鸡蛋在储存过程中微生物及蛋品质的变化研究

为了探讨贮藏时间对鸡蛋微生物及蛋品质产生的影响,从某大型养殖场随机采集同批次健康鸡蛋,在模拟市场销售的条件下贮藏,期间检测新鲜鸡蛋的菌落总数、大肠菌群和新鲜度评价指标,每隔2 d检测1次,27 d结束。结果表明,随着贮藏时间的延长,鸡蛋细菌总数总体上呈逐渐增加趋势,鸡蛋外壳细菌总数从103CFU/枚增长至109 CFU/枚,而鸡蛋内容物细菌总数也从0 CFU/枚增长至105 CFU/枚;检出了大肠菌群,但未超出国家农业部无公害鸡蛋标准。随着贮藏时间的延长,鸡蛋蛋重降低,气室高度增加,浓蛋白减少,在第12天开始出现散黄现象。试验表明,新鲜鸡蛋的保存期不宜超过12 d。     

储存时间对鸡蛋微生物和蛋品质影响研究

本研究探讨了鸡蛋在28℃夏季高温、80％~90％湿度条件下，不同储存时间对鸡蛋微生物和蛋品质变化情况的影响。结果表明，随着存放时间延长，鸡蛋外壳和内容物菌落总数呈上升趋势，变化范围分别在6.50×10²~2.35×10⁵ CFU/g和0~35.5 CFU/g之间。存储21 d后，鸡蛋外壳菌落总数超出农业部无公害鸡蛋标准。而大肠菌群数基本小于30 MPN/100 g，低于农业部无公害鸡蛋标准。试验中被检鸡蛋随着贮藏时间增加，气室高度增加，浓蛋白减少而稀蛋白增多，第12 d时已有部分鸡蛋出现散黄现象。可见，鸡蛋品质各指标与存放时间呈明显的相反趋势。     

常温贮存鸡蛋的细菌数量变化规律研究

本文研究鸡蛋贮存期间的蛋壳和蛋内容菌落总数的变化规律.在25℃环境下贮存过程中,每隔5天,参照国家标准GB 4789.2-2016测定新鲜鸡蛋蛋壳和蛋内容菌落总数,到20天时结束.结果 表明在第15天鸡蛋蛋壳表面细菌呈现急剧增长的趋势,在第10天,蛋液细菌呈现增长趋势.这表明随着鸡蛋贮藏时间的延长,鸡蛋蛋壳及内容物菌落总数不断增加,蛋壳表面细菌总数变化比内容物变化快.     

不同品牌市售鲜鸡蛋贮存过程中微生物变化比较研究

鸡蛋是人类膳食的重要组成部分,其产出与贮运销售过程中均存在沙门氏菌等致病菌污染隐患,直接影响鸡蛋的消费安全。作者对北京市场德青源、留民营等4种品牌包装鲜鸡蛋及散装鸡蛋在贮存过程中细菌总数、大肠菌群数及沙门氏菌数量变化进行了测定,研究了贮存过程中各品牌鸡蛋蛋壳、蛋清及蛋黄中的细菌总数,大肠菌群数随时间的变化情况及沙门氏菌的检出情况。研究结果发现,不同品牌的鸡蛋蛋壳表面在贮存初期细菌总数介于9.315×10²～1.367×10⁴ CFU/个,且随着贮存时间的延长呈上升趋势;品牌鸡蛋贮存初期蛋内容物均未检出污染细菌,而在贮存6 d后检出污染细菌,细菌总数与大肠菌群存在随着贮存时间的延长而增加的变化。除A品牌鸡蛋外,市售鲜蛋均存在沙门氏菌污染,蛋壳表面污染率为1.67%～8.3%,内容物中污染率为1.67%～5%。其中散装鸡蛋的细菌总数,大肠菌群数及沙门氏菌检出率均高于其它几种品牌的鸡蛋。     

科技动态

适当辐照可延长软罐头包装凤爪货架期四川省原子能研究院高鹏等使用0、3、5、10kGy的60Coγ射线辐照软罐头包装凤爪,分别在贮存0、30、60、90d时检测样品中的菌落总数、大肠菌群、致病菌、TBARS值,并进行了感官评价试验。结果表明,贮藏90d后,辐照组的菌落总数分别为6.1×103、1.4×103、765CFU/g,在整个贮存期间均低于对照组,且未检出大肠菌     

