SOME ASPECTS OF RAW MEAT TENDERNESS. A Study of Some Factors Affecting Its Change with Cooking and a New Means of Measurement

A hand-operated biting instrument which is quick and simple to use was developed to investigate the possibility of assessing the tenderness of raw meat at the carcass or wholesale cut stage. Comparison with the Warner-Bratzler shear device revealed an overall close relationship for cooked meat (r = 0.96, n = 66), greater response in terms of proportional change in readings per unit change in tenderness (P < 0.01) but a greater variability in a series of readings on meat cores from the same steaks (P < 0.001). Relationships between readings on raw and cooked samples were low. It is suggested that this may be due to the fact that the effects of cold shortening and aging on cooked meat tenderness are not apparent on the tenderness of raw meat. The response to cold shortening in terms of tenderness appears to develop as meat is heated from 50°C to 60°C while the response to aging is already partially developed at a cooking temperature of 50° C. It is concluded that although the instrument may be better than existing methods under some situations due to its simplicity, it is unlikely to be useful on raw meat     

Some observations on the absorption spectra of various myoglobin derivatives found in meat

The three principal myoglobin states of haem pigment, oxymyoglobin, metmyoglobin reduced myoglobin, and the ferrous nitrous oxide form, nitrosomyoglobin, were prepared as pure pigments in solution. The absorbance spectra of these solutions were determined and extinction coefficients calculated. The position of the absorption peaks showed some small differences compared to published data, in particular the use of absorbance readings at 525 nm as an isobestic point for all three could be questioned. The use of mathematical transforms to first or second difference functions showed merit for the identification of mixtures of some of the myoglobin forms. The second difference function separated the broad absorbance band in the Soret region into two separate troughs, thereby resolving a mixture of oxymyoglobin and reduced myoglobin. It is suggested that based on absorption spectra, similar mathematical transforms could be applied to the interpretation of reflectance spectra of meat and meat products. Further evaluation of such mathematical transformations is required on a range of meat reflectance spectra.     

The practical application of 3-methylhistidine in determining the lean meat content of food products

Protein-bound 3-methylhistidine, which is present at similar concentrations in various meat species but absent from non-meat proteins, was used to estimate the lean meat content of a range of retailed meat products. The results of the application of this novel method were compared and contrasted with those using standard methods of product analysis. The presence of textured soya protein in products was determined using polyacrylamide gel electrophoresis. Formulae for the calculation of the fat-free lean meat content on the bases of (i) the 3-methylhistidine index for muscle protein and (ii) the connective tissue content, are given. The lean meat contents of products calculated on these bases were found to be of the same order as, but generally lower than, those obtained using standard methods. This was considered to be due to the presence of non-meat proteins, of added connective tissue and/or certain types of offal. These would not be included in the lean meat content, as calculated by the 3-methylhistidine index, but could be legitimately included in the meat content calculated using standard methods according to current practice. A new interpretation of 'meat' in terms of 3-methylhistidine content is given.     

ELISA-test for cooked meat species identification on gelatine and gelatine products

The results of the ELISA-test with a commercial cooked meat species identification kit on gelatine and gelatine containing products can be influenced by different gelatine types and concentrations leading to false positive readings. The test cannot be applied especially to meat products containing relatively high amounts of soluble collagens because their extracts form solid gels in the test wells. In this case the different reagents added will penetrate the gels and react with each other. The kit may not speciate reliablely commercial gelatine in isolation or in products where gelatine is the sole animal protein source.     

测定肉串源性成分的液相色谱-串联质谱与聚合酶链式反应方法对比研究

采用液相色谱-串联质谱（liquid chromatography-tandem mass spectrometry,LC-MS/MS）与聚合酶链式反应（polymerase chain reaction,PCR）方法分别对北京市场中的200 个烤肉串样品进行源性成分分析。其中PCR方法按照出入境标准进行操作,LC-MS/MS方法为自建方法,原理是基于测定物种的特异性多肽链进行物种鉴别。结果表明：2 种检测方法所得到的结果一致,肉串总体掺假比例为21%,其中羊肉串掺假比例为28%,牛肉串掺假比例为14%,主要掺假物种为猪和鸭;通过大批量样品实验对比,LC-MS/MS方法的准确性更高,实验操作也更为简便、耗时短、成本低,可用于日常食品的肉源性成分检测。     

