Diminution of Campylobacter colonization in neonatal pigs reared off-sow

Pigs may be a natural reservoir of Campylobacter and can be colonized as early as 24 h after birth. The purpose of the present study was to evaluate what effect early removal of piglets from Campylobacter-positive sows has on Campylobacter prevalence in neonates. In two trials, piglets were removed from sows within 24 h of birth and were reared in nurseries isolated from sows for 21 days. From the neonates rectal swabs were cultured for Campylobacter, and Campylobacter status of the isolated piglets was compared to that of littermates reared on sows. The nurseries consisted of wire-floored farrowing crates that were equipped with heaters and self-feeders. In trial I, the Campylobacter prevalence in nursery-reared piglets was 13 of 14 on day 2 and 0 of 14 on day 20. Campylobacter prevalence in the sow-reared piglets was 8 of 9 from days 2 to 20. In trial II, 12 of 29 on day 2, and 5 of 26 on day 20, of the nursery-reared piglets were culture positive for Campylobacter. For the sow-reared piglets, Campylobacter prevalence was 7 of 15 on day 1 and 15 of 15 (100%) on day 20. These data suggest that successful permanent colonization of the gut by Campylobacter is probably related to constant exposure of piglets to Campylobacter-positive feces. Campylobacter prevalence may be diminished in neonates that are reared off-sow in isolated nurseries.     

Investigation of Campylobacter in reared game birds

A total of 103 pooled samples of neck skin and meat from pigeons for the table and neck skin of pheasant were analyzed bacteriologically to determine the presence of Campylobacter. Colonies suspected of being Campylobacter were grown from 15.8% of pigeon neck skin samples, 12.5% of pigeon meat samples, and 50% of pheasant neck skin samples after culturing, and in 6.9% of pigeon neck skin samples (4 x 10(2) to 2 x 10(3) CFU/g) assessed quantitatively without preculturing. PCR confirmed the presence of Campylobacter spp. in 5.26 and 3.44% of samples of pigeon neck skin and meat, respectively. Species identified from pigeon neck skin samples by PCR were C. jejuni (3 of 3) and C. coli (1 of 3); no C. lari was identified. No species were identified by PCR in pheasant neck skin. We conclude that the small number of Campylobacter-positive pigeon samples presents a low risk of Campylobacter infection to Italian consumers, particularly since pigeon is always well cooked before consumption, although there is always the possibility of cross-contamination with raw or insufficiently cooked foods particularly during food preparation.     

不同条件下蔬菜中亚硝酸盐含量的变化

研究8种蔬菜在室温下(20～25℃)、低温下(4℃)贮藏后水浸泡和不用水浸泡情况下亚硝酸盐含量的变化.试验结果表明:室温条件下贮藏的蔬菜亚硝酸盐含量在1～2 d内会达到高峰,然后出现下降,随着时间继续延长,亚硝酸盐含量会逐渐升高.亚硝酸盐含量低温条件下较室温下低.不论室温下还是低温下贮藏的蔬菜,用水浸泡1 h后,其亚硝酸盐含量都会比不浸泡低.     

Survival of Escherichia coli O157:H7 and Campylobacter jejuni in bottled purified drinking water under different storage conditions

Survival of Escherichia coli O157:H7 and Campylobacter jejuni that were separately inoculated into bottled purified drinking water was investigated during storage at 22, 4, and -18 °C for 5, 7, and 2 days, respectively. Two inoculation levels were used, 1 and 10 CFU/ml (10(2) and 10(3) CFU/100 ml). In samples inoculated with 10(2) CFU/100 ml, C. jejuni was not detectable (>2-log reduction) after storage under the conditions specified above. E. coli O157:H7 was detected on nonselective and selective media at log reductions of 1.08 to 1.25 after storage at 22 °C, 1.19 to 1.56 after storage at 4 °C, and 1.54 to 1.98 after storage at -18 °C. When the higher inoculation level of 10(3) CFU/100 ml was used, C. jejuni was able to survive at 22 and 4 °C, with 2.25- and 2.17-log reductions, respectively, observed on nonselective media. At these higher inoculation levels, E. coli O157:H7 was detectable at 22, 4, and -18 °C, with log reductions of 0.76, 0.97, and 1.21, respectively, achieved on nonselective media. Additionally, E. coli O157:H7 showed significant differences in culturability (P<0.05) on the nonselective and selective culture media under the different storage conditions, with storage at -18 °C for 2 days being the treatment most inhibiting. The percentage of sublethal injury of E. coli O157:H7 ranged from ～33 to 75%, indicating that microbial examination of bottled water must be done carefully, otherwise false-negative results or underestimation of bacterial numbers could pose a health risk when low levels of pathogens are present.     

