Fatty acid content and composition of english beef, lamb and pork at retail

We have determined the fatty acid content and composition of retail samples of meat and assessed them with respect to UK dietary recommendations. Fifty beef sirloin steaks, pork chops and lamb chops were purchased from four supermarkets on separate occasions. The percentage of muscle (boneless basis) in the samples was 84.4 ± 4.3, 69.8 ± 7.7 and 78.9 ± 7.1 for beef, lamb and pork, respectively, with fatty acid contents of 3.84 ± 1.3, 4.73 ± 1.66 and 2.26 ± 0.7 g per 100 g muscle, respectively. Adipose tissue fatty acid contents were 70.0 ± 8.2, 70.6 ± 8.6 and 65.3 ± 9.4 g per 100 g tissue. A range of C20 and C22 polyunsaturated fatty acids (PUFA) was present in the muscle of all three species and pork adipose tissue but their concentrations in lamb and beef adipose tissue were too low to measure. The mean P:S ratios for beef, lamb and pork muscle were (adipose tissue values in parentheses): 0.11 (0.05); 0.15 (0.09) and 0.58 (0.61), and the n−6:n−3 ratios were 2.1 (2.3), 1.3 (1.4) and 7.2 (7.6). We conclude that the muscles of red meat species are a valuable source of PUFA, particularly the C20 and C22 n−3 fatty acids, in the human diet and that, considered as part of a varied diet, the low P:S ratio of the ruminant muscle, the high n−6:n−3 ratio of pork and the total fatty acid contents do not detract significantly from the nutritional value of lean meat.     

Content of Zinc in Selected Muscles from Beef, Pork, and Lamb

Zinc concentration was measured in four muscles from beef, pork, and lamb: longissimus dorsi (LD), biceps femoris (BF), gluteus medius (GM), and triceps brachi (TB). Within a species, BF, GM, and LD had similar zinc concentrations but TB was significantly (P<0.01) higher in zinc. The means for the four muscles ranged from 39.8–53.5, 13.9–28.0, and 28.2–36.9 μg Zn/g wet weight for beef, pork, and lamb, respectively. The zinc concentration of muscle may relate to protein synthesis and the predominant type of energy metabolism occurring in the muscle. The mean zinc concentration of the four muscles between species was significantly (P< 0.01) different.     

Calpain-calpastatin and toughness in M. longissimus from electrically stimulated lamb and beef carcasses

Shear strength, pH, temperature, μ-calpain, m-calpain and calpastatin levels were measured over a two-week post-slaughter period in Longissimus lumborum et thoracis (LD) from six lamb and six beef carcasses. All carcasses were subjected to high voltage electrical stimulation. The toughness of the beef LD determined by a MIRINZ tenderometer at 24 h post-slaughter showed a strong correlation (r=0.91) with pH of the LD at 3 h. Beef LD toughness at 14 days was correlated (r=0.84) with initial m-calpain levels. In both lamb and beef, LD toughness at 4 and 14 days respectively was also correlated with initial levels of calpastatin (r=0.85, 0.83, respectively). The strong correlation between calpastatin and the rate of tenderisation indicates that the calpain system is closely linked to the proteolytic breakdown of myofibrillar proteins. There is also evidence of an interaction between pH and μ-calpain activity. The μ-calpain, m-calpain, calpastatin, pH and temperature kinetic changes which occurred during the post-mortem ageing of beef and lamb LD were applied to a computer program which predicted rate of meat tenderisation by calculating in situ calpain activity. The closeness of fit between the predicted rate of meat tenderisation and the observed tenderness values of beef and lamb LD indicates that the post-mortem activity of μ-calpain is the major determinant of variations in tenderness. However, application of the meat tenderisation predictive program to LD from individual animals revealed that the program was not sufficiently robust for this use.     

Precision in the measurement of meat texture

The relationships between the level of precision, the variability within muscles and the number of measurements required to assess toughness were quantified in an attempt to rationalise the measurement of meat texture. Variability within M. longissimus dorsi was higher than in other hindquarter muscles of lamb and beef and was less in pork than in beef or lamb. Ten replicate determinations on lamb and beef and seven on pork M. longissimus dorsi would be suited to research work. Under these conditions, 95% of values for each muscle would lie within one-sixth of the texture scale from the mean for 85% of muscles and would lie within one-tenth of the texture scale from the mean for 50% of muscles.     

