Ham Model Research Articles

Modeling of the carbide growth kinetics in the low alloyed steels

Thermodynamic and kinetic modeling was performed to determine the kinetics of the carbides growth in the low alloyed steels of 15Cr2NiMoV type after heat treatment.Two stages of the carbides growth were examined: diffusion growth within the framework of Ham model and coalescence (coagulation) in the context of Lifshitz-Slyozov-Wagner (LSW) model.The results of modeling are consistent with the data of transmission electron microscopy.

Experimental validation of a HAM-BES co-simulation approach

High levels of humidity in buildings lead to building pathologies. Moisture also has an impact on the indoor air quality and the hygrothermal comfort of the building’s occupants. To better assess these pathologies, it is necessary to take into account the heat and moisture transfer between the building envelope and its indoor ambience.In this work, coupled heat, air and moisture transfer model in multilayer walls (HAM) was established. Thereafter, the HAM model is coupled dynamically to a building behavior code (BES). The coupling concerns a co-simulation between COMSOL Multiphysics and TRNSYS softwares.Afterward, the HAM-BES co-simulation accuracy was verified by conducting an experimental validation using an experimental device devoted to assess the hygrothermal response of building walls under several hygrothermal conditions.The comparison between numerical and experimental results showed good agreement with acceptable errors margins.

Selection of reference genes to quantify relative expression of ochratoxin A-related genes by Penicillium nordicum in dry-cured ham

Penicillium nordicum is an important and consistent producer of ochratoxin A (OTA) in NaCl-rich foods such as dry-cured ham. OTA is a toxic secondary metabolite which provokes negative effects on consumer health. Once OTA is produced in ham, this mycotoxin is difficult to remove. Since gene expression always precedes OTA production, analysis of expression of OTA-related genes by reverse transcription real-time PCR (RT-qPCR) could be a valuable tool to predict OTA contamination in ham. However scarce RT-qPCR protocols are properly validated leading to inconsistent data analyses. The objective of this study was to examine reference genes suitable for normalisation in designing and developing new RT-qPCR methods for quantifying the relative expression of genes involved in OTA biosynthesis (otapks and otanps) by P. nordicum on a dry-cured ham model system after 7 days of incubation. Firstly, primers based on three housekeeping genes commonly found in moulds, β-tubulin, COI and ITS, and on the otapks gene were designed. The primer pair F/R-npstr previously developed on the otanps gene was also used. Although most of the designed primers met the requirements needed to be used in qPCR assays, the primer pairs β-tubF1/R1, COI-F1/R1, ITSF2/R2 and otapksF3/R3 for the β-tubulin, COI, ITS and otapks genes, respectively, were selected due to their lowest Cq value. Next, the two assumptions of the 2−ΔΔCT method to evaluate the relative expression of the otapks and otanps genes were fulfilled for two of the three endogenous genes tested, β-tubulin and COI. However, β-tubulin was considered more proper as reference gene than COI under the environmental conditions assayed since its expression values by day 7 were more related to OTA production. Therefore, the two RT-qPCR methods for the analysis of the relative expression of the otapks and otanps genes have been properly validated and can be used as control tools to avoid or minimise the presence of OTA in ham.

Impact of coupled heat and moisture transfer effects on buildings energy consuption

Coupled heat, air, and moisture transfers through building envelope have an important effect on prediction of building energy requirements. Several works were conducted in order to integrate hygrothermal transfers in dynamic buildings simulations codes. However, the incorporation of multidirectional hygrothermal transfer analysis in the envelope into building simulation tools is rarely considered. In this work, coupled heat, air, and moisture (HAM) transfer model in multilayer walls was established. Thereafter, the HAM model is coupled dynamically to a building behavior code (BES).The coupling concerns a co-simulation between COMSOL Multiphysics and TRNSYS software. Afterward, the HAM-BES co-simulation accuracy was verified. Then, HAM-BES co-simulation platform was applied to a case study with various types of climates (temperate, hot and humid, cold and humid). Three simulations cases were carried out. The first simulation case consists of the TRNSYS model without HAM transfer model. The second simulation case, 1-D HAM model for the envelope was integrated in TRNSYS code. For the third one, 1-D HAM model for the wall and 2-D HAM model for thermal bridges were coupled to the thermal building model of TRNSYS. Analysis of the results confirms the significant impact of 2-D envelope hygrothermal transfers on the indoor thermal and moisture behavior of building as well as on the energy building assessment. These conclusions are shown for different studied climates.

