猪宰后肌肉中钙激活蛋白酶活性变化的研究

该文研究杂种野猪和本地白猪屠宰后，肌肉中钙激活蛋白酶系的活性变化，同时，对肌肉的全蛋白提取液作SDS-PAGE分析。结果表明：杂种野猪肉的钙激活蛋白酶活性较高，但表现酶活性的自溶率变化在早期较慢；电泳图谱可看到，杂种野猪蛋白降解较慢，在宰后冷藏40 h的电泳图可看到小分子物质降解较少。     

蛋白质组学在生鲜肉肉色变化机制研究中的应用

肉色是影响消费者购买欲望的最直观因素。宰后生鲜肉肉色的变化机制和肉色改善一直是肉类科学领域研究的热点。肉色体系复杂,其稳定性受动物宰前因素、从肌肉向可食用肉转化过程和宰后商业流通链条件等因素的影响。目前,仍有许多影响途径和作用机制不够清楚。研究者已采用蛋白质组学技术发现了许多与肉色相关的蛋白标志物和可能影响途径。该文基于近年的研究,综述了不同处理条件下与肉色相关的差异蛋白,主要包括结构性蛋白中的肌动蛋白、肌球蛋白和肌联蛋白,以及肌浆蛋白中的伴侣蛋白、热休克蛋白、代谢酶类和氧化还原酶类等,分析了差异蛋白表达对肉色的影响及其表达调控肉色体系的可能机制,为今后肉色变化机制的研究和肉色稳定性的调控提供了思路。     

Simultaneous immunoaffinity column cleanup and HPLC analysis of aflatoxins and ochratoxin A in Spanish bee pollen

Bee pollen is a major substrate for mycotoxins growth when no prompt and adequate drying is performed by the beekeeper after collection by bees. Regulatory limits for aflatoxins and ochratoxin A are currently in force in the European Union for a rising list of foodstuffs, but not for this. An immunoaffinity column cleanup process has been applied prior to the analysis of aflatoxins B(1), B(2), G(1), and G(2) and ochratoxin A (OTA). Optimization of the HPLC conditions has involved both a gradient elution and a wavelength program for the separation and fluorimetric quantitation of all five mycotoxins at their maximum excitation and emission values of wavelength in a single run. The higher limit of detection (mug/kg) was 0.49 for OTA and 0.20 for aflatoxin B(1). Repeatability (RSDr) at the lower limit tested ranged from 9.85% for OTA to 6.23% for aflatoxin G(2), and recoveries also at the lower spiked level were 73% for OTA and 81% for aflatoxin B(1). None of the 20 samples assayed showed quantifiable values for the five mycotoxins.     

Glutathione peroxidase activity, TBARS, and alpha-tocopherol in meat from chickens fed different diets.

This study investigated the effect of feeding broilers with diets differing in dietary fat source (lard, sunflower oil, olive oil) and vitamin E (basal vs supplemented with 200 mg of alpha-tocopheryl acetate/kg) on meat lipid oxidative stability. The diets differed by their degree of unsaturation and included the natural antioxidant alpha-tocopherol (vitamin E). Glutathione peroxidase (GSHPx) activity was measured in raw meat and ranged from 3.62 to 8.06 nmol NADPH/min/mg protein. The enzyme activity was influenced by the degree of unsaturation of the diet. Capillary gas chromatography analyses showed that dietary alpha-tocopherol accumulated in the muscle tissue and contributed to a better oxidative stability of the raw and cooked meat. Thigh meat alpha-tocopherol levels ranged from 2.73 to 3.62 microg/g in unsupplemented chickens whereas levels from 8.69 to 13.37 microg/g were observed in the thigh meat from alpha-tocopherol supplemented animals. The inclusion of olive oil and alpha-tocopherol in the animal diet gave lower thiobarbituric acid reactive substance (TBARS) values and lower GSHPx activity. High correlations were found between the parameters studied. The results suggest that the glutathione peroxidase activity could be used as an indicator of the meat oxidative stability. A negative relationship was observed between GSHPx activity and tissue alpha-tocopherol levels, and a positive relationship was evidenced between TBARS and antioxidant enzyme activity.     

Optimization and validation of analytical conditions for cholesterol and cholesterol oxides extraction in chicken meat using response surface methodology

The analytical conditions for the extraction of cholesterol and cholesterol oxides in chicken meat were optimized by means of response surface methodology. The separation and identification were performed by normal phase HPLC using UV and refractive index (RI) detectors, and the confirmation of the 11 cholesterol oxides identities in the samples was verified by HPLC-APCI-MS. The developed methodology showed good analytical performance, presenting recovery levels from 84 to 103% and detection limits varying from 0.01 to 0.06 microg/g for UV detection and from 1.98 to 2.12 microg/g for RI detection. The present study demonstrated the presence of 22 R-hydroxycholesterol, 24 S-hydroxycholesterol, and 22 S-hydroxycholesterol for the first time in chicken meat.     