Identification of calpastatin, μ-calpain and m-calpain in Atlantic salmon (Salmo salar L.) muscle

A soft fish muscle is generally considered as a poor quality trait among consumers and producers. This degradation and softening of post mortem muscle is thought to be partly caused by proteolytic enzymes such as the calpain system. Separation and identification of μ-calpain and m-calpain and their inhibitor – calpastatin, from Atlantic salmon (Salmo salar) muscle were for the first time assessed in this study. A two-step chromatography approach was used, starting with a hydrophobic interaction column and followed by an anion exchange column. Calpastatin was successfully separated from calpain by hydrophobic interaction chromatography, and following the anion exchange chromatography, two forms of calpastatin (I and II) and two forms of calpain (micro (μ) and milli (m)) were revealed. The proteolytic activity of μ-calpain was detectable with column chromatography, but not consistently detected with casein zymography, and m-calpain was detected with both chromatography and casein zymogram. The proteolytic activity of m-calpain per g muscle was 15 times higher than that of μ-calpain. μ-Calpain had a temperature optimum of 15 °C and a maximum calcium requirement at 0.2 mM, while m-calpain had temperature optimum at 25 °C and a maximum calcium requirement of 0.6 mM. The two forms of calpastatin differed in inhibitory activity with calpastatin II having the highest activity. Both calpastatins tolerated heat treatment, as previously seen for mammals, and they kept their activity when stored at −80 °C, but not at −20 °C. The calpain to calpastatin ratio was 1:4.5 as observed for beef muscle. This study provides evidence that two calpain isoforms, likely to be μ- and m-calpain, in addition to two forms of calpastatin exist in Atlantic salmon muscle.     

Usefulness of various biochemical and histochemical characteristics as indices of muscle type in lamb carcasses

Contractile and metabolic characteristics of five different muscles from an homogeneous group of seven lambs were studied. Muscle typing was assessed by measuring myofibrillar ATPase and lactate deshydrogenase activities, myosin (FM1, FM2, FM3, SM1, SM2) and LDH (M₄, M₃H, M₂H₂, MH₃, H₄) isoforms levels as well as fibre types composition (SO, SOG, FOG, FG). On this basis, muscles were classified as slow-twitch oxidative (diaphragm and supraspinatus), intermediate (triceps brachii), fast-twitch oxidative-glycolytic (longissimus dorsi) and fast-twitch glycolytic (tensor fascia latae). Discriminant factor analysis of data revealed that variables enabling a better discrimination of muscles (FG, SM1, FM2, FM1, H₄) exhibited the lowest efficiency to discrimate animals. Furthermore, in contrast to LDH isoforms and fibre type composition subsets of variables, myosin isoforms analysis allowed a quite total identification of muscle classes since, 97·5% of the muscles were well ranged in their respective classes. Although animals were zootechnically similar, animal variability was important and animal effect was essentially detected through changes in the following set of variables: M₃H, MH₃, SO and ATPase.     

Measurement and Content of Nonheme and Total Iron in Muscle

A method for determining the nonheme iron content of meats was evaluated and used to determine the nonheme and heme iron content of selected muscles from beef, pork, and lamb. The method allows a quantitative determination of nonheme iron in meat and is influenced to only a minor degree by the presence of heme iron. Heating meat in a boiling water bath increased the nonheme iron content of the meat. Possibly, heating accelerates oxidative cleavage of the prophyrin ring thereby allowing release of the iron from the heme complex. Total iron content differed between muscles in pork and beef but not in lamb. Heme iron, expressed as percent of the total iron, in raw pork, lamb, and beef average 49, 57, and 62%, respectively.     

Levels of calpain and calpastatin in meat subjected to high pressure

The levels of μ-, m-calpain and calpastatin were assayed in pressurized rabbit muscle.

The crude calpain level from the pressurized muscle at 100 MPa was almost the same with that of control. Above 100 MPa, the level of calpain decreased rapidly with increased pressure. At 300 MPa, the calpain level was almost inactivated. When the crude extract was pressurized, the calpain level followed the same tendency as that in the pressurized muscle.

When the extracts from control or pressurized muscle were subjected to DEAE-Sephacel column chromatography, μ- and m-calpains and calpastatin lost their activity with increasing pressure, but the degree of loss was different for each.

Calpains resisted changes in pressurization at 200 MPa and were inactivated over 200 MPa. Inactivation of calpastatin at 100 MPa was faster than that of calpains.

