Effect of nisin on the storage of sous vide processed Korean seasoned beef

Seasoned beef called Jangzorim in Korea is produced by boiling in soy sauce, and is a popular food in Korea. The aim of this study is to evaluate the microbial safety and physical qualities of sous vide processed seasoned beef, and the effect of nisin during storage. Sous vide processed packages with or without nisin (100 IU or 500 IU) were stored at 4 °C or 25 °C for 60 days, and samples measured for quality at regular intervals throughout this storage period. In the case of 25 °C storage, the number of mesophilic microorganisms in seasoned beef packages without nisin increased markedly, but with nisin there was no observed increase. Psychrotrophic microorganisms, anaerobic microorganisms, and B. cereus cells showed similar trends, although C. perfringens was not detected in all samples. At 25 °C storage, changes in the cutting force of packages containing nisin showed no significant change, packages without nisin decreased markedly. The colour of packages without nisin showed a drastic decrease in lightness (‘L’) while no changes were observed in packages with nisin.     

Effects of pulsed light on the organoleptic properties and shelf-life extension of pork and salmon

The aim of our study was to assess the impacts of a pulsed light (PL) technology on the shelf-life, microbial inactivation, chemical and sensorial qualities of raw pork roast (RPR), roast pork (RP) and raw salmon (RS). In the first step, the effects of PL on aerobic flora and Pseudomonas fluorescens were investigated. Afterwards samples were evaluated in terms of their colour, shelf-life and lipid peroxidation. A maximum rate of microbial inactivation, 3.4 log (CFU/g), was found in the case of RP samples and was accompanied by improved shelf-life. Significant colour changes were found for the RP and RPR samples exposed to PL dose of 30 J cm⁻². The PL treatments at 3 and 10 J cm⁻² did not induce the lipid peroxidation. Malondialdehyde (MDA) content substantially increased in RS and RP samples submitted to 30 J cm⁻², i.e. by 39.3% and 25.5%, respectively. In conclusion, PL technology has a potential for inactivation of both, aerobic flora and P. fluorescens, however moderate fluencies has to be applied in order to obtain satisfying level of decontamination and high product quality.     

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.     

Effects of processing and storage variables on penetration and survival of Escherichia coli O157:H7 in fresh-cut packaged carrots

The effects of severity of slicing and peeling, and of storage atmosphere and temperature on the survival of Escherichia coli O157:H7 at and below the cut surfaces of fresh-cut carrot discs were determined. Slicing with a blunt machine blade enhanced penetration of E. coli O157:H7 and its subsequent survival during storage at 8 °C. Significantly (P < 0.05) higher numbers of cells (0.5 log CFU g⁻¹) penetrated deeper (475–500, 725–750 and 975–1000 μm) into carrot tissue sliced with a blunt machine blade compared to those sliced with a razor blade. Counts on Day 3 and Day 5 of storage remained higher in carrot tissue sliced with a blunt machine blade at all depths sampled. There were no significant effects of peeling method on penetration and survival. Storage of carrot slices in sub-optimal atmospheres (20%CO₂/1%O₂ resulted in increased survival of cells at the surface and within the tissue compared to storage in more optimal atmospheres (5% CO₂/3% O₂). Increasing storage temperature from 4 to 10 °C resulted in growth of E. coli O157:H7 at all sample depths. For all experiments, E. coli O157:H7 cells colonising the surface generally survived better than cells that penetrated into the tissue. The data are relevant to improving microbial safety in the fresh-cut sector by demonstrating that cutting with sharp blades (e.g. during harvesting and processing) reduces the depth of potential contamination by E. coli O157:H7. This may also have implications for more efficient anti-microbial dipping and reduced pathogen survival during storage.     

