紫外线对水产养殖循环水的杀菌效果

为了研究循环水水产养殖系统紫外杀菌的效果,在循环水系统中对单灯管紫外装置杀灭养殖水中粪大肠菌群的效果进行了试验,研究了紫外灯功率、循环水流速和水的紫外光线透射率对杀菌效果的影响。结果表明,单位水体的紫外线功率越大,杀菌效果越好;水体通过紫外灯杀菌器的流速越大,单次通过杀菌器的杀菌量减少,但由于水体循环次数增加,总杀菌效果加大;254?nm紫外线透射率越大,杀菌效果越好。在理论分析和试验数据的基础上,建立了循环水紫外线杀菌系统的模型,并得到了粪大肠菌群的一价失活系数为0.0062?m2/J。对失活速率常数较小的菌群,增大紫外灯功率杀灭效果较好,而增加日循环次数杀灭效果提高不明显。该研究的结果可为循环水系统紫外线杀菌系统的设计和运行提供依据。     

Research Issues in Inactivation of Listeria monocytogenes Associated with New Zealand Greenshell Mussel Meat (Perna canaliculus) Using High-Pressure Processing

ABSTRACT

New Zealand Greenshell mussels are currently shucked by heat processing, and this can be used as a listericidal step. Shucking by high pressure processing (HPP) has potential benefits in product quality and increased yield, but processors need to understand the effects of this technology on the safety of their product with respect to Listeria monocytogenes. L. monocytogenes was mixed with minced mussel meat, and 2 g samples (in foil pouches) were subjected to HPP at various pressures, times, and temperatures. Of 10 tested strains of L. monocytogenes, the most resistant to HPP at 400 MPa (Food Science Australia strain 2655 isolated from Australian processed meat) was selected for subsequent work. This strain showed two-phase inactivation kinetics in response to time at 400 MPa. Approximately 5 log₁₀ cells/g were rapidly inactivated in a log-linear fashion with time while the remaining cells were inactivated at a slower rate. There was also some evidence of a shoulder in the inactivation curves. In the temperature range tested (10°C–40°C), the log-linear inactivation rates showed linear increases with increasing processing temperature at 400 MPa with a z value of 29.1 min.     

Incidence,Growth, and Inactivation of Listeria monocytogenes in Cooked and Peeled Cold-Water Shrimp

ABSTRACT

Cooked and peeled cold-water shrimp (Pandalus jordani) naturally contaminated with Listeria monocytogenes were obtained from a processor for a series of studies to determine the level of contamination and growth characteristics of this bacterium in the naturally contaminated product. L. monocytogenes was isolated from every 25-g sample of individually quick frozen (IQF) shrimp that was tested. The level of contamination in each composite sample ranged from 5 to 16 colony forming units (CFU) per 25 g. When individual shrimp taken from the 25-g sample portions were tested separately, samples positive for L. monocytogenes ranged from 1 of 12 to 5 of 15 shrimp tested. The project also evaluated the effectiveness of three methods to inactivate the bacterium: ozone, chlorine dioxide, and steam as possible product reconditioning strategies. Ozone and chlorine dioxide were both found to be ineffective reconditioning treatments for shrimp naturally contaminated with L. monocytogenes. Experiments with steam conducted at the laboratory and later at the shrimp processing plant verified that shrimp contaminated with L. monocytogenes could be safely reconditioned by steam pasteurization. Steam was used successfully to pasteurize several thousand pounds of contaminated shrimp in the processing plant. When the naturally contaminated product was packaged in either oxygen-permeable or impermeable films and stored at 5°C and 10°C, the product was deemed spoiled by sensory evaluation after 9 days of storage, at which time the L. monocytogenes population were 3 × 10⁴ CFU per g. By comparison, when an isolate (strain 4311) from naturally contaminated shrimp was inoculated onto the pasteurized shrimp at a concentration of 12 cells /25g, the L. monocytogenes population reached 3.0 × 10⁸ per g after 9 days of storage. The pasteurization process used in this study would not be effective in inactivation of Clostridium botulinum. Ready-to-eat-shrimp must therefore be stored below 3°C or frozen.     