Moisture transfer in building envelope and influence on heat transfer

The performance of building envelope is important to maintain proper temperature and humidity in the room. The heat and moisture transfer in the multilayered building envelope component are studied by founding a transient HAM model. The numerical results indicated that relative humidity varied with location and time in the envelope. Away from the outside surface, condensation or evaporation will occur to maintain the balance of vapor. Affected by the moisture transfer, temperature is lower than that without considering moisture transfer.

Integration of a hygrothermal transfer model for envelope in a building energy simulation model: experimental validation of a HAM–BES co-simulation approach

The present paper focuses on studying a new methodology to predict the overall behavior of buildings, which combines two simulation tools: COMSOL Multiphysics© and TRNSYS. The first software is used for the modeling of heat, air and moisture transfer in multilayer porous walls (HAM model—Heat, Air and Moisture transfer), and the second is used to simulate the hygrothermal behavior of the building (BES model—Building Energy Simulation). The combined software applications dynamically solve the mass and energy conservation equations of the two physical models. In this context, a coupled heat, air and mass transfer model is proposed. This model incorporates simultaneously the diffusive, convective and conductive effects on the building elements. Heat transfer is considered in the strongly coupled situation where the mass and heat flux are temperature, vapor pressure and total pressure dependents. The model input parameters are evaluated experimentally through the development of various experimental prototypes in the laboratory. Thereafter, an experimental setup has been established in order to evaluate the hygrothermal process of building walls. The experimental procedure consists to follow the temperature and relative humidity evolutions within the envelope thickness, submitted to controlled and fixed boundary conditions. Finally, using the developed experimental device, comparison between experimental data and numerical solution of the HAM–BES co-simulation platform was undertaken. Results showed good agreement with acceptable errors margins.

Identification and control of moulds responsible for black spot spoilage in dry-cured ham

The aims of this work were to identify moulds responsible for black spot spoilage in the drying and cellar stages of dry-cured ham processing and evaluate the effectiveness of preventive actions for controlling this alteration. Four mould strains isolated from spoiled hams were identified by morphological characteristics and the ITS and β-tubulin sequencing. Two of them were Cladosporium oxysporum, one was C. cladosporioides and the remaining one was C. herbarum. These spoiling strains reproduced the black spots on dry-cured ham-based media and ham slices. Additionally, the effect of water activity (aw) conditions reached throughout dry-cured ham ripening and the activity of the protective culture Penicillium chrysogenum CECT 20922 against the spoiling moulds were evaluated. In the dry-cured ham model system the growth of the Cladosporium strains was minimised when the aw approaches 0.84 or in P. chrysogenum CECT 20922 inoculated dry-cured ham slices. Therefore such combination could be used to avoid the black spot formation in dry-cured ham.

Hygrothermal behavior modeling of the hygroscopic envelopes of buildings: A dynamic co-simulation approach

High levels of humidity in buildings lead to building pathologies. Moisture also has an impact on the indoor air quality and the hygrothermal comfort of the building’s occupants. To better assess these pathologies, it is necessary to take into account the heat and moisture transfer between the building envelope and its indoor ambience. In this work, a new methodology was developed to predict the overall behavior of buildings, which combines two simulation tools: COMSOL Multiphysics© and TRNSYS. The first software is used for the modeling of heat, air and moisture transfer in multilayer porous walls (HAM model: Heat, Air and Moisture transfer), and the second is used to simulate the hygrothermal behavior of the building (BES model: Building Energy Simulation). The combined software applications dynamically solve the mass and energy conservation equations of the two physical models. The HAM-BES coupling efficiency was verified. In this paper, the use of a coupled (HAM-BES) co-simulation for the prediction of the hygrothermal behavior of building envelopes is discussed. Furthermore, the effect of the 2D HAM modeling on relative humidity variations within the building ambience is shown. The results confirm the importance of the HAM modeling in the envelope on the hygrothermal behavior and energy demand of buildings.

