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。     

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.     

Direct and highly species-specific detection of pork meat and fat in meat products by PCR amplification of mitochondrial DNA

Highly species-specific primers for pork D-loop mtDNA have been designed. Use of these and restrictive PCR amplification conditions has improved a reliable and rapid method for detecting a PCR-amplified 531 bp band from pork. It has been proved useful for detecting both pork meat and fat in meat mixtures, including those dry-cured and heated by cooking. Absence of response in PCR-amplified samples or mixtures from bovine, ovine, chicken, and human was also demonstrated. Furthermore, wild boar and pork samples can be also easily distinguished by a simple AvaII restriction analysis.     

Molecular degradation rate of rice and corn starches during acid-methanol treatment and its relation to the molecular structure of starch

The degradation rates of rice and corn starches with different contents of amylose treated in methanol containing 0.36% HCl at 25 degrees C for 1-15 days were evaluated by monitoring the weight average degree of polymerization of starch. A two-stage degradation pattern during acid-methanol treatment was found for the starches studied, which were the slow (first) and the rapid (second) degradation stages. Waxy starches showed a shorter time period of the first stage than that of nonwaxy starch. Rice starch showed a shorter time period of the first stage and a higher degradation rate of the second stage than the counterpart corn starch with similar amylose content. Despite the botanic source and amylose content of starch, the degradation rate of starch in the second stage significantly (p < 0.05) correlated to the S/L ratio (r = -0.886) and polydispersity (r = 0.859) of amylopectin branch chains of native starch.     

高氧气调包装对不同品种冷却猪肉贮藏品质及持水性的影响

为了研究不同品种冷却猪肉在高氧气调包装贮藏过程中,蛋白氧化对猪肉品质及持水性的影响,试验以氟烷基因(NN)型杜长大三元杂交猪和不含NN基因型的三门峡黑猪为研究对象,分析了2个品种猪肉经高氧气调包装(80%O2+20%CO2),于(4±1)℃下贮藏过程中肌肉色泽、蛋白质氧化、水分分布、保水性以及肌肉微观结构的变化。结果表明,随着贮藏时间的延长(0~10 d),2个品种猪肉的肌原纤维蛋白羰基含量显著升高(P0.05),巯基含量显著降低(P0.05),表明猪肉肌原纤维蛋白的氧化程度随着贮藏时间的延长而加剧;肌原纤维蛋白发生持续性氧化,肌原纤维蛋白骨架的完整性遭到不同程度破坏,肌束膜破裂,纤维束间隙增大,结构疏松,保水性降低,不易流动水逐渐态变为自由水;与贮藏初始相比,第3天时杜长大三元杂交猪和三门峡黑猪的不易流动水均显著降低(P0.05),第5天杜长大三元杂交猪的自由水显著增加(P0.05),而黑猪的自由水在第10天时显著性增加(P0.05);贮藏5 d以上时,2个品种猪肉的蒸煮损失率均较对照组的蒸煮损失显著增大(P0.05);2个品种猪肉的L*值、a*值、b*值均呈现先增加再降低的趋势,L*值在第7天时达到最大值,a*值在第3天时达到最大值,杜长大三元杂交猪和黑猪的b*值分别在第5天和第7天时达到最大值;2个品种的猪肉经高氧气调包装,其色泽、蛋白质氧化、水分态变、保水性、微观结构等指标变化规律相似,表明高氧气调包装对2种猪肉的贮藏品质及持水性的影响效应具有一致性。研究结果为高氧气调包装冷却猪肉贮藏品质及汁液流失控制提供依据。     

Capillary gas chromatographic determination of prometryn and its degradation products in parsley

