Changes in meat quality characteristics of bovine meat during the first 6 days post mortem

The development of some quality parameters in bovine meat during the first 6 days of post mortem ageing was studied in two commercial groups (heifer and bull). In the first day bull meat is harder and springier. Meat pH falls during the first 24 h post mortem in both groups, reaching values around 5.5, and it did not change during the next 5 days. Water-holding capacity (expressed as percentage of expelled water) increased in heifer meat. Instrumental texture measures (texture profile analysis, TPA) showed a decrease in hardness, springiness and chewiness in bull raw meat. Sensory analysis showed that assessors perceived a decrease in hardness and in springiness in bull meat and a decrease in juiciness and in chewiness (number of chewings before swallowing) in heifer meat. Ageing showed no effect on assessors’ pleasantness either in heifers’ or in bulls’ meat. During the first 3 days, heifer meat was juicier. Heifers’ meat produced a greater pleasantness on the sixth day. Both meats were not very different for most quality parameters studied in this work.     

Differentially expressed proteins during fat accumulation in bovine skeletal muscle

The objective of this study was to identify the proteins involved in bovine intramuscular fat (IMF) development. Global proteins were monitored in bovine skeletal muscle at muscle-developing versus IMF-increasing stages and with higher versus lower IMF scores, respectively. We identified two differentially expressed (two-fold or more) proteins at the IMF-increasing stage, up-regulated heat shock protein beta 1 (HSPB1) and down-regulated ATP synthase D chain (ATP5H), and two down-regulated proteins with higher IMF scores, carbonic anhydrase 2 (CA2) and myosin light chain 3 (MYL3). In vitro, after adipogenic differentiation, the mRNA expression of HSPB1 and ATP5H did not be changed, but that of CA2 and MYL3 decreased significantly (P < 0.05). After myogenic differentiation, the mRNA expression of HSPB1 increased significantly (P < 0.05), but expression of other genes did not vary. We suggested that CA2 and MYL3, which expressed down during adipogenic differentiation, could be indicative markers for negative regulation of IMF development.     

Effect of salt addition on the thermal behavior of proteins of bovine meat from Argentina

Research was undertaken to investigate how the addition of sodium chloride (NaCl) and/or sodium tripolyphosphate (TPP) to sous vide cooked meat pieces produces an increase in water holding capacity (WHC). Semitendinosus muscles were injected to obtain tissue final concentrations of 0.70% NaCl, 0.25% TPP, 0.70% NaCl+0.25% TPP, and 1.20% NaCl+0.25% TPP. SDS-PAGE analysis showed increased protein solubilization in those treatments which included NaCl. Thermal analysis of whole muscles and isolated myofibrils showed the destabilizing effect of NaCl and a global stabilizing effect of TPP. Both salts together induced a destabilizing global effect, where TPP assisted NaCl in breaking the meat structure. It is suggested that the WHC increments are related to conformational changes in myofibrillar proteins and to the weakening of myofibrillar structure by the removal of myofibrillar proteins.     

Sensory acceptability of raw and extruded bovine rumen protein in processed meat products

The use of bovine rumen protein (raw and extruded) as a replacement for extruded soy protein concentrate in three meat products (pork sausage, chicken hamburger, and kibbe) was investigated. Similarity between rumen and soy protein meat products was assessed using triangle tests and sensory acceptability evaluated by consumer panelists using a nine-point hedonic scale. The addition of raw rumen protein was detected in all meat product types tested, while extruded rumen protein was only detected in kibbe. The addition of raw rumen protein decreased the acceptability of pork sausage aroma and flavor, but improved kibbe appearance, texture and overall acceptability. The addition of extruded rumen protein reduced the acceptability of chicken hamburger texture, but improved pork sausage flavor. Replacement of soy protein by bovine rumen protein is feasible based upon sensory results, but depended upon its form and the type of meat product to which it was added.     

Determination of IgG levels in bovine bulk milk samples from different regions of Spain

Colostrum addition to milk for consumption is an unlawful practice. Furthermore, the higher whey protein/casein ratio of colostrum compared with milk causes severe technological problems. A high concentration of immunoglobulins has been generally accepted as an index of colostrum presence in milk. In this work, the levels of IgG have been determined by a non-competitive ELISA in 3,248 bulk bovine milk samples from different regions of Spain throughout one year. The mean value for IgG concentration obtained from all the samples was 0.257±0.122 mg/ml, within the range generally considered as acceptable for mature milk. The mean concentration obtained for all the samples collected in the spring was 0.288±0.125 mg/ml, significantly higher than the values found at the other seasons. The finding of some samples with very high values of IgG would suggest that the determination of immunoglobulin levels periodically would be a good parameter to control milk quality.     

