电子鼻在牦牛肉和牛肉猪肉识别中的应用

为了探索电子鼻对肉类掺假识别的可行性,利用电子鼻对牦牛肉、牛肉和猪肉样品进行了分析。通过对所获得的数据进行主成分分析（principal component analysis,PCA）、判别因子分析（discriminant factor analysis,DFA）和偏最小二乘回归分析（partial least-squares analysis,PLS）。结果表明：几种肉类在电子鼻传感器上有不同的特征性响应图谱,电子鼻能够有效识别猪、牛肉;同时电子鼻能够识别不同部位的牦牛肉和普通牛肉;但不能识别不同部位的猪肉。在牛肉馅中掺入不同比例的猪肉馅时,电子鼻也能进行识别。采用偏最小二乘回归分析对数据进行处理,电子鼻响应信号和猪肉馅掺入比例之间有很好的相关性（决定系数R2为0.9762）,PLS模型预测误差在1.27%～7.00%之间。试验证明电子鼻可用于肉类的识别。     

Detection of pork and lard as adulterants in processed meat: liquid chromatographic analysis of derivatized triglycerides

A new method is described for detection of pork and lard as adulterants in processed beef and mutton mixtures. The unsaturated triglycerides in the fat are ozonized and then derivatized. The mixture of derivatized and saturated triglycerides is analyzed by liquid chromatography using a reverse-phase column and a UV detector. Pork fat has larger amounts of triglyceride containing saturated fatty acid at the C-2 position than does the fat of other meat. The ratio of triglyceride containing saturated fatty acid vs triglyceride containing unsaturated fatty acid at the same (C-2) position (SSU/SUS) in a sample is compared with those of pure meats. The presence of pork in the sample causes the ratio to increase compared with ratios for pure beef or mutton. The increase in the SSU/SUS ratio is significant for the addition of 1% pork in beef. In the case of mutton, the addition of 3% pork causes a noticeable change. The method is reliable and is also applicable to samples containing only fat. Processing (heating or cooking) does not affect the ratios.     

Authentication of animal fats using direct analysis in real time (DART) ionization-mass spectrometry and chemometric tools

A combination of direct analysis in real time (DART) ionization coupled to time-of-flight mass spectrometry (TOFMS) and chemometrics was used for animal fat (lard and beef tallow) authentication. This novel instrumentation was employed for rapid profiling of triacylglycerols (TAGs) and polar compounds present in fat samples and their mixtures. Additionally, fat isolated from pork, beef, and pork/beef admixtures was analyzed. Mass spectral records were processed by principal component analysis (PCA) and stepwise linear discriminant analysis (LDA). DART-TOFMS profiles of TAGs were found to be more suitable for the purpose of discrimination among the examined fat types as compared to profiles of polar compounds. The LDA model developed using TAG data enabled not only reliable classification of samples representing neat fats but also detection of admixed lard and tallow at adulteration levels of 5 and 10% (w/w), respectively. The presented approach was also successfully applied to minced meat prepared from pork and beef with comparable fat content. Using the DART-TOFMS TAG profiles of fat isolated from meat mixtures, detection of 10% pork added to beef and vice versa was possible.     

Beef- and bovine-derived material identification in processed and unprocessed food and feed by PCR amplification

This research developed and evaluated a PCR procedure to detect beef in heated and unheated meat, sausages, and canned food, using a specific and sensitive method. To confirm the effectiveness and specificity of this fragment, we tested 45 cattle blood DNA samples (from different breeds) and obtained positive results. With 125 samples tested from other species, the specific beef amplification was not detected. Feed components intended for cattle nutrition were also checked, and bovine-derived material was detected. Using this method we can detect the degree of contamination up to 0.01% raw beef in pork. In the same way, 1% beef was detected in cooked meat mixtures and bovine-derived material in concentrate mixtures. Beef has been identified in both heated and unheated meat products, sausages, canned food, and hamburgers. In conclusion, specific PCR amplification of a repetitive DNA element seems to be a powerful technique for the identification of beef in processed and unprocessed food, because of its simplicity, specificity and sensitivity. Furthermore, feed components intended for cattle nutrition can be checked. The procedure is also much cheaper than other methods based on RFLPs-PCR, immunodiffusion, and other techniques that need expensive equipment.     

