Microbiological quality assessment of garri with reference to thermonuclease activity

The microbiological quality of garri obtained from open markets and traditional processing industry in Benin City with reference to staphylococcal contamination was investigated. Enumeration of the total heterotrophic bacteria, total fungal propagules and Staphylococcus aureus in food samples was carried out using appropriate media. The staphylococcal thermonuclease activity determination was used as an indicator of previous (substantial) growth of S. aureus and possible presence of staphylococcal enterotoxins. The total heterotrophic bacterial count of the open markets’ samples was 7.75±2.87×10³ cfu/g with corresponding staphylococcal count of 1.65±0.82×10³ and fungal propagule count of 2.50±1.14×10² cfu/g. Samples obtained immediately after processing from the traditional garri industry revealed total heterotrophic bacterial count of 5.00×10¹ cfu/g; staphylococcal count of 5.00×10⁰ cfu/g and no fungal count. The zone diameter of thermonuclease activity was 8.13±0.52 mm for open markets’ samples while traditional processing industry samples have 7.83±0.54 mm. From the study, it was found that there was contamination and growth of S. aureus and possibly the presence of staphylococcal enterotoxin in the product. The public health significance of the microorganisms with the production of thermonuclease and enterotoxins by S. aureus are discussed.     

Microbiological characteristics of cake prepared from rice flour and sticky rice flour

Microbiological, chemical and sensory changes in MiGao (a traditional Chinese steamed cake) were studied during five days of storage at 25 °C. Microorganisms examined for were: Enterobactericeae, lactic acid bacteria, Gram-positive, catalase-positive cocci, Staphylococcus aureus, Bacillus strains, yeasts and moulds, and pH and moisture content were also analyzed. Total plate counts in the products under study in the third day of storage were in the range <10³ CFU/g and the shelf-life of the product was estimated to be only two or three days by the panelists. During the first two days, Gram-positive bacteria were dominant, mainly represented by Staphylococcus epidermidis. Bacillus strains occurred by the third day, reaching a maximum level of 1 × 10⁶ CFU/g after five days of storage. No Enterobactericeae or Lactic acid bacteria were detected in the processed products throughout the storage period. All the isolated strains from the mannitol salt agar belonged to the genus Staphylococcus. The predominant species were S. epidermidis and S. aureus. Most Bacillus strains, isolated from the tryptone soya agar, belonged to the species Bacillus brevis. The count of yeasts and moulds increased slowly but remained low throughout the storage period.     

Microbiological quality of fruit juices sold in Tripoli–Libya

Fruit juices are becoming an important part of the modern diet in many communities. Data regarding the microbiological quality of foods, particularly fruit juices, sold in Libya and the neighboring North African countries are few if not lacking. Using standard microbiological procedures, 146 fruit juice samples sold in Tripoli were examined. Total bacterial counts (TBC) of samples examined ranged between <1 and 3 × 10⁵ CFU/ml (mean = 5 × 10⁴). Almond juice showed the highest TBC ranging between 1.8 × 10³ and 3 × 10⁵ (mean = 1.7 × 10⁵). Staphylococcus aureus was detected in 8 (5.5%) samples, Streptococcus spp. in 4 (2.7%), coliforms in 33 (22.6%), Escherichia coli (none were of serogroup O157) in 3 (2.1%), Klebsiella pneumonia in 17 (11.6%), Aeromonas spp. in 3 (2.1%), Pseudomonas aeruginosa in 6 (4.1%), Candida albicans in 18 (12.3%), Candida spp. in 109 (74.7%) and other yeasts in 85 (58.2%). Many of these organisms can cause disease in humans, which indicates that a large number of juices tested did not fulfill the Libyan guidelines for the microbiological quality of juices. Application of the HACCP system should be introduced into the food industry sector to improve the quality of fruit juices and other foods manufactured in Libya.     