不同处理条件对乳铁蛋白抑菌性的影响

对不同处理条件下乳铁蛋白(Lactoferrin LF)的抑菌性进行了研究.结论表明:LF经过70 ℃以下的巴氏杀菌,不会影响到其抑菌活性.LF在弱碱性的条件下抑菌效果最好,环境pH值的变化时,LF针对金黄色葡萄球菌的抑菌活性变化较大,在pH值为6～10之间,LF对沙门氏菌有抑菌效果.LF在人工胃液中抑菌效果明显增加.     

不同温度条件下玉米穗红外干燥试验研究

针对玉米收获后由于气候原因导致霉变发芽、公路晾晒造成严重污染,或采用“先脱粒后干燥”工艺导致籽粒破碎严重等问题,按照“玉米穗干燥→脱粒→玉米籽粒干燥”分段干燥工艺设计了一种玉米穗红外干燥试验台.试验结果表明,采用等温干燥时,较佳的干燥温度为58℃左右;采用变温干燥时,宜选用“先低后高”的变温方式,且在保证干玉米品质的前提下,应尽量选用较高的起始干燥温度;无论采用等温干燥还是变温干燥,其干燥温度均不得高于60℃.该玉米穗红外干燥试验台干燥均匀性好、设备的空间利用率高,解决了收获期玉米霉变或采用“先脱粒后干燥”工艺而导致的籽粒破碎率严重等问题,为玉米穗红外干燥机的研制提供了参考.     

Sources and spread of thermophilic Campylobacter spp. during partial depopulation of broiler chicken flocks

The practice of partial depopulation or thinning (early removal of a portion of birds from a commercial broiler flock) is a reported risk factor for Campylobacter colonization of residual birds because of the difficulty in maintaining biosecurity during the thinning process. The effect of this practice was studied in detail for 51 target flocks, each at a different growing farm belonging to one of seven major poultry companies throughout the United Kingdom. On 21 of these farms, the target flock was already colonized by Campylobacter, and at slaughter all cecal samples examined were positive, with a mean of 8 log CFU/g. An additional 27 flocks became positive within 2 to 6 days of the start of thinning and had similarly high levels of cecal carriage at slaughter. Just before the thinning process, Campylobacter was isolated frequently from the farm driveways, transport vehicles, equipment, and personnel. Strains from seven farms on which flocks became colonized after thinning were examined by pulsed-field gel electrophoresis typing. An association was found between strains occurring at specific sampling sites and those isolated subsequently from the thinned flocks. The results indicated that particular strains had spread from one farm to another when the farms were jointly owned by the same company and employed the same bird-catching teams and/or vehicles. These results highlight the need for better hygiene control in relation to catching equipment and personnel and more effective cleaning and disinfection of vehicles and bird-transport crates.     

对米根霉在不同条件下产酸情况的研究

乳酸是目前世界上公认的3大有机酸之一,其广泛应用于食品、医药、化工、制革、纺织、环保和农业等诸多领域。用微生物发酵法生产L-乳酸可以达到较高的纯度要求。根霉属中的米根霉(Rhizopus oryzae)是目前发酵生产L-乳酸的重要菌株,本课题研究的是从自然界选取的米根霉在不同条件下的产酸情况。采用分析方法包括还原糖的测定,pH测定,NaOH滴定确定乳酸产量。通过对不同条件下产酸情况的分析,可以优化产酸条件,提高产酸率。最终确定出在葡萄糖浓度为130g/L,氯化铵作为氮源,其浓度在2.0g/L的条件下,实验室菌株的最佳产酸量是44.2g/L,葡萄糖的转化率是40.1%。     

不同冻结条件下罗非鱼片的质构分析

对不同条件(-7,-21,-31℃)下冻结的罗非鱼片进行质地剖面分析(TPA)。研究罗非鱼片的硬度、内聚性、弹性、胶着性、咀嚼性的参数变化;分析罗非鱼片的干耗、汁液流失率的品质变化特征。结果表明,随着冻结温度的降低,弹性呈下降趋势;硬度、内聚性、胶着性、咀嚼性呈上升趋势;干耗、汁液流失率也呈现明显下降趋势,说明低温快速冻结条件比缓冻条件抑制罗非鱼体内酶活性更有效,减少蛋白质分解变性,从而保持鱼片的风味和品质。     