乳酸菌对牦牛发酵肉制品中肌肉蛋白降解作用的研究

为了研究牦牛肉发酵过程中乳酸菌对肌肉蛋白的降解作用,以青海大通牦牛肉为原料,嗜酸乳杆菌作为发酵剂,经1.5%食盐干腌后,进行发酵肉的制作。在发酵过程中分别对蛋白质水解指数、发酵肉的p H值、菌落总数、大肠菌群、乳酸菌总数、风味物质进行了测定。研究发现,牦牛肉在发酵过程中,蛋白质水解指数发酵第13d达到最大值;p H值第5d降到最低值,此后p H值变化差异均不显著(P0.05);菌落总数先缓慢上升,后趋于稳定,在8.00lg(CFU/g)上下波动;大肠菌群数均在发酵第5d达到最大值,从发酵第5d开始均呈下降趋势;乳酸菌总数变化菌落总数变化保持一致;风味物质发酵组与未发酵组相比,烃类物质种类减少了,醇类、醛类、酸类、酮类和芳香族类的种类都增加了。     

鸡蛋储存过程中细菌生长繁殖规律分析

试验旨在研究新鲜鸡蛋在常温与冷藏保存条件下细菌生长繁殖规律,为鸡蛋的合理保存与消费提供参考。新鲜鸡蛋分2组,分别进行常温与冷藏储存,检测各组鸡蛋0、7、14、21和28 d蛋壳表面及蛋内容物细菌总数。结果显示:蛋壳表面的细菌总数,保存前(0 d)为8.5×10~3cfu/m L,常温与冷藏条件下均出现稳定增长,常温保存增长较快。28 d时常温与冷藏保存细菌总数分别达到3.99×10~4cfu/m L和3.25×10~4cfu/m L(P0.05);蛋内容物中细菌总数,保存前(0 d)与冷藏保存7 d均未检出细菌,常温保存14 d后细菌总数快速增加,常温和冷藏条件下28 d分别达到3.97×10~3cfu/m L和8.15×102cfu/m L(P0.01)。蛋壳表面与内容物细菌总数随保存时间延长呈上升趋势,低温保存能够抑制细菌生长,延长鸡蛋的保质期。     

青海省部分地区牛奶中几种微生物指标的检测

为掌握我省部分地区牛奶中微生物含量,本实验对2008年10月至11月青海省重点地区的8批次70份鲜牛奶样进行了菌落总数、大肠菌群、沙门氏菌的检测。结果表明,菌落总数(Cfu/mL)是:1.4×105;大肠菌群(MPN/100mL)是:7.6×104,均低于国标GB/T 4789.1～4789.31—2003的要求(菌落总数:5.0×105,大肠菌群:1.0×105)沙门氏菌检测均为阴性。说明我省的鲜奶基本符合国标要求,无公共卫生安全隐患。     

鲜豆浆中菌落总数的测定

通过稀释平板计数法对鲜豆浆进行菌落总数的测定,在牛肉膏蛋白胨培养基平板上有3种菌落产生,菌落总数为8.3×108CFU/mL。取刚煮沸的鲜豆浆进行测定,菌落总数达610CFU/mL;保持沸腾至少2min,然后再进行测定,发现菌落总数为0CFU/mL。     

贮藏条件对山羊奶微生物变化的影响

本试验研究了在手工挤奶条件下,不同贮藏温度、时间对生鲜山羊奶的菌落总数、芽孢总数、大肠菌群的影响。试验结果表明：在室温（20℃）贮藏条件下,菌落总数12h后为6．3×10^5个／mL,超过生鲜牛奶国家标准所规定的水平（5×10^5个／mL）,芽孢总数12h后的测定值为71个／mL,较开始的5个／mL变化不大,大肠菌群12h后为≥2．4×10^4个/100mL,即全部呈阳性;在冷藏条件（0～4℃）下。12h后菌落总数为4．6×10^4、芽孢总数为63个／mL,大肠菌群为≥2．4×10^4个/100mL,说明生鲜山羊奶最好在冷藏条件下储运。     