Microbiological safety and quality of commercial sufu – a Chinese fermented soybean food

In this study, the microbiological safety and quality of commercial sufu were investigated. Twenty-three samples of three different types of sufu were obtained, mainly in China and some in The Netherlands. Chemical parameters analysed included moisture, pH, free amino N, NaCl, ethanol, sucrose, glucose, and fructose. Concentrations of NaCl, ethanol, glucose and fructose varied from 6.2%, 0.5%, 0% and 0% to 14.8%, 6.3%, 6.2% and 4.8%, respectively. Microbiological analyses were done for total count of mesophilic aerobic bacteria (TMAB), bacterial endospores, total count of halotolerant bacteria at 10% (THB10) and at 17.5% NaCl (THB17.5), lactic acid bacteria (LAB), fungi, Enterobacteriaceae, and the following pathogens: Bacillus cereus, Clostridium perfringens, Staphylococcus aureus and Listeria monocytogenes. High levels (>10⁵ CFU/g) of TMAB and bacterial endospores were found in most samples, and 85% of TMAB was identified as Gram-positive. Considerable levels (10⁵ and 10⁷ CFU/g) of LAB were detected in two samples of white sufu, and isolates of LAB were identified as most probably Lb. casei. One-third of the samples contained less then 10³ CFU/g B. cereus, but three samples had over 10⁵ CFU/g indicating potential hazard to consumers. All samples had less than 10³ CFU/g C. perfringens, except sample R11 (10⁵ CFU/g). S. aureus could not be detected in any of the samples tested since the competitive microflora (usually bacilli) disturbed typical features on the selective medium used; however S. aureus enterotoxin A was detected in some of the white and grey sufu samples. Fungi, Enterobacteriaceae, and L. monocytogenes were not detected in any of the samples. Based on these results, a microbiological guideline for safe commercial sufu is proposed.     

Effect of usage Urtica dioica L. on microbiological properties of sucuk, a Turkish dry-fermented sausage

The effect of dried-ground Urtica dioica L. on microbiological characteristics of Turkish dry-fermented sausage (sucuk) were investigated. Dried-ground Urtica dioica L. was added to sucuk batters by the rate of 0%, 1%, 3% and 5%, and microbiological analysis were made on the 0, 3, 7, 10 and 14 days of ripening period.

According to the results, both the level of Urtica dioica L. and ripening time had a significant effects on the total aerobic mesophylic bacteria, lactic acid bacteria, Micrococcus/Staphylococcus, yeast-mould and Enterobacteriaceae counts (p<0.01). It was determined that the interactions ripening time × the levels of Urtica dioica L. had a significant effects on the counts of total aerobic mesophylic bacteria, lactic acid bacteria, Micrococcus/Staphylococcus, yeast-mould and Enterobacteriaceae (p<0.01). Enterobacteriaceae count were also found to be under the detectable level (<100 cfu/g) in sucuks (in day 14 of ripening) containing 3% and 5% Urtica dioica L.     

Potential application of low dose gamma irradiation to improve the microbiological safety of fresh coriander leaves

A local market survey of fresh, raw coriander leaves, which is a component of many ready-to-eat, Indian dishes showed large variation in their bacterial load (7.0×10⁶–1.36×10⁸ cfu/gm) and mold and fungi (3.0×10³–1.0×10⁴ cfu/gm) and presence of potentially pathogenic bacteria such as faecal coliforms, Listeria and Yersinia. Conventional chlorination treatment affected the structural integrity of leaves leading to enhancement of rotting. Exposure to a low dose of 1 kGy was efficient for bacterial decontamination and elimination of potential pathogens without affecting the keeping quality of coriander leaves upto two weeks storage at 8–10 °C, measured visually in terms of degree of yellowing and rotting. Irradiation at higher doses led to the increased rotting during storage. The total chlorophyll contents as well its components, chlorophyll a and b did not change significantly on irradiation and subsequent storage. Similarly, the total carotenoid levels remained unaffected by exposure to 1 kGy dose, however, a dose dependent enhancement in their extractability was observed in irradiated leaves. No qualitative differences were observed in the GLC profile of volatile oils of control and irradiated (1 kGy) samples. There were no significant quantitative changes in the constituents of the major aroma compounds obtained from these two samples. Effects of irradiation on storage of the seasoning were also assessed.     