Smallholder dairy processing in Zimbabwe: the production of fermented milk products with particular emphasis on sanitation and microbiological quality

Microbiological quality and hygienic practice during the production of naturally sour milk (NSM), made of unpasteurised milk, and cultured milk (CM), made of pasteurised milk, were studied at three smallholder dairies in Zimbabwe. Petrifilm™ was used for the determination of Escherichia coli, coliforms and aerobic mesophilic count (AMC). AMC Petrifilms used as contact plates showed that 52% of utensils at the dairies (N=80) were not acceptably clean (>100 CFU per $\text{20}\text{cm}{}^2$). E. coli was found in 81% of the samples of NSM (N=31) and in all samples of CM (N=70). Approx. 39% of NSM samples and 47% of the CM samples contained more than 1000 CFU E. coli ml⁻¹. The high numbers of E. coli found in pasteurised milk emphasise the need for improved hygiene practice at the dairies. Since NSM is not pasteurised, the hygiene at the farm is additionally important for production of NSM. The hygiene and handling at the farm should therefore be especially emphasised at the dairies where NSM is commonly produced.     

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 extending processing plant operating time on the microbiological quality and safety of broiler carcasses

In Australia, increased consumer demand for chicken meat and socioeconomic pressures have forced poultry operations to extend plant operating time with delayed spin-chiller emptying and cleaning to maximise water use efficiency. There are concerns that these measures may compromise the microbiological quality and safety of the product. Therefore, the objective of this trial was to determine the microbiological status of broiler carcasses collected hourly during 24 h and 48 h continuous chiller operation within a three week period (total n = 196). Carcass rinses were analysed for total viable count, Escherichia coli and Campylobacter spp. counts, and Salmonella prevalence. Corresponding spin-chiller parameters (pH, oxidation-reduction potential [ORP], core temperature and HOCl concentration) were recorded. There was no statistically significant difference (P > 0.05) in bacterial populations and spin-chiller parameters when various sized chickens were processed. Therefore, the microbiological data and consequent quality were shown to be statistically equivalent between carcasses sampled from 24 h to 48 h continuous processing using a fully automated (water temperature, pH and chlorine control) spin-chiller. However, improvements to processing, including rehang and scald hygiene, and weight-specific hypochlorous acid concentrations, should be researched in order to further reduce bacterial contamination.     

Food safety aspects of fresh Nile perch (Lates niloticus) fillets from Lake Victoria imported to the European market: Helminth parasites and microbiological status

Nile perch (Lates niloticus) is a popular, usually low priced food fish in many countries worldwide, and the most important export fish from Lake Victoria and its adjacent countries Uganda, Tanzania and Kenya. Despite its high import figures, the constantly increasing demand within the EU for ‘new’ fish species and the results of initial studies indicating high coliform bacterial loads, food safety aspects regarding its microbiological as well as parasitological status have been hitherto widely neglected. In the present study imported fresh fish fillets as well as superchilled fish from a German retail market and a Dutch wholesaler were examined to evaluate the current microbiological and parasitological quality. A total of 200 fresh fillets as well as 20 superchilled fish (beheaded, eviscerated, descaled) samples were screened for the presence of helminth parasites by visual inspection, candling, the UV-press method and artificial digestion method. The study includes as well a quantitative test on the recovery rate of metacercarial cysts. Microbial assessment was performed on ten fresh fillets and on the skin and tissue of 20 superchilled fish. Helminth parasites were neither detected in the edible parts nor in the skin of imported products. Results of the microbiological examination revealed low levels of bacterial contamination of superchilled fish samples, whereas high total viable counts and high levels of naturally present bacterial pathogens of the genus Aeromonas spp. and Pseudomonas spp. were identified from the fresh fillets. Our findings indicate that hygienic production conditions have improved in comparison to previous studies. As total viable counts as well as specific spoiling bacteria were high in fresh fillets, we recommend adequate heat treatment of fresh Nile perch fillets before consumption.     

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.     

