Reactive transport in porous media: a comparison of model prediction with laboratory visualization

Groundwater transport models that accurately describe spreading of nonreactive solutes in an aquifer can poorly predict concentrations of reactive solutes. The dispersive term in the advection-dispersion equation can overpredict pore-scale mixing, and thereby overpredict homogeneous chemical reaction. We quantified this experimentally by imaging instantaneous colorimetric reactions between solutions of aqueous CuSO4 and EDTA4- within a 30-cm long translucent chamber packed with cryolite sand that closely matched the optical index of refraction of water. A charge-coupled device camera was used to quantify concentrations of blue CuEDTA2- within the chamber as it was produced by mixing of the two reactants at different flow rates. We compared these experimental results with a new analytic solution for instantaneous bimolecular reaction coupled with advection and dispersion of the product and reactants. For all flow rates, the concentrations of CuEDTA2- recorded in the experiments were about 20% less than predicted by the analytic solution, thereby demonstrating that models assuming complete mixing at the pore scale can overpredict reaction during transport.     

Understanding short-chain fatty acids accumulation enhanced in waste activated sludge alkaline fermentation: kinetics and microbiology

Most of the studies on sewage sludge treatment in literature were conducted for methane generation under acidic or near neutral pH conditions. It was reported in our previous studies that the accumulation of short-chain fatty acids (SCFAs), the preferred carbon source of biological wastewater nutrient removal, was significantly enhanced when sludge was fermented under alkaline conditions, but the optimal pH was temperature-dependent (pH 10 at ambient temperature, pH 9 at mesophilic, and pH 8 at thermophilic), and the maximal SCFAs yields were in the following order: thermophilic pH 8 > mesophilic pH 9 > ambient pH 10 > ambient uncontrolled pH. In this study the kinetic and microbiological features of waste activated sludge fermented in the range of pH 7-10 were investigated to understand the mechanism of remarkably high SCFAs accumulation under alkaline conditions. The developed sludge alkaline fermentation model could be applied to predicate the experimental data in either batch or semicontinuous sludge alkaline fermentation tests, and the relationships among alkaline pH, kinetic parameters, and SCFAs were discussed. Further analyses with fluorescence in situ hybridization (FISH) and PCR-based 16S rRNA gene clone library indicated that both the ratio of bacteria to archaea and the fraction of SCFAs producer accounting for bacteria were in the sequence of thermophilic pH 8 > mesophilic pH 9 > ambient pH 10 > ambient uncontrolled pH, which was in correspondence with the observed order of maximal SCFAs yields.     

Apparent diffusion model assessment in extraction processes by means of a Luenberger observer

In this work a clear methodology is proposed that allows the estimation of diffusion-concentration functional relationship in extraction processes, which are modelled by Fick’s second law. A criterion is proposed for deciding when the diffusivity should be considered a constant value (comparable to those obtained by the standard regression technique) and when a function depending on concentration. The methodology is based in a Luenberger observer. The diffusion-concentration relationship is refined by an optimization procedure making use of a numerical solution of the diffusion equation. The robustness of the methodology is assessed by a noise propagation analysis. The methodology is illustrated for oil extraction from tung seeds with experimental data taken from the literature.     

Genetic evaluation of mastitis resistance using a first-passage time model for wiener processes for analysis of time to first treatment

