四重荧光定量PCR法鉴定肠炎、鼠伤寒以及伤寒沙门氏菌

目的建立四重荧光定量PCR体系鉴定肠炎沙门氏菌、鼠伤寒沙门氏菌以及伤寒沙门氏菌。方法针对沙门氏菌属特异性ompC基因、肠炎沙门氏菌sdf基因、鼠伤寒沙门氏菌STM4495和伤寒沙门氏菌STY2021序列设计引物和TaqMan探针,建立多重荧光定量PCR体系,进行特异性与敏感性研究。结果 28株不同血清型的沙门氏菌均扩增出ompC基因,其他13株非沙门氏菌均未出现ompC的非特异性扩增。sdf、STM4495、STY2021的探针和引物分别特异性扩增出肠炎沙门氏菌、鼠伤寒沙门氏菌以及伤寒沙门氏菌,而25株其他血清型沙门氏菌以及13株非沙门氏菌均未见扩增曲线。敏感性试验显示,该体系的最低检测限分别为48 pg/mL(ompC)、560 pg/mL(sdf)、530 pg/mL(STM4495)、35 pg/mL(STY2021)。结论该方法特异好、灵敏高、能够快速检测沙门氏菌并鉴定肠炎沙门氏菌、鼠伤寒沙门氏菌以及伤寒沙门氏菌。     

Effects of sodium bicarbonate, vinegar, acetic and citric acids on growth and survival of Yersinia enterocolitica.

The effects of sodium bicarbonate, vinegar, acetic and citric acids on growth and survival of Yersinia enterocolitica in a laboratory medium were investigated. Acetic acid was found to be the most effective agent used, which completely inhibited the growth of the test organism at concentration of 0.156% (v/v) in the media incubated at 22 degrees C for 48 h. The antimicrobial activity of acetic acid and vinegar on the survival of the test bacterium in media incubated at 22 degrees C for 60 min was dependent on the inocula levels.     

柑桔培养基中乳酸菌的生长状况研究

采用正交试验对乳酸菌在脱脂乳和桔汁、桔皮汁等培养基及不同发酵温度、时间和菌种条件下，产酸和菌数等进行了测定。结果表明乳酸菌在柑桔培养基中生长良好     

酸和盐胁迫对乳酸菌活性的影响

该研究以13株食品常见乳酸菌为研究对象,考察酸和盐胁迫对其活性的影响,探究这13株乳酸菌的最适酸、盐生长条件及耐酸、耐盐能力。结果表明,适当的低盐浓度（1%、2%）对部分乳酸菌的生长有促进作用,植物乳杆菌和副干酪乳杆菌的最适盐浓度为1%,保加利亚乳杆菌和嗜酸乳杆菌的最适盐浓度为2%;盐浓度进一步增大,13株乳酸菌的生长受到抑制;盐浓度为10%时,除戊糖片球菌、乳酸乳球菌乳酸亚种、嗜热链球菌和乳酸片球菌外,其余9株菌的生长抑制率都＞95%。当pH值为5～7时,13株乳酸菌都生长良好,pH=6时,7株乳酸菌活性均最高;随着酸胁迫的增强,13株乳酸菌生长受抑制程度增大;pH为1～3时,13株乳酸菌的生长抑制率都＞90%,高盐及高酸对9株杆菌的抑制作用强于4株球菌。     

冷应激及包埋对乳酸菌冻干发酵剂的影响

将嗜热链球菌、保加利亚乳杆菌、嗜酸乳杆菌按3∶2∶1比例制备乳酸菌冻干发酵剂.比较不同温度冷应激处理对乳酸菌冻干存活率的影响,结果表明,20℃,处理4h时,冻干存活率为96.3％.选择发酵的固定化细胞制作条件:海藻酸钠2.25g/L、CaCl2 4.0g/L.包埋后乳酸菌冻干存活率为95.6％.     

