采用计算机视觉进行孵化鸡蛋成活可能性的自动检测

本研究将计算机视觉技术与遗传神经网络相结合,建立一套适合于孵化鸡蛋可成活性自动检测的计算机视觉系统,通过计算机视觉技术获取了孵化鸡蛋的角度直方图,并提取了孵化鸡蛋表面颜色特征,采用遗传算法优化了多层前馈神经网络的拓扑结构与权值,提高了神经网络的学习质量和学习速度,实现了孵化鸡蛋可成活性的自动检测,实验结果表明,该方法准确率较高,并具有鲁棒性和高速度。     

Determination of pyrethroids in chicken egg samples: development and validation of a confirmatory analytical method by gas chromatography/mass spectrometry

The aim of this study was to develop and validate an efficient analytical method based on gas chromatography/tandem mass spectrometry (GC/MS/MS) for detection and quantification of six pyrethroids residues (Phenothrin, Permethrin, Cyfluthrin, Cypermethrin, Deltamethrin and Fenvalerate) in chicken eggs. The method was based on a preliminary liquid–liquid extraction of albumen‐free yolk samples, followed by a clean‐up by solid‐phase extraction. GC/MS/MS analyses were carried out in the selected reaction monitoring mode. Validation parameters such as specificity, detection capability, decision limit, precision, recovery, stability and ruggedness were determined, resulting in compliance with Decision 2002/657/EC. No complicated apparatus are required; moreover, low volumes of organic solvents and a nonintensive manual labour are required. These low costs and simple procedure, based on rapid and safe operations, may represent a useful tool in the routine analysis of pyrethroids pesticides, in the place of the currently used conventional techniques.     

HS-SPME结合GC-MS分析煎鸡蛋的挥发性风味成分

采用顶空固相微萃取与GC-MS联用方法对煎鸡蛋中挥发性成分进行提取与分析,考察萃取头、萃取温度和吸附时间对分析结果的影响,得到优化的顶空固相微萃取条件为:黑色萃取头(75μm Carboxen/PDMS),吸附温度75℃,吸附时间70 min。在优化的条件下分析,共鉴定出50种挥发性风味成分,其中,醛类16种(40.588%)、含氮化合物14种(23.639%)、醇类8种(7.156%)、烃类3种(4.800%)、酚类及杂环化合物3种(1.755%)、酮类3种(0.868%)及含硫化合物3种(0.563%)。鉴定出含量较高(相对质量分数大于2.5%)的物质有:2,5-二甲基吡嗪、3-甲基丁醛、2-甲基吡嗪、壬醛、苯甲醛、反,反-2,4-癸二烯醛、辛醛、2-甲基丁醛、反-2-癸烯醛、3,7-二甲基-1,6-辛二烯、1-辛烯-3-醇。     

小麦粉中虫卵的快速检测技术的研究与比较

为了建立一种快速检测小麦粉中昆虫虫卵的方法,比较研究了浮选法、尿酸检测法、几丁质检测法和染色法4种方法检测小麦粉中虫卵的效果及优缺点的比较。结果表明浮选法最高检出率为5.59%,不适用于虫卵检测;几丁质检测法只能证明虫卵中有几丁质,但无法定量;尿酸检测法中检测出的尿酸浓度与虫卵数成正相关,相关系数R2为0.998 6,最低检出限为0.1粒卵/g;利用溴甲酚绿和酸性品红将小麦粉染色的结果是溴甲酚绿将虫卵染成黄橙色,小麦粉染成褐绿色;酸性品红将虫卵和小麦粉都染成紫色,但小麦粉被染颜色更深。染色法虫卵检测率约为75%,初步可以用于小麦粉中虫卵的快速检测。随机取样的小麦粉检测与实际发生虫量比较发现尿酸检测法的检测率为73.3%,染色法的检测率为85%。说明了尿酸法和染色法可以初步用于小麦粉中昆虫虫卵的检测,其灵敏度和操作规范有待进一步优化和研究。     

菹草类胡萝卜素的研究——菹草与红心鸭蛋类胡萝卜素特性的初步比较

用菹草喂养蛋鸭能生产优质红心蛋,通过薄层层析及紫外可见吸收光谱等研究,发现菹草含有一类特殊的红色类胡萝卜素,菹草红色类胡萝卜素及部分黄色类胡萝卜素与红心蛋色素有很好的对应关系,证明了红心鸭蛋的红色素来源于菹草;菹草红色类胡萝卜素易溶于丙酮、乙醇、甲醇等极性溶剂,其丙酮溶液的可见吸收光谱峰波长为480nm;菹草和红心鸭蛋中都含有β-胡萝卜素;对菹草类胡萝卜素的部分特性作了初步研究。     