A Wiener process is a Brownian-motion process initiated in a certain state in a state space, and the first passage time is defined as the time of the process to reach a predefined absorbing state where the process stops. Time from 31 d prepartum to first treatment of clinical mastitis (CM) was modeled as first passage times of such Wiener processes. Two processes were used to allow for several risk factors, and for each process, initiation was at some arbitrary time point, in a certain health state with drift toward or away from absorption (disease). The drift parameter of each process was expressed as linear functions of covariates (year of calving and sire). First passage time was defined as the time from process initiation until the first health status process reached zero (absorption). The model was fitted to records for 36,178 first-lactation daughters of 245 Norwegian cattle sires using a Bayesian approach and Markov chain Monte Carlo methods. Genetic evaluation of sires was carried out by calculating the posterior probability of no CM (the value of the survival function) by d 331, i.e., 300 d after first calving. Alternatively, sire evaluation was based on the integrated area under the survival curve. These measures were highly correlated (0.999), which indicates a small degree of crossings of the sire-dependent survival curves. Hence, sire-specific hazards were close to proportional, resulting in a higher rank-correlation to sire evaluations from a survival model with proportional hazards than to the results from a multivariate threshold model.     

A model for the hot water decontamination of sides of beef in a novel cabinet based on laboratory data

A predictive model for the hot water decontamination of sides of beef in a novel design of cabinet is presented and its usefulness illustrated. The model is based on laboratory data and permits assessment of bacterial reductions, production rates, unit energy costs and changes to cabinet dimensions and ambient temperatures. The advantages of a 'standard' cabinet recommended for a wide range of abattoir production rates are outlined. For a production rate of 135 sides h⁻¹, 90% and 99% reductions in bacteria at the site of minimum treatment (the neck) could be achieved at costs of less than 0.016% and 0.03% respectively of the value of the meat. The model assumes limited exposure of the sides to the hot water to prevent a permanent impairment of meat bloom. A graphical summary is presented and limitations of the model are discussed.     

Understanding the distribution system as a bioreactor: a framework for managing heterotrophic plate count levels

It is important to manage the level of heterotrophic plate count (HPC) bacteria in drinking water. Since the vast majority of HPCs measured in the distribution system are normally actually produced there, managing HPC numbers implies managing the distribution system as a bioreactor. This paper proposes a new concept, the HPC Production Index (HPI), which is the ratio of HPC production in a given distribution system to that produced by an essentially biostable water entering that same system. HPI is related to various physical, chemical and water quality factors such as contact time, disinfectant residual and level of biodegradable organic matter, which affect the performance of the distribution system as a bioreactor. HPI therefore provides a conceptual framework for managing distribution system HPC levels.     

A rat model for functional characterization of pregnancy-induced denervation and postpartum reinnervation in the myometrium and cervix: a superfusion study

The pregnancy-induced rapid degeneration of the adrenergic nerves innervating the uterus is a well-known but poorly understood phenomenon. Since most of the published investigations were carried out by histological assay, our aim was to describe the loss of the adrenergic function during pregnancy and the re-innervational procedure in the postpartum period. Myometrial and cervical samples from rats were loaded with [3H]noradrenaline and then transferred into a chamber for superfusion. After a wash-out period, fractions were collected. The fifth and fifteenth fraction tissues were stimulated with an electric field. The [3H]noradrenaline contents of the fractions were determined, together with the amount remaining in the tissue. The myometrial [3H]noradrenaline release was substantially decreased in early pregnancy, and absent in the late stage. Differences in release profile were detected between the implantation sites and the interimplantation areas. As a refinement of the results of previous histochemical studies, the noradrenergic functions of the cervix were found to be deeply affected in the early postpartum period. The pregnancy-induced denervational procedure can be followed by means of a superfusional technique after [3H]noradrenaline loading. As our technique is considered to be similar in sensitivity to histological methods, superfusion can be regarded as a model for functional investigations of pregnancy-induced denervation.     

