Efficacy of chlorine dioxide gas and freezing rate on the microbiological quality of frozen blueberries

Blueberries are prone to microbial contamination, with growth of bacteria, yeasts and molds during bulk freezing negatively impacting quality and marketability. As a follow-up to our previous work, the combined impact of ClO₂ gassing and freezing rate on the microbiological quality of frozen blueberries was examined. Sixteen lugs of blueberries (∼9.1 kg/lug) were stacked inside a large plastic container at a commercial blueberry processing facility. In each of four trials, one container was exposed to ClO₂ gas (4 ppm) using three 3-kg sachets while one ungassed container remained untarped. Before and after commercial processing, 50-g samples of gassed and ungassed blueberries were quantitatively examined for mesophilic aerobic bacteria (MAB), yeasts, and molds. After processing, additional 50-g samples were placed in a −20 °C freezer under different conditions where the berries reached a temperature of −3 °C after 3 h (quick-frozen), 2 days (intermediate-frozen) and 5 days (slow-frozen). Fruit was sampled periodically during 6 months of frozen storage at −20 °C. MAB yeast and mold populations decreased ∼2 and 1 log CFU/g, respectively, in ClO₂-gassed and ungassed fruit, with MAB, yeast and mold populations increasing ∼1 log CFU/g during quick freezing to −3 °C and ∼2 log CFU/g during intermediate and slow freezing to −3 °C. Based on these findings, ClO₂ gassing followed by quick freezing provides an effective means for meeting the current microbiological standards being imposed by buyers of frozen blueberries.     

The occurrence and effect of unit operations for dairy products processing on the fate of aflatoxin M1: A review

Mold contamination has challenged the safety of feed production and processing because of its undeniable role in the spoilage and the possible consequent toxicity impact on human health and the economy. Aflatoxin M₁ (AFM₁) is a hepatocarcinogenic derivative of aflatoxin B₁ excreted into the milk after ingestion of feed contaminated by certain molds. Because of the important role of dairy products, especially milk in the human diet, there is a huge concern about the presence of AFM₁ in milk and dairy products. In this article, the occurrence of AFM₁ and the fate of AFM₁ during processing of milk and dairy products, such as yoghurt and cheeses, since 1996 until today, was reviewed. The evaluation of mechanisms by which AFM₁ is affected by each processing step is of major importance to provide useful and accurate information to develop risk assessment studies and risk management strategies.     

Effect of Anisakis simplex (sl) larvae on the spoilage rate and shelf-life of fish mince products under laboratory conditions

Wild caught marine fish are commonly infected with anisakid nematodes lodging in the intestinal linings or in the fish muscle. One of the most commonly found nematode parasites in marine fish is Anisakis simplex. During production of mince from the muscle of wild caught Anisakis-infected fish, the larvae would be disrupted during mince production. Any bacteria within or on the surface of such larvae are during the mincing process evenly distributed throughout the mince, and could thus possibly affect the spoilage rate of the final products. To explore if or how any bacteria associated with muscle-invading Anisakis larvae may affect the spoilage rate of fish mince, a controlled storage trial was conducted. Fillets of farmed Atlantic cod (Gadus morhua), exclusively fed on dried and heat-treated compound feed and hence expectably free from Anisakis larvae, were aseptically collected and homogenised. Fish mince aliquots were added different volumes of Anisakis homogenate based on larvae which were freshly sampled from the visceral cavity of NE Atlantic blue whiting (Micromesistius poutassou). The volumes of added parasite homogenate (parasite(+)-samples) reflected different infection intensities from 15 (low) to 50 (high) larvae per 100 g fish fillet, representing an actual Anisakis intensity range in the flesh of blue whiting. The samples were kept at 4 °C for 15 days and subjected to microbiological, sensory and chemical evaluation at 3 days intervals. Upon visual examination and plate count measurements (PC) on Iron Agar Lyngby (IAL), the samples without any parasite additives (no[parasite]) spoiled differently and more rapidly than any of the parasite(+)-samples. However, H₂S-producing bacteria were only recorded in the latter samples, which were also the only ones that showed increased levels of the spoilage indicator substance trimethylamine (TMA). Moreover, the parasite(+)-samples changed their sensory characteristics at a later stage compared to the no[parasite]-samples. Although some cultures of H₂S-producing bacteria were found on IAL, molecular identification by PCR-DGGE of the actual bacteria was not conclusive. Psychrobacter sp. which has no or only little spoilage activity, was identified in all samples until trial day 9, but was probably outgrown by the stronger spoilers Pseudomonas fluorescence/fragi and Photobacterium phosphoreum. Thus, and somewhat unexpected, our findings indicate that – under the present trial conditions – fish mince contaminated with bacteria which originate from Anisakis larvae, spoiled less rapidly than samples without any parasite-related bacteria present. Moreover, the shelf-life of fish mince was apparently not reduced by the presence of bacteria transferred to the mince by Anisakis larvae.     

