Dielectric Properties of Pork Muscle

Dielectric properties were measured across a frequency range from 200 MHz to 20 GHz and temperature range from 25 to 85°C for pork meat samples (grouped in four different quality classes). Dielectric properties varied widely with frequency and the loss tangents of different meat quality classes followed different trends. Discriminant analysis indicated that 2400 MHz was most significant (P < 0.05) for separation of the different classes. There were significant changes (P < 0.05) in the dielectric properties within the range of the temperatures corresponding to protein denaturation temperatures. There was clear segregation between the firm and non-exudative (red, firm, and non-exudative; pale, firm, and non-exudative) and the soft and exudative (red, soft, and exudative; pale, soft and exudative) samples. The results showed that dielectric properties could be useful in meat quality classifications.     

Development of a dielectric spectroscopy technique for the determination of key biochemical markers of meat quality

Dielectric measurements of different standard solutions (nucleotides, nucleosides, lactic acid and myoglobin) were assayed simulating the concentrations of these substances in early postmortem meat. These assays were performed for considering the potential use of dielectric spectra for the quality control of meat. Good correlations among solutions of Adenosine Triphosphate (ATP), Inosine Monophosphate (IMP) and lactic acid with loss factor at punctual frequencies (0.5, 0.915 and 1 GHz) were found. The other assayed substances did not present a marked effect over the electromagnetic spectra. Good correlations of dielectric properties with IMP and lactic acid content of real pork meat samples were also found at 0.5 GHz. This work is presenting prospective data of dielectric spectra for certain key biochemical markers in order to consider its potential application as a non-destructive control sensor for the prediction of pork meat quality.     

Application of microwaves dielectric spectroscopy for controlling pork meat (Longissimus dorsi) salting process

Salting treatment is a common operation in the production of high quality meat products, one of its main problems is the difficulty to control the simultaneous water and salt fluxes into the product and control the protein fibers transformation throughout process. Dielectric properties of salted porcine meat are strongly related to its structure and composition. Thus, dielectric properties measurement appears as a promising method for controlling on-line the salting process in meat industry. Dielectric spectroscopy studies have been performed on raw and salted Longissimus dorsi pork samples. Dielectric spectra were measured in the frequency range from 500 MHz to 20 GHz by an Agilent 85070E open-ended coaxial probe connected to an Agilent E8362B Vector Network Analyzer immediately after salting process and also 16 h. Salt content, moisture, water activity and volume were also measured. It has been demonstrated that the dielectric properties are a good tool to analyze the share of the added sodium chloride molecules in the muscle tissue during the salting treatment (bounded and solved ions).     

Measuring changes in radio-frequency dielectric properties of chicken meat during storage

Changes in dielectric properties of stored chicken meat were tracked by using a radio-frequency dielectric spectroscopy method. For this purpose, the dielectric properties were measured with an open-ended coaxial-line probe and a vector network analyzer over a broad frequency range from 200 MHz to 20 GHz at 23 °C. Chicken meat samples were stored in a refrigerator for 8 days at 4 °C. Dielectric constant and loss factor were measured daily over that period. The dielectric constant decreased with frequency and storage duration with a slope change at about 4 GHz. The dielectric loss factor increased with storage duration for frequencies below 3 GHz and remained almost constant above that. The frequency dependence of the dielectric loss factor was dominated by ionic conduction in the lower frequency range and dipolar relaxation of water above 3 GHz. For frequencies below 3 GHz, both the dielectric loss factor and loss tangent increased linearly with storage duration. A three-dimensional representation of the dielectric loss factor as a function of storage duration and conductivity provided analytical expressions that can be used to track chicken meat aging from measurement of the dielectric properties at a single frequency.     

食品及环境样品中肠球菌快速检验方法的 建立及优化

目的建立并优化食品及环境样品中肠球菌的快速检验方法。方法用mEI培养基作为选择性培养基,肠球菌tuf基因为靶基因设计引物,建立食品及环境样品中肠球菌的快速检验方法。通过添加肠球菌和非肠球菌标准菌株,验证方法的检测限、灵敏度及特异性,并使用优化后的方法对北京市丰台区某大型生鲜猪肉集贸市场的地面、墙壁、污水和生鲜猪肉等样品中的肠球菌进行检验。结果所建方法的检测限为1 CFU/100cm2和1 CFU/25 g(mL),且与10种非肠球菌无交叉反应;地面涂抹、墙壁涂抹、污水和生鲜猪肉等样品中均检验出肠球菌,检出率为100%。结论建立了简便、快速、灵敏、特异的肠球菌检验方法;集贸市场内部环境和生鲜猪肉存在肠球菌污染。应加强市售生鲜肉中肠球菌的监测,并采取相应措施降低其污染水平。     

