Inactivation and induction of sublethal injury of Listeria monocytogenes in biofilm treated with various sanitizers

This study determined the effects of different sanitizers (one phenolic-based, one chlorine-based, two QACs-based and one levulinic acid and SDS-based) on Listeria monocytogenes biofilm. The induction of the sub-lethal injury state and the biofilm formation characteristics as a result of exposure to sanitizers were also evaluated. The results revealed that QACs-based and phenolic-based sanitizers most effectively reduced L. monocytogenes, resulting in a reduction of 3.7–6.9 log CFU/ml and 4.9–8.2 log CFU/ml after a 60-min treatment for 37°C- and 15°C-grown biofilms, respectively. An enhanced level of sanitizer resistance was observed in biofilms when they were multiply exposed to QACs-based and phenolic-based sanitizers, with a reduction of 0.7–3.5 log CFU/ml and 1.6–>9.3 log CFU/ml for 37°C- and 15°C-grown biofilms, respectively. As biofilm cells became less sensitive, especially to QACs-based sanitizers, an increase in the percentage of sublethally injured cells was observed to the levels dependent upon sanitizer concentration. Confocal laser scanning microscopy (CLSM) analysis revealed that biofilm cells experienced cell membrane damage when exposed to QACs-based and phenolic-based sanitizers, providing more protection to cells located inside the biofilm matrix. This study highlights the ongoing need for improvement in intervention methods to control L. monocytogenes in food processing plants.     

Reduction of histamine in fish sauces by rice bran nuka

Fish sauce products often contain a quantity (>1000 mg/L) of histamine (Hm). We investigated the Hm-reducing activity of 39 traditional fermented food products, including fish- and radish-nukazuke (fermented food with rice bran (nuka)), radish- and turnip-kojizuke (fermented food with malted rice (koji)), miso (fermented soy paste), natto and yogurt, in fish sauce products. The nuka-paste portion of radish-nukazuke showed the highest Hm-reducing activity. The addition of the nuka-paste (20%, w/v) to sardine fish sauce (iwashi-ishiru) reduced the Hm content to about 600–700 mg/L from 1200 mg/L. The Hm-reducing activity of nuka-paste was regarded as water-soluble, heat tolerant, and of high molecular weight. Although raw-nuka showed the Hm-reducing activity, the fermentation process slightly increased the activity of the raw-nuka and their extract solution. These results indicated that nuka, a byproduct of rice polishing, could be utilized for Hm reduction of fermented fish products.     

Reduction of Campylobacter jejuni counts on chicken meat treated with different seasonings

To analyze the potential of various seasoning combinations in reducing Campylobacter jejuni counts on fresh chicken meat, fresh chicken drumstick samples were inoculated with a mixture of two C. jejuni strains at log 4–5 CFU/g and subsequently treated with six different seasonings. After addition as a dry powder to the meat’s surface, all seasoning combinations adsorbed water from the meat and formed a gel on the meat’s surface. The samples were placed in individual packages containing a modified gas atmosphere (N₂ 80% and CO₂ 20%) and stored at 4 °C for seven days and C. jejuni counts in CFU/g were determined at the beginning, after 15 min, 1 h, 1 day and 7 days. The most effective seasoning combination contained, among other ingredients and food additives, sodium lactate and potato protein fractions; it reduced counts by mean 1.52 to 1.66 log CFU/g in seven days. The other seasoning combinations without potato protein fractions decreased counts in the range of mean 1.05 to 1.16 log CFU/g; simultaneously, the counts in control meat samples decreased by mean 0.21 log CFU/g. The death rate estimates after 1 h storage was in the range of ?0.25 log CFU/g/h to ?0.34 log CFU/g/h.In conclusion, various combinations of seasonings decreased the counts of C. jejuni, with the highest C. jejuni death rate during the first hour and further minor reductions in C. jejuni counts with additional storage time. These types of treatments may decrease human exposure to Campylobacter from fresh poultry meat.     

Comparative efficacies of various chemical sanitizers for warewashing operations in restaurants

This study compared the efficacies of two traditional with two experimental sanitizers for use in tableware cleaning operations in restaurants and foodservice operations. This was done by investigating the maximum number of cleaning cycles that a single recommended quantity of each sanitizer could treat and still produce a 5-log bacterial reduction on test tableware items. Cream cheese and whole milk were inoculated with Escherichia coli K12 and Listeria innocua and subsequently used for contamination of the tableware items. These items were washed with automatic (49 °C) and manual (43 °C) dishwashers then treated with electrolyzed-oxidizing water (EO), quaternary ammonium compound, sodium hypochlorite and an acidic sanitizer. For the lowest efficacies, after six and eight manual washing cycles in the same solution, ≥5 log reductions were achieved on both E. coli K12 contaminated trays and plates, respectively, exposed to the chlorine and quaternary ammonium sanitizers. For automatic washing with chlorine sanitizer, the minimum wash cycles for the bacteria were seven and nine for the trays and plates, respectively. For drinking glasses contaminated with bacteria, 14 and 17 washing cycles produced ≥5 log reductions for manual and automatic washings, respectively.     