Assessing quality parameters in dry-cured ham using microwave spectroscopy

Microwave spectroscopy has been applied in numerous non-food industry applications, and recently also in the food industry, for non-destructive measurements. In this study, a dry-cured ham model was designed and chemical analyses were performed for determining water activity, water content and salt content (sodium chloride) for all samples. These chemical parameters were also measured using microwave spectroscopy, with a rectangular microwave cavity resonator. Results indicate that microwave spectroscopy may be a promising technique for determination of water activity, salt content and water content in dry-cured ham using either reflected or transmitted signals.

Investigating simultaneous transport of heat and moisture in hygroscopic materials by a semi-conjugate CFD-coupled approach

Hygroscopic materials have been widely used to alleviate humidity variation in buildings. Nevertheless, research efforts are so far scarce on the conditioning mechanisms of these materials on the envelope structure, indoor temperature, humidity, and air flow distribution. In this paper, a semi-conjugate approach (CFD–HAM) which couples CFD model with simultaneous transfer model of heat and moisture in hygroscopic material was proposed. The proposed model could be used for the assessment of moisture buffering effect of hygroscopic materials and humidity-induced envelope problems such as energy lost, condensation, and moulding. In addition, the validity of the proposed CFD–HAM model was verified by the consistency between the simulated and experimental results of an air-conditioned test chamber experiment.

Hot Water Shrinkage as a Post-Lethal Intervention against L isteria Monocytogenes : Preliminary Assessment in a Turkey-Based Virginia Ham Model

This preliminary laboratory trial evaluated the potential of hot water shrinkage to reduce post-lethal surface contamination by Listeria monocytogenes (Lm) in a turkey-based Virginia ham model. We inoculated triplicate of ham slices (10 cm2, 2-cm thick) with 105 cfu/cm2 of Lm (ATCC 19114). Subsequently, they were vacuum-packaged and placed in a thermostated water bath at 75, 80, 85 and 90C for 0, 20, 25 and 30 s. Treatment at 75–85C for up to 30 s did not affect Lm survival, while nearly 4-log reduction was observed at 90C for 30 s. The strong correlation (r = 0.9685–0.9891) between results and estimated lethalities (from previous inactivation data) highlights the potential of the 90C/30 s regimen as an effective post-lethal intervention. However, these results should be used with caution as they may vary under different industry conditions. Further research is needed to develop an appropriate pathogen reduction model for this process. Practical Applications Hot water shrinkage has a promising application in controlling post-lethal surface contamination by Listeria monocytogenes in some deli meats. This intervention is likely to be cheaper than regular post-package pasteurization. It is also feasible, from a productivity standpoint, in many medium-sized companies. The latter may work only for products with a smooth surface and a composition similar to that of the turkey-based Virginia ham tested in this study.

Growth inhibition of lactic acid bacteria in ham by nisin: A model approach

Lactic acid bacteria (LAB) have been described as spoilage organisms in vacuum-packed cooked ham. A Fractional Factorial Design was performed to investigate the relative merits of sodium chloride, sodium lactate, sodium tripolyphosphate, sodium erythorbate, nisin and pediocin, in limiting the Lactobacillus sakei growth in broth culture. This allowed rejection of sodium chloride, sodium lactate and sodium erythorbate (no significant effects on growth), and a Central Composite Rotatable Design broth culture study was performed comparing the effects of nisin and pediocin. From this study, nisin was identified as a more important variable for inclusion into a cooked ham model (significant effects on growth parameters: logarithmic increase in the population, exponential microbial growth rate and lag phase extension). The validation of this outcome in a model formulation of vacuum-packed sliced cooked ham (0.001%, 0.007% and 0.013% of nisin) stored for 60days, confirmed the inhibitory effect of nisin on total LAB growth.

Modeling regional linkage of financial markets

With the development of globalization and regional economic integration, regional markets linked with a common currency emerge, in which investors from domestic market are allowed to trade in foreign markets. Empirical studies have evidenced extensively the existence of co-movement of asset prices or cross-correlation in market returns among these markets, especially in global event. However, there is no theoretical model in literature that can provide economically plausible justifications for these stylized facts. This research intends to fill up such a gap with a simplest possible nonlinear dynamic model. Based on the classical market-maker framework of Day and Huang (1990), a two-market HAM model is developed, which does not only prove in theory the existence of price co-movement but also replicate in simulation this typical characteristic, along with other well known stylized facts characterizing individual financial market. Moreover, theoretical analysis suggests meaningful implications for market opening policy. In particular, in terms of financial stability, a relatively small market may not benefit from market linkage and market opening is essentially a double-edged sword.