From the results, it was concluded that calpain levels remained in muscle pressurized up to 200 MPa, whereas calpastatin levels were decreased by the pressurization. Thus the total activities of calpains in pressurized muscle appear to have been increased by the pressure treatment and this may result in tenderization of meat.     

Gamma Irradiation Effects on Thiamin and Riboflavin in Beef, Lamb, Pork, and Turkey

A study was made of the loss of thiamin and riboflavin due to gamma irradiation of beef, lamb and pork longissimus dorsi, turkey breast and leg muscles. Thiamin losses averaged 11%/kiloGray (kGy) and riboflavin losses 2.5%kGy above three kGy. The rate of loss of thiamin in beef was higher than that in lamb, pork and turkey leg, but not turkey breast. with losses of 16%/kGy in beef and 8%/kGy in lamb. The rate of thiamin loss was not related to sulfhydryl, protein, moisture, fat or water content, pH or reducing capacity by redox titration. Loss of riboflavin was not different among species. Any detriment from such slight losses would seem to be more than compensated by the advantage of controlling bacteriological contamination by irradiation processing.     

Concentrations in beef and lamb of taurine, carnosine, coenzyme Q(10), and creatine

Levels of taurine, carnosine, coenzyme Q(10), and creatine were measured in beef liver and several muscles of beef and lamb and in cooked and uncooked meat. The amino acid taurine has numerous biological functions, the dipeptide carnosine is a buffer as well as an antioxidant, coenzyme Q(10) is also an antioxidant present within mitochondria, and creatine along with creatine phosphate is involved with energy metabolism in muscle. Large differences were shown for all compounds between beef cheek muscle (predominantly red fibres) and beef semitendinosus muscle (mainly white fibres), with cheek muscle containing 9.9 times as much taurine, and 3.2 times as much coenzyme Q(10), but only 65% as much creatine and 9% as much carnosine. Levels in lamb relative to beef semitendinosus muscles were higher for taurine but slightly lower for carnosine, coenzyme Q(10) and creatine. Values for all the compounds varied significantly between eight lamb muscles, possibly due in part to differences in the proportion of muscle fibre types. Slow cooking (90 min at 70?°C) of lamb longissimus and semimembranosus muscles led to significant reductions in the content of taurine, carnosine, and creatine (P<0.001), but a slight increase in coenzyme Q(10). There was also a four-fold increase in creatinine, presumably due to its formation from creatine. It is concluded that biologically, and possibly nutritionally, significant levels of taurine, carnosine, coenzyme Q(10), and creatine are present in beef and lamb, but that these levels vary between muscles, between animals, and with cooking.     

宰后早期猪肉、牛肉和鸡肉中能量代谢及蛋白质磷酸化

目的:探讨畜禽肉宰后能量代谢的差异及其可能的原因。方法:于宰后45 min测定鸡肉、灰白(pale soft exudative,PSE)猪肉、正常猪肉和牛肉中糖原、ATP/ADP/AMP含量及乳酸脱氢酶(lactate dehydrogenase,LDH)活性,并提取肌浆和肌原纤维蛋白进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(sodium dodecyl sulfatepolyacrylamide gel electrophoresis,SDS-PAGE)和液相色谱-串联质谱鉴定,分析各组肉的磷酸化水平差异。结果:牛肉中糖原含量显著高于其他组(P0.05),正常猪肉组糖原和ATP含量显著高于PSE猪肉组和鸡肉组(P0.05),而PSE猪肉组的LDH活性显著高于其他组(P0.05);肌浆蛋白SDS-PAGE ProQ染色表明,宰后45 min PSE猪肉组中6个条带的磷酸化水平显著低于正常猪肉组(P0.05),而另有6个条带的磷酸化水平显著高于正常猪肉组(P0.05)。牛肉组和鸡肉组中分别有3个和1个条带的磷酸化水平偏低,1个条带和8个条带的磷酸化水平明显偏高。而肌原纤维蛋白电泳表明,牛肉中大部分蛋白质的磷酸化水平处于最高值,而鸡肉组处于最低值,猪肉介于两者之间;PSE猪肉组中7个条带的磷酸化水平显著低于正常猪肉(P0.05);6个条带的磷酸化水平显著高于正常猪肉(P0.05)。结论:宰后异质肉的形成受宰后糖原和ATP消耗速率、LDH活性的影响,同时与肌肉中糖酵解酶的磷酸化水平有关。     

