sensory characteristics of dry fermented sausages ripened with starter cultures.     

Muscle fibre orientation and its effect on measurements of tenderness of bovine longissimus dorsi muscle

The muscle fibre orientation within a particular cooked beef steak was found to vary considerably and to be markedly affected by vacuum packaging, freezing and/or cooking. Shear force values, initial-bite tenderness (panel) and cooking loss were highly dependent on, and overall tenderness (panel) was only slightly dependent on muscle fibre orientations. These measures were affected by fibre orientation to a greater extent in tough than in tender meat. At each of three fixed muscle fibre orientation, correlations between tenderness measures were significant (P<0.05), their magnitude depending on the fibre orientation. At a fixed fibre angle correlations of tenderness measures with cooking losses were not significant. However, on a withinanimal basis, cooking loss was related to shear value and to initial-bite tenderness apparently through an effect of fibre orientation. This effect may constitute a major source of variation in the measurement of tenderness and cooking loss.     

Preliminary investigations on the effects of ageing and cooking on the Raman spectra of porcine longissimus dorsi

The influence of ageing and cooking on the Raman spectrum of porcine longissimus dorsi was investigated. The rich information contained in the Raman spectrum was highlighted, with numerous changes attributed to changes in the environment and conformations of the myofibrillar proteins.Predictions equations for shear force and cooking loss were developed from the Raman spectra of both raw and cooked pork. Good correlations and standard errors of prediction were obtained for both WB shear force and cooking loss, with the raw and the cooked samples showing almost identical results R² = 0.77, root mean standard error of prediction (RMSEP)% of mean = 12% for shear force; R² = 0.71, RMSEP% of mean = 10% for cooking loss. The Raman spectra were also able to predict the extent of cooking that occurred within the pork (R²_val = 0.94, RMSEP% of range = 5.5%).Raman spectroscopy has considerable potential as a method for non-destructive and rapid determination of pork quality parameters such as tenderness. Raman spectroscopy may provide a means of determining changes during cooking and the extent to which foods have been cooked.     

The effect of temperature on the drip,denaturation and extracellular space of pork longissimus dorsi muscle

Pork longissimus dorsi muscles were cut across the muscle into slices as soon as possible after slaughter. The slices were held at temperatures ranging from 10 to 37°C during the first 24 h post-mortem. 1–2% drip was obtained from slices held at 10°C and increased to 10–14% at 37°C. As the amount of drip increased, the protein concentration of the drip fell from about 150 mg/ml to 100 mg/ml. Some of this decrease could be attributed to the denaturation of sarcoplasmic protein, which amounted to a maximum of 19% in the samples with the highest drip. It is also suggested that diffusion of fluid from the myofilaments or sarcoplasmic reticulum could dilute the sarcoplasm. Denaturation of the myofibrillar proteins, as measured by their ATPase activity, was also observed but this was measurable only at holding temperatures above 30°C. The extracellular space which was 2–5% of the muscle section when the holding temperature was 10°C and drip was low, increased to a maximum of 16–25% at 37°C when drip was high. It is suggested that this is a contributory factor to the increase in drip with increasing temperatures.     

Carcass traits, muscle characteristics, and palatability attributes of lambs expressing the callipyge phenotype

Dorset×Suffolk crossbred wethers expressing a normal phenotype (normal, n=10) and callipyge phenotype (CLPG, n=9) were fed individually and slaughtered upon reaching maximum growth potential. Carcass weight did not differ (P>0.05), but fat thickness was lower (0.30 vs. 0.56 cm), ribeye area was greater (24.4 vs. 16.6 cm²), and USDA yield grade was improved (1.6 vs. 2.6) for CLPG carcasses (P < 0.05). Carcasses from CLPG demonstrated higher cutability and a more desirable muscle to bone ratio, with less fat and more lean as a percentage of total side weight (P<0.05). Biceps femoris (BF), semitendinosus (ST), semimembranosus (SM), longissimus thoracis et lumborum (LTL), and triceps brachii (TB) were used to compare muscle characteristics of both phenotypes. Muscle from normal lambs had lower calpastatin activity, higher fat percentages and lower moisture percentages (P<0.05). Total amount and solubility of collagen were not affected by phenotype nor was sarcomere length. Shear force and trained sensory attributes were evaluated for BF and LTL only. Shear force values did not differ between normal and CLPG BF while CLPG LTL had higher (P< 0.05) shear force values than normal LTL. Biceps femoris did not differ between phenotypes in trained sensory panel ratings. However, CLPG LTL received the lowest sensory ratings for connective tissue amount and myofibrillar and overall tenderness (6.11, 4.97, and 4.95, respectively) and the normal LTL received the highest ratings (P < 0.05; 7.10, 7.00, and 6.90, respectively). The CLPG phenotype had a positive influence on carcass characteristics but had a negative influence on tenderness of some muscles, possibly through the myofibrillar component of the muscle.     