Assessing Water Activity in Dry-Cured Ham using Microwave Spectroscopy

Abstract Microwave spectroscopy have been applied in numerous applications in the non-food industry, and recently also in the food industry, for non-destructive measurements. In this study, a dry-cured ham model was designed and water activity, water content and salt content (sodium chloride) were determined for all samples using chemical analysis. The water activity was also measured using microwave spectroscopy, with a rectangular microwave cavity resonator. Attained results indicate that microwave spectroscopy might be a promising technique for determination of water activity in dry-cured ham.

Building phenomenological models that relate proteolysis in pork muscles to temperature, water and salt content

Throughout dry-cured ham production, salt and water content, pH and temperature are key factors affecting proteolysis, one of the main biochemical processes influencing sensory properties and final quality of the product. The aim of this study was to quantify the effect of these variables (except pH) on the time course of proteolysis in laboratory-prepared pork meat samples. Based on a Doehlert design, samples of five different types of pork muscle were prepared, salted, dried and placed at different temperatures, and sampled at different times for quantification of proteolysis. Statistical analysis of the experimental results showed that the proteolysis index (PI) was correlated positively with temperature and water content, but negatively with salt content. Applying response surface methodology and multiple linear regressions enabled us to build phenomenological models relating PI to water and salt content, and to temperature. These models could then be integrated into a 3D numerical ham model, coupling salt and water transfers to proteolysis.

Characterizing and modeling the evolution of silicon oxide precipitates during thermal cycles

The effects of oxidizing annealing cycles on Si high-quality wafers (as used to monitor IC production tools or SOI applications) were studied using different techniques (nano-scale observations and chemical analysis in Transmission Electron Microscope (TEM), but also large scale measurements, such as Laser Scattering Tomography (LST) and chemical etching (CE), thus coupling local analyses with global measurements of defects density and size) to determine their characteristics. Interstitial oxygen loss during cycles was also measured using Fourier Transform Infra-Red spectroscopy (FTIR).It appeared that each cycle is composed of a defect nucleation stage and a growth stage, and that the distribution of these defects (mainly oxide precipitates) along wafer radius essentially depends on the initial point defect density. The evolution of these precipitates was described by a diffusion-and-growth model derived from Ham's model and taking into account various phenomena: oxygen loss, point-defect distribution and cycle effects (up/down ramp and high-temperature plateau). Extensions and limits of the model are also discussed.

VirulentCoxiella burnetiipathotypes productively infect primary human alveolar macrophages

The intracellular bacterial pathogen Coxiella burnetii is a category B select agent that causes human Q fever. In vivo, C. burnetii targets alveolar macrophages wherein the pathogen replicates in a lysosome-like parasitophorous vacuole (PV). In vitro, C. burnetii infects a variety of cultured cell lines that have collectively been used to model the pathogen's infectious cycle. However, differences in the cellular response to infection have been observed, and virulent C. burnetii isolate infection of host cells has not been well defined. Because alveolar macrophages are routinely implicated in disease, we established primary human alveolar macrophages (hAMs) as an in vitro model of C. burnetii-host cell interactions. C. burnetii pathotypes, including acute disease and endocarditis isolates, replicated in hAMs, albeit with unique PV properties. Each isolate replicated in large, typical PV and small, non-fused vacuoles, and lipid droplets were present in avirulent C. burnetii PV. Interestingly, a subset of small vacuoles harboured single organisms undergoing degradation. Prototypical PV formation and bacterial growth in hAMs required a functional type IV secretion system, indicating C. burnetii secretes effector proteins that control macrophage functions. Avirulent C. burnetii promoted sustained activation of Akt and Erk1/2 pro-survival kinases and short-termphosphorylation of stress-related p38. Avirulent organisms also triggered a robust, early pro-inflammatory response characterized by increased secretion of TNF-α and IL-6, while virulent isolates elicited substantially reduced secretion of these cytokines. A corresponding increase in pro- and mature IL-1β occurred in hAMs infected with avirulent C. burnetii, while little accumulation was observed following infection with virulent isolates. Finally, treatment of hAMs with IFN-γ controlled intracellular replication, supporting a role for this antibacterial insult in the host response to C. burnetii. Collectively, the current results demonstrate the hAM model is a human disease-relevant platform for defining novel innate immune responses to C. burnetii.

