Optimization of high pressure processing parameters of Indian white prawn (Fenneropenaeus indicus)

The effect of pressure (150, 250 and 350?MPa), ramp rate (200, 400 and 600?MPa/min) and holding time (3, 6 and 9?min) on the quality indices (dependent variable) of Indian white prawn (Fenneropenaeus indicus) was optimized using response surface methodology. Box–Behnken response surface design was used with 15 runs. Second-order response surface model was fitted to the experimental data and the model adequacy was measured by R² value. The linear and quadratic effect of pressure, ramp rate and holding time was significant for tri-methylamine, total volatile base nitrogen and total plate count. Based on the ridge analysis and response surface plots, the optimum combination obtained was 250?MPa pressure, 400?MPa/min ramp rate and 6?min holding time for high pressure (HP) processing of Indian white prawn. Validation of the experiment indicated that the developed model was appropriate to predict quality indices in Indian white prawn processed by HP processing.     

Effect of high pressure treatment on liquid whole egg

In our tests, we artificially infected liquid whole egg samples with Salmonella enteritidis, Listeria monocytogenes, and Staphylococcus aureus bacteria, and then treated the samples in “Food Lab900” high hydrostatic pressure (HHP) instrument for 3–17 min at 200–400 MPa. Subsequently, the change of the viable cell count of the specific bacteria has been tested. In addition to the samples infected with various bacteria, non-infected samples were also treated in each test and the change in viable cell count, colour and viscosity of the samples upon the effect of the treatment. In summary, it can be concluded that in each test of our investigations, the viable cell count of S. enteritidis critical for egg products is reduced significantly, while the reduction of the total viable cell count was around two magnitudes. Additionally, based on our results, microbial destruction, reduction of enthalpy (denaturation of egg white) caused by the treatment at HPP, and colour change are primarily affected by the pressure level, while the changes in rheological properties are also significantly affected by the duration of high pressure treatment (p<0.05).     

Carbon isotopic analyses for source apportionment studies of the greenhouse gases carbon dioxide and methane

We investigated the environmental water sources used in mid-summer by three Sonoran Desert phreatophytic riparian tree species, Salix gooddingii, Populus fremontii, and the exotic Tamarix spp., at sites that differed in water table depth. Salix gooddingii was most sensitive to water table decline, as evidenced by lower predawn water potentials. Although P. fremontii was less sensitive to water table decline than S. gooddingii, its leaf gas exchange was the most responsive to atmospheric water stress imposed by high leaf-to-air vapor pressure deficit. Tamarix spp. was least sensitive to water table decline and showed no reduction of predawn water potential over the measured range of depth to groundwater. Comparison between D/H of xylem and sampled environmental water sources suggest that S. gooddingii and P. fremontii used groundwater at most sites with no change in water source as depth to groundwater varied. In contrast, xylem D/H of Tamarix spp. was depleted in deuterium compared to groundwater at most sites, suggesting use of water from an unsampled source, or discrimination against deuterium during water uptake. This study highlights the difficulty in sampling all water sources in large-scale studies of riparian ecosystems with complex subsurface hydrogeology.     

Sulfur Isotope Fractionation in the Biogeochemical Sulfur Cycle of Marine Sediments

Abstract

The sulfur isotopic record of sedimentary sulfides (mainly pyrite) and sulfates shows considerable variations in time and plays an important role in the biological and geochemical interpretation, e.g., of the evolution of life and the oxygen partial pressure of Earth's atmosphere (e.g. [1]). From a comparison of experimental results with Desulfovibrio spp. it can be inferred that the S isotope fractionation during reduction of sulfur compounds is controlled by the number of electrons transferred (Fig. 1). Sulfur isotope discrimination in the sulfur cycle of marine sediments is dominated by dissimilatory bacterial sulfate reduction (BSR), and [2] used laboratory experiments with mesophilic bacteria to postulate that high sulfate reduction rates with abundant sulfate at enhanced temperature dominated the Ocean water chemistry during early Archean time. Experiments with pure cultures of thermophilic sulfate reducers [3] and natural hydrothermally influenced communities [4], however, demonstrated that isotope discrimination is close to average fractionation by mesophiles and that temperature is not directly influencing isotope discrimination during BSR.     