An evaluation of the effect of storage and processing temperatures on the microbiological status of sous vide extended shelf-life products

The microbiological and organoleptic quality of selected sous vide products was monitored over a storage period of up to five weeks at 3°C and 8°C, respectively. Sous vide products stored at the recommended temperature of 3°C showed negligible microbial growth and were found to be organoleptically acceptable throughout the storage period. Total plate counts at the end of the fourth week of storage were in the range <10–7×10³ CFU/g for all 19 products under study. Listeria monocytogenes, Salmonella, Clostridium perfringens, Bacillus cereus and Enterobacteriaceae were not detected in any of the processed samples. At 8°C, under temperature abuse conditions, while some products had acceptable microbial levels of 10²–10⁴ CFU/g after three weeks, others such as chicken chasseur had counts above 10⁶ CFU/g by the second week of storage. Lactic acid bacteria and Pseudomonas species were dominant in the microbial flora of spoilt samples and B. cereus (>3×10⁴ CFU/g) was isolated from spoilt chicken chasseur samples in the fourth week of storage at 8°C. Critical factors affecting sous vide product safety are discussed.     

Microbiological safety of kinema, a fermented soya bean food

Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 10⁴ cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 10⁵ cfu/g in 10 of the 15 samples. Escherichia coli exceeding 10⁵ cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus, 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus. It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable.     

Occurrence of pathogenic bacteria in raw milk, cultured pasteurised milk and naturally soured milk produced at small-scale dairies in Zimbabwe

The presence of selected pathogenic bacteria in raw milk (RM), cultured pasteurised milk (CPM), and naturally soured raw milk (NSRM) sold at three small-scale dairies in Zimbabwe was determined. Mean levels of Escherichia coli in RM, CPM and NSRM were 4.5, 7.1 and 7.8 log₁₀ CFU ml⁻¹, respectively. Enterotoxigenic E. coli (ETEC), producing heat-stable enterotoxin (ST1) was found in 16 of the samples. Presumptive Staphylococcus aureus was identified in 7 of 12 RM, 15 of 27 CPM and 20 of 21 NSRM samples at mean levels of 5.2, 7.3 and 7.8 log₁₀ CFU ml⁻¹, respectively. Klebsiella pneumonia spp., Enterobacter cloacae, Proteus mirabilis, Hafnia alvei, Citrobacter spp., Serratia marcescens and Aeromonas hydrophilia were found in 27 samples. The high number of S. aureus, E. coli, identification of ETEC-ST1 and the other pathogenic microorganisms found in pasteurised and unpasteurised milk products represent a health hazard to the consumers and emphasises the need for improved hygiene practice at all levels in the dairy.     

Determination of heavy metals in milk by potentiometric stripping analysis using a home-made flow cell

A method is described for sensitive and reliable determination of trace concentrations of cadmium, lead and copper in real samples by stripping potentiometry with a home-made flow cell. The selection of the experimental conditions was made using experimental design methodology. The optimum conditions for the method include an acetic acid–acetate buffer mixture (pH 3.4) as supporting electrolyte, an electrolysis potential of −1.1 V and a flow rate of 3 ml min⁻¹. The detection limits were 6.51 × 10⁻¹⁰ mol l⁻¹ for cadmium, 4.60 × 10⁻¹⁰ mol l⁻¹ for lead and 8.59 × 10⁻¹⁰ mol l⁻¹ for copper, with an electrolysis time of 900 s. The relative standard deviations at this concentration level were 0.038, 0.086 and 0.095, respectively. In order to check the analytical accuracy, standard solutions have been used and recoveries close to 100% were obtained. The method was successfully applied to the determination of cadmium, lead and copper in powdered milk, using the method of standard additions.     