Evaluation of Rapid Fat, Moisture, and Protein Determination in Meats and Meat Products using an Automatic Meat Analyzer

The Hobart FMP-1 Automatic Meat Analyzer has been developed for rapid (approximately 5 min), simultaneous determination of the fat, moisture and protein content of meat and meat products. Results were compared with those using official AOAC methods for raw beef and pork and cooked sausage samples. Analyses of the data indicated that, except for determination of fat content of raw pork and protein content of raw beef, the Hobart FMP-1 was not significantly different from the official AOAC methods within the sampling parameters studied. From a practical meat operations standpoint, these differences were not considered to be of major concern as the machine can be calibrated to adjust for bias.     

Dielectric analysis of hen egg white with denaturation and in cool storage

Dielectric relaxation spectra (DRS) of fresh hen raw egg white solutions and thermally denatured gels were measured at frequencies between 1 MHz and 3 GHz by using the coaxial line reflection method with a network analyser and an open-ended coaxial probe. The values of the dielectric constant ε of the denatured gels were higher than those of the raw solutions at frequencies lower than 100 MHz and then became close to each other with the increase in the frequency. No significant change in effective conductivity σ was found on denaturation, implying that this process does not affect the binding of water. The gels were stored at 5°C for 13 days to be subjected to a dehydration process that led to a corresponding decrease in dielectric constant and conductivity. When the dielectric data had been measured, the molecular motions and water status in the egg whites were analysed.     

Low frequency dielectric measurements to assess post-mortem ageing of pork meat

The use of dielectric properties at low frequencies to estimate the progress of pork meat (Longissimus dorsi) ageing was evaluated. Dielectric measurements were perfomed at 140 Hz, 1 kHz and 300 kHz in perpendicular to the long axis of the meat muscle fibers at 12, 24, 48 and 168 h post-mortem. Principal Component Analysis (PCA) was used to describe the relationships between meat physical/biochemical parameters and dielectric parameters of pork meat. Good correlations were found between the ageing indexes (AI^σ and AI^?′) calculated from dielectric properties and some parameters of texture such as hardness and chewiness. Moreover, both indexes correlated well with free amino acids content, and with K value. The high degree of correlation confirms the viability of using the ageing indexes obtained from dielectric measurements to evaluate the degree of ageing of pork meat, giving information about some important eating quality parameters.     

原料肉特性对湖南腊肉品质的影响

为比较瘦肉型的杂交商品猪肉和本地猪肉对湖南腊肉品质的影响,实验选取三元杂交商品猪的背最长肌(A)和腹部五花肉(B)、本地宁乡猪的背最长肌(C)和腹部五花肉(D)为原料加工湖南腊肉。测定了加工过程中腊肉理化指标变化和腊肉的颜色、挥发性性成分等。实验结果表明:在腊肉成品中,相同部位原料肉加工的腊肉,杂交商品猪肉的水分含量显著高于宁乡猪加工的腊肉样品(AC,BD),但食盐含量和亚硝酸盐含量呈现相反的变化趋势,即商品杂交猪肉腊肉具有较低的食盐含量和亚硝残留量(AC,BD);4组实验腊肉样品中,L*值均呈下降趋势,两个品种的猪肉中背最长肌的a*值呈现先下降后上升趋势,腹部五花肉的变化规律不明显;样品A、B、C、D分别鉴定出挥发性成分40种、24种、54种、23种。说明了不同原料肉品种和不同部位对湖南腊肉的品质有一定影响。     

拉曼光谱法快速检测猪肉脯中的掺伪鸡肉

目的 肉脯掺假制假事件层出不穷,严重损害消费者权益,为了快速无损的检测肉脯掺假的质量安全问题,建立拉曼光谱技术快速、准确、无损的检测猪肉脯样品中是否掺假鸡肉。方法 试验制备33份猪肉中掺入不同比例鸡肉的肉脯样品,采集拉曼光谱数据,分别采用标准正态变换、多元散射校正、卷积平滑、归一化、一阶导数等5种不同预处理方法,对原始光谱数据进行预处理,采用连续投影算法、竞争性自适应重加权算法及随机蛙跳算法对光谱数据进行特征波长筛选,建立偏最小二乘法(partial least squares,PLS)模型对猪肉脯进行定性定量判别。结果 拉曼光谱数据经过多元散射校正处理的效果最佳,竞争性自适应重加权算法竞筛选效果更佳,构建猪肉脯中猪肉含量(%)的PLS定量模型,其预测集相关系数(Rp₂⁾和预测均方根误差分别为0.9762、7.2998。建立的PLS判别模型的校正集和预测集总判别正确率分别为100%和98.33%。拉曼光谱分析技术可有效鉴别猪肉脯是否掺伪及其猪肉含量的比例,为肉脯掺假的快速准确地无损检测提供技术支持。结论 拉曼光谱分析技术可有效用于定性鉴别猪肉脯是否掺伪及定量分析猪肉肉脯中掺入鸡肉的比例,为肉脯掺假的快速无破坏性检测的应用提供支持。     

