三相液相微萃取-高效液相色谱法测定饮品中有机酸

建立了-种利用三相液相微萃取技术进行样品前处理. 高效液相色谱进行测定饮品中酒石酸、苹果酸和柠檬酸的分析方法. 研究表明,该样品前处理方法集萃取、富集,净化为一步,具有快速、有效、绿色的特点;酒石酸、苹果酸和柠檬酸的检测限(S/N=3)分别为0. 62μg·mL-10. 35 μg·mL-1、0. 16 μg·mL-1.回收率在88%～103. 2%之间,相对标准偏差小于5%.     

单胞菌产几丁质酶的酶学性质研究

对从海水中分离得到的嗜水气单胞菌所产的几丁质酶的酶学性质进行研究.其最适pH为7.0左右,最适反应温度为45 ℃左右.在40 ℃以下有良好的热稳定性,12 h仍有50%残余酶活.Mg2 对酶有激活作用,Cu2 和Al3 对酶有明显的抑制作用.该酶对底物的亲和力很大,水解几丁质的Km值为29.15 g/L.     

葡萄酒酿造过程中酸的添加

在葡萄汁或葡萄醪(酒)中加入酸。会引起pH值的降低和滴定酸的增加，优化pH环境，有利于增加SO2的作用效果；抑制与氧化和微生物败坏的有关反应；增加色密度和红葡萄酒的色调；增加酶和皂土作用的效果和提高陈酿潜力。添加的酸有酒石酸、苹果酸、柠檬酸；添加时间为破碎后和分离后。     

Effect of High Hydrostatic Pressure on Aeromonas hydrophila AH 191 Growth in Milk

Abstract: Exposure to high pressure is an efficient method of bacterial inactivation that is particularly important for reducing the microbial load present in foods. In this study, we examined the high pressure inactivation of Aeromonas hydrophila AH 191, a virulent strain that produces aerolysin, a cytotoxic, enterotoxic, and hemolytic toxin. High pressure treatment (250 MPa for 30 min at 25 °C in 0.1 M PBS, pH 7.4) of A. hydrophila grown in milk reduced bacterial viability by at least 9 orders of magnitude. Under these conditions, the enterotoxic, hemolytic, and cytotoxic activities of A. hydrophila culture supernatants were unaltered. These results indicate the need for caution in the use of high pressure for food processing since although truly toxigenic bacteria may be inactivated, their toxins may not be, thus posing a risk to human health. At higher pressure (350 MPa) the inactivation of bacteria was much more effective. Scanning electron microscopy showed a significant decrease in the number of bacteria after higher pressurization (350 MPa for 1 h) and transmission electron microscopy showed irregular shaped bacteria, suggestive of important cell wall and membrane damage, and cytoplasm condensation. Practical Application: High pressure inactivates Aeromonas hydrophila efficiently but is enhanced when combined with moderate temperature (40 °C). The biological activities of toxins from this bacterium are unaltered under these conditions.     

滤纸片法筛选抑制嗜水气单胞菌群体感应的乳酸菌及抑制作用分析

采用滤纸片法从传统发酵蔬菜中筛选抑制嗜水气单胞菌群体感应的乳酸菌菌株,应用96?孔板法测定其对生物膜的抑制率,光学显微镜和扫描电镜观察其对嗜水气单胞菌生物膜形成的影响,同时以蛋白酶、嗜铁素、群集及泳动为指标研究其对嗜水气单胞菌毒力作用的影响。结果表明：来源于辽宁锦州酸菜的乳酸菌菌株SCT-2对嗜水气单胞菌群体感应有明显抑制作用,当其代谢产物粗提物质量浓度为8?mg/mL时,对嗜水气单胞菌生物膜抑制率为45.16%,光学显微镜下显示菌株SCT-2粗提物可有效抑制嗜水气单胞菌生物膜的形成,扫描电镜结果进一步表明菌株SCT-2粗提物不仅降低了嗜水气单胞菌生物膜的生成量,而且使其生物膜断裂。8?mg/mL的SCT-2粗提物可使嗜水气单胞菌蛋白酶和嗜铁素的分泌量分别减少27.18%和22.11%,对信号分子的降解率为32.27%,且对嗜水气单胞菌的群集和泳动现象抑制明显。经生理生化和16S?rRNA鉴定菌株SCT-2为植物乳杆菌（Lactobacillus plantarum）。从传统东北酸菜中获得对嗜水气单胞菌群体感应有抑制作用的植物乳杆菌SCT-2,为开发一种抑制嗜水气单胞菌群体感应的乳酸菌生物制剂提供了理论支持。     

