An improved microbial assay for the detection of chloramphenicol residues in shrimp tissues

An improved microbial assay was developed for the detection of chloramphenicol (CAP) residues in shrimp muscle using Photobacterium leiognathi (L-2 strain) isolated from squid, as test organism, using a pad plate technique. CAP spiked in shrimp muscle tissues at concentrations ranging from 1 to 100 μg/kg was extracted using ethyl acetate and ammonium hydroxide. The assay showed a maximum inhibition zone of 23.0 mm for 100 μg/kg and a minimum inhibition zone of 9.3 mm for 1 μg/kg. The method had a good recovery of 95.63% with a minimum detection limit of 1 μg/kg. It can be performed within 18 h following simple extraction. The method therefore proved to be advantageous over chromatographic procedures as it was inexpensive, quite sensitive and can be adopted for rapid screening of CAP in shrimp tissues.     

Reduction of pesticides residues on okra fruits by different processing treatments

For the first time, the effect of washing, water boiling, chemical boiling, steaming and cooking treatments on the reduction of residues of indoxacarb, fenarimol, acetamiprid and chlorfenapyr in okra fruits was investigated. Residues were analyzed using quick, easy, cheap, effective, rugged, and safe (QuEChERS) method combined with liquid chromatography tandem-mass spectrometry (LC–MS/MS). Our results show that some treatments could significantly decrease pesticide residues. The reduction of residues by washing treatment was not correlated to water solubility: Chlorfenapyr (non-systemic pesticide) was decreased by 90 % and acetamiprid (systemic pesticide) was removed by 48 %. Therefore, we suggest that pesticide residues were washed off by removing the loosely attached pesticides on the okra fruit surface. The time of exposure in both boiling and steaming treatments has no significant effect on reduction of pesticides residues. Additionally, cooking after the washing and boiling treatments reduced the pesticides residues. In particular, acetamiprid was reduced after the cooking treatment to 90 %.     

Restoration of kefir grains subjected to different treatments

The aim of the study was to find a way to recover the quality of kefir grains that had been subjected to the following treatments: homogenisation, rinsing the grains with water, freeze‐drying and milling, freezing in liquid nitrogen and then frozen storage, and cool storage. The grains were studied in respect of their later replication in milk, their size and their microbiota composition. The daily transfer of treated kefir grains, except freeze‐dried ones, into fresh milk was effective in respect of the recovery of their growth dynamics, size and microbiota balance. The growth dynamics of grains in milk seems to be a very good indicator of their vital and technological functions.     

Changes in 4-hexylresorcinol residues during processing of deepwater pink shrimp (Parapenaeus longirostris)

Hexylresorcinol has been used as an alternative to sulphites for prevention of melanosis or black-spot of the shrimp carapace. In order to estimate consumption of 4-hexylresorcinol, residual levels have been evaluated in deepwater pink shrimp (Parapenaeus longirostris) following dip treatments and different processing technologies (freezing, cooking and washing). The effect of 4-hexylresorcinol on the microbial growth in the dipped shrimp as well as change in the inhibitory solution during repeated utilization was also followed. The use of 4-hexylresorcinol at concentrations of 0.10 or 0.25 mg/kg led to the detection in pink shrimp of residue levels considerably higher than the limit level of 2 mg/kg. Furthermore, the processing technologies studied also showed a very low efficiency in the reduction of residues from the initial loads to acceptable values. Though the tested initial bacterial load of the shrimp was higher than it is normally expected onboard the solution of 4-hexylresorcinol did not evidence any tendency for an increase of the bacterial counts even after 29 h of utilization. No decrease in the 4-hexylresorcinol concentration is visible even after 8 dips and 29 h of solution use.     

Chemical characteristics,oxidation and proteolysis in cheese produced from fresh or stored milk subjected to heat treatments

Cheese produced from fresh, stored or heat pretreated (65°C for 15 s) milk subjected to pasteurisation (72°C or 77°C for 15 s) was studied for chemical characteristics and proteolysis after 4 and 21 days of storage. Antioxidant activity was higher in cheese from fresh milk than in cheese from stored and heat pretreated milk. Malondialdehyde content as an index of lipid oxidation increased in cheese made with pretreated and preserved milk than in cheese made with fresh milk. Antioxidant activity and lipid oxidation were not significantly affected by pasteurisation temperature. Proteolysis increased during cheese maturation regardless of milk heat treatments.     

