On the directional dynamics of additive cellular automata

We continue the study of cellular automata (CA) directional dynamics, i.e. , the behavior of the joint action of CA and shift maps. This notion has been investigated for general CA in the case of expansive dynamics by Boyle and Lind; and by Sablik for sensitivity and equicontinuity. In this paper we give a detailed classification for the class of additive CA providing non-trivial examples for some classes of Sablik’s classification. Moreover, we extend the directional dynamics studies by considering also factor languages and attractors.     

Kinetics of water adsorption in microporous aluminophosphate layers for regenerative heat exchangers

The performance of thick aluminophosphate molecular sieve layers for heat exchanger applications is evaluated. The aluminophosphate AlPO-18 (AEI structure type code) molecular sieve sorbent is coated on aluminium supports prior the sorption measurements. Two AlPO-18 samples with different morphological appearance, i.e. nano-sized crystals with monomodal size distribution and micron-sized crystals of varying sizes, are used to prepare layers with thickness in the range of 80–750 μm. As a binder component, polyvinyl alcohol (PVOH) was utilized in order to prepare mechanically stable layers, which are mechanically stable over numerous measuring cycles. The sorption measurements are conducted under canonical conditions at 40 °C. The AlPO-18 layers showed decreased mass flows with increasing the thickness. Additionally, the layers comprising nanosized crystals showed higher equilibrium loadings and faster kinetics compared to films based on micron-sized crystals. Following the kinetic studies of pressure, temperature and heat flow, it can be concluded that the heat transport is the rate limiting mechanism for thick aluminophosphate layers. Importantly, the diffusion limitation plays a role only for relatively thin microporous aluminophosphate layers (<200 μm). Below this thickness complete heat transfer is achieved within 2 min which allows fast heat exchanger cycles. Thus, the application of microporous aluminophosphate layers for heat transformation and storage applications is considered possible.     

Effect of the inoculum size on Listeria monocytogenes growth in structured media

Obtaining quantitative data concerning the relative impact of various factors that may influence bacterial growth is of great importance for microbial risk assessment and predictive microbiology. The objective of this work was to investigate the effect of the initial Listeria monocytogenes density on all the growth parameters of this pathogen (lag phase duration, growth rate and maximum population density attained) on a sterile solid model system mimicking smoked fishery products, and in real cold-smoked salmon, a product likely to be contaminated with L. monocytogenes. Growth of the pathogen was monitored using a sensitive enumeration method, recently developed, based on membrane filtration followed by the transfer of the filter on a selective media [Gnanou Besse, N., Audinet, N., Beaufort, A., Colin, P., Cornu, M. and Lombard, B., 2004. A contribution to the improvement of Listeria monocytogenes enumeration in smoked salmon. International Journal of Food Microbiology, 91, 119-127.]. Depending on the experimental conditions, we found a significant effect of the inoculum size, both on lag phase duration, and on the maximal population attained. Moreover, the effect of the inoculum size on the growth of L. monocytogenes was dependent on a complex set of interactions. Factors which have appeared to impact on this effect include the cells physiological state, the background microflora, the texture of the media and the packaging system. It is important to understand how these interactions affect the growth of Listeria in order to predict and control its development in food.     

Characterization of the cultivable microbial community in a spinach-processing plant using MALDI-TOF MS

A better and regular control of the production chain of fresh fruits and vegetables is necessary, because a contamination of the product by human- and phyto-pathogenic microorganisms may result in high losses during storage and poses a threat to human health. Therefore, detailed knowledge about the occurrence and the diversity of microorganisms within single processing steps is required to allow target-oriented produce safety control. Recently, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was successfully used to identify bacterial colonies. Bacteria can be identified with high accuracy by comparing them with generated spectra of a reference database.     

Sustainable sunflower processing — I. Development of a process for the adsorptive decolorization of sunflower [Helianthus annuus L.] protein extracts

A novel process for the production of light-colored sunflower protein isolates was developed, combining mild-acidic protein extraction with adsorptive removal of phenolic compounds. Four commercial food-grade adsorbent and three ion exchange resins were tested with regard to their affinity towards polyphenols. Amberlite™ XAD 16HP and FPX 66 showed optimal decolorization of the sunflower crude extracts. In contrast, ion exchange resins exerted maximal binding of monomeric phenolic compounds, but were less effective in removing colored compounds. Adsorption behavior of individual resins was assessed by adding resin to protein extracts varying the amounts of resin, protein concentration of the solutions and temperature. Furthermore, a D-optimal experimental design was applied to optimize adsorptive polyphenol removal from sunflower protein extracts using a styrene–divinylbenzene copolymer. Adsorption isotherms were determined for 5-O-caffeoylquinic acid and total phenolics, respectively. Optimal conditions were deduced from experiments at different temperatures, with different flow rates and extract concentrations. Finally, adsorbent and ion exchange resin columns were connected in series and successfully applied to produce light-colored sunflower protein on a pilot scale under the conditions optimized in laboratory experiments, thus demonstrating that this technology can easily be integrated into existing process lines.

Industrial relevance

A vital necessity to exploit novel protein sources arises from the increasing demand for human nutrition. Residues originating from sunflower oil production are rich in proteins and might serve as a source of plant proteins, which has not been valorized so far. This is due to their high contents of phenolic compounds that may interfere with the proteins lowering their nutritional value and impairing their sensory properties. Therefore, a process for mild-acidic protein extraction combining adsorption and ion exchanger technology for the removal of polyphenols from crude sunflower extracts was developed in the present study.