Bacteriology of washed and unwashed eggs. I. Bacterial counts of egg contents after storage

The influence of egg washing on the bacterial counts of egg contents after subsequent storage was studied. Unwashed eggs were compared to eggs subjected to industrial large-scale machine washing. The washing procedure consisted of sprinkling under pressure with a 43 °G water solution of detergent, rinsing with 47°G tap water, and drying in a stream of hot air (60–65°G). The eggs were stored at 4°C for eight weeks and at 30 °G for 12 days. At the end of the storage periods, the total bacterial count, the number of hemolytic bacteria, and the number of coli-aerogenes in the egg contents were examined. A total of slightly more than 400 eggs were used in the investigation.No coli-aerogenes bacteria were detected in any washed or unwashed eggs. For eggs, stored at 4°C, the logarithmic total bacterial counts were for washed eggs 2.07; 2.42, and for washed 2.08; 1.95 (mean and median values, respectively). The corresponding values for eggs stored at 30 °G were for unwashed eggs 1.40; 1.30, and for washed eggs, 1.62; 1.48. These differences between unwashed and washed eggs are not significant.Hemolytic bacteria were detected in 35.2 % of unwashed and in 33.0 % of washed eggs after cold storage and no significant difference was seen between the number of bacteria in these eggs (logarithmic mean values 2.43 and 2.47, respectively). Nor was any significant difference seen between the counts of the hemolytic bacteria in eggs stored at 30 °G, where these bacteria were detected in 19.6 % of unwashed and in 23.9 % of washed eggs (logarithmic mean values of number of bacteria 2.10 and 2.46, respectively). The importance of obtained results is discussed from the point of view of food hygiene with references to the relevant literature.     

Bacterial shell contamination in the egg collection chains of different housing systems for laying hens

The bacterial eggshell contamination of eating eggs in different commercial housing systems; two conventional cages, one organic aviary system and one barn production, were compared. The total counts of aerobic bacteria and the total counts of Gram-negative bacteria on the shell were used to detect key points where contamination occurred and to study the progress of contamination in the egg collection and transportation chains. The key points in the chain were those where eggs accumulated on a short conveyor belt, initial shell contamination in the alternative housing systems and extra nest-boxes placed on the ground. The high bacterial load of floor eggs (>6.3 log CFU total aerobic flora/eggshell) explains why they cannot be used for eating. On average higher initial shell contamination with total counts of aerobic bacteria was found for eggs from the alternative housing systems compared to the conventional systems; respectively 5.46 compared to 5.08 log CFU/eggshell. However, initial contamination with total counts of Gram-negative bacteria on the shells was less in the alternative systems: 3.31 compared to 3.85 log CFU/shell. Initial bacterial shell contamination tended to correlate positively with the concentration of bacteria in the air of the poultry houses. Storing shell eggs, whether temporarily refrigerated or not, for 9 d or more, resulted in a decrease in bacterial eggshell contamination for both bacterial variables.     

Effects of inulin on performance, egg quality, gut microflora and serum and yolk cholesterol in laying hens

1. The present study was conducted to investigate the effects of inulin on laying hens. A total of 360 Brown Nick laying hens were divided randomly into 6 groups of 60 with 6 replicates of 10 hens and fed on diets containing 0 (control), 0·1, 0·5, 1·0, 1·5 or 2·0% inulin during the 4-week trial. 2. Dietary supplementation of inulin reduced cholesterol concentration (mg/g yolk) and content (mg/egg) in eggs. Cholesterol content in eggs decreased linearly with increasing levels of dietary inulin level. 3. Supplementation of inulin in diets decreased coliform bacteria counts and pH in the caecum. The lowest coliform bacteria counts (6·30 ± 0·03 log10 cfu/g) and pH (6·47 ± 0·01) were obtained in the 2·0% inulin group, the two indices decreasing by 21·6% and 3·0% respectively, compared with the control group. Coliform bacteria count and pH were changed linearly in accordance with increasing levels of dietary inulin level. Caecal Bifidobacteria counts were increased in the 2·0%-inulin group. 4. Inulin supplementation of layer diets did not appear to have any adverse effects on laying rate, egg weight, feed intake, feed conversion efficiency, cracked-egg rate, eggshell thickness or Haugh unit compared with the control laying hens. 5. Therefore, dietary supplementation with inulin may lead to the development of low-cholesterol chicken eggs as demanded by health-conscious consumers.     