The effect of freezing and thawing on the magnetic resonance imaging parameters of water in beef, lamb and pork meat

A new multisample magnetic resonance imaging (MRI) technique has been used to measure the values of T ₁, T ₂, magnetization transfer (MT) rate and liquid proton density ratio ( M ₀%) for water in fresh and frozen–thawed beef, lamb and pork; four samples from the longissimus dorsi muscle of 25 different individuals per species were studied. The effect of two different chilling regimes, standard and tenderloin, were also studied. Standard chilled pork and lamb had a significantly higher M ₀% than tenderloin chilled samples, but there was no correlation between M ₀% and fresh weight; the differences in M ₀% are thought to be due to differences in MR (magnetic resonance)-visible water. There was a significant decrease in water content, T ₁ relaxation time, and a significant increase in MT rate in the frozen–thawed samples when all the data were pooled for each species. However, individual animals differed in the magnitude and direction of the change; this means that because of interanimal variation, measurements of MR parameters from a single sample of meat cannot be used at present to authenticate it.     

PENETRATION OF SUBSTANCES INTO MUSCLE

The rate and depth of penetration of two dye markers, hematoxylin and eosin, into beef muscle were compared. The effects of temperature, aging, meat texture, and type of muscle were investigated. Samples (1 cm³) were placed into dye markers, and then were sectioned at selected time intervals and examined microscopically. Hematoxylin penetrated into the meat slower than eosin; depth of hematoxylin penetration decreased with decreasing temperature, firmer meat texture and aging. Penetration rate was faster at the beginning than at the end of the test period. Penetration rate and depth of oxygen into beef, lamb, and pork were investigated also. The samples (8 cm³) were placed in a modified atmosphere package containing 80% oxygen and 20% carbon dioxide. The samples were cut at selected time intervals up to 26 h after addition of oxygen and oxygen penetration rate and depth were measured. Oxygen penetration was deeper in beef than in pork and deeper in pork than in lamb. Oxygen penetration rate was faster initially and then slowed as time progressed.     

Effect of ion fluid injection on beef tenderness in association with calpain activity

Sodium pyrophosphate plus sodium chloride (PPi) was injected into pre-rigor, hot boned biceps femoris (BF) and semimembranosus (SM) muscle from 12 heifer carcasses. The PPi injection caused higher pH values between 10 and 48 h post-mortem than found in the controls for both muscles (P<0.05). PPi injection resulted in faster decreases in the activities of μ-calpain and calpastatin than in the control for both muscles with time post-mortem (P<0.05). There were significant differences between treatments in both the BF and SM (P<0.05). There was evidence that PPi-injection elevated pH, and accelerated activation of calpains, resulting in improved tenderness. The rates of degradation of titin and troponin-T as well as the appearance of 95 and 30 kDa peptides were faster in the PPi-injected muscles than the controls. PPi-injection elevated muscle pH, which was attributed to acceleration of the calpain activation. It is concluded that PPi-injection improved beef tenderness by accelerating activation of calpain.     

Identification of animal meat muscles by visible and near infrared reflectance spectroscopy

Visible (VIS) and near infrared reflectance spectroscopy (NIRS) was used to identify and authenticate different meat muscle species. Samples from beef (n: 100), lamb (n: 140), pork (n: 44) and chicken (n: 48) muscles were homogenised and scanned in the visible (VIS) and near infrared (NIR) region (400-2500 nm) in a monochromator instrument in reflectance. Both Principal Component Analysis (PCA) and dummy partial least-squares regression (PLS) models were developed to identify different meat species. The models correctly classified more than 80% of the meat sample muscles according with the muscle specie. The results showed the potential of VIS and NIR spectra as an objective and rapid method for authentication and identification of meat muscle species.     

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.     

