Investigation of methods to detect mechanically recovered meat in meat products - III: Microscopy

Carcasses from 36 Large White gilts, 70–80 kg live weight, were randomly allocated to three experimental groups. Pigs in the first group were electrically stimulated with low voltage during bleeding (85v, 14Hz for 64 s) and split before cooling. The left sides were rapidly chilled in air at -15°C for 75 min and then at 1°C until 24 h post-slaughter; right sides were chilled conventionally in air at 1°C for 24 h. In the second group, two different treatments were used 20 min post-slaughter: left sides were stimulated with low voltage, and right sides with high voltage (700 v, 12·5 Hz for 90 s). Both sets of sides were chilled rapidly. Carcasses from the third group were not stimulated, and sides chilled either rapidly or conventionally. Drip loss, colour and texture were measured in M. longissimus thoracis et lumborum at 3 and 10 days post-slaughter.

At 3 days post-slaughter the high voltage, treatment gave meat which was the most tender, was not pale and lost no more drip than unstimulated controls. Low voltage stimulation during bleeding gave meat which was 18% more tender than the unstimulated controls, but the improvement in tenderness was not as great as the 28% achieved with high voltage. Unexpectedly, low voltage stimulation applied 20 min after slaughter, was almost as effective in improving tenderness (by 17%) as low voltage applied during bleeding.

Tenderness improved from 3 days to 10 days in all stimulated samples, but not in unstimulated controls. The results suggest a degree of coldtoughening in the latter, even with conventional chilling, and a positive effect of electrical stimulation on tenderness, independent of its protective action against cold-shortening.     

Investigation of methods to detect mechanically recovered meat in meat products - IV: Immunology

The possibility of using immunological techniques as a method for the detection of mechanically recovered chicken meat in meat products has been investigated in this preliminary study. Antibodies were raised against a low molecular weight fraction (≤ 30 kDa) of chicken bone marrow proteins and an enzyme-linked immunosorbent assay (ELISA) developed. The system was used to test for the presence of mechanically recovered meat (MRM) in a range of product types, from raw chicken meat through to heat processed samples. The results show that it is possible to raise antibodies to chicken bone marrow proteins which show a strong reactivity with chicken and turkey MRM but show little reaction with extracts of MRM and hand deboned meat of other common meat species. However, blood, skin and soya all affected the accuracy of the ELISA.

This study has demonstrated the potential for the use of an immunological procedure as a rapid test for MRM. The selectivity of the antiserum would, however, have to be increased before this procedure could be considered as a suitable technique for the detection of MRM in meat products.     

Investigation of methods to detect mechanically recovered meat in meat products - I: Chemical composition

The proximate composition (fat, moisture, nitrogen, ash and collagen) and the calcium, iron and total purine contents of samples of mechanically recovered meat (MRM) derived from beef, lamb, pork, chicken and turkey were analysed. The data obtained illustrate the variability in the composition of mechanically recovered meats derived from different meat species. The effect of including a high proportion of bones containing marrow in the starting material, the effect of recovery machine type (Yieldmaster and Protecon) and the effect of employing different operating conditions, were investigated. MRM produced using the Yieldmaster machine was generally found to contain higher concentrations of ash and calcium than that produced using the Protecon machine. Although operating conditions appeared to have little effect on the composition of mechanically recovered chicken meat, some differences were identified in mechanically recovered turkey and pork produced under different conditions. Comparison of the composition of MRM with that of meat removed manually, from close to the bone, from similar source materials highlighted a number of differences between the     

Investigation of methods to detect mechanically recovered meat in meat products - II: Gel electrophoresis

This study investigated the use of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) as a method for differentiating between mechanically recovered and hand deboned meat. Twenty-nine samples of mechanically recovered meat (MRM), including some heat treated samples, were obtained. The samples were derived from several animal species and processed using different machine types and a range of processing conditions. They were examined using SDS-PAGE and the separation patterns obtained compared with those of hand deboned meat (HDM) reference samples. There were obvious differences in the relative intensities of several bands within the profiles obtained which distinguished MRM from HDM. These were more obvious for red meat than poultry meat samples. A few differences were found between MRM samples produced using different machines but no apparent differences between samples produced using different machine operating conditions were observed. The technique was tested using composite MRM-HDM mixtures. It was possible to suggest an order of percentage incorporation of MRM at levels of down to 5–10% for red meat and 25% for poultry meat. With further development and refinement, it may be possible to use the technique to detect and possibly quantify MRM present in all types of meat products, including cooked meat products.     