紫外线诱导栉孔扇贝雄核发育的研究

研究了利用紫外线诱导栉孔扇贝雄核发育的条件。表明紫外线(254nm)对卵子染色质失活是有效的。在强度为2.8mW·cm-2·s 1的紫外线下照射20s的卵子与正常精子混合后能保持一定的受精率(60.2%),且D形幼虫发生率为0。染色体检查结果显示此时单倍体率最高(49.2%)。说明在强度为2.8mW·cm-2·s-1的紫外线下照射20s是获得雄核发育单倍体的适宜条件。研究发现受精率和D形幼虫发生率随照射时间的增加而下降,遗传失活的卵子与正常精子受精后其胚胎发育至D形幼虫前期停止。实验中各处理组均出现非整倍体。出现的原因可能由于紫外线照射剂量对卵子染色体遗传失活的作用程度不同以及DNA的光修复。     

鸡葡萄球菌灭活疫苗的研究

本项研究制出了三种鸡葡萄球菌灭活疫苗,即无佐剂灭活疫苗;油包水乳剂疫苗(以下简称单相油乳剂疫苗);油包水-水包油乳剂疫苗(以下简称双相油乳剂疫苗).用油乳剂疫苗对鸡免疫接种一次,能产生良好的免疫力;无佐剂灭活疫苗免疫接种三次,才能产生较好免疫力。单相油乳剂疫苗粘性较大,不易注射。三种类型的疫苗相比较,双相油乳剂疫苗优点较多,这种乳剂疫苗稳定,粘性很小,容易注射.免疫保护指数为88.6～94.2。20～25日龄雏鸡免疫接种一次能健康度过葡萄球菌病的严重危害时期。     

鸡传染性支气管炎的诊断及综合防治研究

对衡阳地区一些鸡场相继发生一种疑似NIB的疫病进行了研究。经实验室检查分离到2株病毒(H1株,W1株),根据分离毒鸡胚培养传代后的鸡胚病变、死亡及侏儒胚胎的出现以及生物学特性及幼鸡2次攻毒试验证明,2株分离毒均为NIBV,结合临床资料综合诊断为NIB。采集具有典型病变的脏器制成组织灭活苗治疗NIB,结合其它的综合措施,对衡阳地区8群共21500只发病鸡进行治疗,其死亡率分别为8%~15.8%,对照组死亡率均在32%以上,差异极显著(P<0.01)。     

香菇金针菇远缘亲本原生质体融合及融合子检测

采用１５ｇ／Ｌ溶壁酶处理获得了香菇单核体Ｌ３８－Ｓ０３，Ｌ５２－＾ａｄｅ和金针菇单核体Ｆｖ１１－Ｓ２３的原子质体。１ｇ／Ｌ焦磷酸二乙酯灭知的Ｌ３８－Ｓ０３和腺嘌呤缺陷型Ｌ５２－＾ａｄｃ的原生质分别与８ｇ／Ｌ碘代乙酰胺灭知的Ｆｖ１１－Ｓ２３的原生质体进行ＰＥＧ－Ｃａ＾２＋促融合，在ＲＣＭ，ＩＲＭＭ培养基上再生，得到１４２个融合子，其中１７个菌株能结实出菇。筛选出Ｆ０１，Ｆ０２和Ｆ０３的３个融合子菌株     

超临界CO2杀灭大肠杆菌过程中菌体蛋白变化的研究

通过SDS-聚丙烯酰胺凝胶电泳,结合超临界CO₂对大肠杆菌的杀菌曲线,研究超临界压力、温度和处理时间对大肠杆菌菌体蛋白的影响。结果表明：超临界CO₂在杀灭大肠杆菌过程中,可显著降低菌体碱溶性（pH8.0）蛋白的溶解性,但对菌体总蛋白含量和种类没有影响;37 ℃下超临界CO2处理大肠杆菌30 min,压力为10MPa时,大肠杆菌存活率为2.8%,菌体碱溶性蛋白的溶解性显著降低,但当压力增加到50MPa时,大肠杆菌存活率和碱溶性蛋白溶解性变化不明显;超临界温度和处理时间对菌体碱溶性蛋白溶解性的影响与大肠杆菌在超临界CO₂中的存活趋势基本一致可,随处理时间的延长和温度的增加大肠杆菌存活率逐渐降低到0,碱溶性蛋白溶解性逐渐降低,直至部分蛋白带消失,但菌体总蛋白含量和种类并没有明显变化;升高温度比增加压力更能显著地导致菌体碱溶性蛋白变性,溶解性下降。     

实验条件下山羊绒洗净因素对口蹄疫病毒的影响

模拟我国和蒙古国洗净羊绒企业山羊绒洗涤工艺,进行了不同的洗涤水温及作用时间、不同的烘干温度及作用时间对口蹄疫病毒灭活作用的检测。结果表明,水温在64℃以下处理60min不能灭活羊绒中的口蹄疫病毒NM-zg99毒株,65℃处理60min、66℃处理45min、75℃处理10min、80℃处理5min能灭活羊绒中的口蹄疫病毒;高温烘干对羊绒中口蹄疫病毒的灭活与温度和作用时间密切相关,70℃处理约35min、75℃处理约25min能灭活口蹄疫病毒,80～90℃处理20min、95～105℃处理15min、110℃处理10min能使口蹄疫病毒失活。该试验结果为我国制定进口洗净毛、绒检验标准提供了参考数据,并对洗净羊绒企业改进羊毛、绒洗涤工艺具有指导意义。