Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.     

Plant-Origin Stabilizer as an Alternative of Natural Additive to Polymers Used in Packaging Materials

Over the past 25 years, cannabis plants have gained major popularity in the research community. This study aimed to evaluate the antioxidant capacity and stabilization efficiency of cannabidiol (CBD) extract in two different polymers: polylactide (PLA) and ethylene–norbornene copolymer (Topas) that are used in packaging materials more often. The research technology included weathering in a special chamber, surface free energy and color change measurements, surface morphology and Fourier-transform infrared spectroscopy (FTIR) analysis, thermogravimetry, and determination of the oxidation induction time or temperature (OIT) values, based on which the effectiveness of the cannabidiol extract could be estimated. Obtained results showed that the addition of CBD to polymer mixtures significantly increased their resistance to oxidation, and it can be used as a natural stabilizer for polymeric products. Moreover, samples with cannabidiol changed their coloration as a result of weathering. Therefore, this natural additive can also be considered as a colorimetric indicator of aging that informs about the changes in polymeric materials during their lifetime. On the other hand, surface properties of samples with cannabidiol content did not alter much compared to pure Topas and PLA.     

MFI‐Zeolithsynthesen auf Innenwänden von Rohrreaktoren aus Chrom‐Nickel‐Stahl

A coating method was developed that allows the carrier‐based synthesis of MFI zeolite on the inner surface of steel pipes. Besides varying the synthetic route, the type and concentration of the reactants the influence of other parameters on the growth of ZSM‐5‐crusts on the inner surface of the steel pipes was studied. It was confirmed that the deposition characteristics of zeolitic structures on the inner wall of tubes depend on the chosen pathway and are sensitive to all these parameters. Appropriate ways to control the layer formation were developed.     

Development and application of oligonucleotide probes for in situ detection of thermotolerant Campylobacter in chicken faecal and liver samples

Based on Campylobacter 16S- and 23S-rRNA sequence data oligonucleotide probes specific for thermotolerant campylobacters and for members of the genus Campylobacter have been developed. The 16S-rRNA-targeted probe CAMP 653, recommended for a comprehensive detection of members of the genus Campylobacter, specifically detected all Campylobacter strains used in this study. Detection of thermotolerant species has been achieved by the 23S-rRNA-targeted probe CAJECO1427. Optimal hybridisation conditions have been derived for both probes from melting profiles of fluorescence-labelled probe-target hybrids recorded in fluorescence in situ hybridisation experiments (FISH). The FISH assay was evaluated both by spiking poultry faecal samples with Campylobacter jejuni and by detecting Campylobacter in naturally colonized chickens. C. jejuni was reliably detected at levels of 10(6) cfu/g faeces after a 3- h enrichment step in Blood Preston Selective broth. Low level contaminations (相似文献   

Preliminary studies on the effect of processing on the IgE reactivity of tomato products

Tomatoes and tomato products, obtained from a market, from companies or prepared in research laboratories, were tested in order to investigate how different processes could modulate the IgE reactivity of these products. The protein fraction of the samples was extracted by using a low‐temperature method in order to avoid degradation, and then separated on SDS PAGE to evaluate the protein profile. All the separated samples were blotted onto nitrocellulose membranes and then individually tested with pooled human sera that had been obtained from patients allergic to tomato, in order to evaluate the potential IgE binding of the protein bands. Heat treatments conventionally employed for the production of tomato‐based products were found to strongly degrade proteins thus dramatically reducing their IgE reactivity; characteristic protein profiles were found for specific processes such as hot and cold break. Ultra‐high‐pressure treatments were found to generally preserve the integrity of tomato proteins and this was reflected by the unaltered IgE reactivity observed. Copyright © 2007 Society of Chemical Industry     

Evaluation of the reliability of transport networks based on the stochastic flow of moving objects

In transport networks, human beings are moving objects whose moving direction is stochastic in emergency situations. Based on this idea, a new model—stochastic moving network (SMN) is proposed. It is different from binary-state networks and stochastic-flow networks. The flow of SMNs has multiple-saturated states, that correspond to different flow values in each arc. In this paper, we try to evaluate the system reliability, defined as the probability that the saturated flow of the network is not less than a given demand d. Based on this new model, we obtain the flow probability distribution of every arc by simulation. An algorithm based on the blocking cutset of the SMN is proposed to evaluate the network reliability. An example is used to show how to calculate the corresponding reliabilities for different given demands of the SMN. Simulation experiments of different size were made and the system reliability precision was calculated. The precision of simulation results also discussed.     