Metabolomic approach for the detection of mechanically recovered meat in food products

Mechanically recovered meat (MRM) is generated by mechanical treatment of remnants following hand deboning. EU regulations exclude MRM from the definition of meat; as a consequence there is a need for robust analytical procedures to differentiate MRM from hand-deboned meat (HDM) and desinewed meat. Present study represents the development of an analytical platform for the detection of adulteration of meat products with MRM. Small molecular weight compounds were extracted from meat samples and analysed using GC–MS. Obtained metabolite profiles were modelled with OPLS-DA for the accurate classification of MRM, HDM and desinewed pork and chicken samples. Separation of three classes of products for fresh chicken and pork meat samples was achieved. In addition, the procedure also enabled proper prediction of samples not included in the model as well as pork commercial meat products. Compounds that could be potential markers for MRM detection in commercial products were also selected.     

Assessing the quality of mechanically and manually recovered chicken meat

The biochemical composition and histological characteristics of meat recovered mechanically by the auger/sieve (a/s) and the hollow drum/belt (hd/b) principles from two different chicken carcass parts were compared with meat recovered manually. The quality of meat recovered mechanically by the hollow drum/belt principle was equal to or higher than the quality of manually recovered meat. The degradation of muscle structure was highest in the meat recovered by the a/s principle and lowest in the manually recovered meat. For the biochemical measurements with the exception of collagen, determinations of a single sample were sufficient to achieve a repeatability of 0.9, whereas for the histological measurements at least 8 samples were necessary. It is suggested that a quality-grading scale based on biochemical composition and level of degradation of muscle fibre structure should be established for all types of minced meat regardless of whether the meat is obtained by mechanical or manual procedures and that legislation concerning the use of MRM should be based on such a scale.     

Proteomic approach for the detection of chicken mechanically recovered meat

Mechanically recovered meat is cheaper than raw meat and thus has been incorporated into many meat-derived products. EU regulations exclude mechanically recovered meat from the definition of meat; as a consequence analytical procedures are needed to differentiate it from hand-deboned meat. The present pilot study has utilized a proteomic approach to find potential markers for the detection of chicken mechanically recovered meat. Intact proteins were extracted from raw meat and then analyzed with OFF-GEL electrophoresis followed by SDS-PAGE and identification of potential markers by nano-LC-MS/MS. It was shown that it is possible to extract, separate and identify key proteins from processed meat material. Potential chicken mechanically recovered meat markers--hemoglobin subunits and those similar to myosin-binding protein C were also identified.     

Optimization of conditions for myofibril preparation from mechanically recovered chicken meat

The influence of various conditions affecting the isolation of a myofibrillar preparation (MP) from chicken mechanically recovered meat (MRM), i.e. the time of additional chopping in a bowel chopper, washing time, the number of washings, and the water to MRM ratio, on the recovery of dry matter and myofibrillar protein, and fat content in the preparation was investigated. The following particular steps were determined to be the most desirable parameters: chopping MRM for 10 minutes, washing time of 15 minutes, 3 (or 2) consecutive washings, 3:1 water to MRM ratio (v/w). Under these conditions a significant decrease of fat content (93% on average) was found in comparison to the content in MRM. The removal of fat, sarcoplasmic protein and connective tissue increased the concentration of myofibrillar protein. The number of aqueous washings of MRM had the biggest influence on the protein and fat content in the concentrate. Electrophoretic analysis (SDS-PAGE) of protein in the preparation obtained under optimal conditions showed that myosin heavy chains (MHC) and actin constituted approximately 50% of all the proteins in the preparation.     

Enzymatic modification of protein preparation obtained from water-washed mechanically recovered poultry meat

Studies were conducted on a protein preparation obtained from washed mechanically recovered poultry meat (MRPM). The effect of addition of 3 g/kg microbial transglutaminase (MTG) to poultry meat protein was evaluated in terms of texture changes by dynamic mechanical analysis (DMA) and nuclear magnetic resonance (NMR) to determine water content in the preparation and its effect on protein. Samples with the addition of MTG were pre-incubated at 5–6 °C for 1.5, 3, 4.5, 6, 7.5, 9 and 24 h. The largest changes for both texture parameters and rheological properties were observed in the interval of approx. 4–7 h incubation. The protein preparation with the enzyme added had significantly higher values of the moduli of elasticity (G₁) and losses (G₂) in comparison to the control system. Samples with the addition of MTG also showed a higher water-binding capacity. From the NMR studies it was found that the greatest amount of water was bound by protein in the period of approx. 2.5–5 h incubation. After that time an increase was found in the amount of free water in the sample, which suggests that it was displaced from the system by stronger protein–protein bonds.     