牛初乳中sIgA的分离纯化

为进一步开发利用牛初乳中生物活性物质sIgA,有必要建立快速分离纯化sIgA的方法。利用凝胶层析和亲和层析等技术进行分离sIgA。采用非还原SDS-PAGE和HPLC进行检测。结果表明:分离纯化的sIgA纯度为97.52%,质量浓度为5.03 g/L。成功建立了纯化牛初乳中sIgA的方法,为实现sIgA的规模化生产提供参考。     

Antioxidant activity of bovine and porcine meat treated with extracts from edible lotus (Nelumbo nucifera) rhizome knot and leaf

Lotus (Nelumbo nucifera) is an extensively cultivated vegetable in eastern Asia, particularly in China. Both lotus rhizome knot (LRK) and lotus leaf (LL) are waste products of the lotus industry. Extracts from LRK and LL are proposed as antioxidants for meat. Porcine and bovine ground meat samples were subjected to three treatments: CONTROL (with no additives), LRK (lotus rhizomes knot extract 3% w/w), and LL (lotus leaf extract 3% w/w). Raw and cooked samples were stored at 4 °C and the antioxidant activity was determined at 1, 3, 6 and 10 days. Antioxidant activity was significantly increased in all meat samples with the addition of both LRK and LL, but LRK was more effective against lipid oxidation. The results show the potential for using LRK and LL extracts in the meat industry to prolong shelf life.     

Purification and characterisation of an alanine aminopeptidase from bovine skeletal muscle

A monomeric alanine aminopeptidase was purified to a single band in SDS–PAGE from bovine skeletal muscle by using a procedure including ammonium sulphate fractionation, adsorption on DEAE–cellulose, gel filtration on Ultrogel ACA 34, and adsorption on hydroxyapatite. Molecular weight determination by gel filtration and sodium dodecyl sulphate–polyacrylamide gel electrophoresis yielded a molecular size of 60 kDa. The aminopeptidase activity was optimal at pH 8.0 and 37 °C. It was totally abolished by Co²⁺ and Zn²⁺ ions, and almost completely inhibited by bestatin and Mn²⁺. The activity was strongly inactivated by phenylmethansulfonyl fluoride, Mg²⁺, and Fe³⁺ ions but stimulated by pepstatin and EDTA. However the activity was not affected by Ca²⁺, puromycin and iodoacetate. When compared with its activity toward Ala-β-naphthylamides (Ala-βNA), the enzyme exhibited 15–17% as much activity toward Pro- and Leu-βNA, 4–6% activity toward Met- and Arg-βNA, and negligible or no activity toward Glu- and Ser-βNA.     

牛乳腺炎金黄色葡萄球菌肠毒素A基因的克隆及序列分析

根据Genbank上公布的金黄色葡萄球菌肠毒素A的全序列,利用生物学软件Primer 5.0和oligo 6.0设计了一对特异性引物来扩增靶序列片段,经克隆预测序,结果表明扩增片段长度为101 bp,锦州分离株与标准菌株的基因片段序列相似性为100%,与Genbank上公布的金黄色葡萄球菌菌株(EF520720.1)SEA基因相似性达到99.14%。高度相似性结果为进一步研究建立分子检测技术奠定了实验基础。     

Glial fibrillary acidic protein and myelin basic protein as markers for the immunochemical detection of bovine central nervous tissue in heat-treated meat products

Because bovine central nervous tissue (CNT) is the main risk material in transmission of the infective agent of bovine spongiform encephalopathy, a suitable test is needed to enforce the ban on CNT in human foodstuffs in the United States and the European Union and to ensure that meat products are free of CNT To detect bovine CNT in heat-treated meat products, we used immunohistochemistry and Western blots with antibodies against glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP). Both antigens were resistant to processing methods used for meat products. The anti-GFAP antibody showed a high degree of tissue specificity, whereas the anti-MBP antibody had high species specificity, clearly differentiating between porcine and bovine CNT Therefore, immunochemistry performed with both proteins provides an effective means for detecting bovine CNT in meat products.     