钙激活酶-钙激活酶抑制蛋白系统对成肌细胞融合与分化的影响

钙激活酶－钙激活酶抑制蛋白系统在肌肉发育中起着重要的作用。在成肌细胞培养中,成肌细胞融合并分化形成多核肌细胞,其中钙激活酶抑制蛋白的含量与细胞膜的融合相关。成肌细胞融合需要钙激活酶的活性,融合率取决于细胞中钙激活酶与钙激活酶抑制蛋白的比例。本研究发现ＥＤＴＡ、３ＧＴＡ、ＧＳＴ－ｃａｌｐａｓｔａｔｉｎ可抑制成肌细胞的融合。ＧＳＴ－ｃａｌｐａｓｔａｔｉｎ是用ＩＰＴＧ诱导表达的分子量为４５ＫＤ的融合蛋白     

宰后牦牛肉成熟过程中钙激活酶与嫩度指标的相关性分析

以10头甘南牦牛为研究对象,对宰后8d成熟期间肌原纤维小片化指数、剪切力、肌纤维直径、μ-钙蛋白酶(μ-calpain)、m-钙蛋白酶(m-calpain)、钙蛋白酶抑素(calpastatin)的活力进行了测定,同时研究了3种酶活力与肌原纤维小片化指数、剪切力、肌纤维直径3个嫩度指标之间的相关性.结果表明:μ-calpain、m-calpain、calpastatin 3种酶与剪切力值及肌纤维直径均呈正相关;3种酶与肌原纤维小片化指数呈负相关,其中μ-calpain与calpastatin呈显著负相关(P＜0.05).因此,钙激活酶活力的变化可能导致了肌原纤维小片化指数的增加,肌原纤维的弱化和肉的嫩化,μ-calpain可能是牦牛肉嫩化的主要贡献者.     

Modelling post-mortem tenderisation-IV: Role of calpains and calpastatin in conditioning

A generalised model, based on published data, was developed quantifying the mechanism by which the activities of calpains I and II are responsible for post-mortem tenderisation. Tenderisation is proposed to result from the activities of 'free' activated-calpains, the activities of which are controlled by the changes in the calcium ion concentration, the binding of calpains to calpastatin, the inactivations of 'free' activated-calpains and their proteolysis of calpastatin. At the low myoplasmic ('free') calcium ion concentrations prevailing soon after slaughter, calpains are largely 'inert' and little tenderisation occurs. As the pH declines, the 'free' calcium ion concentration rises and activates calpain I: however, most of this activated-calpain I is then bound to calpastatin. With a futher decline in pH, the binding of activated-calpain I to calpastatin is reduced and the level of 'free' activated-calpain I rises and tenderisation increases. A comparable process occurs with calpain II at higher 'free' calcium ion concentrations which occur as the pH declines further. As the level of 'free' activated-calpains rises, their proteolysis of calpastatin also increases, causing a lowering of levels of calpastatin and reducing the inhibition of calphins. Concurrently, 'free' activated-calpains are inactivated. This balance between inhibition, inactivation and activity of calpains and their decrease as the pH declines maintains the proteolytic activity of calpains and produces the gradual process of tenderisation, initially by calpain I and at the later stages mainly by calpain II. Eventually, the activities of calpains decline to zero and tenderisatin stops. Equations were derived to describe the changes from stunning to the completion of conditioning, and parameters were calculated to determine the activities of calpains and tenderisation in beef M. longissimus dorsi.     

Lead and cadmium in meat and meat products consumed by the population in Tenerife Island, Spain

The aim of this study was to determine the levels of lead and cadmium in chicken, pork, beef, lamb and turkey samples (both meat and meat products), collected in the island of Tenerife (Spain). Lead and cadmium were measured by graphite furnace atomic absorption spectrometry (GFAAS). Mean concentrations of lead and cadmium were 6.94 and 1.68 µg kg^-1 in chicken meat, 5.00 and 5.49 µg kg^-1 in pork meat, 1.91 and 1.90 µg kg^-1 in beef meat and 1.35 and 1.22 µg kg^-1 in lamb meat samples, respectively. Lead was below the detection limit in turkey samples and mean cadmium concentration was 5.49 µg kg^-1. Mean concentrations of lead and cadmium in chicken meat product samples were 3.16 and 4.15 µg kg^-1, 4.89 and 6.50 µg kg^-1 in pork meat product, 6.72 and 4.76 µg kg^-1 in beef meat product and 9.12 and 5.98 µg kg^-1 in turkey meat product samples, respectively. The percentage contribution of the two considered metals to provisional tolerable weekly intake (PTWI) was calculated for meat and meat products. Statistically significant differences were found for lead content in meats between the chicken and pork groups and the turkey and beef groups, whereas for cadmium concentrations in meats, significant differences were observed between the turkey and chicken, beef and lamb groups. In meat products, no clear differences were observed for lead and cadmium between the various groups.