禽舍微生物气溶胶含量及其空气动力学研究

采用Andersen-微生物空气样品收集器，选用普通营养琼脂和金黄色葡萄球菌选择培养基对一个种鸡场舍环境空气进行监测。其需氧菌含量从3.12×104到9.01×105，金黄色葡萄球菌含量波动于2.0×103～3.3×104CFU/m3之间。根据微生物气溶胶颗粒在Andersen-收集器不同层级上的分离情况得知，22.5%的需氧菌、1.8%的金黄色葡萄球菌气溶胶颗粒的空气动力学直径(d50)为Φ0.65～2.1μm，它们能进入人、畜的肺泡，对人畜呼吸道构成感染威胁。     

不同储存温度下鸡蛋表面和内部真菌动态研究

试验旨在通过检测商品鸡蛋在不同储存温度和时间蛋壳表面和内容物中真菌的数量和类别，了解真菌污染的动态变化，为改善鸡蛋储存条件并延长保鲜期提供参考。采取冀南某养殖小区不同养鸡场180枚新鲜鸡蛋，分别在25和4 ℃无菌环境下储存42 d，每7 d进行一次蛋壳和蛋液的真菌数量和类别检测。真菌数量检测参照国家标准GB 4789.15-2016；真菌种类鉴定采用形态观察结合rDNA-ITS序列分析法。试验结果显示，鸡蛋内外真菌检出率和数量均随储存时间延长而显著增长；蛋壳比蛋液真菌检出时间早、检出率高，蛋液处理组真菌检出率在21~28 d快速增长；在相同时间点，25 ℃处理组真菌数量（菌落数）显著高于4 ℃处理组，蛋壳处理组显著高于蛋液处理组（P<0.05）；在蛋壳和蛋液中共分离鉴定了168个真菌菌株，分属于18个种（属），其中优势属为青霉属（Penicillium sp.），优势种为草酸青霉（Penicillium oxalicum）；蛋液与蛋壳处理组的总菌落数和分离株数分别呈显著（P<0.05）和极显著相关（P<0.01）。综上，在采样养殖场环境下，鸡蛋的真菌污染普遍存在；样品真菌检出率和菌落总数均随储存时间延长呈明显上升趋势；冷藏（4 ℃）是防止鸡蛋真菌污染扩展的有效方法；蛋液的真菌污染可能主要来自蛋壳表面的真菌污染；样品鸡蛋污染真菌的多样性较高，其优势种属多为环境常在菌，但污染真菌中也有部分致病或产毒种类。     

Pathogenesis of Salmonella enteritidis infection in laying chickens. I. Studies on egg transmission, clinical signs, fecal shedding, and serologic responses

Laying hens were inoculated orally, intracloacally (IC), or intravenously (IV) with Salmonella enteritidis phage type 8 isolates from a human (E700-87) eggs (Y-8P2), or the ovary of a hen (27A). Oral or IV inoculation of 2 x 10(8) to 4 x 10(8) colony-forming units (CFU) of E700-87 caused depression, anorexia, reduced egg production, diarrhea, and some mortality. Lower doses resulted in milder clinical signs. S. enteritidis was cultured from the shells of a few eggs but not from egg contents. Fecal shedding persisted for up to 6 weeks in some birds. Isolate Y-8P2 (10(6) CFU) also caused anorexia, diarrhea, and a drop in egg production. Hens inoculated orally or IC were less severely affected than those inoculated IV. Fecal shedding was intermittent and lasted up to 18 days. Eggshells from the IC-inoculated birds had the highest rate of contamination, and S. enteritidis was isolated from the albumen of 11 and yolk of three of 726 eggs. Oral inoculation of 10(6) CFU of isolate 27A resulted in a bacteremic infection with seeding of the liver, spleen, peritoneum, ovule, and oviduct. However, the birds remained clinically normal with normal egg production. S. enteritidis was cultured from the yolk and albumen of a small number of eggs until 11 days postinfection. Antigen prepared from S. enteritidis detected antibody in more sera than did commercially available S. pullorum antigen in agglutination tests.     