基于实时荧光定量PCR和数字PCR的肉制品中牛源性成分检测

为了能够快速有效的检测出肉制品中牛源性成分,采用实时荧光定量PCR和数字PCR检测方法,检测肉制品中牛源成分。先依据牛肉单复制基因组特异区域,通过多序列比对设计特异性引物与探针,再利用苯酚-氯仿法提取标准品基因组DNA,确立实时荧光定量PCR和数字PCR两种方法的反应条件,测定DNA模版纯度及浓度可得实验提取的DNA溶液不含杂质,在此基础上构建牛源性成分荧光定量PCR标准曲线,检测两种方法的特异性、抗干扰性与肉制品中牛源性成分。分析实验结果可知,引物与探针在两种方法中均对牛肉有荧光信号显示,两种方法具有牛源性特异性,检测数值与实际样品数值基本一致,且两种方法抗干扰性较好,当存在其他肉类干扰时,仍可准确监测出牛源性,两种方法的最大误差分别为3.8%和4.0%;可定量检测不同肉制品中牛源性成分,两种方法均未检测出样品10牛肉丸中牛源性成分,验证了市面上确实存在假肉情况。说明所用方法能够准确、快速地检测出肉制品中的牛源性成分,适用于市场中肉制品的检测,对保障消费者的权益和健康具有十分重要的意义。     

新型物理场辅助解冻技术提升原料肉品质的研究进展

冷冻贮藏是工业化生产中保存肉制品生产原料的常用方法,它可以保持原料肉的新鲜品质。但冷冻肉生产之前必须经过解冻,而解冻方式不当极易对肉的蛋白质结构及颜色、风味和质地造成不利影响。目前工业化运用的常见解冻方式包括空气解冻及水解冻等,这类传统方式虽易于操作,但解冻时间长、微生物滋长迅速,严重破坏了原料肉的品质。在此基础上,新型物理场辅助解冻技术逐渐衍生,其能够控制蛋白质在氧气存在下被氧化的时间,降低生肉的微观损伤和汁液流失,最大程度恢复其原有品质,满足生产者及消费者的需求。本文综述新型物理场辅助解冻技术提升原料肉品质的作用机制与应用,以及其与传统解冻技术的交叉融合,以期为新型物理场辅助解冻技术的工业化应用和发展提供理论和技术指导。     

Determination of Sex Origin of Meat and Meat Products on the DNA Basis: A Review

Sex determination of domestic animal's meat is of potential value in meat authentication and quality control studies. Methods aiming at determining the sex origin of meat may be based either on the analysis of hormone or on the analysis of nucleic acids. At the present time, sex determination of meat and meat products based on hormone analysis employ gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography-mass spectrometry/mass spectrometry (HPLC-MS/MS), and enzyme-linked immunosorbent assay (ELISA). Most of the hormone-based methods proved to be highly specific and sensitive but were not performed on a regular basis for meat sexing due to the technical limitations or the expensive equipments required. On the other hand, the most common methodology to determine the sex of meat is unquestionably traditional polymerase chain reaction (PCR) that involves gel electrophoresis of DNA amplicons. This review is intended to provide an overview of the DNA-based methods for sex determination of meat and meat products.     

基于最大类间方差自适应阈值的五花肉肥瘦自动识别方法

对五花肉的检测常使用化学检测或人工检测方法,但这两种常用方法都需要花费较大的成本和检测时间,且误差较大。为了提高识别准确度,降低检测成本,实现自动化检测。本文以猪肉腹部的五花肉为研究对象,使用最大类间方差自适应阈值法对图像R基色图层进行背景分离,并对图像进行中值滤波处理,从而获取图像的五花肉区域。针对五花肉图像中肥肉与瘦肉对比度不强的特点,采用有限对比度自适应直方图函数来增强肥瘦肉之间的对比度,再使用最大类间方差自适应阈值法分割五花肉图像的肥肉与瘦肉区域。通过实际图像样本的实验结果表明,本文方法比传统新近方法的识别准确率高。这说明本文方法通过自动阈值进行图像滤波处理方法可以有效区分肥肉和瘦肉区域,对其进行有效检测和识别。     

QUANTITATIVE DETERMINATION OF METMYOGLOBIN AND TOTAL PIGMENT IN AN INTACT MEAT SAMPLE USING REFLECTANCE SPECTROPHOTOMETRY