Colour of bovine subcutaneous adipose tissue: A review of contributory factors, associations with carcass and meat quality and its potential utility in authentication of dietary history

The colour of bovine subcutaneous (sc) adipose tissue (carcass fat) depends on the age, gender and breed of cattle. Diet is the most important extrinsic factor but its influence depends on the duration of feeding. Cattle produced under extensive grass-based production systems generally have carcass fat which is more yellow than their intensively-reared, concentrate-fed counterparts and this is caused by carotenoids from green forage. Although yellow carcass fat is negatively regarded in many countries, evidence suggests it may be associated with a healthier fatty acid profile and antioxidant content in beef, synonymous with grass feeding. Nonetheless, management strategies to reduce fat colour of grass-fed cattle are sought after. Current research suggests that yellow colour of this tissue is reduced if pasture-fed cattle are converted to a grain-based diet, which results in accretion of adipose tissue and dilution of carotenoids. Colour changes may depend on the initial yellow colour, the carotene and utilisable energy in the finishing diet, the duration of finishing, the amount of fat accumulated during finishing and the rate of utilisation of carotene from body fat. Differences in nutritional strategies which cause differences in fatty acid composition may be reflected by differences in fat colour and carotenoid concentration. Fat colour and carotenoids are prominent among a panoply of measurements which can aid the authentication of the dietary history and thus to some extent, the origin of beef, although this potential utility is complicated by the simultaneous rather than discrete use of forages and concentrates in real production systems.     

The amount and composition of the proteins in drip from stored pig meat

In order to elucidate the mechanism of drip formation, measurements have been made of the amount of drip, and its protein concentration, from 80 pigs chilled conventionally. The correlation between amount of drip and protein concentration was poor but significant (r = −0·41, P < 0·001).

The individual protein components of 20 drip samples were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Relative protein composition varied with amount of drip. As the amount of drip increased above about 12% the absolute amounts of some proteins decreased; these proteins were creatine kinase and/or phosphoglycerate kinase (under the system used, these two proteins comigrate and therefore cannot be distinguished), myokinase, and an unidentified protein of molecular weight 137000. Drip contained similar proteins to a sarcoplasmic extract and in similar amounts.

These results show that drip is mainly sarcoplasmic in origin and we suggest that the systematic changes in individual proteins as the amount of drip increases may be explained by denaturation of some or all of these proteins and possibly by dilution with fluid from within the myofibril.     

A validated matrix solid-phase dispersion method for the extraction of organophosphorus pesticides from bovine samples

A method based on matrix solid-phase dispersion (MSPD) was developed for the quantitative extraction of five organophosphorus (OPPs) pesticides from bovine samples. The determination was carried out by high performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection. The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, chlorfenvinphos, diazinon, fenitrothion, and parathion-methyl. The method was validated, yielding recovery values higher than 94%, except for chlorfenvinphos in liver (55%), and precision values, expressed as relative standard deviations (RSDs), which were less than or equal to 15% in liver and 11.5% in muscle at spiking levels of 0.25, 2.5 and 5 μg g⁻¹. Linearity was studied from 0.5 to 15 μg g⁻¹, and the limits of detection (LODs) were found to be lower than 0.1 μg g⁻¹_. This method was applied to the analysis of real samples with confirmative analyses performed using gas chromatography–mass spectrometry (GC–MS) in selected ion monitoring mode (SIM).     

Concentration characteristics of bovine β‐defensin 1 and 2 in fresh bovine milk and infant formula

The aim of this study was to determine the concentration of defensins BNBD‐1 and BNBD‐2 in fresh bovine milk and infant formula, and to compare the defensin concentrations of bovine milk and human milk. Abundant BNBD‐1 and BNBD‐2 was found in fresh bovine colostrum. However, compared to fresh bovine milk, BNBD‐1 and BNBD‐2 concentrations in infant formula were very low. The BNBDs concentration ranges were also less than β‐defensins in human milk. The BNBD‐2 concentration in fresh bovine milk was higher than that of BNBD‐1.     

The effect of glycosylation on the interfacial properties of bovine caseinomacropeptide

The two major fractions of bovine caseinomacropeptide (CMP), the glycosylated gCMP and non-glycosylated aCMP, were studied for their emulsifying properties. The main finding was that aCMP showed significantly better emulsifying properties than gCMP. While aCMP showed an emulsifying activity index (EAI) of 150.7 g/m², gCMP achieved a value of 98.5 g/m². Stability of emulsions was 1.4 times higher for aCMP as compared to gCMP. Droplet size measurements and creaming studies showed a strong influence of pH on both fractions with minimal emulsion stabilities at pH 4.1 (gCMP) and 4.9 (aCMP). Investigation of the flocculation behaviour and variations of the ionic strength indicate that the glycan side chains induce a combination of electric, steric and hydrophilic effects, preventing an ordered adsorption of gCMP molecules at the oil/water interface, while aCMP builds a stable network at the surface. For further elucidation, zeta potential measurements for both fractions were performed, resulting in isoelectric points of 3.15 for gCMP and 4.15 for aCMP in bulk solution. Finally, a hypothesis of surface adsorption of CMP is presented as a function of glycosylation and pH based on experimental data supported by an approach using protein modelling techniques.     