Effect of coffee filtrate, methylglyoxal, glyoxal, and caffeine on Salmonella typhimurium and S. enteritidis survival in ground chicken breasts

The antimicrobial effect of roasted coffee filtrate (CF) and dicarbonyls on Salmonella Typhimurium and Salmonella Enteritidis in raw ground chicken breast meat (GCB) was investigated. Coffee was brewed and filtered before addition to GCB. Coffee filtrate with and without added caffeine, methylglyoxal, and/or glyoxal was added to GCB and then inoculated with Salmonella Typhimurium and Salmonella Enteritidis. Ground chicken samples were stomached with peptone water at days 1, 3, 5, and 7, plated on XLD agar with a TSA overlay, and Salmonella survivors were enumerated. CF alone gave less than a 1 Log reduction in all runs compared to control GCB with no treatment. Methylglyoxal (2.28 mg/g GCB) had the greatest antimicrobial effect against Salmonella Typhimurium and Salmonella Enteritidis in GCB with average Log reductions of 2.27 to 3.23, respectively, over the 7 d duration of the experiment compared to control GCB with no treatment. A 1 Log reduction was observed in GCB with CF, 0.93 mg glyoxal, and 1 mg caffeine/g chicken compared to the control and GCB with only CF. Heat-produced coffee compounds could potentially reduce Salmonella in retail ground chicken and chicken products.     

离心条件对乳酸菌离心存活率的影响

研究了以11%脱脂乳为液体培养基进行培养时,离心力、离心时间和离心温度对乳酸菌在离心过程中损失率、存活率的影响。结果表明:延长离心时间,离心损失率和离心存活率均逐渐降低;在同一离心时间条件下,增大离心力,离心损失率和离心存活率均显著降低(p>0.01);在11%脱脂乳液体培养基中培养的保加利亚乳杆菌、嗜热链球菌,其最适离心条件为:5000r/min离心10min,离心温度为20℃,此时乳酸菌的离心存活率为94.32%。     

乳酸链球菌素和柠檬酸对甜樱桃中沙门氏菌的抑制

为了研究沙门氏菌污染采后甜樱桃果实的生长繁殖状况及其控制情况,分别采用乳酸链球菌素(Nisin)、柠檬酸及二者复配溶液处理人工接种沙门氏菌的甜樱桃,观察和分析Nisin和柠檬酸的抑菌效果。结果表明,Nisin与柠檬酸处理均具有抑菌效果,并且随着溶液中Nisin从10μg/m L上升至100μg/m L、柠檬酸从1 g/L上升至5 g/L时,抑菌效果显著增强,(p<0.05)。研究还发现,Nisin溶液100μg/m L、柠檬酸溶液5 g/L、Nisin 10μg/m L与3 g/L柠檬酸复配溶液和Nisin 50μg/m L与柠檬酸1 g/L复配溶液这4种处理具有相似的抑菌除菌效果,处理5 min菌落浓度可以降低至104cfu/m L;Nisin 50μg/m L与3 g/L柠檬酸复配溶液处理样品15 min时,沙门氏菌的菌落降至检测限以下,无法检出;当贮存时间一直延长至第10 d时,Nisin和柠檬酸处理仍然保持一定的抑菌效果,充分除菌抑菌。      

The effect of nitrite,garlic and starter culture on the survival of Salmonella typhimurium in Turkish soudjuk

The effects of nitrite, garlic and starter cultures on the survival of Salmonella typhimurium were evaluated during manufacture and storage of Turkish soudjuk. Sodium nitrate (0·2 g kg^?1) and garlic (8 g kg^?1) added to the sausage did not have any significant effect on the survival of S typhimurium. The use of a commercial starter culture had a pronounced effect on the survival of the test organism. An initial inoculum of 2·5 × 10⁵ g^?1 S typhimurium cells decreased to an undetectable level within 12 days of the ageing period when the starter culture was used.     

Studies on antimutagenic effect of milk cultured with lactic acid bacteria on the Trp-P2-induced mutagenicity to TA98 strain of Salmonella typhimurium.