Behaviour of E. coli 0157:H7 strains in model system and in raw meat by hpp: Microbial and technological aspects

Abstract

Verotoxigenic Escherichia coli (VTEC) is an important pathogen which can cause serious illnesses in humans. It is of particular importance to the meat industry to be able to completely destroy E. coli. A technique used to destroy E. coli could be the high pressure process. For this reason a mixture of 8 strains of E. coli 0157:H7 was inoculated in raw minced meat and in broth. These samples were treated at pressures up to 700 MPa at WC, causing up to 5 decimal reductions. HP treatment is also effective in decreasing microbial contamination and increasing the shelf-life of raw minced meat under refrigerated conditions. The texture of raw minced meat improved with HP level, while the colour was less characteristic in HP-treated samples; a combined HP-treatment caused less colour change than an individual HP-treatment. No difference in colour of cooked minced meat was observed in untreated and HP-treated samples. The texture of cooked minced meat improved in HP-treated samples.     

Poly 3-hydroxybutyrate-co-3-hydroxyhexanoate films can be degraded by the deep-sea microbes at high pressure and low temperature conditions

ABSTRACT

We have isolated several poly 3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBH) degradable bacteria from the deep-sea sediment samples. The isolated microbes were involved into α-, γ- Proteobacteria group and the phylum Firmicutes, which were commonly diverged in the ocean environment. Four bacterial strains, Bacillus sp. MH10, Alteromonas sp. MH53, Psychrobacillus sp. PL87 and Rheinheimera sp. PL100, were selected as more active strains for the PHBH bio-degradation at high pressure and cold temperature conditions, and showed that those strains were piezotolerant up to 20–30?MPa. Our findings indicated that the PHBH could be well degraded not only in the ocean environment, but also at the deep-sea bottom, by means of those marine microorganisms.     

The usage of high hydrostatic pressure (HHP) to control food-borne pathogens in hummus

ABSTRACT

With the increasing demand for fresher, higher quality, minimally processed and safer food, there is a strong necessity to develop non-thermal processing techniques. Also for hummus, which is popular all around the world. In this work, the effect of refrigerated storage on the survival of pathogens in hummus treated by high hydrostatic pressure (HHP) (500?MPa/10?min/room temperature) was evaluated. The cocktail of two Salmonella, four Listeria monocytogenes and two Escherichia coli strains was used in this study. All pathogen types were able to survive in hummus during 60 days of refrigerated storage. HHP-treated samples plated on day 0 successfully achieved a?>?5 log cfu/g reduction for all pathogen types. No residual survivors were present after 30 and 60 days in any of the HHP-treated samples. These results demonstrate that HHP may be a useful technique for the inactivation of pathogens and therefore helpful in designing non-thermal HHP conditions for pressurization of hummus.     

Evaluation of quality changes of beetroot juice after high hydrostatic pressure processing

ABSTRACT

Freshly squeezed commercially available beetroot juice, a popular beverage in Poland, is a good source of betalains, but as a root vegetable can contain undesirable microflora from the soil. The objective of this study was to investigate the effect of new preservation technique, high hydrostatic pressure, on the beetroot juice quality. Samples of beetroot juice were treated with pressure 300, 400 and 500?MPa/20°C/up to 10 min. Reduction in the total count of spoilage microorganisms reached 3.8, 4.1 and 4.5 log cfu/mL, depending on the pressure. After this treatment beetroot juice showed a 11.3–12.2% decrease in betacyanins content and 7.7–8.9% in betaxanthins content. A significant reduction of the number of spoilage microorganisms with a slight degradation of pigments indicates the possibility of industrial application of high pressure to the preservation of beetroot juice.     

High Pressure Processing at Subzero Temperature: Effect on Spoilage Microbiota of Poultry

Mechanically recovered poultry meat (MRPM) was treated at 350 and 450 MPa for 5 and 15 min at m 20 °C and then stored at 2 °C. Counts of mesophilic, psychrotrophic and lactic acid bacteria were determined at 1, 4 and 15 days of storage. Initial counts were ca. 7 log CFU/g for the three populations. High pressure induced lethalities of ca. 1.5 log CFU/g for mesophiles and psychrotrophs and, in some cases, ca. 2.5 log CFU/g for lactic acid bacteria. At 4 days, counts in pressurized samples increased less for mesophiles and psychrotrophs ( h 0.5 CFU/g) than for lactic acid bacteria ( S 1 log CFU/g). At 15 days, counts of the three populations were ca. 9 log CFU/g in all samples. High pressure processing at subzero temperature does not extend shelf-life of MRPM.     

Towards an easy carbon dioxide reduction in aqueous solution

Abstract

The homogeneous hydrogenation of carbon dioxide into formate anion has been investigated in aqueous solution, using water soluble ruthenium(1I)-phosphine (meta-monosulphonated triphenylphosphine, TPPMS; and 1,3,5-triaza-7-phosphaadamantane, PTA) complexes as catalysts. These reactions take place in amine free medium under mild conditions, bicarbonate anion is more active than carbon dioxide in the reduction. The initial turnover frequenc of the reduction increases with increasing H₂ pressure, as it was observed in situ by C and 'H NMR spectroscopy. High pressure FT-IR were used to find evidence for the formation of the catalytically active ruthenium hydride species.     