Influence of the addition of mechanically recovered meat on the physico-chemical properties of meat model blends

The physico-chemical properties of meat model blends (basic composition: fresh lean pork, pork back fat, 2% NaCl, water with ice), with added mechanically recovered pork (MRM), were studied. Fresh MRM was added at levels of 10% and 20% substitution of meat protein with or without further substitution by 10% sodium caseinate or soya isolate. The addition of MRM to meat blends caused an increase in the pH, the water-holding capacity, the viscosity, the dominant wavelength and colour purity. No effects on emulsifying capacity were observed but thermal cooking losses and lightness of colour were reduced. The addition of blends of MRM and soya isolate or sodium caseinate caused lower values of the investigated features than those observed when only MRM was used.     

HPLC测定肉制品中山梨酸方法的改进

通过分析用HPLC测定肉制品中山梨酸的国家标准GB/T5009.29-2003和行业标准SB/T10389-2004,发现2种方法测定肉制品中山梨酸的前处理方法存在一定的不足,因此,本文建立了一种新型的HPLC测定肉制品中山梨酸的前处理方法——蒸馏法。此法利用山梨酸或其盐在酸性条件下能随水蒸气一同蒸发的特点,在磷酸存在的条件下,用水蒸气蒸馏的方法将样品特别是固体或者半固体样品中的防腐剂山梨酸蒸馏出来,从而达到了固体样品中的山梨酸与干扰物质分离的目的。样品前处理简便快捷,干扰物少,对色谱柱的污染少。在此基础上,以0.02mol/L甲醇和乙酸铵溶液(5∶95)为流动相,流速为1mL/min,紫外检测器在波长230nm条件下测定馏出液中山梨酸含量。结果显示:蒸馏法的平均回收率为90.7%,明显高于使用标准方法所得的平均回收率88.2%。     

肉及肉制品中彩虹色斑点现象的调查分析

彩虹色斑点是近年来发现存在于肉及肉制品中的一种非正常颜色。对我国几家大型屠宰场的猪、牛分割肉及南京各大超市销售的部分肉制品进行了调查,结果表明:猪肉的各部位均无彩虹色斑点现象;牛肉半腱肌中彩虹色斑点的发生率为83%,其他部位从高到低分别为背最长肌(21%),腰大肌(7%),股二头肌(5%)。牛肉制品中帕斯雀牛肉、烤牛肉和酱牛肉彩虹色斑点最明显,猪肉制品中西式火腿片和咸肉最明显。     

Immunological detection of keratan sulfate in meat products with and without mechanically separated chicken meat

Keratan sulfate is a glycosaminoglycan found in the structure of cartilage proteoglycans, aggrecan and fibromodulin. This study was undertaken to detect this glycosaminoglycan in meat products containing mechanically separated chicken meat (MSCM) having cartilage particles. Dry-defatted samples of MSCM and meat products with or without MSCM were digested with papain, and a non-dialyzable fraction from each papain digest was examined by immunodiffusion analysis using anti-keratan sulfate monoclonal antibody (IgM). No precipitine line was formed with the antibody for all samples of meat products without MSCM, while a sample of MSCM and all samples of meat products with MSCM gave clear precipitine lines with the antibody. The immunodiffusion test described here appears to be a simple sensitive specific method for qualitative analysis of keratan sulfate, which in combination with other methods may be useful for detection of MSCM in meat products.     

Immunological detection of keratan sulfate in meat products with and without mechanically separated chicken meat

Keratan sulfate is a glycosaminoglycan found in the structure of cartilage proteoglycans, aggrecan and fibromodulin. This study was undertaken to detect this glycosaminoglycan in meat products containing mechanically separated chicken meat (MSCM) having cartilage particles. Dry-defatted samples of MSCM and meat products with or without MSCM were digested with papain, and a non-dialyzable fraction from each papain digest was examined by immunodiffusion analysis using anti-keratan sulfate monoclonal antibody (IgM). No precipitine line was formed with the antibody for all samples of meat products without MSCM, while a sample of MSCM and all samples of meat products with MSCM gave clear precipitine lines with the antibody. The immunodiffusion test described here appears to be a simple sensitive specific method for qualitative analysis of keratan sulfate, which in combination with other methods may be useful for detection of MSCM in meat products.     