The inhibitory effects of cultured milk using 76 strains of lactic acid bacteria isolated from milk products were investigated on the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P2), a tryptophan pyrolysate for Salmonella typhimurium TA98. Each cultured milk sample displayed its characteristic antimutagenic effect against the mutagenicity of Trp-P2. The milk cultured with Lactobacillus acidophilus LA106 (LA2) showed the highest inhibition of 82.1% among the strains used. Milk samples cultured with Lactococcus lactis subsp. lactis, Lll103 (10-3) and Lll102 (KM) also exhibited higher inhibition percentages.     

Effect of phenolic acids on glucose and organic acid metabolism by lactic acid bacteria from wine

The influence of phenolic (p-coumaric, caffeic, ferulic, gallic and protocatechuic) acids on glucose and organic acid metabolism by two strains of wine lactic acid bacteria (Oenococcus oeni VF and Lactobacillus hilgardii 5) was investigated. Cultures were grown in modified MRS medium supplemented with different phenolic acids. Cellular growth was monitored and metabolite concentrations were determined by HPLC-RI. Despite the strong inhibitory effect of most tested phenolic acids on the growth of O. oeni VF, the malolactic activity of this strain was not considerably affected by these compounds. While less affected in its growth, the capacity of L. hilgardii 5 to degrade malic acid was clearly diminished. Except for gallic acid, the addition of phenolic acids delayed the metabolism of glucose and citric acid in both strains tested. It was also found that the presence of hydroxycinnamic acids (p-coumaric, caffeic and ferulic) increased the yield of lactic and acetic acid production from glucose by O. oeni VF and not by L. hilgardii 5. The results show that important oenological characteristics of wine lactic acid bacteria, such as the malolactic activity and the production of volatile organic acids, may be differently affected by the presence of phenolic acids, depending on the bacterial species or strain.     

藤茶中二氢杨梅素对乳酸菌生长及活性的影响

该研究通过生长曲线和流式细胞术实验初步探索了藤茶中二氢杨梅素对嗜酸乳杆菌（Lactobacillus acidophilus）、德氏乳杆菌保加利亚亚种（Lactobacillus delbrueckii subsp. bulgaria）、嗜热链球菌（Streptococcus thermophilus）三种乳酸菌生长的影响。结果表明,二氢杨梅素添加量在100～1 000 μg/mL时,对三种乳酸菌均有显著促进其生长并提高其菌液活菌数量的作用（P＜0.05）;当二氢杨梅素添加量＞1 000 μg/mL时,对三种菌的生长和菌液中活菌的数量均表现出不同程度的抑制,其中德氏乳杆菌保加利亚亚种对二氢杨梅素最为敏感。在发酵后的菌液分析中,未明显观察到二氢杨梅素含量的降低,说明二氢杨梅素通过对生长环境进行调节影响乳酸菌生长。     

Effectiveness of trisodium phosphate, acidified sodium chlorite, citric acid, and peroxyacids against pathogenic bacteria on poultry during refrigerated storage

The effects of dipping treatments (15 min) in potable water or in solutions (wt/vol) of 12% trisodium phosphate (TSP), 1,200 ppm acidified sodium chlorite (ASC), 2% citric acid (CA), and 220 ppm peroxyacids (PA) on inoculated pathogenic bacteria (Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Salmonella Enteritidis, Escherichia coli, and Yersinia enterocolitica) and skin pH were investigated throughout storage of chicken legs (days 0, 1, 3, and 5) at 3 +/- 1 degrees C. All chemical solutions reduced microbial populations (P < 0.001) as compared with the control (untreated) samples. Similar bacterial loads (P > 0.05) were observed on water-dipped and control legs. Type of treatment, microbial group, and sampling day influenced microbial counts (P < 0.001). Average reductions with regard to control samples were 0.28 to 2.41 log CFU/g with TSP, 0.33 to 3.15 log CFU/g with ASC, 0.82 to 1.97 log CFU/g with CA, and 0.07 to 0.96 log CFU/g with PA. Average reductions were lower (P < 0.001) for gram-positive (0.96 log CFU/g) than for gram-negative (1.33 log CFU/g) bacteria. CA and ASC were the most effective antimicrobial compounds against gram-positive and gram-negative bacteria, respectively. TSP was the second most effective compound for both bacterial groups. Average microbial reductions per gram of skin were 0.87 log CFU/g with TSP, 0.86 log CFU/g with ASC, 1.39 log CFU/g with CA, and 0.74 log CFU/g with PA for gram-positive bacteria, and 1.28 log CFU/g with TSP, 2.03 log CFU/g with ASC, 1.23 log CFU/g with CA, and 0.78 log CFU/g with PA for gram-negative bacteria. With only a few exceptions, microbial reductions in TSP- and ASC-treated samples decreased and those in samples treated with CA increased throughout storage. Samples treated with TSP and samples dipped in CA and ASC had the highest and lowest pH values, respectively, after treatment. The pH of the treated legs tended to return to normal (6.3 to 6.6) during storage. However, at the end of storage, the pH of legs treated with TSP remained higher and that of legs treated with CA remained lower than normal.     