GC-MS分析法在猪肉氯霉素残留检测中的应用

建立了猪肉中残留氯霉素(CAP)的GC-MS分析方法。样品中CAP用乙酸乙酯提取,脂肪用正己烷去除,BondElut-C18柱纯化样品,BSTFA-TMCS衍生后用NCI源选择m/z为466的特征离子为目标离子,在SIM模式下进行GC-MS分析。被检测CAP质量浓度在0.08~100μg/kg内,方法的线性关系良好,相关系数为0.998。方法的最低检测限达到0.08μg/kg。用此方法对市场上销售的猪肉样品进行测定,结果显示:只有一份样品CAP残留量为(0.236±0.007)μg/kg,另4份猪肉样品中未检出CAP残留。应用本方法测定新鲜猪肉中CAP残留,基本上满足了灵敏、快速、准确可靠的分析方法要求。     

Tetracycline residues in meat and bone meals. Part 2: The effect of heat treatments on bound tetracycline residues

The stability of bound tetracycline residues during heat treatments at 133°C and 100°C for up to 45min was investigated. An intermediate product from a rendering plant was mixed with bone splinters that contained bound tetracycline (TC) and chlortetracycline (CTC) residues. The mixture was heated in an auto-clave at 133°C for 20, 30 and 45min and at 100°C for 20 and 30 min and subsequently dried at 103°C for 4 h. Two different extraction procedures with hydrochloric acid were used, one with and one without the previous sedimentation of bone particles. Tetracycline concentrations were determined by HPLC analysis before and after the heat treatment. A complete destruction of tetracyclines during heat treatment at 133°C could not be demonstrated, but there was a significant decrease of TC by about 50%. CTC was less resistant to the same temperature, which brought about a reduction of 90-100% . Treatments at 100°C did not bring about any reduction, except for CTC after extraction without sedimentation. The possible toxicological relevance of the findings is discussed. Further research has to be done on possible degradation products of the tetracycline derivatives.     

虾加工副产品制备虾味香料的研究

以虾加工副产品为原料,通过热反应制备得到天然、香气持久的虾味香料。通过试验确定,热反应型虾味香料的最优配方为:虾蛋白水解液10 g,氨基酸添加量0.4 g(谷氨酸:胱氨酸:甘氨酸:精氨酸质量比为4∶3∶2∶1),还原糖添加量为1.0 g(木糖:葡萄糖质量比为1∶1),反应温度100℃,反应时间40 min。     

虾加工副产品中虾油提取工艺研究

通过比较碱性蛋白酶、中性蛋白酶、风味蛋白酶、复合蛋白酶和胰蛋白酶对虾加工副产品的酶解,确定风味蛋白酶作为最佳水解酶,并确定其起始pH值为6．5,考察了酶添加量、料液比、酶解时间和温度对虾油提取率的影响,确定最优工艺：酶添加量1．0g／100g,料液比1g：8mL,酶解时间2．5h,酶解温度50℃。     

市售动物源性食品中氯霉素类药物残留量的调查研究

目的 了解市售动物源性食品中氯霉素类药物的残留水平。方法 取鱼、虾、猪肉可食部分, 用干冰冷冻粉碎、均质后冷冻存放。预处理样品经溶剂提取, 正己烷脱脂后, 用液相色谱/质谱联用法(LC-MC/MS)检测, 采用内标法定量。结果 全部样品中氯霉素的检出率最高(按检出限0.03μg/kg判定), 达31 %(71/229),氟甲砜霉素和甲砜霉素的检出率分别为9.60%(22/229)和1.31%(3/229)。不同类样品氯霉素的检出率差异较大, 明虾中均未检出, 花粉的检出率最高(100%, 3/3), 其他检出率由高到低分别为养殖鱼(82.1%, 23/28)、牛奶(75.0 %, 24/32)、猪肉(46.7%, 7/15)、国产蜂蜜(16.0%, 12/75)和进口蜂蜜(5.6%, 2/36)。氟甲砜霉素仅在鲜猪肉、牛奶和养殖鱼中检出, 而甲砜霉素仅在国产蜂蜜和鲜猪肉中检出, 含量均较低。结论 市售动物性食品中氯霉素违规使用的问题依然存在, 提醒各有关部门应加强食品中违禁药物残留的风险监测和药物使用的清理整顿工作。     

食品中氯霉素残留检测技术研究新进展

氯霉素作为一种高效广谱抗生素,广泛应用于各种动物的传染性疾病控制,但它在食品中的残留对人体健康构成潜在危害。本文综述了目前食品中氯霉素残留的检测技术,主要有微生物学法、免疫分析法、色谱分析法、电化学方法、生物芯片及其他方法。     

小龙虾基体中氯霉素残留降解因素分析

目的 研究温度和氯霉素初始浓度对小龙虾中氯霉素降解的影响.方法 将氯霉素初始添加浓度为0.5、5.0、50μg/kg的小龙虾阳性模拟样品放置在?18、4、25和37℃恒温条件下,分别在2、4、6、12、24、36、48 h时测定其氯霉素残留量.结果 温度对小龙虾中氯霉素降解影响较为显著(P<0.01),本质在于微生物降...     