Combination of microbubbles with oxidizing sanitizers to eliminate Escherichia coli and Salmonella Typhimurium on Thai leafy vegetables

Microbubbles (MB) technology was applied in a washing process a few studies have been done with food materials, particularly to reduce the microbial contamination on leafy vegetables. This study determined the effectiveness of MB (Ø ∼ 50–70 μm) combined with three sanitizers acidic electrolyte water (AEO, 20 and 40 mg/L, ORP 910–1010 mV, pH 2.7–3.1), chlorine dioxide (ClO_2, 3 and 5 mg/L, ORP 550–680 mV, pH 7.1–7.5), and sodium hypochlorite (NaOCl, 40 and 80 mg/L, ORP 900–990 mV, pH 6.5–6.7) in order to inactivate Escherichia coli and Salmonella Typhimurium on artificially contaminated sweet basil (Ocimum basilicum Linh) and Thai mint (Mentha cordifolia Opiz.). Although air MB alone did not possess antimicrobial activity, washing with MB combined with the two oxidizing sanitizers (NaOCl and AEO) for 5 min resulted in an effective reduction in S. Typhimurium and E. coli on sweet basil and Thai mint with 2–3 log reductions (99.2–99.8%). Washing vegetables with MB and NaOCl at a concentration of free chlorine of 40 mg/L NaOCl or 20 mg/L AEO yielded the best results in killing S. Typhimurium with 1.21–1.90 and 0.67–2.25 log reductions, respectively. In addition, the reduction of E. coli and S. Typhimurium on sweet basil appeared to be higher than on Thai mint. Differences in surface roughness may assist the bubbles and sanitizers to detach bacterial cells and therefore increase the washing efficacy. Furthermore, applying sanitizers in washing solution was a powerful means of killing planktonic E. coli and S. Typhimurium in the wash water and preventing cross-contamination in the washing process.     

Contamination sources of coliforms in two different types of frozen ready-to-eat shrimps

The sources of coliform contamination were studied in two types of processed ready-to-eat (RTE) shrimp products: half-slitted cooked without head-on shrimp for topping on rice as sushi product and cooked peeled with head-on shrimp.The objective of this study was to determine the processing and environmental factors which contributed to the coliform contamination of these two product types. The samples from each step of the processing lines (5476 samples), finished products (1331 samples) and environment (3624 samples) were collected during January–December, 2006. The samples were then analyzed for presence of coliforms and the results were further analyzed using statistical methods. The results of samples from processing lines showed that cooked shrimps for sushi product were frequently contaminated during slitting step (15.05%) because of the improper design of the slitting equipment. 3.85% of the environmental swabs of slitting equipment were contaminated. In addition, rowing (7.23%), sizing (6.93%) and peeling (6.27%) also contributed to coliforms contamination in the product. In case of cooked peeled with head-on shrimp, the rowing step (8.43%) appeared to be the major contributor of contamination, whereas spraying with cooled water also played a considerably significant part as seen from the environmental swab results which showed 14.06% presence of coliforms at the spraying nozzles. In addition the result of workers’ gloves swab also revealed 7.20% of contamination. Using the Monte Carlo Simulation, the correlation of coliform prevalence of finished products, products from processing steps and environmental swab were obtained. The results of both products demonstrated that coliform prevalence of the total samples collected from processing steps and coliform prevalence from environmental swabs correlated with the coliform prevalence in finished products. Identifying these sources helped the plant manager to improve several procedures (such as personal hygiene, cleaning and temperature control including staff supervision) to minimize the coliform contamination in the final products.     