运输季节对生猪应激及猪肉品质的影响

为了研究运输季节对猪宰前应激及宰后猪肉品质的影响,该文以杜大长三元杂交猪为对象,测定了夏、秋和冬3个季节运输条件下猪的血液生化指标、血细胞系数以及宰后猪肉温度、p H值、保水性、色泽和剪切力的变化。结果表明:秋季运输猪血液中白细胞数、血红蛋白、红细胞压积、葡萄糖、促肾上腺皮质激素和皮质醇浓度显著低于夏季和冬季组(P0.05),胴体表面皮肤损伤也显著降低(P0.05)。运输季节对宰后猪肉胴体温度、p H值、色泽及保水性有显著性影响(P0.05)。与秋季运输相比,夏季运输猪宰后45 min胴体温度、滴水损失率、L值显著升高,a*值和剪切力显著下降(P0.05);冬季运输猪宰后猪肉a*值增加(P0.05),但滴水损失率与秋季组相比并无显著性差异(P0.05)。因此猪在秋季运输能显著降低宰前动物应激,提高宰后猪肉品质,夏季和冬季如能对运输环境分别进行防暑和保暖处理可能会对猪应激反应和猪肉品质产生积极的作用。该研究结果对于屠宰行业实际生产过程中缓解生猪宰前运输应激,改善动物福利以及提高猪肉品质提供参考。     

Detection of poultry and pork in cooked and canned meat foods by enzyme-linked immunosorbent assays

Enzyme-linked immunosorbent assays (ELISA) are described for the detection of poultry and pork in cooked and canned meat foods. These assays are based on species-specific, polyclonal antibodies raised against heat-resistant antigens. The heat-resistant antigens were isolated from raw skeletal muscle tissue of pork and chicken and were found to be immunoreactive even after heating to 120 degrees C for 15 min. The poultry ELISA could detect chicken or turkey at the 126 ppm level, and the pork ELISA could detect pork at the 250 ppm level. Samples of frankfurters, bolognas, pressed meats, canned baby foods, and canned spreads were prepared by simple aqueous extractions.     

便携式猪肉阻抗谱检测系统研制

基于生物阻抗谱检测原理,设计并实现了一个非破坏性的便携式肉品阻抗谱检测系统,主要包括信号发生单元和检测单元,信号源能够在0.1～250 kHz范围内自动扫频,检测单元由检测电极和增益、相位检测器构成。探讨了检测电极设计方案,比较分析了六钢针电极和四针石墨电极的性能,同时通过试验证明了系统的稳定性,1 kHz以上系统的变异系数CV＜6%;以组内相关系数ICC来评定在不同温度下系统的可靠性,系统模型中Ri、Re、C的ICC均大于65%,系统稳定可靠。选取猪肉样品进行了新鲜度指标与阻抗谱关系的初步研究,结果表明随着猪肉新鲜程度改变,猪肉复阻抗值、复阻抗实部值、复阻抗虚部值以及特征频率都表现出减小的趋势。     

代谢组学在肉及肉制品品质监测中的应用

代谢组学是通过研究机体受外界干扰前后小分子代谢物(分子量1 500 Da)的变化,进而探究其代谢机制的新兴科学。近年来,代谢组学在肉品科学研究领域受到广泛关注。但目前基于该技术监测宰前因素(遗传因素、肌肉部位及饲喂方式)及宰后成熟(时间、方式)对肉及肉制品品质影响的相关研究仍缺乏系统总结。同时,代谢组学技术的引入,也为肉品货架期预测、肉制品加工工艺优选、产地溯源及真伪鉴别提供了新的思路。因此,该研究概述了近年来代谢组学常用的分析检测技术(核磁共振技术、气相色谱质谱联用技术、液相色谱质谱联用技术)及数理统计方法(主成分分析、偏最小二乘判别分析等),重点对代谢组学在肉品生产诸多环节(动物饲喂、屠宰、加工等)中的最新研究进展进行综述,最后总结了目前肉品代谢组学研究中存在的代谢产物检测有限、试验重复性差等问题并认为多组学联合分析是监测肉品品质的未来发展方向,以期为其在肉品科学领域的应用提供参考。     

Bacteriological and genetic assessment of game meat from Japanese wild boars

Bacterial tests were used to assess bacterial contamination of game meat from Japanese wild boars. The bacterial contamination of wild boar meat was less than that of domestic pork, as determined by aerobic plate counts (APC) and coliform counts. None of the meat examined in this study was contaminated by Salmonella or E. coli O-157. To detect adulteration by domestic pig meat or European wild boar meat, 46 samples of game meat sold as Japanese wild boar were examined genetically. A total of 17 samples showed genetic haplotypes of European and Asian domestic pigs in the D-loop of mitochondrial DNA (mtDNA), and 16 samples showed nuclear glucosephosphate isomerase-processed pseudogene (GPIP) genotypes of European domestic pigs. The European GPIP genotypes of these samples were confirmed by PCR-RFLP analysis. These results indicate that some game meat sold as Japanese wild boar is adulterated by cross-breeding between pigs and wild boars or by contamination with meat from domestic pigs or European wild boars.     