猪K88、K99、987P、F41埃希氏大肠杆菌高密度发酵培养技术的初步探讨

采用高密度发酵和普通深层通气两种方法培养含K88、K99、987P、F41菌毛抗原的四株猪埃希氏大肠杆菌,对其培养液进行活菌数、OD值、pH值、效价的测定。实验结果表明,运用高密度发酵方法培养,各菌活菌数可达4.1×1010~4.9×1010CFU/mL,效价为211~213;运用普通深层通气方法培养,各菌活菌数为0.51×1010~0.59×1010CFU/mL,效价为24~25,可选择高密度发酵方法替代普通深层通气方法培养,用于制备猪埃希氏大肠杆菌K88、K99、987P、F41四价菌毛提纯苗。     

长鬣蜥繁殖生态的研究

2004～2005年,对人工饲养的长鬣蜥繁殖行为和生态习性进行了研究,结果表明：3～7月为长鬣蜥的繁殖期,繁殖行为主要表现为发情求偶、交配和产卵,5～6月为产卵高峰期,每条成熟的雌蜥年产卵2～3窝,平均窝卵数12（7～18）枚;雌蜥每窝产卵间隔33～45 d不等;平均单卵重3.06（2.80～3.50）g;卵径2.63 cm×1.18cm。在自然孵化温度和90%～95%的湿度下孵化期为60～98 d,孵化率52.34%,长鬣蜥幼体初生个体重2.50 g,体全长（头体＋尾）14（4＋10）cm。     

2018年天津市原料奶细菌总数、体细胞数及奶牛乳房炎病原菌、耐药基因调研报告

本研究旨在调查天津市原料奶细菌总数、体细胞数及乳房炎病原菌、耐药基因,了解全市原料奶的质量状况及引起奶牛乳房炎发生的主要原因。采集天津市5家乳品加工企业奶罐车的原料奶样品,用于检测体细胞数和菌落总数;采集天津市奶牛养殖场储奶罐奶样品,用于检测体细胞数;采集奶牛场临床型乳房炎发病乳区的牛奶样品,用于检测乳房炎病原菌及耐药基因。结果显示:2018年天津市乳品加工企业原料奶体细胞数平均值为44.65万/mL,标准差42.41万/mL,变异系数94.97%,最大值为225.50万/mL,最小值为1.20万/mL,SCC≤50万/mL的样品占74.37%,50万/mL200万/mL的样品占3.13%;细菌总数平均值11.54万CFU/mL,标准差26.28万CFU/mL,变异系数227.66%,最大值190.00万CFU/mL,最小值0.095万CFU/mL,细菌总数≤10万CFU/mL的样品占74.37%,10万CFU<细菌总数≤50万CFU/mL的样品占21.25%,50万CFU<细菌总数≤100万CFU/mL的样品占1.88%,100万CFU/mL<细菌总数≤200万CFU/mL的样品占2.50%。2018年天津市奶牛养殖场原料奶体细胞数平均值为38.81万/mL,标准差36.49万/mL,变异系数94.03%,最大值为210.00万/mL,最小值为0.80万/mL,SCC≤50万/mL的样品占79.17%,50万/mL200万/mL的样品占0.83%。乳房炎病原菌检测结果显示:36个样品检出病原菌,总检出率为94.74%;共检出8种病原菌,检出率最高的是乳房链球菌,检出率为73.68%,其他病原体检出率依次为:牛支原体34.21%,牛棒状杆菌13.16%,无乳链球菌10.53%,大肠杆菌5.26%,白色念球菌5.26%,停乳链球菌2.63%,铜绿假单胞菌2.63%。14个样品检出耐药基因,总检出率为36.84%;2种耐药基因的检出率分别为β-内酰胺耐药基因CTX-M934.21%,耐甲氧西林葡萄球菌耐药基因MecA 2.63%。研究表明,2018年天津市原料奶SCC及细菌总数大部分接近欧盟标准,但仍有待进一步提高;引起天津地区临床型乳房炎的3种主要致病菌为乳房链球菌、牛支原体和牛棒状杆菌。