Residue analysis of the herbicide prometryn (2,4-bis(isopropylamino)-6-methylthio-1,3,5-triazine) is widely known, but an analytical method for determining its metabolities or degradation products in addition to the parent chemical has not yet been reported in the literature. The procedure reported here is for the extraction and determination of prometryn and 2 metabolites, 2-amino-4-isopropylamino-6-methyl-thio-1,3,5-triazine and 2,4-diamino-6-methylthio-1,3,5-triazine, in parsley. Crops were extracted with 2-propanol followed by concentration of the extract and partitioning with a minimum amount of hexane in the presence of a large excess of water to remove most of the green pigment. The aqueous phase was divided into 2 equal halves: (A) One-half portion was partitioned with dichloromethane in the presence of saturated sodium chloride solution, the dichloromethane phase was separated, and the aqueous phase was discarded. The organic solvent was evaporated, and the contents were reconstituted in petroleum ether before prometryn analysis. (B) The other half was made slightly alkaline with ammonium hydroxide solution and was partitioned with ethyl acetate in the presence of saturated sodium chloride solution. The ethyl acetate phase was concentrated, centrifuged to remove any turbidity, and analyzed for the 2 metabolities above. Fused silica capillary gas chromatography (GC) with nitrogen-phosphorus (N-P) detection was used for quantitation. The limit of detection was 0.05 mg/kg for all the compounds examined. Recoveries from fortified parsley samples ranged from 59 to 73% at fortification levels of 0.05 to 1.0 mg/kg.     

Foliar analysis of sulphur in different soybean cultivar stages and its relation to yield

Abstract

Six soybean cultivars (maturity group V) were sown in a Typic Argiudoll. Experimental plots were arranged in a randomized block design with three replications. Sampling dates were at different stages: V, R2, R4, and R55. All the varieties showed that the greatest sulfur (S) concentrations were in stage V and the lowest in stage R55. No significant differences were found between the means of the S concentrations during the V, R4, and R55 stages. In the R2 stage, there was a poor correlation with the weight of 1,000 seeds.     

Reconstitution of the flavor signature of Dornfelder red wine on the basis of the natural concentrations of its key aroma and taste compounds

By application of aroma extract dilution analysis (AEDA) on the volatile fraction isolated from a Dornfelder red wine, 31 odor-active compounds were identified by means of HRGC-MS and comparison with reference compounds. A total of 27 odorants, judged with high FD factors by means of AEDA, was quantitated by means of stable isotope dilution assays, and acetaldehyde was determined enzymatically. In addition, 36 taste-active compounds were analyzed by means of HPLC-UV, HPLC-MS/MS, and ion chromatography. The quantitative data obtained for the identified aroma and taste compounds enabled for the first time the reconstruction of the overall flavor of the red wine. Sensory evaluation of both the aroma and taste profiles of the authentic red wine and the recombinate revealed that Dornfelder red wine was closely mimicked. Moreover, it was demonstrated that the high molecular weight fraction of red wine is essential for its astringent taste impression. By comparison of the overall odor of the aroma recombinate in ethanol with that of the total flavor recombinate containing all tastants, it was shown for the first time that the nonvolatile tastants had a strong influence on the intensity of certain aroma qualities.     

满江红在不同培养条件下的生产性能及其与营养成分变化的关系

用人工配制的霍格兰改良培养液以及天然的地下水和池塘水对满江红进行了生产性能的测定并对水体中若干营养成分指标进行了监测。满江红在3种溶液培养条件下繁殖能力随时间的变化均呈增长、平衡、消落趋势,与二次曲线显著拟合。人工培养液中满江红的繁殖系数、固氮酶和过氧化物酶(POD)活性显著高于其它2种水体培养,而超氧化物岐化酶(SOD)的活性差异却不显著。相关分析发现,3种酶活性均同满江红的生产性能呈显著相关:固氮酶和POD酶活性呈正相关,SOD酶呈负相关。随着满江红的繁殖,溶液中若干营养成分含量也发生变化。除pH值外,其余所测定的指标在3种环境中的变化趋势基本一致,即电导率以及硝态氮、磷酸盐含量呈下降趋势,铵态氮维持在一定的低水平内;而水中的化学需氧量(COD)呈上升趋势。满江红繁殖力与溶液环境中成分变化的相关分析看出,环境中的离子态氮含量、化学需氧量的变化对满江红生产性能影响较小,而满江红的生产性能受溶液中的酸碱度、电导率及磷含量的制约。     