Changes in resistance of Salmonella Typhimurium biofilms formed under various conditions to industrial sanitizers

The aim of this study was to understand how different factors including biofilm age, attachment surface (stainless steel and acrylic) and various growth conditions such as different pH (pH 6 and 7) and temperature (28, 37 and 42 °C) affected the resistance of Salmonella Typhimurium biofilm against industrial sanitizers. The sanitizers tested were quaternary ammonium compounds (QAC, 200 ppm), mixed peroxyacetic acid/organic acids (PAO, 0.1%) and sodium hypochlorite (chlorine, 50 ppm). It was observed that, for biofilms formed at pH 7–37 °C, chlorine was the most effective sanitizer, followed by QAC and PAO. For all conditions tested, attachment surfaces didn't cause any significant difference in biofilm resistance against sanitizers. Increasing biofilm age led to an increase in resistance to sanitizers, although such effect was growth condition- and sanitizer-dependent. The resistance of biofilm formed on stainless steel at pH 6–37 °C increased with increasing biofilm ages. The effect of temperature and pH on biofilm resistance was dependent on biofilm ages. For 168-h biofilm formed at pH 6, the resistance to all three sanitizers was highest for 37 °C, followed by 28 and 42 °C; while biofilm formed at 37 °C for 168 h, pH 6 condition increased biofilm resistance to QAC and PAO, but not chlorine, compared with pH 7. These results indicate that the resistance of biofilms against sanitizers was dependent on biofilm age, temperature, and pH.     

Inactivation effect of newly developed low concentration electrolyzed water and other sanitizers against microorganisms on spinach

The efficacy of newly developed low concentration electrolyzed water (LcEW) was investigated to inactivate the pathogens on spinach leaves as a convenient and safe alternative sanitizer and it was compared to other sanitizers. Spinach leaves were inoculated with Escherichia coli O157:H7 and Listeria monocytogenes and dip treated with deionized water (DIW), LcEW, strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl) for 3 min at room temperature (23 ± 2 °C). For all pathogens, the similar pattern of microbial reduction on spinach was apparent with LcEW and SAEW washing. In the present study, it was found that LcEW inactivated, at maximum, 1.64–2.80 log cfu/g and DIW resulted in lowest reduction, 0.31–0.95 log cfu/g of background or pathogenic microflora present on spinach leaves compared to the unwashed control. The findings of this study indicate that LcEW and SAEW did not differ significantly (P > 0.05) in reducing background or pathogenic microflora on spinach and LcEW may be a promising sanitizer for washing vegetables without environmental pollution instead of using electrolyzed oxidizing (EO) water or SAEW.     

Sanitization potency of slightly acidic electrolyzed water against pure cultures of Escherichia coli and Staphylococcus aureus,in comparison with that of other food sanitizers

The sanitization potency of slightly acidic electrolyzed water (SAEW) on pure cultures of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) was evaluated. The potency was compared with that of strong acidic electrolyzed water (StAEW) and sodium hypochlorite (NaOCl) solution. SAEW (ca. pH 5.8 and 21 mg/l available chlorine concentration; ACC) resulted into >5 log₁₀CFU/ml reduction of E. coli and S. aureus after 90 s of exposure. The relative bacterial reduction potency at each exposure time was in the order StAEW > NaOCl > SAEW and increased with exposure time, with relative effect being 90 s > 60 s > 30 s. The results indicate that SAEW with low ACC and near neutral pH can potentially sanitize E. coli and S. aureus within a short period of exposure presenting a potential replacement to NaOCl solution commonly used in the food industry.     

Inhibitory effects of low concentration electrolyzed water and other sanitizers against foodborne pathogens on oyster mushroom

In this study we investigated the effects of low concentration electrolyzed water (LcEW) and several other sanitizers (strong acid electrolyzed water (SAEW), aqueous ozone (AO), 1% citric acid (CA) and sodium hypochlorite solution (NaOCl)) on the inactivation of natural microflora (total aerobic bacteria counts (TBC) and yeasts and moulds (YM)) and foodborne pathogens (Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium and Bacillus cereus) on oyster mushroom. The effects of temperature and treatment time on the antimicrobial activity of LcEW to reduce the populations of foodborne pathogens were also determined. LcEW showed the strongest bactericidal efficacy among all the sanitizers on TBC, YM and pathogens by reductions of 1.35, 1.08 and 1.90–2.16 log CFU/g after 3 min treatment at room temperature (23 ± 2 °C), respectively. There was no significant difference between the antimicrobial effects of LcEW and SAEW (P > 0.05). Among those sanitizers, their relative influence of inactivation was LcEW > NaOCl > CA > AO.     