PCR detection of bovine mitochondrial DNA derived from meat and bone meal in feed

Because bovine meat and bone meal (MBM) is thought to be a major source of bovine spongiform encephalopathy, we developed a PCR-based method for detection of bovine MBM in animal feed. We isolated bone particles from feed containing bovine MBM using a separation technique based on specific gravity and then washed bone particles with sodium hypochlorite solution and an EDTA-proteinase K solution. The mitochondrial DNA was extracted from bone particles and amplified using PCR with cattle-specific primers. Bovine DNA was not detected in a milk replacer containing dried skim milk and dried whey, but bovine DNA was detected in the milk replacer that was mixed with bovine MBM. Other cattle-derived materials in feeds did not interfere with the selective detection of bovine MBM. This method allowed detection of bovine mitochondrial DNA in feed with 0.1% added bovine MBM. When the treatment with sodium hypochlorite was excluded, bovine DNA derived from MBM could not be distinguished from bovine DNA derived from other bovine materials. However, the exclusion of this treatment improved the detection limit of bovine MBM in feed. This method appears suitable for the selective detection of bovine MBM in feed.     

Digestion study of proteins from cooked meat using an enzymatic microreactor

A semi automatic flow procedure with photometric detection was developed for the study of meat protein digestion. This system comprised two independent flow pathways, gathered by two compartments. The gastric compartment was simulated by an ultrafiltration cell fitted with a 10 KDa cut off membrane and the intestinal compartment was simulated by a 1 KDa cut off dialysis membrane. The pathways were filled with solutions simulating digestive conditions. The proposed system was employed in digestion studies of whole protein extracts from raw and cooked (100°C) meat. A mathematical modelling for the determination of the digestive kinetic constants was established. The results show that meat cooking leads to an important decrease of protein digestibility by proteases of the digestive tract.     

蛋白质糖基化改性方法和产物验证方法研究进展

介绍了近年来国内外蛋白质糖基化改性方法和产物鉴定方法的研究现状,系统综述了蛋白质糖基化的影响因素,对干热法、湿热法和基于湿热法衍生出的辅助方法在内的蛋白质糖基化方法进行比较分析,总结归纳了产物鉴定方法的原理和使用情况,并展望通过非热加工较为精准的控制糖基化程度,同时保证产物的安全性与营养性。     

Addition of partly reduced bovine serum albumin to a metmyoglobin-fortified washed cod system gives reduced formation of lipid oxidation products and increased degradation of proteins

The aim of the investigation was to study the pro-oxidative system of washed cod with added horse metmyoglobin (metMb) regarding lipid and enzyme oxidation plus protein degradation. The changes were studied at pH 5.6 and 2 °C for 47 h. Bovine serum albumin (BSA) with 0.2 or 3.5 thiol (reduced) groups per molecule was added as an antioxidant protein and as providers of free thiols. BSA with the higher amount of thiols decreased the formation of lipid peroxides and thiobarbituric acid reactive substances (TBARS) in the washed cod system. Metmyoglobin (metMb) addition slowed down the enzymatic release of proteins and protein fragments from insoluble washed cod proteins while the opposite was observed with added reduced BSA. Addition of metMb strongly inactivated the thiol proteases cathepsin B + L and effectively oxidized the low molecular weight thiols in the system while reduced BSA slowed down inactivation of the proteases. The endogenous proteases degraded BSA to a fragment of 41.7 kDa. Formation of this fragment was reduced when metMb was added. BSA (not reduced) did not influence TBARS formation in the washed cod system with metMb, but increased the formation of lipid peroxides after 47 h compared to the system without BSA.     

不同杂交牛肝脏食用品质和营养品质分析

研究不同品种杂交牛肝脏食用品质和营养品质以及氨基酸组成和含量的差异。以安格斯牛×秦川牛杂交牛、安格斯牛×河西地区黄牛杂交牛和鲁西黄牛×利木赞牛杂交牛肝脏为原料,采用相关国标方法或常用方法对3种杂交牛肝脏食用品质和营养品质以及氨基酸含量进行测定,并进行必需氨基酸评分。结果表明,3种杂交牛肝脏色泽正常,pH分别为6.17、6.44和6.22,熟肉率分别为82.46%,77.03%和80.38%,加工性能良好,蛋白质含量分别为20.11、18.82、19.01g/100g,氨基酸含量分别为19.68、17.68、17.63g/100g,其中,必需氨基酸含量分别为7.30、6.46、6.44g/100g,且氨基酸种类齐全,氨基酸评分高于或接近FAO提出的标准模式。3种杂交牛肝脏食用品质和营养品质虽然存在一定的差异,但均可作为优质的牛副产物,有较大开发利用价值。