基于生猪外形特征图像的瘦肉率估测方法

为实现生猪瘦肉率的快速无损检测,以机器视觉为主要技术,通过生猪的外形特征图像进行瘦肉率估测,为饲养者与收购者提供生猪品级的决策依据。采用MATLAB为开发工具,通过图形用户界面(graphical user interface,GUI)实现软件操作界面,以生猪的侧面及背面图像为研究对象,利用图像处理技术从目标中提取体长、体高、胸深、腹长、臀宽、腰宽等数据,以这些体尺的比例(胸深体高比、臀宽体长比、臀宽腰宽比、腹长体长比)为参数,通过径向基函数(radial basis function,RBF)神经网络进行瘦肉率估测。该文分别对7组生猪外形图像进行处理,4项比例指标的平均估测准确率分别为92.90%、92.44%、95.17%、96.51%,瘦肉率的平均估测准确率为94.35%。结果表明,该文所构造的基于生猪外形特征图像的瘦肉率估测方法工作效率高,成本低,可用于估测生猪瘦肉率。     

Proteome analysis of the sarcoplasmic fraction of pig semimembranosus muscle: implications on meat color development

Two-dimensional electrophoresis was used to investigate sarcoplasmic protein expression in pig Semimembranosus muscles sampled 20 min after slaughter. Two groups (light and dark) of 12 animals were selected from 1000 pigs, based on meat L values measured 36 h postmortem. Twenty-two proteins or fragments (p < 0.05) were differentially expressed. Muscles leading to darker meat had a more oxidative metabolism, indicated by more abundant mitochondrial enzymes of the respiratory chain, hemoglobin, and chaperone or regulator proteins (HSP27, alphaB-crystallin, and glucose-regulated protein 58 kDa). Conversely, enzymes of glycolysis were overexpressed in the lighter group. Such samples were also characterized by higher levels of glutathione S-transferase omega, which can activate the RyR calcium channels, and higher levels of cyclophilin D. This protein pattern is likely to have severe implications on postmortem metabolism, namely, acceleration of ATP depletion and pH fall and subsequent enhanced protein denaturation, well-known to induce discoloration.     

Identification of protein degradation during post-mortem storage of pig meat

Eighteen proteins and peptides that were found to change post-mortem in Longissimus dorsi from pig muscle were identified by the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The 18 peptides originate from 9 different proteins including the 3 structural proteins (actin, myosin heavy chain, and troponin T) and the 6 metabolic proteins glycogen phosphorylase, creatine kinase, phosphopyruvate hydratase, myokinase, pyruvate kinase, and dihydrolipoamide succinyltransferase. The molecular weight and estimated sequence length of the identified spots show that these fragments result from proteolytic activity in meat. Identification of the parent proteins and the enhanced post-mortem appearance of the degradation products make these specific peptides good candidates for meat quality markers, and further studies of these specific fragments will lead to a better understanding of the proteolytic activities involved in the post-mortem conversion of muscle to meat.     

便携式生鲜肉品质无损快速检测装置的设计

针对生鲜肉检测部门对可移动、便携式检测设备的实际需求,设计了基于ARM处理器便携式生鲜肉品质无损快速检测装置。介绍了该装置的工作原理、硬件构成、软件系统和功能测试。硬件系统由ARM控制处理单元、光源及检测单元、光谱数据采集单元、LCD触摸屏显示单元和散热单元组成,设计了Linux操作系统和生鲜肉品质参数采集处理应用程序。该系统可实现脱离计算机采集光谱信号、存储、显示及处理分析一体化的功能。该装置体积为184 mm×127 mm×114 mm,装置质量约为3.5 kg。以批量样品验证装置检测精度,试验结果表明,颜色L*、a*、b*3个参数的均方根误差分别为1.49、1.09和0.59,平均检测一个样品时间约为1 s。该装置可以快速获得样品参数,具有体积小、便携、无损伤、快速检测的特点,可用于生鲜肉品质的便携式检测。     

Incorporation of alpha-tocopherol and linoleic acid in fresh lambs by feeding chemically treated dietary supplements containing dl-alpha-tocopheryl acetate and sunflower oil

The effects of feeding chemically treated dietary supplements (CTDS) containing sunflower oil and dl-alpha-tocopheryl acetate (TA) on alpha-tocopherol content and fatty acid profile in edible tissues of lambs were estimated. Compared with lambs fed control diet (CD), lambs fed CD plus 250 IU of either TA or CTDS increased serum alpha-tocopherol. The CTDS-fed lambs further increased serum alpha-tocopherol by 29% over those fed CD plus 250 IU of TA. Lambs supplemented with TA or CTDS increased alpha-tocopherol in muscle and adipose tissues as compared with lambs fed CD. The CTDS-fed lambs had higher levels of alpha-tocopherol in gluteus medius (7.55 vs 6.05 mug/g), psoas major (7.43 vs 6.02 mug/g), and subcutaneous fat (12.6 vs 9.98 mug/g) compared with the TA-fed lambs. Feeding lambs CTDS also substantially increased levels of linoleic acid in the adipose tissues while decreasing the content of palmitic and oleic acids.     