Identification and in vitro cytotoxicity of ochratoxin A degradation products formed during coffee roasting

The mycotoxin ochratoxin A is degraded by up to 90% during coffee roasting. In order to investigate this degradation, model heating experiments with ochratoxin A were carried out, and the reaction products were analyzed by HPLC-DAD and HPLC-MS/MS. Two ochratoxin A degradation products were identified, and their structure and absolute configuration were determined. As degradation reactions, the isomerization to 14-(R)-ochratoxin A and the decarboxylation to 14-decarboxy-ochratoxin A were identified. Subsequently, an analytical method for the determination of these compounds in roasted coffee was developed. Quantification was carried out by HPLC-MS/MS and the use of stable isotope dilution analysis. By using this method for the analysis of 15 coffee samples from the German market, it could be shown that, during coffee roasting, the ochratoxin A diastereomer 14-(R)-ochratoxin A was formed in amounts of up to 25.6% relative to ochratoxin A. The decarboxylation product was formed only in traces. For toxicity evaluations, first preliminary cell culture assays were performed with the two new substances. Both degradation products exhibited higher IC50 values and caused apoptotic effects with higher concentrations than ochratoxin A in cultured human kidney epithelial cells. Thus, these cell culture data suggest that the degradation products are less cytotoxic than ochratoxin A.     

不同品种菠菜叶柄和叶片的硝态氮含量及其与植株生长的关系

温室盆栽试验研究了我国北方不同菠菜品种叶柄和叶片的硝态氮含量及其与植株生长的关系。结果表明,30个菠菜品种地上部分的生长量和硝态氮含量存在显著差异。叶柄和叶片在反映品种间生长量和硝态氮含量变异方面的作用并不相同。叶片占植株地上部鲜重的比例高于叶柄,品种间叶片生长量的差异亦大于叶柄,叶片与植株生长量的正相关关系更为显著。但与生长量的情况不同,叶柄的硝态氮含量、累积总量均显著高于叶片,是菠菜累积硝态氮的主要器官。叶柄硝态氮含量的品种间差异远大于叶片,与植株地上部硝态氮含量的正相关性更为显著。菠菜不同品种之间,叶柄硝态氮含量与地上部鲜重、干重及水分均表现出显著的正相关关系,而叶片硝态氮含量与植株生物量及其各组分之间却无这种关系。     

基于3G技术的生猪及其肉制品溯源移动系统的开发

针对中国规模化养猪场及散养户目前建立养殖电子档案存在的不灵活性及效率较低等技术问题,该研究采用新一代PDA或智能手机作为开发平台,以.Net2005为开发语言,以SQL Server 2005CE为数据库,以TD-SCDMA无线宽带通信与Internet的融合为数据传输技术,提出了生猪养殖过程移动数据采集的数据规范,开发了适用于集生猪养殖档案建立及猪肉产品质量溯源的移动系统。系统运行表明:构建的移动系统可实现对猪只耳标的佩戴、免疫事件、饲料及兽药使用及监督抽检数据的移动采集与无线网络传输,实现了对生猪养殖过程电子档案建立及产品质量安全数据的深度查询。开发的系统既是对规模化养猪场通过桌面系统建立养殖档案的补足与完善,又是猪只散养户建立养殖电子档案的有效方案。此外,该系统为官方兽医提供了一种便捷的移动监管工具执行监管工作。研究进一步指出,随着TD-SCDMA技术的普及通信资费下降,该系统在构建中国猪肉质量安全可追溯体系方面具有广阔的应用前景。     

Enrichment of functional microbes and genes during pyrene degradation in two different soils

Purpose

Stimulating microbial degradation is a promising strategy for the remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAHs). To better understand the functional microbial populations and processes involved in pyrene biodegradation in situ, the dynamics of pyrene degradation and functional microbial abundance were monitored during pyrene incubation in soils. We hope our findings will provide new insights into in situ pyrene biodegradation in soils and help to identify functional microbes from soils.