The effect of the association of sanitizers and surfactant in the microbiota of the Cantaloupe (Cucumis melo L.) melon surface

This work aimed to evaluate the efficiency of 200, 500 and 1000 mg l⁻¹ of free available chlorine (FAC) and 60 mg l⁻¹ of peracetic acid (APA) associated or not with Tween 80 in reducing the mesophilic aerobes, coliforms group and fecal coliforms on cantaloupe melon surface. Also, the action of the organic chloramine in removing the Salmonella enteritidis when attached on the melon surface. All treatments reduced significantly (p<0.05) the microbiota analyzed when compared with a water washing, used as control. The treatment with 1000 mg l⁻¹ of organic chloramine with surfactant reduced the mesophilic aerobes (p<0.05) by 4-log cycles, more than the control. Also this chlorine solution was the most efficient in removing S. enteritidis after attachment of the microorganisms to the fruit surface, between 1 and 24 h.     

Influence of temperature and surface kind on biofilm formation by Staphylococcus aureus from food-contact surfaces and sensitivity to sanitizers

This study aimed to assess the adhesion, detachment kinetic and biofilm formation of Staphylococcus aureus isolates from food services surfaces on stainless steel and polypropylene surfaces when cultivated in a vegetable-based broth at 7 and 28 °C, and the efficacy of peracetic acid (30 mg/L) and sodium hypochlorite (250 mg/L) in removing the bacterial cells from the matrix of the preformed biofilm. The isolates adhered over 4 Log cfu/cm² regardless the surface kind and incubation temperature. Cell detachment was around 3 Log cfu/cm² over the first six contacts with agar characterizing a high persistence of cells on the tested surfaces. Number of cells (5-7 Log cfu/cm²) needed for biofilm formation was noted at all experimental systems already after 3 days of incubation. A range of 2.0-3.3 and 1.5 to 2.1 Log cfu/cm² was observed in the reduction of cells in biofilm matrix caused by peracetic acid and sodium hypochlorite, respectively. The isolates of S. aureus revealed high capability to adhere and form biofilm on the tested surfaces in both assayed incubation temperature.     

Biofilm-forming ability and resistance to industrial disinfectants of Staphylococcus aureus isolated from fishery products

Adhesion and biofilm-forming ability of twenty six S. aureus strains previously isolated from fishery products on stainless steel was assessed. All strains reached counts higher than 10⁴ CFU/cm² after 5 h at 25 °C. Most strains also showed a biofilm-forming ability higher than S. aureus ATCC 6538 – reference strain in bactericidal standard tests – by crystal violet staining. In addition, it seems that food-processing could have produced a selective pressure and strains with a high biofilm-forming ability were more likely found in highly handled and processed products.The efficacy of the industrial disinfectants benzalkonium chloride (BAC), sodium hypochlorite (NaClO) and peracetic acid (PAA) against biofilms and planktonic counterparts was also examined in terms of minimum biofilm eradication concentration (MBEC) and minimum bactericidal concentration (MBC), respectively. Biofilms showed an antimicrobial resistance higher than planktonic cells in all cases. However, no correlation was found between MBEC and MBC, likely due to differences in biofilm extracellular matrix (composition, content and architecture) between strains. BAC resistance increased as biofilms aged. Generally, biofilm formation seemed to attenuate the effect of low temperatures on BAC resistance. PAA was found to be most effective against both biofilms and planktonic cells, followed by NaClO and BAC. Resistance did not follow the same order for each biocide, which remarks the need of using a wide collection of strains in standard tests of bactericidal activity to ensure a proper application of disinfectants. Doses recommended by manufacturers for BAC, PAA and NaClO to disinfect food-contact surfaces were lower than doses for complete biofilm removal (i.e. MBEC) under some environmental conditions common in the food industry, which questions bactericidal standard tests and promotes the search for new strategies for biofilm removal.     

落实“一体化、精细化”措施谱写节能降耗新篇章

十一五期间胜利油田分公司以科学发展观为统领,以创先争优、比学赶帮超暨精细管理活动为载体,以建标、对标、追标、创标为抓手,通过落实一体化、精细化管理等措施,使油田节能工作跨上了一个新台阶,谱写了油田节能降耗新篇章。     

The efficacy of chemical sanitizers on the reduction of Salmonella Typhimurium and Escherichia coli affected by bacterial cell history and water quality