Preservation of acidified cucumbers with a combination of fumaric acid and cinnamaldehyde that target lactic acid bacteria and yeasts

The naturally occurring compound, fumaric acid, was evaluated as a potential preservative for the long-term storage of cucumbers. Fumaric acid inhibited growth of lactic acid bacteria (LAB) in an acidified cucumber juice medium model system resembling conditions that could allow preservation of cucumbers in the presence of sodium benzoate. Forty millimolars of fumaric acid were required to inhibit growth of an extremely aciduric Lactobacillus plantarum LA0445 strain at pH 3.8. Half of this concentration was required to achieve inhibition of L. plantarum LA0445 at pH 3.5. As expected growth of the spoilage yeasts Zygosaccharomyces globiformis and Z. bailii was not inhibited by fumaric acid at near saturation concentrations in the same cucumber juice medium. To usefully apply fumaric acid as a preservative in acidified foods it will be necessary to combine it with a food grade yeast inhibitor. The antimicrobial agent, cinnamaldehyde (3.8 mM) prevented growth of Z. globiformis as well as the yeasts that were present on fresh cucumbers. Acidified cucumbers were successfully preserved, as indicated by lack of yeasts or LAB growth and microbial lactic acid or ethanol production by a combination of fumaric acid and cinnamaldehyde during storage at 30 °C for 2 mo. This combination of 2 naturally occurring preservative compounds may serve as an alternative approach to the use of sodium benzoate, potassium sorbate, or sodium metabisulfite for preservation of acidified vegetables without a thermal process. PRACTICAL APPLICATION: This study evaluates the potential application of alternative preservatives for the long-term storage of cucumbers in a reduced NaCl cover brine solution and without a thermal process.     

Effect of Versagel on the growth and metabolic activities of selected lactic acid bacteria

ABSTRACT:  In this study, the influence of a protein-based fat replacer, Versagel ^® added at 1% and 2% (w/v) to reconstituted skim milk (RSM), on the growth and metabolic activities of selected strains of yogurt starters ( Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus ) as well as probiotic organisms ( Lactobacillus casei , Lactobacillus acidophilus , and Bifidobacterium longum ) was examined. Addition of Versagel resulted in significantly improved growth of S. thermophilus and B. longum but inhibited that of L. casei , L. acidophilus , and L. delbrueckii ssp. bulgaricus . This is also reflected in the extent of reduction of pH in RSM with added Versagel by these organisms. Among the biochemical activities, proteolytic activity of all the organisms except B. longum was adversely affected by the presence of Versagel, although the angiotensin-I converting enzyme (ACE) inhibitory and α-glucosidase (α-glu) inhibitory activities were improved. Versagel at 1% level influenced the growth, while ACE inhibitory and α-glu inhibitory activities of the organisms were better at 2% level.     