Development of inosine monophosphate and its degradation products during aging of pork of different qualities in relation to basic taste and retronasal flavor perception of the meat

Inosine monophosphate (IMP) and its degradation products, ribose and hypoxanthine, are all considered to be important constituents in meat flavor formation and development. The present study explored the fate of IMP during the aging of two qualities of pork (pH >5.7 and 5.5 < pH < 5.6) and the potential relationship between IMP, hypoxanthine, and sensory attributes of pork registered both as retronasal and basic taste responses in whole meat, meat juice, and the remaining meat residue. During aging the concentration of IMP decreased with a simultaneous increase in the concentrations of inosine, hypoxanthine, and ribose. The rates at which IMP was degraded to inosine and inosine to hypoxanthine during aging were found to be in agreement with the known rate constants of the dephosphorylation of IMP and the hydrolysis of inosine, respectively. Moreover, high-pH pork resulted in a significantly higher concentration of hypoxanthine throughout storage compared with low-pH pork due to an initially higher concentration of IMP in high-pH meat. The sensory analysis showed increasing intensity in bitterness and saltiness of pork as a function of aging, with the intensity being most pronounced in the meat juice. The increasing bitterness of the pork as a function of aging coincided with the higher content of hypoxanthine in these samples, thereby suggesting that degradation of IMP to hypoxanthine might influence pork flavor. In contrast, IMP was associated with nonaged meat and the sensory attributes meaty and brothy.     

Establishment and application of a fluorescent polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for identifying porcine,caprine, and bovine meats

A method of fluorescent Polymerase Chain Reaction-restriction fragment length polymorphism (PCR-RFLP) was applied as an analytical and quantitative tool for meat identification. Following alignments of the nucleotide sequences, an oligonucleotide primer pair was designed to amplify the partial sequences within the 12S ribosomal RNA (12S rRNA) gene of mitochondrial DNA from porcine, caprine, and bovine meats. No fragment can be amplified from dog, cat, fish, duck, goose, turkey, and chicken DNA with the primer pair. Using fluorescence sensor capillary electrophoresis, the species-specific DNA fingerprints of pork, goat, and beef were generated by restriction enzyme digestion following a fluorescence-labeling PCR amplification. Species identification was conducted on the meat mixtures. The reliably semiquantitative levels were below 1% for binary mixtures of pork, goat, and beef. Cooking and autoclaving of meats did not influence the generation of the PCR-RFLP profiles or the analytical accuracy.     

待宰时间和致晕方式对生猪应激及猪肉品质的影响

国内外对于生猪宰前因素已经做过大量的研究,但总体来讲,对于待宰时间的研究一直没有形成定论;由于生产成本等问题,国内对于CO2致晕的应用与研究均较少;对于不同的电击晕方式,在同一体系下的成批量的比较涉及很少,另外对于应激指标的选择一直没有统一的标准。该文研究了在电击晕、二氧化碳致晕和不同待宰时间(3、6和12h)条件下,杜大长三元杂交猪血液应激指标和猪肉品质的变化。结果显示:待宰3h的生猪血液指标显著低于另外2种方式,而二氧化碳致晕方式使得生猪血液中乳酸含量、肌酸激酶含量、皮质醇含量和乳酸脱氢酶含量显著低于不击晕和电击晕方式。不同待宰时间对胴体背最长肌宰后24h的温度、pH值、蒸煮损失、明亮度、红色度和黄色度没有显著影响(P>0.05),但是待宰3h的生猪胴体宰后45min的pH值和温度明显较低,汁液损失和剪切力也显著小于待宰6和12h的值;而与不击晕和电击晕方式相比,二氧化碳致晕产生的猪肉宰后45min的pH值和温度较低、汁液损失较大、明亮度较大、红色度和黄色度值较小。因此生猪待宰3h并通过二氧化碳致晕产生的应激反应与猪肉品质影响最小。生产中应加强对待宰时间和致晕方式的控制,并注意利用各种处理方法对肉品质影响的协同作用,从而最大程度实现猪肉品质的改良。     

