Effect of high hydrostatic pressure and reducing sodium chloride and phosphate on physicochemical properties of beef gels

ABSTRACT

The effect of high hydrostatic pressure (HHP) treatment (100–200?MPa, 10?min, 20°C) combined with sodium chloride and sodium phosphate on the physicochemical properties of beef gels was investigated. The water content, cooking losses, color, protein composition by SDS-PAGE analysis and texture parameters of beef gels were determined. The beef gels treated with high pressure at 150?MPa showed a synergistic effect in the increased water content and the decreased cooking losses compared with the unpressurized gels. The L*, a* and b* color values of beef gels were slightly decreased under HHP treatment at 100–200?MPa. In the SDS-PAGE analysis, the staining intensity of the α-actinin protein band was decreased in pressurized samples. The cohesiveness, adhesiveness, gel strength and modulus of elasticity were improved after HHP treatment. Application of high pressure treatment (150–200?MPa) before heat treatment would be beneficial for the manufacturing of low salt and/or low phosphate meat products for a healthy diet.     

Effect of high pressure on heat and ethanol stabilities of milk

Abstract

The effect of high pressure (in range from 200 to 1000 MPa) and periods of exposure time (from 15 to 35min) on the changes of selected physico-chemical characteristics of skim milk, particularly considering its heat and ethanol stability, was studied.

Due to High pressure the conformation of milk proteins and the milk salt system were changing. Pressurization caused slightly change in the ethanol stability of milk. The influence of pressurization on heat stability was more evident. The heat stability of milk increased with an increase in pressure and exposure time.     

High pressure effects on myofibrillar proteins

Abstract

Myofibrillar proteins were extracted from post rigor bovine meat with a potassium phosphate/potassium chloride buffer. Viscoelastic properties of myofibrillar properties were studied in a 0.6MKCl buffer, at pH = 6, used in an oscillating mode. Enthalpy patterns were determined with a differential scanning calorimeter. SDS PAGE was performed.

Results show that high pressure processing denatures myofibrillar proteins, which result in a decrease of myofibrillar protein extractability. Moreover, the viscoelastic properties of myofibrillar extracts are modified by a preliminary high-pressure treatment of meat. The storage modulus (G′) versus temperature graph presents an intermediate peak; the height of this peak and the final value (90°C) are dependant on the level of pressure.

Finally, enthalpy and electrophoresis patterns allow us to understand myofibrillar protein modifications induced by high hydrostatic pressure processing of meat.     

Experimental Investigation on Pressure Drop and Heat Transfer Characteristics of Copper Metal Foam Heat Sink

Abstract

The effect of the cooling performance of a copper metal foam heat sink under buoyancy-induced convection is investigated in this work. Experiments are conducted on copper metal foam of 61.3% porosity with 20 pores per inch. The pressure drop experiment is carried out to find the permeability and foam coefficient of the porous media. It is found that the property of porous media changes by changing the angle of inclination of the porous media from a horizontal to a vertical position while keeping the orientation and porosity the same. The Hazen-Dupuit Darcy model is used to curve-fit the longitudinal global pressure drop versus the average fluid speed data from an isothermal steady-flow experiment across the test section of the porous medium. The study concludes that the permeability and foam coefficient for copper foam is found to be 1.11 × 10^?7 m² and 79.9 m^?1, respectively. The heat transfer study shows that the thermal performance of copper metal foam is 35–40% higher than the conventional aluminum metal heat sink under an actual conventional mode.     

Stirred-style yoghurt-type product prepared from pressure treated skim-milk

Abstract

Acid-set gel formation is an important first step in the production of dairy products such as yoghurt and cottage cheese. Acid-set gels prepared from pressure treated skim milk have increased rigidity and resistance to breaking. Water binding capacity, protein hydration index and resistance to syneresis (separation of an aqueous phase) were also increased. As stirred-type yoghurt has a larger share of the market it is of greater commercial interest. The effects of a range of pressure-time treatments of the milk on the characteristics of stirred type yoghurts prepared at pH 4.1 have been investigated. The viscosity was improved with increasing pressures in the range 100–600 MPa and with the duration of the treatment up to 1 h.     

Influence of Vertical Foam Flow Liquid Drainage on Tube Bundle Heat Transfer Intensity

The results of an experimental investigation of staggered tube bundle heat transfer to upward and downward moving vertical foam flow are presented in this article. It was determined that a dependency exists between tube bundle heat transfer intensity on foam volumetric void fraction, foam flow velocity and direction, and liquid drainage from foam. In addition to this, the influence of tube position of the bundle on heat transfer was investigated. Experimental results were summarized by criterion equations, which can be applied in the design of foam type heat exchangers.     

Air Flow in Aluminum Foam: Heat Transfer and Pressure Drops Measurements

Abstract

Metal foams are cellular structure materials that present open cells, randomly oriented and mostly homogeneous in size and shape. Cellular structure materials, and particularly open-cell metal foams, have been proposed as possible substitutes for traditional finned surfaces in electronics cooling applications. This article presents the heat transfer and pressure drops measurements obtained during air flow through an aluminum foam, which has 40 pores per inch with 0.63 mm pore diameter. The specimen has been inserted in a new open-circuit type wind channel with a rectangular cross-section that has recently been built at the Department of Fisica Tecnica of the University of Padova. The experimental heat transfer coefficients and pressure drops have been collected by varying the air flow rate supplied by the screw compressor that provides a variable volumetric air flow ranging between 0–90 m³h^?1 at a constant gauge pressure of 7 bar. The specific heat flux has been simulated by powering with a 25-kWm^?2 copper heater attached at the bottom of the aluminum foam base plate. The experimental results are reported in terms of heat transfer coefficients, mean normalized wall temperatures, and pressure drops.     

