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 profile of helva sold at retail markets in Izmir city and the survival of Staphylococcus aureus in this product

The objective of this research was to determine the microbiological profile of tahin helva, a low moisture confectionery. A total of 63 tahin helva samples were collected from the retail markets in Izmir, Turkey. These samples were examined by standard procedures for aerobic plate count (APC) and counts of moulds and yeasts, Enterobacteriaceae, Staphylococcus aureus and Salmonella spp. APC of samples ranged from <10 to 1.6 × 10⁵ cfu/g. The counts for moulds, yeasts and Enterobacteriaceae ranged from <10 to 1.8 × 10³, <10 to 7 × 10², <10 to 8.5 × 10² cfu/g, respectively. None of the samples contained S. aureus or Salmonella. The potential for survival of S. aureus in the product stored at refrigeration (4 °C) and room (20 °C) temperatures was evaluated by artificial contamination. S. aureus cells were still recovered after 9 months of storage at both temperatures. The results of this investigation indicate that S. aureus contamination of tahin helva, (a_w of 0.172) may constitute a potential public health hazard, depending on the extent of contamination and mishandled exercise at the sale area and the kitchen.     

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 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 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 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.     

Effect of gamma irradiation on Listeria ivanovii inoculated to iceberg lettuce stored at cold temperature

A low-dose gamma irradiation considerably reduced the total plate counts, psychrotrophic bacteria, lactic acid bacteria, and inoculated Listeria ivanovii on shredded iceberg lettuce. The total plate count of the lettuce irradiated at 1.0 kGy was reduced by 3.38 log₁₀ cfu/g on 0 storage day and to below the limit of detection (<2 log₁₀ cfu/g) as the cold storage was extended. Irradiation at 0.5 kGy effectively reduced the psychrotrophic bacterial counts and lactic acid bacterial counts in the lettuce to below the limit of detection (2 log₁₀ cfu/g). Irradiation at 1.0 kGy reduced L. ivanovii inoculated onto the shredded iceberg lettuce to below the limit of detection. The results showed that an irradiation at 1 kGy eliminates the bacterial contamination from the lettuce sample without any sensorial quality defect.     

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.     

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.     

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.     

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.     

Effects of gamma irradiation on the microbiological,nutritional, and sensory properties of fresh vegetable juice

The radiation pasteurization process was performed to improve the microbiological quality of fresh vegetable juice. Carrot and kale juice were irradiated and their microbiological, nutritional, and sensory properties were evaluated. The contaminating bacteria in the juices before irradiation ranged from 10⁶ to 10⁷ CFU/ml. All the aerobic and coliform bacteria in the carrot juice were eliminated by irradiation at a dose of 3 kGy, whereas about 10² CFU/ml of the bacteria survived in the kale juice irradiated at up to 5 kGy. However, the cells that survived from irradiation in the kale juice did not grow, whereas those of the non-irradiated samples reached 10⁹ CFU/ml after 3 days of storage at 10 °C. Amino acids were stable at up to 5 kGy of an irradiation. Radiation resulted in a dose-dependent reduction of the ascorbic acid content. However, the contents of the total ascorbic acid, including dehydroascorbic acid, were stable at up to 3 kGy of an irradiation. The sensory evaluation results immediately after irradiation were not different in any of the samples. At a 3-day storage, the sensory quality of the irradiated juice was adequate, while the quality of the non-irradiated control was deteriorated.     

Viscometry as a detection method for electron beam irradiation of black pepper

Samples of black pepper (Piper nigrum) packed in polyethylene pouches were irradiated at doses of 4.8 kGy and 9.6 kGy. Untreated and irradiated samples of black pepper were suspended in water, alkalized and after heat gelatinization the apparent viscosity was determined by a rotational viscometer. The black pepper samples showed a considerable loss of viscosity as a function of radiation dose in the dose range required for microbial decontamination of spices. Differences in apparent viscosity of heat gelatinised suspensions remained detectable over the entire four week period between the irradiated and unirradiated samples. Reproducible results obtained with this technique showed that the method is promising for detecting electron beam irradiated black pepper.     

VISCOSITY OF WATER IN OIL EMULSIONS

Increase in water cut in oil fields generally calls for an increase in the capacity of transport pipelines. Proper design and operation of the latter requires good knowledge of the thermophysical properties of flow resistance of crude-oil water mixtures. An experimental program aimed at measurements of oil-water emulsion viscosity for water cuts prior to the inversion point was conducted.

The present work reports on measurements of Nimr crude oil-water mixtures viscosity for different water cuts and a typical range of temperatures representative of field conditions (20°-50°C). Three mixing intensities of 10⁶, 5×10⁶ and 15×10⁶ erg/cm-sec generated by a dynamic coalescer and directly relevant to field conditions were used.

The results suggest that the inversion point occurs around a value of water cut of 35%. Both Newtonian and non-Newtonian (pseudo-plastic) behaviour were observed, and the ASTM viscosity model is found to be applicable to the emulsions. The effect of the mixing intensity on the resulting emulsion viscosity was found to be important at low temperatures and decreased at high temperatures. The experimental data fitted the available correlations in the literature.     

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.     

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.     

STUDY ON COKING KINETICS OF CHINESE GUDAO VACUUM RESIDUE

Using a molten metal bath as heat source of reaction, the coking kinetics of Gudao vacuum residue in temperature ranges of 400 - 440°C and 460-500°C were studied and kinetic models were developed. The order of reaction, pre-frequency factor and apparent activation energy of thermal-cracking were determined as 1.0, 7.853 × 10¹⁰ min^-1 and 175.3KJ/mol respectively. The results laid a solid foundation for technological computation, reconstruction and design of the tubular furnace using the residuum as its feedstock.     

页岩油原地量和可动油量评价方法与应用

页岩总油含量（TOY）和可动油含量（MOY）的计算是页岩油资源潜力评价的核心技术。根据对两次热解样品总有机碳含量（TOC）非均质性的认识,提出了一种基于两次热解数据来评价样品TOC含量非均质性的方法及一种校正吸附油含量的计算方法,并运用该方法对江汉盆地29个潜江组页岩样品和渤海湾盆地32个沙河街组页岩样品进行评价,结果显示：①TOC含量偏差平均值分别达到0.16%和0.34%,说明两组样品都存在一定的非均质性;②校正前、后吸附油含量的差值分别为0.85 mg/g和0.84 mg/g,说明进行等价TOC校正可以使吸附油含量、总油含量和可动油含量的计算结果更准确。同时,提出了一种基于页岩油密度及地层体积系数计算蒸发烃损失量的方法。采用以上新方法对鄂尔多斯盆地延长组7油层组（长7油层组）页岩油进行评价,结果显示：①吸附油含量占总油含量的63%,可动油含量占总油含量的37%,总油含量是游离烃量（S₁）的3.5倍,蒸发烃损失量约占总烃含量的9%,占S₁含量的29%;②长7油层组页岩油原地量为111.2×10⁸ t,可动油量为40.1×10⁸ t,说明长7油层组页岩油勘探潜力大。     

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.     

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.