Washing fresh produce with potable water helps to remove microorganisms, providing about a 1- to 2-log reduction, but this process can also pose an opportunity for cross-contamination of bacteria in the washing tank. The objective of this study was to evaluate the efficacy of three chemical sanitizers, sodium hypochlorite, chlorine dioxide, and a silver-copper solution on the reduction of S. Typhimurium and extended-spectrum beta-lactamase (ESBL) E. coli as well as to evaluate the impact bacterial cell history and water quality had on sanitizer efficacy. This was investigated with three scenarios representing different contamination routes and history of cells: (i) on starved and non-starved cells in potable water, (ii) on starved and non-starved cells in lettuce wash water and on lettuce leaf punches, and (iii) on non-starved cells in organically loaded process wash water (PWW). Sodium hypochlorite (NaClO) and chlorine dioxide (ClO₂) were more effective in preventing cross-contamination in the potable water than the silver-copper solution. Starved and non-starved bacterial cells displayed minor differences in their susceptibility to sanitizing agents in the (i) potable water and (ii) lettuce wash water demonstrating that other conditions greater influenced sanitizer efficacy. Particularly, the organic load of the water, wash water temperature, and pathogen attachment and release from the produce were shown to affect a sanitizer's efficacy during washing. Furthermore, results emphasize that chemical sanitizer use should focus more on wash water disinfection, rather than produce decontamination, to prevent pathogenic cross-contamination during processing. Future research should investigate the feasibility of ClO₂ application during pilot-scale processing.     

Efficacy of sanitizers in reducing Escherichia coli O157:H7, Salmonella spp. and Listeria monocytogenes populations on fresh-cut carrots

Shredded carrots were inoculated with Escherichia coli O157:H7, Salmonella or Listeria monocytogenes and washed for 1 or 2 min with chlorine (Cl; 200 ppm), peroxyacetic acid (PA; 40 ppm) or acidified sodium chlorite (ASC; 100, 200, 500 ppm) under simulated commercial processing conditions. After washed, the carrots were spin dried, packaged and stored at 5 °C for up to 10 days. Bacterial enumeration was significantly (P ⩽ 0.05) reduced by 1, 1.5 and 2.5 log CFU/g after washing with ASC 100, 250 and 500 ppm, respectively. All sanitizers reduced pathogen load below that of tap water wash and unwashed controls. During storage at 5 °C the bacterial load of all treatments increased gradually, but to different extent in different treatments. ASC inhibited bacterial growth more effectively than the other sanitizers and also maintained the lowest pathogen counts (<1 log CFU/g) during storage. Organic matter in the process water significantly (P ⩽ 0.05) reduced the antibacterial efficacy of Cl, but not that of PA or ASC. Therefore, ASC shows the potential to be used as a commercial sanitizer for washing shredded carrots.     

减阻剂减阻效果的评价与分析

针对临邑-濮阳管道添加HG减阻剂的输油工况,建立并运用旋转圆盘装置进行了管输原油加剂模拟实验。对临濮线加HG减阻剂的减阻效果和影响因素进行了分析,确定了减阻率与雷诺数;减阻率与剪切强度;减阻率与加剂浓度;减阻率与输油温度等关系,为减阻剂减阻效果的评价和研究提供了一种新的方法。     

天然气水合物储运天然气技术

随着世界能源需求的不断增长以及天然气资源的大力开发和利用,必然要求不断完善天然气储运技术。天然气水合物储运天然气技术具有安全可靠、成本低等优势,备受瞩目。概括了目前天然气主要的储运方式,简单介绍了天然气水合物的特性,从天然气水合物的制备、储存、运输、分解等几个方面分析了天然气水合物储运技术,比较分析了天然气水合物技术与其他天然气非管输技术的经济性。     

八面河油田稠油掺水降粘集输技术

为了降低八面河油田稠油集输环节的生产运行成本,针对生产所需的稀油资源相对贫乏,污水资源相对充足且管理方便的实际情况,大力开展稠油集输掺污水降粘试验,对稠油掺污水降粘集输的现状、机理和生产工艺进行分析,形成了和目前油田生产相配套的典型工艺设计,基本解决各区块稠油开采集输问题,实现了油田污水余热资源的有效利用。在掺水降粘集输技术成功应用的同时,八面河油田还针对实际生产中存在的问题展开研究,确立了今后的科技攻关课题。     

硫催化CO／H2O选择性还原间二硝基苯制间硝基苯胺

介绍了硫作为催化剂,NaOH为助剂,用CO／H2O部分还原间二硝基苯（m—DNB）制备间硝基苯胺（m—NA）的方法。考察了反应温度、CO初压、反应时间、硫用量、NaOH用量和溶剂品种等因素对反应的影响。结果表明,以四氢呋喃（THF）作为溶剂,溶剂用量8mL,2．5mmol m—DNB、0．02g硫粉、0．05gNaOH和2mL水在180℃和CO初压为6MPa的条件下反应4h,m—NA的选择性为100％,m—DNB的转化率93．97％,m—NA收率也为93．97％。