Prevention of spoilage by enterocin AS-48 combined with chemical preservatives, under vacuum, or modified atmosphere in a cooked ham model

The effect of enterocin AS-48 in controlling Lactobacillus sakei, Brochothrix thermosphacta, and Staphylococcus carnosus in a cooked ham system has been studied. AS-48 alone showed activity against Lactobacillus, with 60 μg g−1 reducing lactobacilli below detection levels from the beginning to end of storage at 5 °C. Combinations of 40 μg g−1 AS-48 with nitrate/nitrite, pentasodium tripolyphosphate, sodium pyrophosphate, sodium acetate, and sodium lactate reduced L. sakei below detection levels from the beginning to end of storage. Even 20 μg g−1 of enterocin combined with tripolyphosphate permanently eliminated L. sakei. Enterocin AS-48 (40 μg g−1) was also active against B. thermosphacta and S. carnosus, reducing both bacteria by more than 3 log in the cooked ham. Modified atmosphere (40% CO2/60% N2) packaging affected neither bacterial growth nor AS-48 activity against any of the three bacteria. In contrast, storage under vacuum remarkably increased the growth and the inhibitory activity of the enterocin against B. thermosphacta and especially against L. sakei.

Shelf-life extension of cooked ham model product by high hydrostatic pressure and natural preservatives

The inactivation of different spoilage organisms and surrogate pathogens in a cooked ham model product by high pressure (HP) treatment (100–700 MPa, 5–40 °C, 10 min) was investigated. A 5 log reduction could be achieved at ≥ 600 MPa at ≥ 25 °C. Subsequently, the shelf-life of packaged sliced product was studied during storage (7 °C) after treatment at 600 MPa (10 °C, 10 min) in combination with caprylic acid and Purasal®. Without HP treatment, a plate count of 6 log CFU/g was reached after 40 days, both in presence and absence of antimicrobials. HP treatment delayed this initiation of spoilage to 59 days in absence of antimicrobials. However, microbial growth was completely suppressed during at least 84 days in the HP treated products containing caprylic acid or Purasal®. HP treatment increased drip loss but had no or little effect on colour and sensorial evaluation by a taste panel. However, the antimicrobials had a negative influence on the flavour and aroma at the concentrations used. With a steadily increasing number of commercial applications being introduced on the market, HP pasteurization is growing out of its infancy. To further support this development, there is a need of integrated studies that translate fundamental scientific findings from simplified laboratory model systems to the complexity and scale of real food products. In this work, we determined HP processing conditions to control spoilage and pathogenic bacteria in a cooked ham model product, and subsequently conducted a large pilot scale experiment comprising a total of 432 individual packages of sliced cooked ham product, in which the microbiological, physicochemical and sensorial quality was evaluated during refrigerated storage after HP treatment. In addition, the usefulness of the natural preservatives caprylic acid and lactate-diacetate as an additional hurdle was also studied. This study is one of the most comprehensive available in the literature to document the shelf-life extension that can be achieved with HP treatment of cooked ham.

Sensitivity analysis of CFD coupled non-isothermal heat and moisture modelling

CFD (Computational Fluid Dynamics) is a useful tool to study air flow patterns in a room. Current CFD models are able to simulate air flow combined with temperature distributions and species distributions. In this paper a coupled CFD–HAM model is discussed. This model combines CFD with a HAM model (Heat, Air and Moisture) for hygroscopic materials. This coupled model is able to simulate air flow around a porous material and combines this with heat and moisture transport in the porous material. Validation with a small scale experiment in which gypsum board was used as a hygroscopic material showed good results. In this paper a further validation of the model is discussed based on a sensitivity analysis of some model parameters. Especially hygrothermal parameters like sorption isotherm and water vapour permeability proved to have a non negligible influence on the modelling outcome. Adding a hysteresis model showed improvement of the model during desorption. The model was also used to compare two modelling strategies. In one strategy the gypsum board was modelled as a uniform material, in a second approach the material was modelled as being layered. The difference between the two approaches showed to be negligible.