The growth of Aeromonas hydrophila K144 in ground pork at 5 degrees C

The influence of NaCl, pH, atmosphere, and background microflora on the growth and/or survival of Aeromonas hydrophila K144 was studied in ground pork held at 5 degrees C. In ground pork, A hydrophila was sensitive to pH values below 6.0 in the form of either a low starting pH in the pork itself or induced by lactic acid bacteria action on added glucose. Growth of the organism is inhibited by NaCl levels of 3% (w/w) (approx. 4% brine content). A hydrophila grew in vacuum-packaged ground pork; its growth was diminished by the presence of the naturally occurring meat microflora. Except for pH values below 6.0, conditions which inhibited growth permitted survival of the organisms for extended periods. Data indicate that the growth of A. hydrophila in ground pork can be controlled by factors such as NaCl, pH, and background microflora. In general, measures designed to control other foodborne pathogens appear adequate to limit A. hydrophila.     

一起嗜水气单胞菌引起的食物中毒调查

目的 了解本次食物中毒中毒原因及可疑食物污染来源.方法 采用病例对照研究方法,并采集可疑食物及病例标本进行检测.结果 共发生病例48例,症状主要为腹痛(100％)、腹泻(85％)、发热(40％)等.潜伏 期中位数为25 h,进食白切鸡是危险因素(OR=6.0,95％ CI:2.0～17),且与发病呈剂量反应关系((x2趋势=4.5,P=0.03).白切鸡及病例粪便中检出嗜水气单胞菌.结论 进食被嗜水气单胞菌污染的白切鸡是本次食物中毒发生的主要原因,建议加强农村游厨的食品卫生安全知识培训,防止类似事件发生.     

高效液相色谱法对蓝莓果实中8 个有机酸含量的测定

建立同时测定蓝莓果实中8 个有机酸类成分含量的高效液相色谱法,并利用该方法测定26 个不同品种蓝莓果实中的有机酸含量。结果表明,所测品种中塞拉的有机酸含量最高,达25.135 26 mg/g鲜果,最低的为克瑞顿,仅含2.368 31 mg/g鲜果。该方法简便、快速、准确,具有良好的重复性和回收率,可作为蓝莓果实中有机酸含量的测定方法。     

原汁苹果醋中的有机酸

以苹果汁为原料 ,采用液态酒精发酵和醋酸发酵法制作苹果醋 ,采用反相高效液相色谱法分析苹果醋中有机酸 ,研究了苹果品种、醋酸菌种、醋酸发酵方法及过程对有机酸的影响。认为苹果酸是苹果醋中的主要有机果酸 ,其与液态粮食醋有机酸组成的差别主要体现在苹果酸、酒石酸和乳酸的含量上 ,苹果品种是影响原汁苹果醋中有机酸的种类和含量主要因素 ,醋酸菌在醋酸发酵过程中有代谢各种有机酸的作用 ,发酵方法会影响醋酸菌对有机酸代谢作用的程度 ,试验中所采用的 5种醋酸菌在醋酸发酵过程中通过消耗苹果酸、乳酸、琥珀酸 ,而产生和积累柠檬酸。     

Carnosine Increases Irradiation Resistance of Aeromonas hydrophila in Minced Turkey Meat

The effect of carnosine on irradiation inactivation kinetics of Aeromonas hydrophilawas studied. In phosphate buffer, carnosine had no effect on survival of the pathogen, whereas in turkey meat supplemented with carnosine the adverse effect of irradiation on A. hydrophila was reduced. Peroxy radicals were toxic to A. hydrophila , and this effect was counteracted by carnosine. Accordingly, in a kinetic test carnosine was capable of scavenging peroxy radicals. These results indicate that a free radical scavenger antioxidant such as carnosine can increase the radiation resistance of A. hydrophila in meat due to the inhibition of lipid peroxidation caused by radiolysis.     