Effect of plant phenolics on protein and lipid oxidation in cooked pork meat patties

Rapeseed and pine bark are rich sources of phenolic compounds that have in previous studies been shown to exhibit antioxidant and anti-inflammatory properties. In this study, the antioxidant effect of rapeseed and pine bark phenolics in inhibiting the oxidation of lipids and proteins in meat was tested as a possible functional food application. The cooked pork meat with added plant material was oxidized for 9 days at 5 degrees C under light. The suitable level of plant material addition was first screened by following lipid oxidation only. For further investigations plant materials were added at a level preventing lipid oxidation by >80%. The oxidation was followed by measuring the formation of hexanal by headspace gas chromatography and the formation of protein carbonyls by converting them to 2,4-dinitrophenylhydrazones and measured by spectrophotometer. It was shown that rapeseed and pine bark were excellent antioxidants toward protein oxidation (inhibitions between 42 and 64%). These results indicate that rapeseed and pine bark could be potential sources of antioxidants in meat products.     

Analysis of volatiles in meat from Iberian pigs and lean pigs after refrigeration and cooking by using SPME-GC-MS

The volatile compounds generated in meat from Iberian and lean pigs after four different treatments (raw, refrigerated, cooked, and refrigerated cooked meat) were analyzed. The different treatments showed different volatile profiles. Methyl alcohols and ketones (such as 2-ethyl-hexan-1-ol, 2-methyl-butan-1-ol, 3-methyl-butan-1-ol, and 3-hydroxy-butan-2-one) were the most representative in refrigerated meat because of the degradation of carbohydrates and proteins together with the Strecker degradation pathway. Lipid-derived volatiles were the most abundant in cooked meat and refrigerated cooked meat. Meat from different pig breeds presented different volatile profiles, probably due to different enzymatic and oxidative deterioration susceptibility. Otherwise, the fat content and its compositional characteristics also played an important role in the generation of volatiles. As compared to samples from lean pigs, muscles from Iberian pigs showed a higher content of heme iron that may have promoted the generation of higher content of total lipid-derived volatiles during the refrigeration of cooked meat. Despite that, the formation of volatiles with low thresholds and related to intense rancidity perception likely to be derived from polyunsaturated fatty acids was higher in lean pork than in meat from Iberian pigs. This might be expected to lead to a more intense development of a warmed over flavor during refrigeration of cooked samples from lean pigs.     

Amino acid analysis for meat protein evaluation

The Food Safety and Inspection Service procedure for determination of essential amino acid content of mechanically processed products from red meat animals and poultry is based on hydrolysis of a powder prepared by blending samples in acetone-chloroform. The hydrolysis procedure incorporates thioglycolic acid to prevent loss of tryptophan. Aliquots of prepared hydrolysates are injected into a liquid chromatographic system, using gradient elution on an ion-exchange column for separation. The system also uses post-column hypochlorite oxidation coupled with orthophthalaldehyde reagent and fluorescence detection. Modification of the elution program allows concurrent determination of tryptophan with minimal added cost. Chromatograms from beef, pork, and poultry products show adequate separation and quantitation of beta-alanine, 1-methyl-histidine, and 3-methyl-histidine, indicating that the procedure could be used to estimate muscle content of products. A colorimetric procedure for assay of hydroxyproline was introduced and validated as an adjunct method for protein quality estimation.     

质构仪穿透法测定肉制品嫩度的研究

为了量化评定肉制品的食用物理特性——嫩度,试验以猪和牛不同部位的肌肉为材料,使用高精度TA-X12质构仪,模拟口腔咀嚼肌肉的穿透方法,测定了不同肌肉的穿透曲线。并比较分析了不同肌肉的穿透参数(包括3个极值点Y₁,Y₂,Y₃,恒定值Y₄和曲线所包围的面积Y₅),与感官品评嫩度值之间的相关关系。结果表明：质构仪穿透法测得的第一个极值点(Y₁)与猪和牛不同部位的肌肉的感官品评嫩度值相关系数分别为0.9784和0.9984,呈极显著的正相关关系(P<0.01),穿透法第一极值点(Y₁)可作为猪肉、牛肉肉制品的嫩度测定量化参数。     