Materials and methods

Pyrene (60 mg kg^?1) was incubated with two different soils, one is lower PAH-containing agricultural soil (LS), and the other is higher PAH-containing industrial soil (HS). During incubation, triplicate samples were collected on days 0, 3, 7, 14, and 35. Pyrene in soil samples was analyzed using an Agilent gas chromatograph (7890A) equipped with a mass-selective detector (model 5897). DNA in soils was extracted with a FastDNA Spin kit for soil (Bio101, USA). The abundance of functional microbes and genes was monitored by a Taqman or SYBR Green based real-time PCR quantification using an iCycler iQ5 themocycler (Bio-Rad, USA). The diversity of PAH-RHDα GP genes was evaluated by constructing clone libraries and sequencing.

Results and discussion

In both soils, more than 80 % of the added pyrene was degraded within 35 days. After 35-day incubation, there was a significant enrichment of Gram-positive bacteria harboring PAH-ring hydroxylation dioxygenase (PAH-RHD_α GP) genes, and the abundance of Mycobacterium increased significantly. In PAH-RHD_α GP clone libraries from two soils, Mycobacterium was detected, while most sequences were closely related to uncultured Gram-positive bacteria. In addition, two pyrene catabolic pathways might be involved in pyrene degradation, as pyrene dioxygenase genes, nidA and nidA3, were dramatically enriched during incubation. Moreover, the abundance and diversity of potential degraders in two soils showed significantly difference in responding to pyrene stress. This result indicates that soil condition can significantly affect functional microbial populations and biological process for pyrene biodegradation.

Conclusions

These results revealed that Mycobacterium as well as uncultured Gram-positive PAH-RHD_α genotypes may be the important group of pyrene degraders in soils, and two pyrene catabolic pathways, targeted by nidA and nidA3, might potentially contribute to in situ biodegradation of pyrene. This study characterized the response pattern of potential pyrene degraders to pyrene stress in two different soils, which would increase our understanding of the indigenous processes of pyrene biodegradation in soil environment.

     

Cholesterol oxidation in meat products and its regulation by supplementation of sodium nitrite and apple polyphenol before processing

The levels of cholesterol oxidation derivatives (OxChol) in eight commercial species of meat products were examined. These products contained more than 1 mg/100 g of OxChol, and 7beta-hydroxycholesterol + 5beta-epoxycholesterol (111-1092 microg/100 g), 5alpha-epoxycholesterol (80-712 microg/100 g), cholestanetriol (0-368 microg/100 g), and 7-ketocholesterol (708-1204 microg/100 g) were detected. To know the interaction of sodium nitrite supplementation against cholesterol oxidation in meat products, sausage was produced with or without varying levels of sodium nitrite and stored in the refrigerator for 15 days. As a result, cholesterol oxidation in sausage was inhibited by addition of sodium nitrite in a dose-dependent manner. This observation may be associated with inactivation of O(2)(-) radical and stabilization of polyunsaturated fatty acids (PUFAs). In fact, the levels of OxChol in sausage increased, accompanying the decrease of coexisting linoleic acid when sodium nitrite was not added to sausage meat. Thus, cholesterol oxidation in meat products seems to be considarably promoted by the oxidation of coexisting PUFAs. On the other hand, additive apple polyphenol also inhibited linoleic acid oxidation in sausage and then suppressed cholesterol oxidation through its radical scavenging effects. Therefore, apple polyphenol, having a large amount of an oligomer of catechin, may interfere with cholesterol oxidation in meat processing or storage of meat products through its antioxidative action and be useful as a new antioxitant for meat products when it is added to the original meat before processing.     