In situ hybridization of microcolonies using catalyzed reporter deposition with tetramethylbenzidine: a method for detecting low numbers of bacterial cells in drinking water

In this study, catalyzed reporter deposition in situ hybridization (CARD—ISH) with tetramethylbenzidine (TMB) was used for rapid detection of the food pathogens Salmonella typhimurium and Escherichia coli. The bacteria in a sample were concentrated by membrane filtration. The filter membranes with the cells thus removed were incubated on nutrient agar for 4–5 h to allow the formation of microcolonies. Instead of fluorescent tyramide, 3,3′,5,5′-tetramethylbenzidine (TMB), which yields a blue precipitate, was used for signal amplification after in situ hybridization. Microcolonies amplified with TMB produced blue signals, which were sufficiently intense to allow visual evaluation either using a stereomicroscope, or even with the naked eye. Therefore even low cell numbers of hygienically critical bacteria can be detected on the filter membrane without a protracted examination. This enables the detection of low cell numbers (<10 cfu) in a sample of 100 ml tap water within 9–10 h.     

Microscopy of the Drosophila facet eye: vademecum for standardized fixation, embedding, and sectioning

We describe here a standardized method for histological processing of the Drosophila compound eye. Primary fixation with 2.5% glutaraldehyde, obligatorily supplemented with 0.1% household detergent regularly yielded the best structural preservation, as compared with that of other, more complicated fixation protocols tested. Notably, it proved indispensable not only to cut off the fly's head to facilitate the penetration of the reagents but also to open the chitinous head capsule. For this, we locally pierced the cuticle between the eyes, leaving the head structurally almost intact, a prerequisite for precisely aligning the head for microtomy. We developed a two-step re-embedding procedure allowing for exact and reproducible orientation of the fly heads. Thus, highly comparable series of cross sections through a representative number of ommatidia were obtained. The feasibility of our embedding and sectioning approach is finally demonstrated by three-dimensional reconstructions of the middle segments of the R1, R7, and R8 photoreceptor cells. We present reconstructions from structurally modified ommatidia, as seen after RNAi-mediated depletion of the endosomal adaptor protein p14, and from normal ommatidia corresponding to the wildtype.     

A discrete Petri net model for cephalostatin-induced apoptosis in leukemic cells

Understanding the mechanisms involved in apoptosis has been an area of extensive study due to its critical role in the development and homeostasis of multi-cellular organisms. Our special interest lies in understanding the apoptosis of tumor cells which is mediated by novel potential drugs. Cephalostatin 1 is a marine compound that can induce apoptosis in leukemic cells in a dose- and time-dependent manner even at nano-molar concentrations using a recently discovered pathway that excludes the receptor-mediated pathway and which includes both the mitochondrial and endoplasmic reticulum pathways (Dirsch et al., Cancer Res 63:8869–8876, 2003; López-Antón et al., J Biol Chem 28:33078–33086, 2006). In this paper, the methods and tools of Petri net theory are used to construct, analyze, and validate a discrete Petri net model for cephalostatin 1-induced apoptosis. Based on experimental results and literature search, we constructed a discrete Petri net consisting of 43 places and 59 transitions. Standard Petri net analysis techniques such as structural and invariant analyses and a recently developed modularity analysis technique using maximal abstract dependent transition sets (ADT sets) were employed. Results of these analyses revealed model consistency with known biological behavior. The sub-modules represented by the ADT sets were compared with the functional modules of apoptosis identified by Alberghina and Colangelo (BMC Neurosci 7(Suppl 1):S2, 2006).