不同培养条件下酿酒酵母菌的转录组差异分析

从组学水平分析富硒条件下酿酒酵母菌(Saccharomyces cerevisiae)内在分子机制,为酿酒酵母菌富硒研究及富硒基因的挖掘利用提供理论依据。该研究以不加硒培养的酿酒酵母菌作为对照组Kb,以加20μg/mL硒培养的酿酒酵母菌为实验组Se,利用Illumina高通量测序平台对两组进行转录组测序,通过生物信息学方法对数据进行分析处理。结果表明,转录组测序共获得6 445个Unigenes,分别有1 401个(21.74%)、3 665个(56.87%)、5 630个(87.35%)、6 112个(94.83%)、6 077个(94.29%)、5 059个(78.49%) Unigenes被注释到GO、KEGG、COG、NR、Swiss Prot和Pfam数据库,共有6 150个(95.42%) Unigenes得到注释。在GO功能注释中,共得到41个GO功能小类,在KEGG代谢通路分析时,获得了113条KEGG通路。该转录组测序数据质量高,结果覆盖面广,为酿酒酵母菌富硒基因挖掘和研究提供了一定的理论参考。     

香蕉在不同冻结条件下的品质变化

探讨了香蕉分别经复合护色剂和热烫预处理后其在不同冻结温度分别为(-15、-25、-35、-45、-55、-70℃)条件下的冻结状态及其品质变化。复合护色剂与热烫预处理相比,随着冻结温度下降,香蕉在冻结过程其可溶性固形物、L值、p H值变化趋势及对细胞组织结构保护效果均优于热烫处理,结合光学显微镜观察香蕉组织切片,-35、-45、-55、-70℃时,冻结温度对香蕉细胞机械破坏程度无明显差异,综合考虑设备、成本等因素,采用复合护色剂预处理和-35℃温度条件冻结较适宜。     

Pre-harvest surveillance of Campylobacter and Salmonella in Danish broiler flocks: a 2-year study.

In national surveillance programmes of broiler flocks carried out in Denmark during 1998 and 1999, 89,110 samples for Campylobacter representing 8911 broiler flocks were taken at 10 different abattoirs, and 44,550 samples for Salmonella were taken from the same flocks in the broiler houses at the farms. Of the swabs, 42.5% were Campylobacter positive. Most positive samples were found during July, August and September, while the lowest number of positive samples were found during January, February, March and April. Of the flocks, 5.5% were Salmonella positive, but no seasonal variation was observed. For each flock, the presence of Campylobacter and Salmonella was recorded in order to estimate the possible correlation between colonisation with the two pathogens. In conclusion, no significant effects on intensive cleaning and disinfection procedures on Campylobacter occurrence could be demonstrated, and no significant correlation between occurrence of Campylobacter and Salmonella infections in Danish broilers could be demonstrated which is in contrast to previous observations on concurrent colonisation of broilers with these two zoonotic pathogens.     

不同生态条件下的烤烟硼营养研究

在我国7个主产烟省采用"统一栽培法",研究了各生态条件下烤烟营养中硼的积累与分配规律.试验结果表明,烤烟叶片、烟杈(芽)中硼含量明显高于根、茎,其含量以北方高于南方;而根、茎中硼含量正好相反.硼素的积累过程呈明显的Logistic生长曲线关系.大田生长前期南北烟区烟株中硼素积累特征基本一致,但在栽后30 d以后北方烟区烟株中积累量和积累速率远远高于南方烟区.烟株中硼素积累量占全株总积累量的比例为栽后60 d以前南方烟区高于北方烟区,以后则是北方烟区高于南方烟区.在我国南北烟区烟株含硼量(浓度)无明显的差异,但硼积累量差异明显.土壤pH、全氪和速效氮对烟株硼的积累有一定的促进作用,土壤有机质升高则对烟株中硼的积累不利;平均气温、最高温度、10cm地温和日照时数与烟株硼的积累呈正相关.     

荠菜不同贮藏条件几项营养指标的研究

分别对荠菜在不同贮藏条件下的几项营养指标进行了测定。结果表明,随着贮藏时间的延长,荠菜中可溶性蛋白质、维生素C、叶绿素的含量均表现为下降的趋势;总胡萝卜素的含量则表现为上升的趋势。冷藏组可溶性蛋白质、维生素C、叶绿素几项指标损失量均低于保鲜组和对照组;总胡萝卜素增加量也低于保鲜组和对照组。     