Determination of biogenic amines in sucuk

The biogenic amines content of sucuk (Turkish dry fermented sausage) were determined on 30 samples obtained from retail markets and butchers in Turkey. Also, pH and a_w values, microbiological properties, and NPN levels of these samples were analyzed. The most important biogenic amines were tyramine (range 2.4–676 mg/kg), followed by putrescine varied from not detected to 364 mg/kg. Histamine content was under 50 mg/kg in 80% of the samples while it was over 100 mg/kg in only one sample. Tryptamine was detected in 16 of 30 samples in the range of 1.2–82.3 mg/kg.

Lactic acid bacteria, Micrococcus/Staphylococcus and Enterobacteriaceae counts of samples varied from 2.84 to 8.85 log cfu/g, <2.00 to 6.74 log cfu/g, and <2.00 to 5.04 log cfu/g, respectively. pH values were varied between 4.53 and 6.29 while water activity (a_w) were measured to be between 0.761 and 0.960. NPN values were determined to be between 1.47% and 4.10%. Generally, total amine content was high in samples that had high NPN levels.     

Aspects of the safety of fish caught off the coast of Qatar

Uncooked, edible portions (including skin) of 20 species of marine fish popular with consumers in Qatar were examined for levels of copper, zinc, lead and mercury, as well as for the presence of enteric pathogens that might indicate faecal pollution of fishing grounds or careless handling during landing of the catch. The maximum level of detected mercury was 0.24 mgkg⁻¹, while the lead content was below the level of detection in 95% of the species examined; copper and zinc were at levels that might be considered nutritionally desirable rather than toxic. No pathogens were detected, and the total colony counts ranged from 1.0×10³ to 8.0×10⁵ cfug⁻¹. Overall, the results for the parameters examined suggested that local fish can be eaten with confidence.     

Elimination of Yersinia enterocolitica on carrots (Daucus carota L.) by using household sanitisers

In this study, the effects of lemon juice, the mixture of lemon juice–vinegar (1:1) and lemon dressing against Yersinia enterocolitica on carrot were investigated. Carrots inoculated with Y. enterocolitica cells (approximately 10⁶ cfu/ml) were treated with 100%, 75% and 50% lemon juice, a mixture of lemon juice–vinegar, and lemon dressing for 0, 15, 30 and 60 min. Enumeration of Y. enterocolitica populations on CIN agar beside TSA agar by using two methods as then performed. One hundred percent lemon juice was the most effective agent used, completely inhibiting viable cells of Y. enterocolitica on carrot after 15 min exposure. Although no growth was observed on carrots treated with 100% lemon juice for 15 min, there was no statistical difference between the antibacterial effects of 100% lemon juice, 75% lemon juice, the mixture of lemon juice–vinegar and lemon dressing whilst the effect of 50% lemon juice was statistically different from those solutions (P < 0.05) and its definite inhibitive activity was seen after 60 min treatment.     