Changes in meat quality of ovine longissimus dorsi muscle in response to repeated freeze and thaw

Changes in eating and technological quality attributes of ovine longissimus dorsi muscle during repeated freeze and thaw were investigated. Shear force value, L* value, a* value and fiber diameter decreased (P<0.05) but lipid oxidation increased (P<0.05) with repeated freeze-thaw cycles. Sarcomere length and pH decreased (P<0.05) within the first 10 freeze-thaw cycles but increased (P<0.05) after 5 further cycles. Total and myofibrillar protein solubility, and intramuscular free fatty acids concentration decreased (P<0.05) after 1 cycle of freeze and thaw but then increased (P<0.05) gradually with further cycles. Hardness, chewiness, cohesiveness and resilience of comminuted lamb products decreased (P<0.05) with increased freeze-thaw cycles. And therefore, repeated freeze and thaw should be minimized in terms of meat color for commercial value and water holding capacity for further processing.     

Influence of hydrocortison acetate on the evolution of the nutritive utilization of calcium and phosphorus and their contents on the longissimus dorsi muscle during gestation in the rat

The evolution of the nutritive utilization and plasma and muscular content of calcium and phosphorus in rats is studied, as well as the influence that hydrocortisone acetate has (4 mg/100 g weight and day), on them. In pregnant rats injected with saline solution, the retention of calcium is higher on the days 15-18 as a consequence of the increase on the net absorption of the cation. The balance of phosphorus reaches its maximum hight on days 18-21 of gestation, due to the decrease of the urinary excretion during these days. The administration of hydrocortisone acetate to pregnant rats originate a decrease of the net absorption and an increase of the urinary excretion of calcium and phosphorus, which leads to significantly lower balances than those of animals injected with saline solution. The hormone maintains the animals in a negative balance of phosphorus until day 18 of gestation. Besides, it impedes the high retention of calcium which is found with the control pregnant rats on days 15-18. In general, the content in calcium and phosphorus by gram of dry matter of Longissimus dorsi muscle is not modified during gestation. From day 9 of the treatment with hydrocortisone acetate a significant decrease of calcium and phosphorus of the muscle is observed, that in calcium is the more marked the more the treatment is prolonged. This effect seems to be due to the catabolic action of the hormone.     

Associations of genetic and non-genetic factors with concentrations of iron and zinc in the longissimus muscle of lamb

There is a concern regarding the possible decline of nutritional value of meat with an increasing selection for lean meat yield. The selection for reduced fatness reduces muscle aerobicity and possible subsequent mineral concentrations. Average concentrations of iron and zinc of 5625 lamb longissimus muscles were 2.03 and 2.43 mg/100 g, qualifying as a good source claim for the majority of the population. Reduced post-weaning fat depth was associated with decreased concentrations of iron but not zinc, whereas post-weaning eye muscle depth and weaning weight were not associated with either mineral. These results confirm that the impact of lean meat yield selection on these minerals is minimal, but should be monitored to avoid lower levels. Both minerals had a positive relationship with age at slaughter, highlighting age as a key determinant of the concentration of these nutrients. The magnitude of the positive associations of isocitrate dehydrogenase and myoglobin with iron was larger than for zinc, but they strongly indicated the association of these aerobic makers with both minerals.     

The influence of high post-mortem temperature and differing ultimate pH on the course of rigor and ageing in pig Longissimus dorsi muscle

This study was performed in order to assess the effect of temperature and differing ultimate pH (pH_u, 24 h post mortem) on the development of rigor mortis in pig Longissimus dorsi muscle. The rigor development (isometric tension and shortening) was measured continuously during the first 24 h post mortem, using an apparatus wherein muscle strips were held at constant temperatures of 12 or 35°C. pH_u was manipulated by adrenaline injections preslaughter.

The rates of pH fall, adenosine triphosphate (ATP) and creatine phosphate (CP) breakdown were markedly increased at 35°C compared to 12°C. For both temperatures, no delay phase was observed with regard to the development of shortening. Rigor resulted in higher maximum isometric tension and shortening and in shorter time needed to reach maximum values at 35°C than at 12°C. The results are discussed in connection with pH, ATP and CP data. The extent of ageing from 2 to 4 days post mortem, estimated through myofibrillar length determinations, was higher for 12°C than for 35°C.

pH_u affected significantly most of the traits under study, but its effect depended in some cases upon the rigor temperature. At 12°C, the traits related to the kinetics of rigor development were significantly affected by pH_u, but this was not the case at 35°C. Maximum isometric tension was significantly related to pH_u at 35°C (r = 0·86, P < 0·001), but such a relationship was not found at 12°C. Myofibrillar lengths were significantly affected by pH_u, but in an opposite manner from one temperature to another. A positive relationship was found at 12°C and a negative one at 35°C.

These results illustrate the importance of the interaction between the extent of pH fall and temperature with regard to post-mortem changes in pig muscle.