On the Relationship Between Microhardness and Crystal Perfection of Chain-Extended Polyethylene

Abstract

The crystal hardness-crystal perfection correlation of polyethylene (PE) samples crystallized at high pressure from the melt (chain extended) has been studied and compared to melt crystallized samples at atmospheric pressure (chain folded). For this purpose the chain extended PE samples were analyzed by WAXS and the paracrystalline lattice distortion parameter values, g ₁₁₀, were calculated. Results are discussed in the light of structural and thermodynamical predictions. Analysis of data confirm the close existing correlation, previously found for chain-folded crystals, between the crystal hardness and g ₁₁₀, including now both the values for chain-folded and chain-extended crystals.     

Sources of primary production to Arctic bivalves identified using amino acid stable carbon isotope fingerprinting*

ABSTRACT

Benthic invertebrates are a crucial trophic link in Arctic marine food webs. However, estimates of the contribution of different primary production sources sustaining these organisms are not well characterised. We measured the stable carbon isotope values (δ¹³C) of essential amino acids (EAAs) in muscle tissue from two common bivalve genera (Macoma spp. and Astarte spp.) collected in Hanna Shoal in the northeastern Chukchi Sea. Mixing models comparing the δ¹³C_EAA fingerprints of the bivalves to a suite of primary production endmembers revealed relatively high contributions of EAAs from phytoplankton and bacteria in both species. We also examined whether δ¹³C_EAA fingerprints could be produced from the EAAs preserved in bivalve shells, which could allow primary production sources to be estimated from ancient bivalve shells. The δ¹³C_EAA fingerprints from a suite of paired modern bivalve shells and muscle from Macoma calcarea from across the Chukchi Sea revealed a correspondence between the estimates of the dominant primary production source of EAAs derived from analyses of these two tissue types. Our findings indicate that δ¹³C_EAA fingerprinting of marine bivalves can be used to examine dominant organic matter sources in the Arctic marine benthos in recent years as well as in deeper time.     

Optimization of a GaN-based irregular multiple quantum well structure for a dichromatic white LED

GaN-based irregular multiple quantum well(IMQW) structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes(LEDs) are optimized in order to obtain near white light emissions.The hole distributions and spontaneous emission spectra of the IMQW structures are analysed in detail by fully considering the effects of strain,well-coupling,valence band-mixing and polarization effect through employing a newly developed theoretical model from the k · p theory.Several structure parameters such as well material component,well width,layout of the wells and the thickness of barrier between different types of QWs are employed to analyse how these parameters together with the polarization effect influence the electronic and the optical properties of IMQW structure.Numerical results show that uniform hole distributions in different types of QWs are obtained when the number of the QWs emitting blue light is two,the number of the QWs emitting yellow light is one and the barrier between different types of QWs is 8nm in thickness.The near white light emission is realized using GaN-based IMQW structure with appropriate design parameters and injection level.     

Deactivation of Escherichia coli with different volumes in drinking water using cold atmospheric plasma

This experimental study aimed to evaluate the potential of cold atmospheric plasma jet to deactivate Escherichia coli from drinking water. We studied the effect of the volume of water samples on the performance of plasma jet on deactivation of E. coli of 1, 500, 1,000, 1,500, and 2,000 cubic centimetres. The results of deactivation of E. coli in 500 and 1,000 cc water samples were the same as one cc of a water sample and we observed 8-log reduction of E. coli using 50 W. In 1,500 and 2,000 cc water samples at 8 min using a power of 50 W, 4.5 and 2.9 log reduction of E. coli was achieved and while we used 20 W, 2.5 and 1.8 log reduction of E. coli bacteria was performed. This indicated that the increasing volume of water above 1,500 cc caused the reduction of the efficiency of E. coli removal. Also, increasing power caused to increase E. coli removal efficiency. In addition, we monitored changes in pH values and temperature during experiments. Using 20 W, the temperature was increased (natural temperature of the water was 22 °C) 2 °C after 8 min while applying 50 W, the temperatures were raised 5 °C. pH of the water after 8 min in the 1,000 cc water sample, with an input power of 20 W, decreased from 7.1 to 5.5; while the input power was 50 W, pH changed from 7.1 to 4.3. With an increase in plasma irradiation time, the number of E. coli had a significant decrease per min while using in samples of 1 cc. After 8 min, we observed 4-log reductions of E. coli with the input power of 20 W and 8-log reduction of bacteria with the input power of 50 W. In 1,500 and 2,000 cc of water samples using plasma radiation for 8 min, 2.5 log and 1.8 log reduction of E. coli was achieved, respectively. This means that an increasing volume of water above 1,500 cc needs more power and time to deactivate E. coli from the water.     