SUMMARY— A technique for determining the relative quantities of oxymyoglobin, metmyoglobin and total pigment concentration at the surface of on intact meat sample was developed. A Beck-man DK-2 spectrophotometer with reflectance attachment was used and spectra were recorded on the R_A scale. The sample port of the spectrophotometer was modified so that a uniform and high intensity light beam measuring 0.5 × 0.6 cm reached the surface being evaluated. A sample holder was constructed so that known proportions of oxygenated and oxidized meat could be exposed to the light beam. A family of curves representing varying known amounts of metmyoglobin and oxymyoglobin were obtained. The height of the peak at 632 nm (ΔR_A632) was directly related to the amount of metmyoglobin at the surface of the meat sample. For 100% oxymyoglobin, ΔR_A632 was at a minimum and equal to R_A750. For 100% metmyoglobin, ΔR_A632 was at a maximum and the height of the response depended upon the amount of total pigment present. A linear relation was obtained when ΔR_A362 was plotted against percent metmyoglobin or against total pigment determined by the Hornsey (1956) method. The method requires making two readings of the meat samples at a single wave length. One reading of the sample followed by one reading of the same sample after oxidation with K₃ Fe(CN)₆ provides a quantitative evaluation of the metmyoglobin concentration and the total heme pigment concentration. The accuracy of the method may be improved by making multiple readings.     

肉品冷冻工艺及冻结方法

畜禽肉的冷冻在现代肉及肉制品加工工业中起着很重要的作用,常见的肉品冷冻的工艺有两阶段冻结工艺和直接冻结工艺法两种,其又有各自的优缺点。肉品的冻结方法有很多,其中包括许多常用冻结方法和新兴冻结方法。本文对肉品冷冻的工艺及冻结方法及其各自特点进行了总结。     

The efficacy of enzyme immunoassays for the detection of salmonellas

Two commercially available enzyme immunosorbent assay kits for the detection of Salmonella (‘Salmonella Bio-EnzaBead Screen Kit’ and ‘ELISA Screening Kit for Salmonella’) were tested and compared with the standard isolation procedure. For this purpose, buffered peptone water was inoculated with Salmonella reference samples (10), with minced meat (10) or with a combination of Salmonella reference samples and minced meat (25). The minced meat appeared to be naturally contaminated with salmonellas; for this reason interpretation of results was complicated. With the ‘Bio-EnzaBead Screen Kit’ 35 enrichments were found to be positive, in comparison with 28 by the ‘ELISA Screening Kit’ and 32 by the standard isolation method. Evidence suggested that the standard isolation method and the ‘ELISA Screening Kit’ in particular gave a number of false-negative results. The growth of salmonellas in enrichment broths and therefore the Salmonella detection can be influenced by growth of competing micro-organisms. For this reason it was not possible to prove that some positive results with the ‘Bio-EnzaBead Screen Kit’ were true-positive instead of false-positive results. It is concluded that EIA tests are useful alternatives to conventional Salmonella isolation procedures from a selective enrichment broth, although they show similar susceptibility to the influence of competing flora. This latter aspect is discussed in detail.     

CONTROL OF DEFORMATION IN TEXTURE TESTS *

Abstract. The motion of the Instron crosshead during small deformations (e. g. 0.25 mm) in tensile tests performed at the available range of deformation rates was examined. Large errors are introduced in the deformation readings if it is assumed that the deformation rate was constant at the rate selected because, as with any instrument of this type, the crosshead requires time to accelerate to the selected speed. The characteristic behaviour of the food is subject to misinterpretation if the applied deformation profile is unknown. It was found that the errors are larger when the instrument is used incorrectly by performing tensile tests below the crosshead. The work demonstrated some of the limitations that must be recognized when applying the Instron, or any deformation mechanism, to certain texture tests. It is concluded that food behaviour, under small deformations, could be recorded precisely and interpreted correctly providing that both the force and deformation are recorded against time. Control of the crosshead stopping and reversal points was also examined, particularly in relation to the instrumental texture profile analysis. Crosshead acceleration affects the readings and interpretation of the data at the reversal point. If the deformation rate is changed, the stopping point must be adjusted.     

解冻方法对原料肉品质及蛋白质结构影响的研究进展

解冻是将原料肉中形成的冰晶融化为水并恢复其冷冻前状态的过程。解冻对肉类持水力、色泽、嫩度及质构特性等品质方面产生影响,而品质变化是肌肉蛋白质结构变化的外在表现。本文简述了肉制品加工过程中常用解冻方法的优缺点,通过分析解冻过程中蛋白质结构变化解释解冻方法引起肉类品质变化的机理,为正确选择解冻方法和提高原料肉品质提供理论支持。     

肉类颜色的影响因素研究

颜色是消费者购买肉品的首要考虑因素,为了最大化肉品色泽的稳定性,本文从肉品的发色呈色机理,影响肉品色泽稳定性的因素,护色的最新控制方法及发展趋势作了概述,以望为肉品工业的发展奠定良好的基础。     

The assessment of pre-slaughter and slaughter treatments of livestock by measurement of plasma constituents-A review of recent work