Environmental conditions and serotype affect Listeria monocytogenes susceptibility to phage treatment in a laboratory cheese model

Listeria monocytogenes can survive and grow in a variety of environments, including refrigeration, making it difficult to control and highlighting the importance of optimizing control strategies against this pathogen. Listeria phages are attractive biocontrol agents because phages bind to specific wall teichoic acids (WTA) on the bacterial cell wall, inhibiting pathogens without disrupting the normal microbiota or structure of the food. Common stresses found on dairy products can affect cell wall composition and structure and subsequently affect the efficiency of control strategies that target the cell wall. The goal of this study was to determine the effect of a range of pH and temperatures on the effectiveness of a commercial phage cocktail treatment against several strains of L. monocytogenes in a cheese matrix. We developed a laboratory-scale cheese model that was made at different pH, treated with phage, and then inoculated with L. monocytogenes. Cheeses were incubated at 6, 14, or 22°C for 14 d, and bacterial counts were determined on d 1, 7, and 14. Our data show that phage treatment has a limited ability to reduce L. monocytogenes counts at each temperature tested; however, it was more effective on specific strains of L. monocytogenes when cheese was stored at higher temperatures. More specifically, the average counts of L. monocytogenes on phage-treated cheese stored at 22°C were significantly lower than those on phage-treated cheese stored at 6 or 14°C. Similarly, phage treatment was significantly more effective at inhibiting L. monocytogenes on cheese made at higher pH (6 and 6.5) compared with counts on cheese made at pH 5.5, where L. monocytogenes did not grow. Furthermore, serotype was found to affect the susceptibility of L. monocytogenes to phage treatment; serotype 1/2 strains showed significantly higher susceptibility to phage treatment than serotype 4b strains. Overall, our results suggest the importance of considering the efficacy of phage under conditions (i.e., temperature and pH) specific to a given food matrix when applying interventions against this important foodborne pathogen.     

Simulation model for moving food packages in microwave heating processes using conformal FDTD method

A numeric model was developed to couple electromagnetic (EM) and thermal field calculations in packaged foods moving in pressurized 915 MHz microwave (MW) cavities with circulating water at above 120 °C. This model employed a commercial EM package with a customized heat transfer sub-model to solve EM field and thermal field equations. Both methods applied finite-difference time-domain (FDTD) method. An interface was built to facilitate the communication between electromagnetic and thermal models to incorporate the coupling feature which is unique to microwave heating process. Special numerical strategies were implemented to simulate the movement of food packages. The simulation model was validated with a pilot-scale microwave system using direct temperature measurement data and indirect color patterns in whey protein gels via formation of the thermally induced chemical marker M-2. Good agreements were observed. Four cases were studied to investigate the influence of power input and package gaps on heating uniformity. These applications demonstrated the flexibility of the model to allow its usage for system and process optimization.     

Lipids in French fries: a retail and laboratory study

The lipid content of prepared restaurant and takeaway French fries varied from 6.2 to 20.8 g/100 g, and of frozen retail fries from 2.1 to 5.3 g/100 g, as purchased, and from 12.0 to 20.0 g/100 g after finish frying. The lipid composition (fatty acid profile and cholesterol content) of all retail samples reflected the predominant use of animal fat in the Australian industry. Laboratory studies showed that the lipid content of French fries was increased by decreased chip size, and by the common commercial practice of split frying which caused a doubling of fat uptake when compared with single frying. Commercial practices appear to increase the potential of fries as a fat carrier.     

植物乳杆菌混菌发酵对梁平柚果酒理化性质及风味影响

利用从野樱桃发酵底泥中筛选的一株葡萄汁有孢汉逊酵母（Hanseniaspora uvarum）YT-35与商业酿酒酵母（Sacharomyces cerevisiae）共培养发酵野樱桃饮品,以2株菌的单菌株发酵为对照,对不同发酵阶段中的微生物数量、还原糖、乙醇等动态变化分析,利用高效液相色谱（HPLC）对有机酸进行动态检测,采用顶空固相微萃取/气相色谱-质谱（HS-SPME/GC-MS）对发酵饮品的挥发性风味物质进行测定。结果表明,H. uvarum YT-35在共培养发酵前期占据主导优势;与单一S. cerevisiae发酵相比,共培养发酵可以获得低乙醇含量（3.51 g/L）饮品;HPLC结果表明,共培养发酵可降低柠檬酸、苹果酸和奎宁酸的产量,增加冰醋酸的产量;HS-SPME/GC-MS结果表明,共培养发酵可产生更多的酯类风味物质,如己酸乙酯、苯甲酸甲酯、辛酸异戊酯、肉桂酸甲酯、反式肉桂酸乙酯、十八酸乙酯、苯甲酸苄酯和邻苯二甲酸二异丁酯,同时可增强如月桂酸乙酯、辛酸乙酯、苯乙醇、苯甲醇、辛酸和月桂酸等风味物质的含量;聚类分析表明,H. uvarum YT-35与S. cerevisiae共培养发酵野樱桃对丰富饮品中挥发性物质种类及含量提高有重要贡献。本研究旨在为具有不同代谢潜能的混合菌株在提升果汁发酵饮品品质中的研究提供一定科学依据和理论指导。