Athermal effects in ion implanted layers

Abstract

Defect structure and electrical characterization of boron and arsenic implanted layers has been investigated for implantation under athermal (light) excitation. This Photon Assisted (PA) implantation owes its specific properties to an additional electric field acting on charged particles including carriers and charged defects. It was shown that in case of n-type silicon this extra field draws charged vacancies and self-interstitials towards each other and, thus, diminishes transient diffusion of boron. This effect resulted in junctions which are about 20% shallower compared to conventionally processed reference wafers. Experiments using light of an Ar-ion laser and white light of a high pressure Xe arc lamp were compared. Some deactivation of carriers in the deeper laying parts of the p-region was always a by-product.     

Effects of High Pressure Treatment on the Microbiological Quality,Texture and Colour of Vacuum Packed Pork Meat Products

The aim of the study was to define usefulness of high pressure treatment for inactivation of microorganisms and prolongation of shelf life of two types of cooked pork ham and raw smoked pork loin. The samples of ham and loin in the presentation of standard 200 g pieces were vacuum packed in polylayer polyethylene bags and exposed to high pressure treatment in the range of 300-600 MPa and time of exposure of 10-30 minutes. Results indicate that 300 MPa and 400 MPa pressure applied for 10 minutes was insufficient for prolongation of storage period of ham. Pressure of 500 MPa, applied for 10 minutes caused significant decrease of microbiological parameters studied such as: total bacterial count, psychrophylic bacteria, acidophylic bacteria and enterococci in investigated samples, stored in refrigarator conditions for 4 weeks. Pressure of 600 MPa applied for 10 minutes reduced the number of all investigated microorganisms by 10 5 -10 6 fold. Application of this pressure prolonged storage period of traditionally produced ham to 6-8 weeks. Physico-chemical characteristics of ham, measured 24 h after high pressure treatment and after 4, 6 and 8 weeks of storage, did not change when compared to the initial samples. High pressure treatment caused increase in the colour lightness parameters only in pork smoked loin.     

Konstanz summer school 2018 on isotope ecology

Abstract

Biodegradation of polychlorinated biphenyls (PCBs) in soil is considered to be very complex due to various physico-chemical factors involved. Isotope labelling technique is the best to trace fate of the xenobiotic in the environment. In this work, the uniformly ¹⁴C-labelled PCB congener 11 (3,3′-chlorobiphenyl) was chosen as a low chlorinated coplanar biphenyl which was assumed to be readily degraded by microorganisms. Pleurotus ostreatus and two Pseudomonas species, representing white rot fungi and soil bacteria were used separately or in a consortium. The amount of liberated ¹⁴CO₂ and radio-HPLC, HPLC, GC-MS, and radio-TLC analyses of extracts at the end of a two-month experiment showed that the mineralization of PCB 11 was < 0.4%, volatilization < 3.1%, and 30% of radioactivity was irreversibly bound to the soil matrix. The respective contents of all intermediate metabolites were 4.7 to 10.5 and 2.5 to 2.7% where Pseudomonas alcaligenes alone or in combination with P. putida was applied. 3-Chlorobenzoic acid was the major biodegradation product.     

Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones

Bulk samples of carbon multilayer nanotubes with the structure of nested cones (fishbone structure) suitable for transport measurements, were prepared by compressing under high pressure (∼25 kbar) a nanotube precursor synthesized through thermal decomposition of polyethylene catalyzed by nickel. The structure of the initial nanotube material was studied using high-resolution transmission electron microscopy. In the low-temperature range (4.2–100 K) the electric resistance of the samples changes according to the law ln R ∝ (T ₀/T)^1/3, where T ₀∼7 K. The measured magnetoresistance is quadratic in the magnetic field and linear in the reciprocal temperature. The measurements have been interpreted in terms of two-dimensional variable-range hopping conductivity. It is suggested that the space between the inside and outside walls of nanotubes acts as a two-dimensional conducting medium. Estimates suggest a high value of the density of electron states at the Fermi level of about 5×10²¹ eV⁻¹ cm⁻³. Zh. éksp. Teor. Fiz. 113, 2221–2228 (June 1998)