Kinetic analysis of volatile formation in milk subjected to pressure-assisted thermal treatments

Volatile formation in milk subjected to pressure-assisted thermal processing (PATP) was investigated from a reaction kinetic analysis point of view to illustrate the advantages of this technology. The concentration of 27 volatiles of different chemical class in milk subjected to pressure, temperature, and time treatments was fitted to zero-, 1st-, and 2nd-order chemical reaction models. Temperature and pressure effects on rate constants were analyzed to obtain activation energy (E(a)) and activation volume (deltaV*) values. Hexanal, heptanal, octanal, nonanal, and decanal followed 1st-order kinetics with rate constants characterized by E(a) values decreasing with pressure reflecting negative deltaV* values. Formation of 2-methylpropanal, 2,3-butanedione, and hydrogen sulfide followed zero-order kinetics with rate constants increasing with temperature but with unclear pressure effects. E(a) values for 2-methylpropanal and 2,3-butanedione increased with pressure, that is, deltaV* > 0, whereas values for hydrogen sulfide remained constant, that is, deltaV* = 0. The concentration of all other volatiles, including methanethiol, remained unchanged in pressure-treated samples, suggesting large negative deltaV* values. The concentration of methyl ketones, including 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone, 2-nonanone, 2-decanone, and 2-undecanone, was independent of pressure and pressure-holding time. PATP promoted the formation of few compounds, had no effect on some, and inhibited the formation of volatiles reported to be factors of the consumer rejection of "cooked" milk flavor. The kinetic behavior observed suggested that new reaction formation mechanisms were not likely involved in volatile formation in PATP milk. The application of the Le Chatelier principle frequently used to explain the high quality of pressure-treated foods, often with no supporting experimental evidence, was not necessary.     

基于核酸适配体检测动物性食品中氯霉素残留的研究进展

氯霉素是一种禁用于食品动物的广谱抗生素,建立对其残留的快速检测尤为重要;核酸适配体作为新型生物识别元件,稳定性好且易合成,结合核酸适配体对氯霉素进行残留检测是继传统抗体检测之后又一新的突破方向,因此具有良好发展前景。在此综述了近5年基于核酸适配体检测动物性食品中氯霉素残留的研究进展,主要包括比色分析法、荧光分析法、化学发光分析法、表面增强拉曼散射检测法以及电化学生物传感器法等,发现当前适配体在氯霉素残留检测领域缺乏系统深入研究,相关检测应用难以同时兼顾简单快速和灵敏准确的检测需求,特此比较和讨论不同分析方法,并分析其优缺点及发展趋势,以期为动物性食品中氯霉素残留的高效监管提供有益参考。     

蜂产品中氯霉素残留检测方法的研究进展

本文综述了近年来蜂产品中氯霉素残留的主要检测方法及其研究进展, 包括微生物法、免疫分析法、色谱分析法和生物传感器法。其中, 免疫分析法着重介绍了酶联免疫法, 色谱分析法则主要介绍了高压液相色谱和色谱-质谱联用技术。最后, 对现有检测方法进行了比较分析。     

胶体金免疫层析法快速检测氯霉素残留

为建立用于快速检测样品中氯霉素残留含量的胶体金免疫层析试纸条，采用免疫竞争法，将抗氯霉素单克隆抗体一胶体金复合物包被在胶体金结合垫上，并将人工合成的氯霉素抗原包被在硝酸纤维素薄膜表面作为检测线（T线），其与待测样品中氯霉素竞争结合胶体金标记的氯霉素单克隆抗体，并能以颜色直观显示检测的定性结果。检测虾肉等组织试样时，灵敏度最低值可达到1ng／ml，只需5—10min，与类似物无交叉反应。试纸条具有较高的灵敏度及特异性，操作便捷．稳定可靠，可作为氯霉素残留现场监控的有效筛检手段。     

云南省市售蜂蜜中氯霉素和甲硝唑残留检测结果分析

目的了解云南省市售蜂蜜中氯霉素和甲硝唑的残留量状况。方法 2016年7月至2017年7月期间,采用分阶段分层次随机抽样的方法在云南省5个城市中抽取云南地产蜂蜜66份。按照检测标准采用超高效液相色谱-串联三重四极杆质谱法(ultra performance liquid chromatography-triple qudrupole tandem mass spectrometry,UPLC-MS/MS)进行测定。检出率的比较采用X~2检验分析,P0.05为差异有统计学意义。结果 66份蜂蜜样品中氯霉素和甲硝唑残留的检出率分别为30.3%和97.0%。不同城市、不同品种和包装型态间检出率均存在统计学差异。结论云南省蜂蜜中氯霉素和甲硝唑残留情况比较严重,监管部门应予重视。     

单体速冻对虾的生产工艺

介绍了速冻对虾的生产工艺及其操作要点,提出适宜的质量标准,并对速冻对虾生产现存的问题进行了分析与探讨。     

超高效液相色谱——三重四级杆质谱测定乳与乳制品中氯霉素的残留

建立了乳与乳制品中氯霉素残留的超高效液相色谱——三重四级杆测定方法。该方法采用电喷雾电离源、多重反应监测负离子模式,可对氯霉素残留进行定性和定量测定。该方法的检出限为牛奶0.05μg/kg,乳粉为0.1μg/kg,线性范围在0.4～30.0μg/L内的回归方程为y=798.97+1874.56x,r=0.9993,加标回收率75.0%～94.6%,相对标准偏差为4.2%～12.8%。该法具有样品处理简单方便,灵敏度高,分析时间短等优点,可以满足乳与乳制品中氯霉素残留的测定。