Properties of starches separated from potatoes stored under different conditions

Starches from 11 potato cultivars stored at five temperatures (4, 8, 12, 16 and 20 °C) for 120 days were evaluated for physicochemical, thermal and pasting properties. Amylose content and swelling power increased with increase in storage temperatures. The proportion of small size granules was higher in starches from potatoes stored at 4 °C. The starch granules of stored potatoes were slightly rough-surfaced and pitted; the effect was pronounced in those stored at 4 °C. Starches from potatoes stored at 4 °C showed lower onset gelatinization temperature and conclusion temperature than did starches from potatoes stored between 8 and 20 °C. Starches from potatoes stored at higher temperature (20 °C) showed higher peak viscosity, set back, as well as gel hardness, chewiness and gumminess than did starches from those stored between 4 and 16 °C. Amylose content showed significant positive correlation with gumminess and setback while swelling power showed significant positive correlation with peak viscosity and hot-paste viscosity.     

Acute toxicity of mercury to Daphnia magna under different conditions

We investigated the variations of acute toxicity of mercury (Hg) in Daphnia magna under different temperatures, population origins, body sizes, and Hg pre-exposures. We measured Hg concentrations in the water and in the surviving daphnids, and used the subcellular fractionation approach to determine Hg in the metal-sensitive fraction (MSF) to predict Hg toxicity. The 24-h median lethal concentrations and 24-h lethal body burden were 12-55 microg L(-1) and 10-26 mg kg(-1) wet wt, respectively. High Hg tolerance accompanied by reduced Hg uptake occurred in the daphnids under extreme conditions (low temperature and high pre-exposure to Hg). Correlating Hg levels in different compartments and daphnid survival resulted in the following order of sequence: aqueous Hg > whole body Hg > Hg in the MSF. However, the threshold lethal concentration of Hg (concentration causing 1% mortality) based on the concentration of Hg in the MSF was the best indicator of Hg toxicity. Therefore, the subcellular fractionation approach is less useful in explaining acute toxicity than is sub-lethal Hg toxicity. The number of Hg binding sites in the animals varied under different conditions but the affinity of the transporter to Hg generally decreased as the animals' tolerance increased. Mercury tolerance under different conditions could be enhanced by reducing the Hg uptake, enhancing the intrinsic tolerance, and/or increasing the detoxification activity.     

Evaluation of the Labeled Hedonic Scale under different experimental conditions

The present study explored the performance, psychophysical properties, and potential limitations of the Labeled Hedonic Scale (LHS) in two different test conditions. The LHS was first compared against the 9-point hedonic scale in a psychophysical laboratory setting by having subjects evaluate two sets of taste stimuli with different size of hedonic ranges. Both scales showed equal discrimination power, but the LHS was more resistant to ceiling effects and its data satisfied the normality assumption for statistical analysis. In the second experiment, subjects with different levels of prior experience with the 9-point scale were recruited to evaluate juice samples and food item names in a large-scale consumer test, after receiving either common written instructions or detailed instructions emphasizing the use of the LHS. Improper use of the LHS (e.g. categorical ratings) was evident for those who received written instructions, especially among subjects who had previous experience with the 9-point scale. The present results support the efficacy of the LHS in various test settings, while highlighting the importance of providing adequate instructions to subjects to fully utilize its advantages.     

现代高速纸机条件下的品质管理

高速大型纸机相比以前的小型纸机,最主要特点就是单位时间内产量大幅度的提升,人的检验效率远远不能满足纸机的生产效率。要依靠从原辅材料到产成品整个过程的所有参与者、依靠整个过程的细节控制、依靠先进的QCS控制系统及产品走上市场的使用信息等所有过程的控制,关键是过程的稳定和过程的监控及每一位员工的重视,将异常杜绝在生产过程当中。     

不同包装条件下精酥油的品质变化研究

对实验室制作的新鲜精酥油,采用真空、薄膜和普通塑料进行包装,并分别置于4℃和室温下进行贮存,依据相关检测方法及标准,定期测定水分含量、酸价、过氧化值、菌落总数及感官指标,研究精酥油在不同贮存条件下的品质变化。结果表明,在4℃冷藏条件下,真空包装相对于其他两种包装可以更好保持精酥油的水分含量;真空包装能够有效的抑制精酥油在贮存期间内的酸价增加,其次是薄膜包装和普通塑料包装;薄膜包装在抗氧化方面与真空包装效果相差不大,并且在4℃冷藏条件下相较于真空包装可以更好的防止精酥油的氧化;相比于其他两种包装,精酥油在薄膜包装下的菌落总数较低;依据感官评定标准,室温下贮存的精酥油保质期只有61d,而4℃冷藏条件下的精酥油保质期超过76d。