Microbiological Properties of Pork Cheek Meat as Affected by Acetic Acid and Temperature

Our objective was to determine the effect of acetic acid (AA) and temperature in inhibiting Salmonella typhimurium, aerobic plate counts (APCs) and total coliforms on pork cheek meat. Compared with initial APCs of control cheeks, a reduction in log₁₀ CFU/cm² APC by more than 78.6% was found in all samples that were treated with 20 and 40° acetic acid (P < 0.05). Additionally, total coliforms for acidtreated cheeks were lower for both AA treatments (P < 0.05). Cheeks (n = 10/treatment) were also sprayed in a commercial pork slaughter facility carcass wash with 2% AA (25°) and compared to control (non-treated) cheeks. The incidence of Salmonella decreased by 67% for acid-treated cheeks (P < 0.05). A significant decrease in APCs and coliforms occurred for the acid-treated cheeks (P < 0.05).     

Growth of and toxin production by Aeromonas hydrophila and Aeromonas sobria at low temperatures

The effects of different temperatures on the growth and toxin production of Aeromonas hydrophila and Aeromonas sobria were studied. The results showed that these Aeromonas species are not only able to grow at low temperatures (e.g. at 4 and 10 degrees C) but may also produce cytotoxin, hemolysin and enterotoxin under suitable growth conditions.     

Fate of Listeria monocytogenes and Aeromonas hydrophila on Catfish Fillets Cooked in a Microwave Oven

Channel catfish fillets were inoculated with SJ lo⁶ cell/cm² each of Listeria monocytogenes and Aeromonas hydrophila and cooked in a microwave oven to internal temperatures of 55, 60, and 70°C. The fillets were either left uncovered or covered with polyvinylidene chloride films during cooking. A. hydrophila populations were reduced to nondetectable levels on covered fillets cooked to 70 °C. At 60 °C, L. monocyrogenes populatoins were reduced by = 4 logs for covered and by 2 logs for uncovered fillets. Covering fillets increased lethality at each temperature; however, some pathogens could survive at < 60 °C.     

Survival and Growth of Probiotic Lactic Acid Bacteria in Refrigerated Pickle Products

We examined 10 lactic acid bacteria that have been previously characterized for commercial use as probiotic cultures, mostly for dairy products, including 1 Pediococcus and 9 Lactobacilli. Our objectives were to develop a rapid procedure for determining the long‐term survivability of these cultures in acidified vegetable products and to identify suitable cultures for probiotic brined vegetable products. We therefore developed assays to measure acid resistance of these cultures to lactic and acetic acids, which are present in pickled vegetable products. We used relatively high acid concentrations (compared to commercial products) of 360 mM lactic acid and 420 mM acetic acid to determine acid resistance with a 1 h treatment. Growth rates were measured in a cucumber juice medium at pH 5.3, 4.2, and 3.8, at 30 °C and 0% to 2% NaCl. Significant differences in acid resistance and growth rates were found among the 10 cultures. In general, the acid resistant strains had slower growth rates than the acid sensitive strains. Based on the acid resistance data, selected cultures were tested for long‐term survival in a simulated acidified refrigerated cucumber product. We found that one of the most acid resistant strains (Lactobacillus casei) could survive for up to 63 d at 4 °C without significant loss of viability at 10⁸ CFU/mL. These data may aid in the development of commercial probiotic refrigerated pickle products.     

益生菌发酵苹果汁工艺优化及有机酸的变化

以红富士苹果为原料,进行乳酸菌发酵苹果汁工艺条件优化并分析发酵期间苹果汁有机酸的变化。选择Lactobacillus paracasei 20241、Bifidobacterium animalis 6165、Streptococcus thermophilus 6063和Lactobacillus acidophilus 6005混合发酵苹果汁,以活菌数和感官评分为主要指标,在单因素试验基础上进行响应面优化试验,研究不同的菌种比例、接种量、发酵时间等对苹果汁活菌数和感官评分的影响。结果表明,乳酸菌发酵苹果汁的优化工艺条件为菌种比例1∶1∶1∶1、接种量2%、发酵时间24 h、发酵温度37℃,在此条件下得到的活菌数为1.985×108 CFU/mL,感官评分为80.23分。采用最佳工艺条件发酵苹果汁,利用高效液相色谱法对发酵过程中苹果汁有机酸的变化情况进行分析,结果表明:经过发酵后,苹果酸和琥珀酸含量下降明显(P0.05),而乳酸、奎宁酸、柠檬酸、酒石酸、丙酮酸和莽草酸含量均显著提高(P0.05)。     