     

A bench-scale constructed wetland as a model to characterize benzene biodegradation processes in freshwater wetlands

In wetlands, a variety of biotic and abiotic processes can contribute to the removal of organic substances. Here, we used compound-specific isotope analysis (CSIA), hydrogeochemical parameters and detection of functional genes to characterize in situ biodegradation of benzene in a model constructed wetland over a period of 370 days. Despite low dissolved oxygen concentrations (<30 μM), the oxidation of ammonium to nitrate and the complete oxidation of ferrous iron pointed to a dominance of aerobic processes, suggesting efficient oxygen transfer into the sediment zone by plants. As benzene removal became highly efficient after day 231 (>98% removal), we applied CSIA to study in situ benzene degradation by indigenous microbes. Combining carbon and hydrogen isotope signatures by two-dimensional stable isotope analysis revealed that benzene was degraded aerobically, mainly via the monohydroxylation pathway. This was additionally supported by the detection of the BTEX monooxygenase gene tmoA in sediment and root samples. Calculating the extent of biodegradation from the isotope signatures demonstrated that at least 85% of benzene was degraded by this pathway and thus, only a small fraction was removed abiotically. This study shows that model wetlands can contribute to an understanding of biodegradation processes in floodplains or natural wetland systems.     

Understanding critical factors for the quality and shelf-life of MAP fresh meat: a review

Due to increased demands for greater stringency in relation to hygiene and safety issues associated with fresh food products, coupled with ever-increasing demands by retailers for cost-effective extensions to product shelf-lives and the requirement to meet consumer expectations in relation to convenience and quality, the food packaging industry has rapidly developed to meet and satisfy expectations. One of the areas of research that has shown promise, and had success, is modified atmosphere packaging (MAP). The success of MAP-fresh meat depends on many factors including good initial product quality, good hygiene from the source plants, correct packaging material selection, the appropriate gas mix for the product, reliable packaging equipment, and maintenance of controlled temperatures and humidity levels. Advances in plastic materials and equipment have propelled advances in MAP, but other technological and logistical considerations are needed for successful MAP systems for raw chilled meat. Although several parameters critical for the quality of MA packed meat have been studied and each found to be crucial, understanding of the interactions between the parameters is needed. This review was undertaken to present the most comprehensive and current overview of the widely available, scattered information about the various integrated critical factors responsible for the quality and shelf life of MA packed meat with an interest to stimulate further research to optimize different quality parameters.     

Antibacterial effect of water-soluble tea extracts on foodborne pathogens in laboratory medium and in a food model