The effect of heat treatment on the cholesterol oxides,cholesterol, total lipid and fatty acid contents of processed meat products

The effects of heat treatment on the formation of cholesterol oxides and on alterations of fatty acid composition were investigated in processed meat products. Meatballs (beef), hamburger (beef and Chester), sausage (pork, chicken and Chester) and frankfurter (mixed meat, chicken and Chester) were analysed. There was no cholesterol oxide formation caused by heat treatment of the samples analysed. The fatty acid compositions, calculated as g/100 g sample, showed alterations only between the raw and grilled beef hamburger. Only the cholesterol levels were significantly changed when comparing the raw and grilled pork sausages and the raw and grilled Chester hamburger, the values being lower in the grilled samples. Also, the total lipid contents of grilled beef hamburgers were lower than the values.     

Effect of Temperature (−5 to 130 °C) and Fiber Direction on the Dielectric Properties of Beef Semitendinosus at Radio Frequency and Microwave Frequencies

ABSTRACT:  The dielectric properties must be defined to design efficient radio frequency (RF) and microwave (MW) processes by the food manufacturers. The objective of this study was to understand how frequency, temperature, and muscle fiber orientation influence the dielectric properties. The eye of round ( Semitendinosus ) muscle was selected because it contains large, relatively uniform muscle cells with similar muscle fiber orientation and relatively uniform chemical composition throughout the tissue. Dielectric properties were measured using an open-ended coaxial probe technique at 27, 915, and 1800 MHz and temperatures between −5 and 130 °C. Power penetration depth was calculated. Since many commercially prepared, thermally processed, ready-to-eat entrees are made with frozen meat, dielectric property measurements were started from −5 °C. The dielectric constant and dielectric loss factors were often higher for muscle with the muscle fiber measured in a parallel orientation to the probe compared to samples of the same treatment (for example, fresh or frozen) in a perpendicular tissue orientation at the same frequency and temperature. Dielectric constant and loss values for frozen beef tended to be higher than fresh beef at the same temperature and frequency. Tissue orientation appeared to have a greater effect on dielectric loss values at lower frequencies. Penetration depth tended to be greater when the direction of propagation was perpendicular to the muscle fiber.     

Effects of oleoresin-tocopherol combinations on lipid oxidation, off-odor, and color of irradiated raw and cooked pork patties

Lipid oxidation, color, and volatiles of double-packaged pork loins with various oleoresin or oleoresin-tocopherol combinations were determined to establish the best oleoresin-tocopherol conditions that can improve the quality of irradiated raw and cooked pork loins. Rosemary and α-tocopherol combination at 0.05% and 0.02% of meat weight, respectively, showed the most potent antioxidant effects in reducing both TBARS values and the amounts of volatile aldehydes in irradiated raw and cooked pork loins. The antioxidant combination, however, did not affect the production of sulfur volatiles responsible for irradiation off-odor and showed little effects on color changes in irradiated raw and cooked pork loins. Exposing double-packaged irradiated pork to aerobic conditions for 3days during the 10-day storage was effective in controlling both lipid oxidation and irradiation off-odor, regardless of packaging sequences.     

Composition of minced meat part A: Methods

A simplified rapid electrophoretic method is described for the identification of venison, pork, and beef in samples of only a few grams of minced meat. The method is based on the species-specific separation patterns obtained upon electrophoresis of the proteins. Venison, beef, and pork can be identified easily and readily from the patterns given by their raw water-extractable proteins.     

A survey of the dielectric properties of meats and ingredients used in meat product manufacture

The objective of the present study was to improve understanding of interactions between microwave (MW) and radio frequency (RF) radiation and meat/meat products. Dielectric properties at 27.12, 915 and 2450 MHz of lean, fat, aqueous solutions/suspensions and meat blends of typical ingredients used in meat product manufacture were measured. In addition temperature rises of ingredient/meat blends were compared following RF or MW heating. Frequency affected dielectric properties as did composition, with fat having lower dielectric activity than lean. Dielectric properties at MW frequencies appeared more sensitive to composition changes. Ingredients could be subdivided into groups having either lower or higher dielectric activity than lean, with concentration influencing which group an ingredient fell into. When low and high dielectric activity ingredients were incorporated into lean meats dielectric properties did not correlate well with temperature rises indicating the importance of other factors in addition to dielectric properties in determining temperature rise.     