The effect of pulsed UV light on Escherichia coli O157:H7, Listeria monocytogenes,Salmonella Typhimurium,Staphylococcus aureus and staphylococcal enterotoxin A on sliced fermented salami and its chemical quality

Pulsed UV light (PL) applied at a fluence of 3 J/cm² was effective to reduce Listeria monocytogenes, Escherichia coli 0157:H7, Salmonella Typhimurium and Staphylococcus aureus for 2.24, 2.29, 2.25 and 2.12 log CFU/g on the surface of dry fermented salami. Further increase in the fluence of PL treatment did not increase levels of microbial inactivation. However, the time interval between the contamination and PL treatment was found to have a significant impact on the efficacy of PL treatment and should be kept as short as possible. After initial PL treatment slices of fermented salami were packed in vacuum or in 80%CO₂/20%N₂ modified atmosphere and stored at 4 °C to investigate the effect of PL treatment on protein and lipid oxidation as the shelf life of fermented salami is not usually limited by microbial deterioration, but by chemical and sensory alterations. In this study observed lipid oxidation values for PL treated vacuum and modified atmosphere packed fermented salami slices fall within the acceptable threshold for the rancid odor, except for the sample treated with the highest fluence tested (15 J/cm²), packed in modified atmosphere and kept in cold storage for 9 weeks (1.23 mg MDA/kg). All values were below the threshold for rancid flavor, too. The significant rise in protein oxidation of PL treated fermented salami slices, perceived as 28% increase of carbonyl content compared to untreated samples, was observed only after 9 weeks of cold storage in both vacuum and modified atmosphere packed samples. The results of chemical analysis are in agreement with previously published results of sensory analysis. Current results show the applicability of PL to improve microbial safety of sliced fermented salami that are prone to cross-contamination without affecting quality attributes by lipid and protein oxidation.     

油料储运场所用电安全管理中几个易被忽视的“小问题”

对油料储运场所用电安全管理中易被忽视的用电设备维护保养不及时,接地、接零装置管理不规范,使用测量仪表方法不正确,在危险场所随意安装临时用电设备、私搭线路等小问题及其危害的严重性进行了分析,指出产生问题的根源,提出了应采取的防范措施。     

Kinetic evaluation and comparison of the heavy oil and its low temperature oxidized products based on thermal analyses

The main focus of this work was to investigate the thermal behavior of heavy oil and its low temperature oxidized products. The distributed activation energy method (DAEM) calculation results indicated that coke as fuel deposited from static low temperature oxidation (LTO) experiments can significantly reduce the activation energy of oxidized oil in high temperature oxidation (HTO) period, which brought the possibility for application of Tahe ISC technique without artificial ignition devices. The activation energy of the samples during the HTO period showed that after the conversion rate attained roughly 0.3, the remaining reactions became much more likely to occur.     

损伤缺陷对K型试验井架应力分布影响分析

以K型试验井架为例,用有限元分析方法,对无损伤井架以及存在截面腐蚀、立柱穿孔、斜撑缺失、载荷偏心等损伤和缺陷井架进行分析与对比。结果表明,立柱锈蚀、穿孔或开裂等局部损伤使井架立柱损伤部位应力明显增大,而对井架的整体应力分布影响不大;基础下沉对井架的下部立柱、人字架和斜撑的应力分布有影响,而对其余各层影响不大;钩载偏心对井架各层的应力分布有较大影响,斜撑缺失使井架该位置及相邻层立柱和斜撑的应力明显增大,对其余各层的影响不大。对有损伤和缺陷的井架,除按照SY/T 6236—2008标准进行检测评定外,还应对这些局部损伤和缺陷本身进行安全评定。     

Laboratory evaluation of the effect of bentonite on performance of bitumen and hot mix asphalt mixtures

In this research study, bentonite additive was used to modify original binder (60–70 penetration grade). The experimental program included use of five percentages of bentonite (10%, 15%, 20%, 25%, and 30%) by weight of bitumen. Physical properties of modified and unmodified bitumen were evaluated through penetration grade, softening point, ductility, and temperature susceptibility tests. The performance characteristics of mixtures were determined through indirect tensile strength, resilient modulus, and moisture susceptibility tests. The results demonstrate that addition of bentonite improves Marshall stability, tensile strength, and resilient modulus of mixtures, but led to decrease the resistance to moisture damage.     