柠檬酸对泡菜中硝酸盐、亚硝酸盐及其风味物质的影响

以豇豆为原料,分别采用自然发酵、添加不同浓度的柠檬酸制作泡菜,对比分析了其在不同的发酵过程中对硝酸盐、亚硝酸盐、氨基酸态氮及香气的影响。结果表明,添加柠檬酸0.30%能最大程度的降解泡菜中的硝酸盐、亚硝酸盐,使其含量分别达到97.86 mg/kg,2.33 mg/kg;且氨基酸态氮含量为0.52 g/kg,与自然发酵泡菜相近。经柠檬酸处理的泡菜在发酵7 d后共检测出148种香气成分,其中,柠檬酸0.30%处理组香气物质种类最多,为88种,包括酯类20种,醇类13种,醛类19种,酮类5种,挥发性酸类5种,芳香族类9种,烯烃类3种,烷烃类14种,使泡菜风味更协调,整体更和谐。综上所述,添加柠檬酸0.30%至泡菜中最适宜,并以期为泡菜的生产加工提供参考。     

Validation of lactic acid bacteria, lactic acid, and acidified sodium chlorite as decontaminating interventions to control Escherichia coli O157:H7 and Salmonella Typhimurium DT 104 in mechanically tenderized and brine-enhanced (nonintact) beef at the purveyor

After three different outbreaks were linked to the consumption of nonintact meat products contaminated with Escherichia coli O157:H7, the U.S. Food Safety and Inspection Service published notice requiring establishments producing mechanically tenderized and moisture-enhanced beef products to reassess their respective hazard analysis and critical control point systems, due to potential risk to the consumers. The objective of this study was to validate the use of lactic acid bacteria (LAB), acidified sodium chlorite (ASC), and lactic acid (LA) sprays when applied under a simulated purveyor setting as effective interventions to control and reduce E. coli O157:H7 and Salmonella Typhimurium DT 104 in inoculated U.S. Department of Agriculture (USDA) Choice strip loins (longissimus lumborum muscles) pieces intended for either mechanical blade tenderization or injection enhancement with a brine solution after an aging period of 14 or 21 days at 4.4°C under vacuum. After the mechanical process, translocation of E. coli O157:H7 and Salmonella Typhimurium DT 104 from the surface into the internal muscles occurred at levels between 1.00 and 5.72 log CFU/g, compared with controls. LAB and LA reduced internal E. coli O157:H7 loads up to 3.0 log, while ASC reduced the pathogen 1.4 to 2.3 log more than the control (P < 0.05), respectively. Salmonella Typhimurium DT 104 was also reduced internally 1.3 to 2.8, 1.0 to 2.3, and 1.4 to 1.8 log after application of LAB, LA, and ASC, respectively. The application of antimicrobials by purveyors prior to mechanical tenderization or enhancement of steaks should increase the safety of these types of products.     

Influence of acetic, citric, and lactic acids on Escherichia coli O157:H7 membrane lipid composition, verotoxin secretion, and acid resistance in simulated gastric fluid

The effect of organic acid (acetic, citric, and lactic acids) adaptation at equivalent initial pH values (6.4 and 5.4) on changes in membrane lipid composition, verotoxin concentration, and acid resistance in simulated gastric fluid (pH 1.5, 37 degrees C) was determined for Escherichia coli O157:H7 ATCC 43895 (HEC) and an rpoS mutant of E. coli O157:H7 ATCC 43895 (RM, FRIK 816-3). For HEC, lactic acid-adapted (pH 5.4) cells had the greatest D-value (32.2 min) and acetic acid-adapted (pH 5.4) cells had the smallest D-value (16.6 min) in simulated gastric fluid. For RM, D-values of citric and acetic acid-adapted cells were similar to those for nonadapted cells grown at pH 7.3, but D-values increased from 13.1 to 27.9 min in lactic acid-adapted cells (from pH 7.3 to pH 5.4). For both strains, the ratio of cis-vaccenic to palmitic acids decreased for citric and lactic acid-adapted cells, but the ratio increased for acetic acid-adapted cells at pH 5.4. Organic acid-adapted cells produced less total verotoxin than did nonadapted cells at approximately 10(8) CFU/ml. Extracellular verotoxin concentration proportionally decreased with decreasing pH for both HEC and RM. Changes in membrane lipid composition, verotoxin concentration, and acid resistance in HEC and RM were dependent on both pH and organic acid. Deletion of the rpoS gene did not affect these changes but did decrease acid resistance in citric acid-adapted cells. Results indicate that decreased membrane fluidity may have caused increased acid resistance and decreased verotoxin secretion.