Formation and inhibition of cholesterol oxidation products during marinating of pig feet

Cholesterol oxidation products (COPs), formed during the heating of cholesterol-rich foods, have been shown to cause cancer and coronary heart disease. The objectives of this study were to develop a GC-MS method for the determination of COPs in pig feet meat, skin, and juice during marinating and to study the formation and inhibition of COPs as affected by the incorporation of soy sauce and sugar. Results showed that an HP-5MS column could provide an adequate separation of cholesterol, 5α-cholestane (internal standard), and seven COPs, including 7α-OH, 7β-OH, 5,6β-OH, 5,6α-OH, triol, 25-OH, and 7-keto, within 15 min with a temperature-programming method. Most COPs in pig feet meat were generated at a larger amount than in pig feet skin and marinating juice over a 24 h heating period at about 100 °C. The Maillard browning index rose with increasing heating time, whereas the pH showed a slight change in marinated juice. Both reducing sugar and free amino acid contributed to the formation of Maillard reaction products. The incorporation of soy sauce and crystal sugar into fresh juice was effective in inhibiting COPs formation in pig feet, skin, and juice over a 30 min preheating period.     

Formation of tetracycline degradation products in chicken and pig meat under different thermal processing conditions

Tetracycline (TC) and 4-epitetracycline (4eTC) degradation, as well as anhydrotetracycline (ATC) and 4-epianhydrotetracycline (4eATC) formation, has been evaluated in thermally treated chicken breast, pig loin, and pig loin with added back-fat. Samples containing TC and 4eTC residues were submitted to microwave or boiling heating, extracted with a mixture of McIlvaine buffer/methanol (75:25), and analyzed by high-performance liquid chromatography-diode array detection on a phenyl-hexyl reverse phase chromatographic column. The formation of ATC and 4eATC, as well as of two unidentified compounds, was described for the first time in edible meat samples submitted to mild thermal treatments, similar to those applied at home to cook foods. Degradation of TC and 4eTC and formation of ATC and 4eATC versus time of treatment fitted satisfactorily a first-order kinetic. Even if the potential toxic effects of these breakdown compounds should be further investigated, their formation in cooked meat should be taken into account when maximum residue limits are established.     

Chemical analysis of meat products

Meat, particularly muscle tissue, is basically a 3-component system of protein, moisture, and fat. Although this seems a simple analytical system in which to monitor product composition for regulatory compliance, the simplicity quickly erodes when meat is formulated into the broad variety of products commercially available today. Alternative protein sources, as well as preservatives, binders, extenders, emulsifiers, spices, and other flavoring ingredients, add to the analytes of concern and highlight the need for analytical methods suitable to support inspection and labeling requirements to ensure product compliance. Some key issues are noted which involve protein quality analysis, rapid compositional analysis, isolated soy protein analysis, and minced fish in meat products.     

Cholesterol oxides,cholesterol, total lipid,and fatty acid composition in turkey meat

The contents of cholesterol oxides, cholesterol, and total lipid, and the fatty acid composition were determined in frozen turkey meat. The 7-ketocholesterol content varied from 33 microg/100 g in the breast to 765 microg/100 g in the skin, and the levels of 7 beta-hydroxycholesterol varied from not detected in the leg, breast, and skin to 370 microg/100 g in the skin. The values for total lipid (g/100 g) in the wings, legs, breast, and skin were 0.9 +/- 0.4, 1.1 +/- 0.2, 0.5 +/- 0.1, and 12 +/- 3, respectively. The contents for cholesterol (mg/100 g) were 46 +/- 5, 35 +/- 2, 27 +/- 3, and 81 +/- 6 in the wing, legs, breast, and skin, respectively. The main fatty acids identified in all cuts were C18:2n6, C18:1n9, C16:0, C18:0, and C20:4n6.     