The effect of different processing parameters on the efficacy of commercial post-harvest washing of minimally processed spinach and shredded lettuce

The effect of different processing parameters on the efficacy of commercial post-harvest biocidal washes to decrease the bacterial loading on spinach and lettuce has been evaluated. Sampling was performed at two spinach processors (Facility A & B) and a shredded lettuce producer (Facility C). Aerobic colony counts (ACC) and coliform counts were determined on samples taken at pre- and post-wash. In parallel, the heterotrophic plate count (HPC) and coliform levels in wash water was also determined. Processing parameters measured were the temperature of leafy greens (pre- and post-washing) and wash water. The sanitizer levels (peroxyacetic acid, oxidation-reduction potential), pH, conductivity and turbidity were also measured. The wash process in Facility B had a residence time of 50 s for the spinach, maintained a constant hypochlorite concentration and continuously re-charged the tanks with fresh water. In contrast, Facility A had a short residence time (15 s) did not maintain a constant sanitizer (peroxyacetic acid) concentration or re-charge tanks with fresh water. Despite the differences in processing operations there was no statistical difference between the log count reductions (LCR) obtained in ACC and coliform counts although counts were only reduced by <0.6 log cfu/g. The carriage of Escherichia coli on pre-wash spinach was 19% and 25% in Facility A and B respectively. There was a high prevalence (57% positive) of E. coli in the wash water of Facility A with none being recovered in water samples taken from Facility B. Yet, the carriage of E. coli on post-wash spinach was the same in the two facilities (7%). Lettuce harboured a lower level of both ACC and coliforms with LCR being significantly greater than spinach. In general, the LCR in ACC and coliforms could be positively correlated to bacterial counts of pre-washed leafy greens and conductivity (solids content) of the wash water. A negative correlation was found between LCR and water temperature. Interestingly, within the ranges measured the LCR was independent of the bacterial loading of the water. The results of the study confirmed the limited efficacy of biocidal washes to remove field acquired contamination. Although it is thought maintaining a low microbial loading in the wash water and maintaining sanitizer concentration is key the current study suggests high conductivity and low temperature of the wash water enhances the LCR achieved.     

An investigation of the effect of wettability on NMR characteristics of sandstone rock and fluid systems

Predicting reservoir wettability and its effect on fluid distribution and hydrocarbon recovery remains one of the major challenges in reservoir evaluation and engineering. Current laboratory based techniques require the use of rock–fluid systems that are representative of in situ reservoir wettability and preferably under reservoir conditions of pressure and temperature. However, the estimation of reservoir wettability is difficult to obtain from most laboratory experiments. In theory, it should be possible to determine the wettability of reservoir rock–fluid systems by nuclear magnetic resonance (NMR) due to the surface-sensitive nature of NMR relaxation measurements. Thus, NMR logs should in principle be able to give an indication of reservoir wettability, however, as yet there is no proven model to relate reservoir wettability to NMR measurements. Laboratory NMR measurements in representative and well-characterised rock–fluid systems are crucial to interpret NMR log data.A series of systematic laboratory experiments were designed using a range of sandstone core plugs with the aim of investigating the feasibility of using NMR measurements as a means to determine wettability. NMR T₂ spectrum measurements were performed in reservoir core plugs at different saturations and wettability states. The samples were first cleaned by hot solvent extraction, then saturated with brine and a drainage/imbibition cycle performed. At the lowest brine saturation the same samples were aged in crude oil and a further drainage/imbibition cycle performed. NMR transverse relaxation time, T₂, was measured on fully saturated samples, at residual saturations and some intermediate saturation values. The wettability of the samples is evaluated using the Archie's saturation exponent and by Amott-Harvey wettability index.The wettability of the cores studied ranged from mixed-wet to oil-wet. The NMR T₂ results for cleaned and aged reservoir core plugs, containing oil and water, show that fluid distribution and wettability can be deduced from such measurements. The results on aged core plugs suggest that the oil occupies a wide range of pore sizes and is in contact with the pore walls. The results presented in the paper suggest that NMR T₂ relaxation has the potential to be an alternative technique to evaluate rock wettability in the laboratory and in the reservoir.