Development of USDA-FSIS method for isolation of Listeria monocytogenes from raw meat and poultry

A method was developed specifically to detect naturally occurring Listeria monocytogenes in meat because the traditional cold enrichment procedure was extremely slow and other procedures were ineffective. This method could identify beta-hemolytic Listeria colonies in 3-4 days. The use of a 2-stage enrichment, highly selective LPM agar, and a thin-layer horse blood agar plate for the detection of beta-hemolytic Listeria isolates are the important steps of this method. L. monocytogenes was recovered from 20 of 41 samples of frozen ground beef, 12 of 23 samples of pork sausage, and 7 of 22 samples of poultry. These results indicate that L. monocytogenes is common in raw meat and that this method is effective for its recovery.     

冰温贮藏期间淀粉添加对水滑肉品质的影响

水滑肉是我国传统的菜肴,具有爽滑细嫩、鲜香无比的特点。为了探究水滑肉淀粉外壳变化对水滑肉品质的影响,以质构、剪切力、水分含量、回生程度、淀粉热力学特性等为评价指标,研究了在冰温贮藏期间水滑肉品质的变化情况。结果表明：与水煮肉进行对照,在冰温贮藏期间淀粉的添加显著抑制了水滑肉的硬度、咀嚼性及剪切力的增加;水滑肉在贮藏期品质指标劣化,但感官得分优于对照组。在冰温贮藏期间,水滑肉外壳的水分含量、糊化焓值及R_1047/1022依次增加了7.29%、327.42%、5.17%,增长幅度均低于淀粉组 (P＜0.05);肉的存在显著减缓了水滑肉淀粉外壳的回生(P＜0.05)。在冰温贮藏条件下,淀粉外壳的回生与水滑肉的质构指标呈现显著正相关(P＜0.05),即淀粉外壳的回生会劣化水滑肉的硬度、咀嚼性和剪切力。冰温条件下,肉中水分向淀粉外壳转移可能会延缓淀粉外壳的回生,从而延缓其品质劣化;冰温贮藏第8 天可能为水滑肉品质变化的关键点。研究结果可为水滑肉预制菜肴品质研究提供参考。     

Comparative analysis of meat samples prepared with food chopper and bowl cutter

Analyses of meat samples after preparation with either a bowl cutter or by the official procedure with a food chopper were compared for homogeneity of comminution and for differences in fat, moisture, and protein content. Cutting time in the bowl cutter was limited to minimize temperature rise in samples. Beef chuck, pork shoulder, and beef shank, cheek, and tongue were used in the study. Variances of replicate analysis data for the 5 meat types were pooled for either cutter or chopper treatment and for each analyzed component. Sample portions cut and mixed by using the bowl cutter were more homogeneous than those ground with a food chopper. Comparative accuracy was indicated by fat and moisture means: 5 were in good agreement and 5 differed significantly; 3 of 5 paired protein means differed significantly but were within 0.3% protein. Results on precision and accuracy as well as the simplicity and convenience of the bowl cutter procedure favor its use as an alternative to a food chopper for preparing meat samples for analysis.     

Evaluation of the key aroma compounds in beef and pork vegetable gravies a la chef by stable isotope dilution assays and aroma recombination experiments

Although the aroma compounds of meat processed as such have been studied previously, data on complete homemade dishes containing beef and pork meat were scarcely studied. Recently, 38 odor-active compounds were characterized in beef and pork vegetable gravies using GC-olfactometry. In the present investigation, the most odor-active compounds were quantitated in a freshly prepared stewed beef vegetable gravy (BVG) as well as a stewed pork vegetable gravy (PVG) by means of stable isotope dilution assays. Calculation of odor activity values (OAVs; ratio of concentration to odor threshold) revealed 3-mercapto-2-methylpentan-1-ol, (E,E)-2,4-decadienal, (E,Z)-2,6-nonadienal, (E)-2-decenal, (E)-2-undecanal, and 3-hydroxy-4,5-dimethyl-2(5H)-furanone as the most potent odorants in both gravies. However, significantly different OAVs were found for 12-methyltridecanal, which was much higher in the BVG, whereas (E,Z)-2,4-decadienal showed a clearly higher OAV in the PVG. Aroma recombination experiments performed on the basis of the actual concentrations of the odorants in both gravies revealed a good similarity of the aromas of both model mixtures containing all odorants with OAVs > 1 with those of the original gravies.