鸡蛋中药物残留加工因子与监测结果分析

目的分析鸡蛋中药物残留膳食暴露加工因子的确定与监测样品结果。方法按监测计划采集样品并制备模拟样品,应用超高压液相色谱-串联质谱测定15种药物残留含量,并计算加工因子与去除率。结果120份样品检出氧氟沙星5份(2.5～65.8μg/kg),环丙沙星1份(2.4μg/kg)。煮蛋器15 min加工因子为0.10～0.87,微波加热(60s)加工因子为0.10～0.92。结论加工处理过程能显著降低食物中药物残留量,降低人群膳食暴露风险,蒸蛋器加热与微波烹调2种加工处理方式相比较,微波烹调过程对药物残留的去除作用小。监测结果分析表明,在不同地区、不同品种和不同参数间的药物残留检出率无统计学差异。     

UPLC-MS/MS检测鸡蛋中22种喹诺酮类药物残留方法的研究

应用超高效液相色谱串联质谱建立鸡蛋中加雷沙星、曲伐沙星、莫西沙星、奥比沙星、吉米沙星、加替沙星、培氟沙星和环丙沙星等22种喹诺酮类药物残留检测方法。样品经过2%甲酸乙腈提取、正己烷分步去脂,Oasis HLB柱净化后,经Acquity UPLC BEH Shield RP18(100 mm×2.1 mm,1.7μm)分离,以甲醇和0.1%甲酸水溶液为流动相进行梯度洗脱,双通道MRM信号采集模式,22种喹诺酮类药物能在11 min完好分离,方法的最低定量限均低于1.0μg/kg,在2.0~100.0μg/L浓度范围内,22种喹诺酮类药物线性良好,相关系数均在0.99以上;通过2、10、20 g/kg三个浓度的加标回收实验表明,回收率为60.1%~96.2%,RSD%值为1.44%~11.1%。该方法相比现有国标检测药物种类多,新型药物多,对更全面筛查和确证鸡蛋中喹诺酮类药物残留,防范非法添加造成安全隐患具有一定的参考价值。     

Edible coatings for enhancing microbial safety and extending shelf life of hard-boiled eggs

ABSTRACT:  Hard-boiled eggs were coated with chitosan–lysozyme (CL), whey protein isolate (WPI), or Bake sheen (BS), inoculated with Listeria monocytogenes or Salmonella enterica Ser. Enteritidis at 10⁴ CFU/g, and stored for 4 wk at 10 °C. Microbial populations were enumerated weekly. Two nonchallenge studies were also conducted with hard-boiled eggs: coated shell-on eggs packaged in plastic containers or peeled eggs coated and vacuum-packaged. Total plate counts (TPC), coliforms, yeasts, molds, weight loss, pH, and color of eggs were determined during the 10-wk storage at 10 °C. Uncoated eggs served as controls. All the coatings were not effective in inhibiting the growth of L. monocytogenes, but CL coating controlled the growth of S. Enteritidis. At the end of 4-wk storage, the numbers of S. enteritidis on CL-coated eggs were about 4-log₁₀ CFU/g less than that of the controls. Coatings reduced ( P < 0.05) the populations of coliforms and TPC, and completely inhibited mold growth during the 10-wk storage. Coatings also reduced ( P < 0.05) the weight loss of eggs, 4.1% to 4.8% on coated eggs compared with 7.5% in uncoated ones at the end of 10-wk storage. The pH of CL-coated eggs remained stable throughout the storage period, while the control eggs increased from 7.6 to 8.6. Color changes in CL- and WPI-coated eggshells were less ( P < 0.05) than those of BS-coated and the control. The CL coating effectively suppressed the numbers of TPC, coliforms, yeasts, and molds on peeled eggs during the 6-wk storage ( P < 0.05). The results suggest that CL coating on hard-boiled eggs can control the growth of S. Enteritidis and reduce undesirable changes in the interior quality of eggs.     

泥腌、水腌咸蛋的理化指标和滋味品质差异分析

目的 研究单个泥腌与大缸水腌加工咸蛋品质的差异。方法 在18 ℃恒温下、用25.5% (m/m)的盐水水腌和25%的盐泥泥腌咸蛋, 测定腌制过程中咸蛋含盐率、含水率、游离氨基酸、感官评价等指标, 分析泥腌、水腌咸蛋盐分渗透规律、咸蛋含盐含水与感官品质间相关性、氨基酸味道强度值与滋味品质间的关系。结果 水腌咸蛋25 d成熟, 蛋白含盐率4.99%、蛋黄含盐率1.18%, 蛋内进盐量1.87 g, 盐利用率8.68%; 泥腌蛋35 d成熟, 蛋白含盐率3.53%、蛋黄含盐率1.87%, 蛋内进盐量1.48 g, 盐利用率38.95%。咸蛋的R值(蛋白或蛋黄的含盐含水比)、Q值(蛋黄与蛋白的平衡系数)、N值(蛋白蛋黄含盐比)均与感官品质有显著相关性(P＜0.05)。结论 单个泥腌制作的咸蛋蛋白不咸、蛋黄咸鲜, 品质更好, 其盐分利用率高于水腌方式。咸蛋的R值、Q值、N值可作为评价咸蛋综合感官品质和成熟度的定量指标。