Simultaneous HPLC analysis of biogenic amines, amino acids, and ammonium ion as aminoenone derivatives in wine and beer samples

A method has been developed for the simultaneous analysis of biogenic amines, amino acids, and the ammonium ion in wine and beer. Aminoenones formed by the reaction of amino acids, biogenic amines, and the ammonium ion with the derivatization reagent diethyl ethoxymethylenemalonate are separated by HPLC. Reaction takes place in methanolic alkaline medium for 30 min in an ultrasonic bath. Further heating at 70 degrees C for 2 h produces complete degradation of excess derivatization reagent and byproducts. Comparison of the results of ammonium analysis and enzymatic analysis showed a good correlation (r = 0.953). The proposed analytical method has the following advantages: easy derivatization of wines and beers; quantification of 24 amino acids, nine biogenic amines, and the ammonium ion in a single injection; use of the photodiode array detector; complete degradation of excess derivatization reagent during sample preparation; and detection limits below 0.40 mg/L for amino acids and below 0.06 mg/L for biogenic amines.     

HPLC analysis of rosmarinic acid in feed enriched with aerial parts of Prunella vulgaris and its metabolites in pig plasma using dual-channel coulometric detection

This paper describes a sensitive isocratic HPLC/ECD method developed for the determination of rosmarinic acid (RA) in plant material, animal feed, and pig plasma. The plasma sample preparation only includes protein precipitation and adjustment of the pH. The applicability of the method was tested on plasma samples of pigs that were exposed to a 91-day oral intake of RA via feed enriched by aerial parts of Prunella vulgaris. The plasma was directly analyzed using the method described as well as after enzymatic hydrolysis. When no hydrolysis step was included, RA and caffeic acid (CA) were quantified in the plasma. In hydrolyzed plasma samples, several other metabolites were determined, including dihydrocaffeic, ferulic, and dihydroferulic acid. The dual-channel coulometric detection employed, as an alternative to mass spectrometry, offers good selectivity and sensitivity owing to the electrochemical properties of the phenolic constituents.     

Simultaneous transgenic suppression of LePG and LeExp1 influences fruit texture and juice viscosity in a fresh market tomato variety

Tomatoes are grown for fresh consumption or for processing of the fruit. Some ripening-associated processes of the fruit can either contribute to or degrade attributes associated with both fresh and processing quality. For example, cell wall disassembly is associated with loss of fresh fruit firmness as well as with loss of processed tomato product viscosity. Several enzymes contribute to cell wall polysaccharide disassembly. Polygalacturonase (PG, poly[1,4-alpha-d-galactouronide] glucanohydrolase, EC 3.2.1.15) is among the most abundant polysaccharide hydrolases in ripening tomato fruit and is the major contributor to pectin depolymerization. Expansin (LeExp1) is also abundant in ripening fruit and is proposed to contribute to cell wall disassembly by nonhydrolytic activity, possibly by increasing substrate accessibility to other enzymes. Suppression of either LePG or LeExp1 expression alone results in altered softening and/or shelf life characteristics. To test whether simultaneous suppression of both LePG and LeExp1 expression influences fruit texture in additive or synergistic ways, transgenic Lycopersicon esculentum var. Ailsa Craig lines with reduced expression of either LePG or LeExp1 were crossed. Fruits from the third generation of progeny, homozygous for both transgenic constructs, were analyzed for firmness and other quality traits during ripening on or off the vine. In field-grown transgenic tomato fruit, suppression of LeExp1 or LePG alone did not significantly increase fruit firmness. However, fruits suppressed for both LePG and LeExp1 expression were significantly firmer throughout ripening and were less susceptible to deterioration during long-term storage. Juice prepared from the transgenic tomato fruit with reduced LePG and LeExp1 expression was more viscous than juice prepared from control fruit.     

Simultaneous fluometuron and norflurazon analysis in soil extracts and leachates

Abstract

Rapid, methanol‐extraction techniques for fluometuron (N, N‐dimethyl‐N'‐[3‐(trifluoromethyl) phenyl] urea) and norflurazon (4‐chloro‐5‐(methylamino)‐2‐(3‐(trifluoromethyl)phenyl)‐3(2(H)‐pyridazinone) from fortified soils have been reported to attain >90% recoveries. Analytical methods involving chromatographic separation coupled with fluorescence detection have also been described. The objectives of this study were to describe an analytical method for the simultaneous detection of fluometuron and norflurazon using ultraviolet spectro‐scopy in soil leachates and extracts and to examine the influence of residence time on herbicide recovery from fortified soil. The analytical method requires a gradient HPLC system, a reverse‐phase C‐18 column, and ultraviolet spectroscopy at a wavelength of 240 nm. The method is characterized by high reproducibility (spike recovery and diluted sample results are generally within 10% of the expected herbicide concentrations), low limits of detection (less than 1 (μg/L in soil leachates and 20 μg/L in soil extracts, depending on organic carbon content), and an applicable concentration range of more than two orders of magnitude. The recovery of fluometuron and norflurazon from fortified soils was significantly influenced by equilibration time, loading rate, and soil type (assuming zero chemical degradation). Most significantly, as herbicide contact time with the soil increased, recovery decreased. Thus, herbicide recoveries determined in the laboratory may not provide a true measure of herbicide recoveries from field soils.