酶联免疫吸附法快速测定不同样品 基质中三聚氰胺

目的 探求不同样品基质中三聚氰胺残留量的快速检测方法.为快速筛查不同种类食品中非法添加三聚氰胺提供技术保障.方法 采用酶联免疫吸附法在奶制品(奶粉、液态奶)、成品饲料(鸡饲料、猪饲料)、饲料原料(鱼粉、肉骨粉、豆粕、麸皮)、肉类(鸡肉、猪肉、内脏)等样品基质中添加一定浓度的三聚氰胺进行测定,并对检测结果进行分析.结果 酶联免疫试剂盒对奶制品和肉类检出限均能达到1.0 mg/kg;对成品饲料基质中的三聚氰胺的检测,检出限可达到2 mg/kg,而对饲料原料中的三聚氰胺的检测,检出限都不能达到2 mg/kg.结论 对奶制品中的三聚氰胺检测完全符合我国的临时限量标准;对成品饲料中的三聚氰胺残留的检测同样符合其限量标准(2.5 mg/kg),而对饲料原料中的三聚氰胺的检测,由于不同基质中检出限不同,不能直接采用酶联免疫法进行快速筛查;酶联免疫法也适用于肉类中的三聚氰胺的检测.     

Identification of meat species by TaqMan-based real-time PCR assay

In this study, a convenient, sensitive and specific real-time PCR assay was described for the species identification and their quantification in raw and cooked meat products. Specific primers and TaqMan probes were designed on the mitochondrial ND2, ND5 and ATP 6-8 genes for donkey, pork and horse, respectively, and the performance of the method was tested. In the results, no cross-reaction was observed between the donkey and pork species specific primer-probe systems and non-target species (bovine, ovine, chicken and turkey). Only one cross reaction was observed between the horse species specific primer-probe set and 100 ng pork DNA at the ct 33.01 level (corresponding to 0.01 ng horse DNA). The real-time quantitative assay used in this study allowed the detection of as little as 0.0001 ng template DNA from pure meat for each species investigated and experimental meat mixtures. In conclusion, it can be suggested that the TaqMan probe assay used in this research might be a rapid and sensitive method for the routine meat species identifications studies in raw or cooked meat products.     

Dielectric and thermophysical properties of different beef meat blends over a temperature range of -18 to +10°C

Dielectric and thermophysical properties of three different beef meat blends (lean, fat and 50:50 mixture) were evaluated over a range of temperatures from -18 to +10°C. In the region of thawing (-3 to -1°C), dielectric constant (ε') and dielectric loss factor (ε') values for radio frequency (RF) and microwave (MW) were significantly higher (P<0.05) than at other measured temperatures for the three blends. In the same region, thermal conductivity (k), specific heat (c) and thermal diffusivity (α) also showed significant changes (P<0.05). k and α values were significantly lower, while c values were significantly higher in this region than at other measured temperatures for the three blends. RF (27.12MHz) vs. MW (896 and 2450MHz) frequencies had an important effect (P<0.05) on the measured dielectric properties of the beef meat blends, with a general tendency towards higher values at the RF frequency. Finally, composition significantly influenced (P<0.05) the measured dielectric and thermophysical properties at all temperatures used. These data are of potential value to food technologists in the context of rapid defrosting of meat products.     

原料肉中磷酸盐本底含量状况调查与分析

运用比色法,先后对5类1353个生肉样品、5类121个副产品样品,共计1474个原料肉样品进行了磷酸盐本底含量的测定。结果表明,原料肉中磷酸盐本底含量范围为1.49～16.5g/kg,多数处于低端水平;不同种类的生肉中磷酸盐含量存在显著差异(P<0.05),其中生猪肉中磷酸盐含量最高,其次为鸭肉,生羊肉中磷酸盐含量最低;不同种类的副产物中磷酸盐含量存在显著差异(P<0.05),其中生猪肝中磷酸盐含量最高,其次为生牛肝,生猪肠、肺中磷酸盐含量最低。     

基于低场核磁共振技术的注胶肉快速检测

目的:探索并建立一种新的注胶猪肉快速检测方法.方法:以正常猪肉及注射不同种类胶(黄原胶、卡拉胶、明胶、琼脂)的注胶肉为对象,利用低场核磁共振并结合主成分分析法分析处理的检测数据,根据肉品中的水分存在状态及分布结果,对猪肉进行快速检测.结果:正常肉与注胶肉之间、各类注胶肉及不同注胶量之间在主成分得分图上具有很好的区分效果.结论:低场核磁共振技术结合主成分分析法可以快速区分正常肉与注胶肉.