川南地区百亿立方米页岩气产能建设地质工程一体化关键技术

四川盆地南部地区下志留统龙马溪组页岩气资源丰富,但地质、工程条件复杂,页岩气规模效益开发面临着严峻的挑战。为了解决川南地区页岩气"部署设计难度大、优质储层钻遇率提高难度大、复杂缝网形成难度大、单井产量和单井估算最终采收量(EUR)提高难度大"等问题,通过系统梳理和总结10余年的页岩气勘探开发成果,形成了适用于该区的页岩气地质工程一体化高产井培育方法,并开展了现场试验和推广应用。研究结果表明:①所形成的三维地质建模、三维地质力学建模、复杂缝网模拟和产能数值模拟等4项关键技术,为该区页岩气井全生命周期的方案设计、现场实施、实时调整提供了重要的决策依据和指导,有效提高了页岩气单井产量和EUR;②实施地质工程一体化高产井培育方法,可以大幅度提高长宁—威远国家级页岩气示范区页岩气单井产量,其中长宁区块井均测试日产量由10.9×10~4 m~3提高到26.3×10~4 m~3、最高测试日产量达到62×10~4 m~3,威远区块井均测试日产量由11.6×10~4m~3提高到23.9×10~4 m~3、最高测试日产量达到71×10~4 m~3;③推广应用地质工程一体化高产井培育方法,可以实现高产井的"复制",培育了一批EUR超过1.5×10~8 m~3、部分超过2×10~8 m~3的高产井,其中泸州区块4口深层页岩气井,井均EUR达1.98×10~8 m~3。结论认为,所形成的地质工程一体化页岩气高产井培育方法,是破解页岩气规模效益开发难题的有效措施,可以为国内外非常规油气藏的规模效益开发提供借鉴。     

An assessment of the microbial quality of the air within a pork processing plant

The aim of this study was to assess microbial quality of the air in a pork processing plant and from visual inspection to identify factors which may contribute to increase/decrease air-borne contamination. Total viable count (TVC), total coliform count (TCC) and the presence of Staphylococcus, Listeria and Salmonella species were used to evaluate the microbial quality of the air at five locations in the plant, at five time points during production. A visual inspection was used to identify risk factors which may increase the micro flora of the air in the plant. The highest TVC (133 cfu m⁻³), coliform counts (8 cfu m⁻³) and Staphylococcus aureus counts (8 cfu m⁻³) were found in the cooking area, blast chill and raw areas respectively. The higher levels of TVC, coliforms and Staphylococcus could most likely be attributed to people in the area, condensation and mechanically generated aerosol respectively although factors such as psychrometric properties of air and building ventilation factors which were outside of the scope of the current investigation would also need to be considered before a definite conclusion could be made in this regard. Listeria and Salmonella were not detected in the air in the plant. However, the inspection suggested the air in the raw area to be most at risk of microbial contamination, due to higher levels of microbial sources. Overall, microbial levels in the air were low, which suggests that the current control measures such as the positive air pressures from high-risk to low-risk, internal separators and closed drains were effective in reducing the microbial contamination in the air of the plant.     

Synthesis and Surface Active Properties of Novel Nonionic Aryl Oleic Diethanolamide Surfactants

A series of novel aryl oleic diethanolamide (AOD) surfactants with different hydrophobic groups were synthesized. An aromatic ring introduced to a long alkyl chain had a significant effect on reducing water surface tension. The critical micelle concentration (CMC) and the surface tension (γ_cmc) at the CMC were investigated. The CMC was 4.56 × 10^-8 mol/L to 5.83 × 10^-6 mol/L for AOD1:1 (molar ratio of aryl oleic acid: diethanolamide = 1:1) and corresponding γ_cmc was 36.4 mN/m to 39.3 mN/m. The CMC of AOD1:2 (molar ratio of aryl oleic acid: diethanolamide = 1:2) were in 1.21 × 10^-7-9.98 × 10^-6 mol/L and γ_cmc were in 31.6-34.4 mN/m.     

ESTIMATION OF TOXIC COKE DEPOSITS ON FRESH AND REGENERATED Pt/Al2O3 CATALYST FROM METHYLCYCLOPENTANE REFORMING IN H2 AND N2 ATMOSPHERES.

An estimate of the quantity of toxic coke deposited on fresh and regenerated Pt/Alj₂O₃ catalyst has been determined for methylcyclopentane (MCP) reforming in a Berty CSTR at 390°C, W/F=0·11 g min cm^-3, total pressure of 1 atm and MCP partial pressure of 9·2 × 10^-2 atm in H₂ or N₂ carrier. Eleven cycles consisting each of catalyst deactivation, regeneration and reduction were investigated with 3 in H₂ and 8 in N₂. Oxidizable (primary) coke deposits were higher in N₂. However, higher levels of toxic (secondary) coke were deposited in H₂. The ratio of oxidizable to toxic coke lies between 1-15×10³ in H₂ and 22 - 55 × 10³ in N₂ The coke-time profiles for secondary coke removal exhibited maxima suggestive of three types of secondary coke with varying reactivity in H₂. Furthermore, the results strongly suggest that the cokes were layered on acidic coke forming sites with the solid phase transformation of primary to secondary coke occurring at the catalyst-coke interface.     