The measurement of plasma constituents in a blood sample can provide information on the stress status of the animal. The interpretation of results obtained for constituents of blood samples collected at exsanguination must consider the effect of the slaughter process on the constituent. Both electrical and mechanical stunning methods can cause dramatic increases in catecholamine levels and minor increases in glucose levels. Thus, there are difficulties in the interpretation of catecholamine and, to a lesser extent, glucose, values in blood samples collected post-stunning. Cortisol levels appear to be unaffected by stunning methods and measurement of this constituent in post-slaughter blood samples has been used to assist in the evaluation of transport and abattoir treatments. Beta-hydroxybutyrate concentrations may assist in evaluating nutritional stress prior to slaughter while the limited evidence available suggests that beta-endorphin measurements will be of value in assessing pain and other stressors prior to slaughter. Adreno-corticotrophic hormone, calcium and magnesium, free fatty acids, glucose, lactate and thyroid hormones have all been used on occasions to assist in the evaluation of stress status. In some cases it was not possible to demonstrate a clear relationship between plasma constituents that indicate stress, and stress-related meat quality defects.     

生鲜肉新鲜度新型快速表征技术研究进展

新鲜度不仅是影响生鲜肉品质分类的重要因素，还直接决定产品的货架期，因此构建生鲜肉新鲜度的表征体系至关重要，传统表征方法操作繁琐且所需时间长，不利于快速得到检测结果，难以满足当前需求；因此，快速准确的生鲜肉新鲜度表征技术始终是产业界的迫切需求和学界的研究热点。本文主要论述了目前表征生鲜肉新鲜度的新体系，包括感官仿生技术、智能响应技术和频谱分析技术等，重点阐述了各新型表征技术的研究进展、优势与缺点以及未来的突破方向，最后对该领域未来的发展趋势作出展望，以期为今后生鲜肉新鲜度表征技术的研发提供参考。     

肉类掺杂掺假的高光谱成像检测研究进展

肉类的掺杂掺假是国内外普遍关注的公共安全问题,对社会经济、健康、环境等方面具有潜在影响。近年来,不法商家为牟取暴利导致肉类掺杂掺假现象层出不穷、多种多样,针对此类问题研究行之有效的检测技术与方法以保障肉品真实性具有重要意义。高光谱成像技术以快速、非侵入、图谱合一等优势在食品农产品检测领域发展迅速,不仅可同时提取图像及光谱特征信息,还具备让肉类掺杂掺假"快速现形"的能力,具有较好的未来市场应用前景。该文介绍了肉类掺杂掺假现状,简述了高光谱成像原理及相关研究中数据解析方法,在探讨现有肉类掺杂掺假定性判别及定量预测研究进展基础上展望进一步研究突破方向,以期为相关肉品市场监管办法提供参考,也为其他类农产品掺假检测研究提供方法和思路借鉴。     

Biochip Technology for the Detection of Animal Species in Meat Products

The verification of declared components in meat products is an essential task of food control agencies worldwide. To date, the ELISA and species-specific polymerase chain reaction (PCR) are two commonly applied analytical tools employed by many authorized food control laboratories. These trusted methods however do not allow the simultaneous detection of all the animal species present in a meat sample. Additionally, detection of undeclared components resulting from inadvertent contamination or deliberate adulteration of the meat products requires additional processing of the samples, resulting in increased expenditure. The use of DNA biochip analysis that allows simultaneous processing of many meat products, while concomitantly generating results for the detection of all animal species present in the meat products is thus highly desirable. In this work, two commercially available animal chip detection systems (CarnoCheck Test Kit and MEAT^species LCD Array) are compared in terms of sensitivity, robustness, reproducibility, and ease of handling. The two animal species differentiation biochip methods compared well in efficiency and could simultaneously detect from eight to 14 animal species in the meat products. Detection limits were found to be in the range of 0.1% to 0.5% in meat admixtures, with good reproducibility of results. More than 70 commercially available meat samples were analyzed in this work, with the results validated against traditional PCR methodology. Both biochip methods performed well and could be implemented for routine use in any food control agency.     

肉类嫩度形成机理及嫩化调控研究进展

嫩度是原料肉的重要品质指标之一,与肉制品的出售价格及消费者满意程度和重复购买的意愿紧密相关。近年来,新兴的植物肉、细胞培养肉等人造肉追求模拟传统肉制品的感官体验,其中包括肉类独特的质地。本文对肉类嫩度的主要影响因素及近年来的研究进展进行综述。首先,简要介绍嫩度的定义及测定方法;其次,围绕肌节长度、结缔组织和蛋白酶解三方面重点介绍肉类嫩度的影响因素及机理;最后,简述肉类嫩度的调控方法及最新的研究进展,以期为传统肉品领域以及模拟肉、3D打印肉等相关研究开发提供参考。