Microbiological quality of mechanically recovered poultry meat treated with high hydrostatic pressure and nisin

The combined effect of high hydrostatic pressure processing, addition of nisin and acidification on aerobic mesophilic and psychrotrophic bacterial populations of mechanically recovered poultry meat (MRPM) kept under refrigeration (2°C) was evaluated 1, 15 and 30 days after pressurization. Nisin (0, 12.055, 100 and 200 ppm) and glucono-delta-lactone (GdL; 0 and 1%) were added to MRPM. Vacuum-packaged samples were treated at 350 or 450 MPa and 2°C for 15 min using both continuous pressurization and three-cycle oscillatory pressurization for 5 min per cycle. In some samples a reduction of mesophile counts between 3.0544 and 5.0538 log cfu g⁻¹was found. Psychrotrophes seemed to be more sensitive; in samples with 100 ppm of nisin and GdL treated at 450 MPa with cycles they were reduced to undetectable levels (a lethality of approximately 7.055 log units). Cycle pressurization showed slightly better results than continuous pressurization. The combination of 350 MPa, 100 ppm of nisin and 1% of GdL was enough to extend the shelf life of MRPM during the 30 day chilled storage.     

A SYBR Green real-time PCR assay to detect and quantify pork meat in processed poultry meat products

Species identification in meat products has grown in interest in recent years since these foodstuffs are susceptible targets for fraudulent labelling. In this work, a real-time PCR approach based on SYBR Green dye was proposed for the quantitative detection of pork meat in processed meat products. For the development of the method, binary meat mixtures containing known amounts of pork meat in poultry meat were used to obtain a normalised calibration model from 0.1 to 25% with high linear correlation and PCR efficiency. The method revealed high specificity by melting curve analysis, being successfully validated through its application to blind meat mixtures, which confirmed its adequacy for pork meat determination. The fully applicability of the method was further demonstrated in commercial meat products, allowing verification of labelling compliance and identification of meat species in processed foods.     

Enzymatic modification of selected functional properties of myofibril preparation obtained from mechanically recovered poultry meat

The effect of addition of 3 g/L of commercially available transglutaminase preparation to protein extracts obtained from mechanically recovered poultry meat was studied. The content of free thiol groups (–SH), thermal drip and gel texture were determined. After pre-incubation at 7–8 °C for 1, 3, 5 and 24 h, the samples were subjected to one-step heating at 50, 60, 70 and 80 °C and two-step heating at 50/80, 55/80 and 60/80 °C. The addition of preparation and the extension of pre-incubation time led to decrease of free -SH groups content. After heating, the number of thiol groups decreased, the texture was improved, but thermal drip from gels increased. The amount of –SH groups in gel extracts subjected to one-step heating decreased with simultaneous increase of mechanical strength of gels. Protein gels subjected to two-step heating exhibited higher firmness than gels subjected to one-step heating. Thus, the 3 g/L addition of transglutaminase preparation in combination with one-step thermal processing at 70 °C and pre-incubation for 3 h contributed to improvement of texture properties of model gels and low thermal drip.     

Modification of functional quality of raw myofibril preparation obtained from water-washed mechanically recovered chicken meat

The aim of this study was to evaluate the effect of enzymatic modification of poultry myofibril preparation on its selected functional properties, that is, solubility of proteins, polymerisation rates of myosin and actin, thermodynamic properties and texture. The myofibril preparation (MP) from mechanically recovered chicken meat, produced by washing and separation of fat and connective tissue, was subjected to the action of the transglutaminase preparation added at 0.3 % for a period ranging from 0.5 to 24 h at a temperature of 6–7 °C. The highest dynamics of a reduction in protein solubility was observed up to 3 h of incubation. A reduction in solubility influenced the electrophoretic pattern of proteins. A significant decrease was found for the intensity of the myosin band in successive modification periods. The addition of the enzyme also influenced a reduction in enthalpy for proteins of the tested system, occurring most dynamically up to 3 h of incubation. The most distinct changes characterising a high increase in all the texture parameters of MP were found in the initial period of enzymatic modification, that is, up to 4.5 h.     

Identification of mechanically separated meat in meat products: a simplified analytical approach by ion chromatography with conductivity detection

Due to food safety concerns, the European Food Safety Authority asked for novel approaches for identifying mechanically separated meat (MSM) in meat products. In this work, a novel and simplified approach for MSM identification in meat products is presented. This approach is based on the calcium and magnesium determination by suppressed cation-exchange chromatography coupled to conductivity detection, after sample mineralisation. One hundred samples of meat products were analysed. The difference between calcium and magnesium concentration (MSM_index) was identified as the most significant parameter useful for discriminating the presence of MSM in the product. The approach was also validated by analysing simulated meat samples containing increasing percentages of MSM. Meat samples with MSM_index higher than 390 mg kg⁻¹ can be classified as MSM products, even if the MSM was obtained at high or low pressure. The protocol is applicable for MSM identification in meat products with MSM percentage higher than 25%.