Combined effect of electrolyzed oxidizing water and chitosan on the microbiological,physicochemical, and sensory attributes of American shad (Alosa sapidissima) during refrigerated storage

This study evaluated the combined effect of electrolyzed oxidizing water (EOW) and chitosan (CH) on the quality and shelf-life of American shad (Alosa sapidissima) stored at 4 °C for 25 days. A CH solution (2% w/v; pH 3.7) was used to coat the fish flesh after washing with EOW (pH 2.4; oxidation-reduction potential, 1185 mV; free chlorine level, 70–80 ppm). Control and treated fish samples were analyzed for microbiological (total viable count), physicochemical (pH, total volatile basic nitrogen, thiobarbituric acid, texture, and color), and sensory characteristics. The results revealed that EOW + CH was more effective than either treatment alone (EOW or CH) in inhibiting microbial growth, protein decomposition, and lipid oxidation. Furthermore, EOW + CH maintained better texture, color, and sensory characteristics of fish. This treatment extended the shelf-life of American shad fillets by 9–10 days during refrigerated storage.     

天然气脱硫脱碳装置优化改造运行效果分析

介绍了HAZOP(Hazard and Operability Study:危害与可操作性分析)技术发展现状,结合天然气净化领域的生产工艺流程特点,尤其是在役生产装置的特点,以实例论述了HAZOP技术的工作过程和应用方法,总结了通过HAZOP分析工作发现的问题和提出的建议,并提出了开展天然气净化厂在役装置HAZOP分析需要注意的问题,为天然气净化厂提高装置运行的安全性和可操作性提供了改进方向,也为今后天然气净化厂乃至其他石油化工生产厂在役装置进行HAZOP分析提供了参考和借鉴。     

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.     

The effect of non-thermal processing technologies on microbial inactivation: An investigation into sub-lethal injury of Escherichia coli and Pseudomonas fluorescens

In recent years, there has been an increased interest in food processing technologies that could lessen the thermal impact on food products. In the present study, thermosonication (TS) and pulsed electric fields (PEF), applied individually or in combination (TS/PEF), were investigated to determine their effects on inactivation and sub-lethal injury of Pseudomonas fluorescens and Escherichia coli. TS was applied at a low (L) and high (H) wave amplitude (18.6 μm and 27.9 μm, respectively), while PEF was applied at a low and high electrical field strength (29 kV cm⁻¹ and 32 kV cm⁻¹, respectively). In addition, the inhibitory effects of TS/PEF combined were assessed. For P. fluorescens, when applied individually, TS and PEF resulted in ≤9% and ≤47% inactivation, respectively, with 8% sub-lethal injury following PEF treatment. However, TS/PEF treatment caused ≤48% inactivation and ≤34% sub-lethal injury, respectively. For E. coli, TS caused ≤6% inactivation, and ≤2% sub-lethal injury, while PEF treatment alone caused inactivation and sub-lethal injury of 86% and 29%, respectively. TS/PEF caused a maximum of 66% inactivation, while sub-lethally injuring approximately 26% of the of E. coli population. The present study confirms the ability of TS and PEF to inactivate microorganisms, but shows that some bacteria were not killed, but sub-lethally injured.     

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.     

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。     

The effect of household processing on the decline pattern of dimethomorph in pepper fruits and leaves

The effects of various household processes, including washing, boiling, frying, parboiling, and drying under different conditions (water amount, boiling times, and temperatures) on the residual levels of dimethomorph were evaluated in pepper fruits and leaves grown under plastic greenhouse conditions. The original quick, easy, cheap, effective, rugged, safe (QuEChERS) method (after modification) and liquid chromatography–tandem mass spectrometry (LC/MS/MS) were used for extraction and analysis to determine the sample residues. The results of recovery tests in processed and unprocessed pepper fruits and leaves ranged from 73.6 to 106.2% with relative standard deviations of 1.62–12.4%. Among various processes, washing and parboiling (78.4–85.8% at single and 75.7–89.9% at double dose) and drying after washing and parboiling (95.3–97.3% at single dose) were the most effective household methods to attenuate the analyte residues in pepper fruits and leaves, respectively. We conclude that processing leads to extensive reduction of pesticide residue levels in pepper fruits and leaves, particularly following washing and cooking operations.     