Analysis of the early stages of lipid oxidation in freeze-stored pork back fat and mechanically recovered poultry meat

An analytical method that can detect low levels of oxidation in food earlier than a sensory panel would be a valuable tool for food manufacturers as well as research institutes. Two model matrixes, pork back fat and mechanically recovered poultry meat (MRPM), were freeze-stored in air at -20 degrees C for 26 weeks. Peroxide value, thiobarbituric acid reactive substances, volatiles analyzed with dynamic headspace gas chromatography-mass spectrometry (GC-MS) and a gas-sensor array technique (electronic nose), chemiluminescence, and front-face fluorescence were evaluated against sensory analysis with regard to detection of early oxidation and correlation with sensory data. Fluorescence and GC-MS could detect oxidative changes in pork back fat earlier than the sensory panel and the electronic nose at the same time. The three methods were highly correlated with sensory attributes (r = 0.8-0.9). GC-MS gave the best results with regard to detection of small oxidative changes in MRPM.     

Phenol and terpene quenching of singlet- and triplet-excited states of riboflavin in relation to light-struck flavor formation in beer

Phenolic compounds present in beer were shown by fluorescence spectroscopy and laser flash photolysis to deactivate both singlet- and triplet-excited states of riboflavin with bimolecular rate constants close to the diffusion control ranging from 2.8x10(9) to 1.1x10(10) M-1 s-1 and from 1.1x10(9) to 2.6x10(9) M-1 s-1, respectively. Enthalpies of activation were low (up to 33.2 kJ mol-1), and entropies of activation were positive, ranging from 17 to 92 J mol-1 K-1, as derived from temperature dependence, indicating a compensation effect. From a Stern-Volmer analysis of the singlet-excited riboflavin quenching by phenols it was found that high amounts of phenolic compounds (>0.3 M) would be needed to hinder triplet-excited riboflavin generation. On the other hand, a phenolic content of 0.36 mM is likely to quench 90% of the triplet-excited state. Phenol photodegradation was found to be complex, and using ESI-MS analysis it was not possible to identify specific photooxidation products of the phenolic compounds; only the photoproducts of riboflavin could be detected and structurally assigned. The rate of reaction of triplet-excited riboflavin with phenolic compounds in acetonitrile/citrate buffer (pH 4.6, 10 mM) is 550 times faster than the reaction with iso-alpha-acids from hops, indicating that triplet-excited quenchers such as phenols may be involved in the early steps in light-struck flavor formation in beer through radical formation. Terpenes present in herb-flavored beers were found to be nonreactive toward singlet- and triplet-excited-state riboflavin, and any protection depends on other mechanisms.     

Model studies on the efficacy of protein homogenates from raw pork muscle and dry-cured ham in binding selected flavor compounds

The binding of sarcoplasmic and myofibrillar proteins extracted from postrigor pork muscle and from 7 and 12 months dry-cured hams with volatile compounds such as 3-methyl-butanal, 2-methyl-butanal, 2-pentanone, hexanal, methional, and octanal was studied using solid phase microextraction and gas chromatography analysis. The binding ability of sarcoplasmic proteins from pork muscle was higher than the ability shown by 7 and 12 months dry-cured ham sarcoplasmic homogenates and also higher than the binding ability of myofibrillar homogenates. The effect of the ionic strength on the binding was also studied. This effect was more important on myofibrillar proteins due to its ability to produce changes on the protein conformation that affect their binding ability. However, the sarcoplasmic protein binding ability was more related to the small compounds present in this homogenate than with the aqueous phase ionic strength.     

土壤磷有效性及其与土壤性质关系的研究

选取我国14个不同地点土样,测定理化性质、全磷、速效磷、水溶性磷含量,采用通径分析研究土壤磷有效性与土壤性质的关系。结果表明,土壤磷有效性是各个土壤性质综合作用的结果。土壤CEC、有机碳、粘粒、砂粒、碳酸钙含量对土壤速效磷比例影响显著,土壤CEC、粘粒、砂粒含量对土壤速效磷比例贡献为正值,而土壤有机碳对土壤速效磷比例贡献为负值;土壤pH和CEC含量对土壤水溶性磷含量影响显著,土壤pH对水溶性磷比例贡献为正值,土壤CEC对土壤水溶性磷比例贡献为负值。本文所选土样基本符合土壤磷有效性与土壤性质之间通径分析的结果。