The microbial inhibition of foodborne pathogens was determined in brain heart infusion broth with 10% (wt/vol) water-soluble extracts of green, jasmine, black, dungglre, and oolong tea against Escherichia coli O157:H7, Salmonella enterica serovar Enteritidis, Listeria monocytogenes, and Staphylococcus aureus. The mixed culture (approximately 6.0 log CFU/ml), which was composed of the four pathogens, was inoculated into brain heart infusion broth with and without tea extracts. After incubation at 35 degrees C for 0, 1, 3, and 5 days, proper dilution of each sample was spiral plated on each selective agar. Viable cell counts were performed after incubation at 35 degrees C for 24 to 36 h. Green, jasmine, and black tea exhibited an approximately 5.0 log suppression of S. aureus compared with the control from days 1 to 5. Green and jasmine tea also suppressed the growth of L. monocytogenes by approximately 3.0 log CFU/ml on day 5. In contrast, no tea extracts inactivated E. coli O157:H7 and Salmonella Enteritidis. Based on the result in liquid medium, green and jasmine teas of 0.1% (vol/wt) were individually evaluated for their antimicrobial activity against L. monocytogenes and S. aureus in a food model (ground beef) stored at 7 degrees C for 0, 1, 3, 5, and 7 days. Viable cell counts of total bacteria, L. monocytogenes, and S. aureus in ground beef were not significantly different among green and jasmine tea and the control.     

大米蛋白的BN大鼠致敏动物模型建立

以大米蛋白为过敏原,腹腔注射致敏雌性棕色挪威大鼠(BN大鼠),建立大米蛋白过敏BN大鼠动物模型。观察BN大鼠全身主动过敏反应及体重、体温、免疫脏器指数变化,检测其血清特异性Ig G、总Ig E和特异性Ig E水平,并测定血浆组胺释放水平及各组大鼠的血象变化。结果显示,实验第42 d大米蛋白激发实验后,实验组大鼠全部呈过敏反应阳性,且体温降低,脾脏指数显著增大(p<0.01),体内白细胞和嗜酸粒细胞数目升高(p<0.05);实验组血清特异性Ig G显著升高(p<0.01),总Ig E以及血浆组胺释放量均高于对照组(p<0.05),实验第14 d和42 d血清特异性Ig E高于对照组,第28 d无明显变化(p<0.05)。本实验结果证明BN大鼠是评价大米蛋白致敏性较为理想的动物模型。      

Development and evaluation of a laboratory scale conch for chocolate production

In this study a laboratory scale conch was developed with the purpose of testing new formulations using small amounts of chocolate mass. The equipment was built with working parts of others machines and the chocolate manufactured with the conch was evaluated in relation to the viscosity, moisture, acidity and polyphenol concentration. The resulting chocolate was tempered and then evaluated by a sensory panel. The results were always compared with an industrial conching process. The material used in the assays was dark chocolate (40% cocoa). Data were submitted to variance analysis ( anova ) and when there was significant difference among the averages, the Tukey's test was applied. It was verified that the reduction of moisture and viscosity of the mass in the laboratory scale was similar to industrial scale. The parameters acidity and polyphenols showed no significant alterations when comparing both process scales. However, in the sensory analysis a flavour difference between the processing scales was perceptible.     

Health biomarkers in a rat model after intake of organically grown carrots

BACKGROUND: Organic food is perceived as being of better quality and healthier than conventional foods although the scientific research on organic foodstuffs is highly contradictory. The aim of the present study was to investigate if intake of carrots from four different cultivation systems grown in two consecutive years would influence various biomarkers of health in a rat model. All rats were fed a diet with 40% carrot content. The carrots were grown under conventional (C), ‘minimalistic’ organic (O1), organic (O2), or ‘very’ organic cultivation systems (O3). A control group (CO) being fed standard rat chow was included. RESULTS: The plasma α‐tocopherol concentration was higher in the O2 carrot‐based diet group than in the C carrot based‐diet group in one year, while all other health biomarkers or nutrient content differences were observed between the CO diet and the carrot‐based diets. CONCLUSION: This well‐controlled field study demonstrated no clear influence of cultivation methods or harvest year on the nutritional quality of carrots or effect of cultivation methods on health‐related biomarkers in a sensitive rat model. However, the experimental set‐up and selected biomarkers could be used as a framework for further studies of health in relation to organic foodstuff. Copyright © 2012 Society of Chemical Industry