The impact of high pressure thermal sterilization on the microbiological stability and formation of food processing contaminants in selected fish systems and baby food puree at pilot scale

To this day there is no implementation of the high pressure thermal sterilization (HPTS) in the food industry. HPTS could result in better food quality, lower thermal load applied to the product and less unwanted food processing contaminants (FPCs) such as furan.Based on findings for selected foods at lab-scale extrapolated temperature-time combinations for a 12 log₁₀ inactivation of Bacillus amyloliquefaciens were chosen for a scale-up with a 55 L vessel (HPHT system Hiperbaric). Temperature-time-combinations at 600 MPa were between 100 and 115 °C and 0.45–28min. The scale-up resulted in a reduction of furan, depending on the food system, between 41 and 98% to retorting. Results at pilot scale were similar to lab-scale experiments. The performed storage trials (standardized method NF V 08-408) showed that only for the baby food puree two selected treatment conditions (107.5 °C, 9.8 min and 115 °C, 0.45 min at 600 MPa) resulted in an unstable product. Overall the results of the scale-up process support the idea that the HPTS could be feasible for the implementation in the food industry.     

Laboratory evaluation of the effect of SBS and Lucobite on performance properties of bitumen

In this research, the effects of two additives namely SBS (3, 5%) and Lucobite (3, 5%) on the performance properties of binder were evaluated. The binder fatigue and rutting performance was evaluated through linear amplitude sweep (LAS) and multiple stress creep and recovery (MSCR) test, respectively. Results indicated that 3% SBS modified binder has the highest percent recovery value and the lowest Jnr value, but had the highest sensitivity to a sudden increase in the stress level inside the asphalt mixture. The LAS test results demonstrated that the fatigue behavior of asphalt binders modified with 3% Lucobite, is the highest one.     

The effect of high pressure on the microbiological quality and other characteristics of cooked sausages packed in a modified atmosphere or vacuum

The aim of this study was to analyse the effect of high pressure (HP) on the shelf life and other selected characteristics of two types of cooked sausages, which were packed under vacuum or modified atmosphere. The total viable count in samples treated with 600 MPa/5 min decreased during 35 days of storage (4 ± 2 °C) to a maximum of 1.3 log CFU/g. Microbial counts of 4–5 log CFU/g were detected in control samples not subjected to HP. Instrumental colour analysis did not reveal any statistically significant differences between the meat products subjected to HP and the control samples during the course of the experiment. No statistically significant differences were found during the sensory evaluation when meat samples subjected to HP and control samples were assessed.     

油气管道环焊缝缺陷适用性评价现状与展望

油气管道的环焊缝质量好坏与管道能否安全运行密切相关,近年来管道环焊缝问题日益突显,因此准确评价管道环焊缝缺陷的适用性对于保障管道安全运行具有重要的意义。为了给环焊缝缺陷安全评定提供参考,系统总结了现行的环焊缝缺陷适用性评价方法并归纳为6种类型,剖析了各类方法的原理、特点及适用性,从焊接缺陷、内外部载荷及材料性能等3个方面分析了目前环焊缝缺陷适用性评价过程中遇到的瓶颈问题,并针对高钢级管道环焊缝所暴露出的新问题,提出了环焊缝缺陷适用性评价的未来展望。研究结果表明:①环焊缝缺陷可分为体积型缺陷和平面型缺陷两大类;②对于体积型缺陷,主要考虑塑性失效模式,推荐采用修正的Miller方法 ;③对平面型缺陷,应同时考虑塑性失效和断裂失效模式,推荐采用BS 7910:2015标准中基于失效评估图(FAD)的方法,并根据可用材料参数及保守性选用通用失效评估曲线(FAC)或特定FAC。结论认为,该研究成果有助于保障管道的安全运行。