中国页岩气开发进展、潜力及前景

中国作为北美之外最大的页岩气生产国,随着页岩气勘探开发的持续快速推进,在埋深3 500 m以浅的海相页岩区已经建成200×10⁸ m³的页岩气年产规模。未来全国埋深3 500 m以浅页岩气能否继续稳产上产、埋深超过3 500 m的深层页岩气的开发潜力如何,既是评价和判断未来中国页岩气资源开发潜力和发展前景等的前提,也是决定能否在川渝地区建成"天然气大庆"的关键。为此,通过总结中国页岩气理论认识和工程技术发展成果,分析页岩气资源的开发潜力,预判了未来的发展前景。研究结果表明:①在页岩气理论体系方面,明确了海相深水陆棚笔石黑色页岩形成条件及页岩气富集机理,建立了"甜点区"和"甜点段"地质理论,初步构建基于"人造气藏"的页岩气开发理论,建立了四川盆地南部地区深层优质页岩厚度大、保存条件好、发育微裂缝与超压的页岩气富集高产模式;②在页岩气工程技术方面,水平井多段压裂等关键工程技术实现了跨代发展,支撑了中国仅用6年时间就实现了页岩气年产100×10⁸ m³、其后又用2年时间实现了年产200×10^8<...     

Application of electrolyzed oxidizing water on the reduction of bacterial contamination for seafood

For reducing bacterial contamination, electrolyzed oxidizing water (EO water) has been used to reduce microbial population on seafood and platform of fish retailer. The specimens of tilapia were inoculated with Escherichia coli and Vibrio parahaemolyticus, and then soaked into EO water for up to 10 min. EO water achieved additional 0.7 log CFU/cm² reduction than tap water on E. coli after 1 min treatment and additional treatment time did not achieved additional reduction. EO water treatment also reduced V. parahaemolyticus, by 1.5 log CFU/cm² after 5 min treatment and achieved 2.6 log CFU/cm² reduction after 10 min. The pathogenic bacteria were not detected in EO water after soaking treatment. In addition, EO water could effectively disinfect the platform of fish retailer in traditional markets and fish markets.     

Survival of Campylobacter jejuni on vacuum or carbon dioxide packaged primal beef cuts stored at −1.5 °C

The ability of two Campylobacter jejuni strains (MOO3, a cattle isolate, and MOO8, a sheep isolate) to survive on chilled, preservatively packaged primal beef cuts was examined. Each of the strains was inoculated separately (10⁵ cfu g⁻¹) onto 500 g beef steaks, packaged under vacuum or 100% carbon dioxide, and stored, with uninoculated controls, for 41 days at −1.5 °C. Bacterial numbers were determined at 0, 1, 3, 6, 13, 20, 27, 34 and 41 days by dilution, plating on both Columbia Sheep Blood Agar and Campylobacter Blood-Free Selective Agar and incubation at 42 °C for 48 h under microaerophilic conditions. In addition, an aerobic count on all samples was determined by dilution, plating on Plate Count Agar and incubation at 25 °C for 72 h. No significant changes in numbers of the C. jejuni strains or aerobic bacteria occurred during storage at −1.5 °C on steaks packaged under either vacuum or carbon dioxide. The ability of these pathogens to survive standard preservative packaging conditions is different from that reported in the literature and therefore a cause for concern. Strict hygienic practice or the implementation of decontamination technologies are recommended as mechanisms to assure safety of meat with respect to this pathogen.