传统发酵蔬菜中拮抗温和气单胞菌的乳酸菌的筛选与鉴定

目的:从传统发酵蔬菜中筛选对温和气单胞菌具有拮抗作用的乳酸菌。方法:采用双层琼脂扩散法筛选,通过生理生化反应和16S rRNA序列分析进行鉴定,研究蛋白酶、p H和温度等因素对乳酸菌无细胞上清液（CFS）抑菌活性的影响,采用扫描电镜分析乳酸菌无细胞上清液对温和气单胞菌细胞结构完整性的影响。结果:从腌渍酸黄瓜中筛选出对温和气单胞菌（10⁶CFU/m L）具有较强抑制活性的菌株LZH2-5,经鉴定为植物乳杆菌（Lactobacillus plantarum）。LZH2-5无细胞上清液经胰蛋白酶、木瓜蛋白酶、中性蛋白酶、碱性蛋白酶和胃蛋白酶处理后其抑菌活性分别丧失29.38%、23.93%、22.30%、19.47%和14.59%;经40、60、80℃处理30 min后其拮抗活性基本不变,在100℃和121℃处理30 min后活性分别下降了16.66%和25.40%,在p H3.0⁴.0范围内保持其抑菌活性,粗提物的最小抑菌浓度12.0 mg/m L。扫描电镜表明经LZH2-5 CFS处理使温和气单胞菌的细胞结构破坏并溶解。结论:从腌渍酸黄瓜中筛选的植物乳杆菌LZH2-5对温和气单胞菌具有较强抑制作用,初步分析抑菌活性物质为细菌素类,可作为水产品养殖过程中控制温和气单胞菌的拮抗制剂出发菌株。      

Combined effects of Lactobacillus casei inoculum, modified atmosphere packaging and storage temperature in controlling Aeromonas hydrophila in ready-to-use vegetables

Carbon dioxide concentration, Lactobacillus casei inoculum size and storage temperature were varied according to a Central Composite Design in order to assess the effects of these variables and their interactions on the growth of Aeromonas hydrophila and lactic acid bacteria in ready-to-use mixed salad vegetables packaged under modified atmosphere. The growth curve parameters, modelled according to the Gompertz equation, were analysed to generate polynomial equations. The model obtained emphasized the role of L. casei inoculum size in controlling A. hydrophila and permitted identification of appropriate combinations of the selected variables to reduce A. hydrophila survival. The use of these hurdles may increase the shelf-life and the microbiological safety of ready-to-use vegetables.     

混合培养条件下酵母菌菌株生长影响因素的初步研究

为研究两种酵母菌在混合培养条件下各菌株生长相互影响的因素,本文考察了初糖浓度及p H对两种酵母菌Saccharomyces cerevisiae(简称Sc)和Issatchenkio orientalis(简称Io)生长的影响,以纯培养作对比,研究了混合培养条件下两种酵母菌有机酸代谢的差异性。结果表明,低糖浓度、低p H以及有机酸代谢的差异是造成混合培养条件下Sc生长受到抑制的主要因素;Io代谢葡萄糖速率较Sc快,在初糖浓度为1%的混合培养中,Io优先竞争性地消耗葡萄糖,混合培养体系中Io/Sc(菌落数量比值)为70;Io较Sc耐酸,在p H3.5下,Io/Sc达56;有机酸代谢中,Io可特异性地生成2.52 g/L的乳酸,Sc可特异性地生成1.14 g/L的乙酸,混合培养中,Io可吸收代谢Sc产生的乙酸,而Io产生的乳酸则对Sc的生长产生抑制作用。从细胞生长与有机酸代谢角度分析果酒酵母菌混合培养细胞行为影响的因素,为多菌种混合发酵在果酒产业中的应用提供理论基础。     

乳杆菌有机酸耐受性及发酵果蔬汁性能分析

选择3株从醋醅中筛选得到的高性能乳杆菌,考察培养基中不同浓度和种类有机酸对其发酵的影响,并比较其对12种典型果蔬汁的发酵效果.结果表明鼠李糖乳杆菌LR-S、植物乳杆菌LP-D和植物乳杆菌LP-F分别对苹果酸、柠檬酸和酒石酸具有较好的耐受,进而对这些有机酸为主体的果蔬原料发酵更具优势.在桑葚汁等有机酸复杂的原料中双菌顺序...