On the nature and the practical relevance of the molecular modifications induced in wheat proteins by high pressure treatment

Abstract

Modifications induced by the combined application of pressure (up to 800 MPa) and temperature (up to 80° C) were studied on wet and dry semolina, and on fresh pasta as such and after cooking. Rheological and immunochemical properties of the treated products were investigated, along with parameters indicating the extent of protein denaturation. No modification occurs in semolina treated at less than 45% water, below 60°C/800MPa for 10min. Egg noodles prepared from pressure/heat treated semolina had increased protein digestibility and low recognition by anti-gliadin antibodies either before or after cooking. The same effects were observed in heat/pressure treated pasta, but were lost upon subsequent cooking, although we found decreased immunochemical reactivity after heat/pressure treatment of cooked pasta. No sensory difference was found between cooked and pressure-treated semolina products.     

Numerical simulation of thermal and fluiddynamical transport effects on a high pressure induced inactivation

The current paper deals with the effects of convective transport and heterogeneous thermal conditions on the uniformity of a high pressure induced inactivation by means of mathematical modelling and numerical simulation. The inactivation of B. subtilis α-amylase dissolved in TRIS-buffer is chosen as an example for a pressure induced transformation. Two different processes are considered. The first represents a direct treatment where the pressure increase is achieved by mass augmentation of the enzyme solution. The second is an indirect treatment, where the enzyme solution is packed and the pressure increase is achieved by inflow of a pressure medium into the pressure chamber. Aspects of the viscosity of the matrix as well as the heat transfer properties of the packaging material are considered. In both cases, significant process uniformities can be determined.     

Quantitative analysis of dissociation of LDH by high pressure native PAGE

ABSTRACT

High pressure native polyacrylamide gel electrophoresis has been designed to visualize the dissociation/association process of protein complexes. This paper reports this methodology in more quantitative way by inspecting pressure dissociation of pig heart lactate dehydrogenase, a tetrameric protein, which was extensively investigated in spectroscopic methods. We observed the change of electrophoresis pattern with pressure up to 150?MPa. By optimizing the buffer system and careful image analysis of the stained gels, we quantified all the dissociates in the process of pressurization. We discussed the characteristics of our methodology by comparing the result with the previously reported.     

Visualization of ke V-ion-induced spikes in metals

Abstract

Using gliding averages, the density, temperature, and pressure evolution in a keV-ion induced spike in copper is presented. The particular event visualized has been selected since it represents the average features of ion-beam induced mixing. Equilibration between potential and kinetic energy in the molten spike core is discussed, emphasizing the role of the latent heat of melting. Re-fueling of heat to the spike by condensing adatoms is exemplified.     

Effects of combination treatments of lysozyme and high power ultrasound on the Salmonella typhimurium inactivation and quality of liquid whole egg

An investigation was conducted into the utilization of treatments combining ultrasound and lysozyme (US + Lys) to deactivate Salmonella typhimurium (S. typhimurium) in the liquid whole egg (LWE). Furthermore, US + Lys and heat treatment (HT) with a similar microbial inactivation effect were comparatively evaluated by examining their impact on the quality attributes of LWE. The LWE was treated with US at 35–45 °C and 605–968 W/cm² for 5–35 min, and with HT at 58–64 °C for 3–4 min. Lysozyme (Lys) alone achieved a minimal degree of inactivation in S. typhimurium, while it was enhanced with the application of US alone when the treatment temperature, time, and energy were increased. Furthermore, US and US + Lys caused a reduction of 3.31 and 4.26 log₁₀ cycles in S. typhimurium, respectively at 968 W/cm² and 35 °C for 20 min, indicating a synergistic relationship between US and Lys for the effective inactivation of S. typhimurium. Similarly, HT and HT + Lys achieved a reduction of 4.10 and 4.75 log₁₀ cycles at 64 °C/3 min, respectively. The L* and b* values of the LWE following US and US + Lys application were significantly higher than untreated and heat-treated LWE, indicating that US treated LWE had a brighter and yellower appearance. The protein solubility (PS) slightly decreased after all treatments, while the pH increased. Furthermore, the foaming capacity (FC) and foam stability (FS) were decreased, revealing that LWE had a lower FC and unstable foam after all treatments. Therefore, US and US + Lys could increase the viscosity and gelation temperature (Tg) of LWE, indicating that LWE exhibited higher heat resistance after US treatment. These results indicated that US + Lys might be a promising pasteurization technology in the processing of LWE.     

Stability diagram of rice starch as determined with FTIR

Abstract

In this study, we followed in situ changes in the infrared spectrum at different conditions of pressure and temperature. Cooperative changes were observed when temperature or pressure was increased. Plotting the midpoints of cooperative transitions in a pressure-temperature plane results in an outline similar to the stability curve of proteins. We can assume that it is the first time that the pressure-temperature dependent gelation diagram is determined in situ for starch.     

Structure ortimization of two-phase titanium alloy by way of hydrostatic extrusion

Abstract

Two-phase titanium alloy was deformed up to 50% by hydrostatic pressure. Deformation combined with various schemes of heat treatment sufficiently changes morphology and internal structure of all constitutent alloy phases. Structural changes cause improvement of mechanical properties.     

High pressure equipment for food processing

Abstract

Processing food with pressure improves the quality and shelf life of the product. The pressure required is normally 600 to 900 MPa (approximately 6000 to 9000 atm). Equipment for high pressure food processing is available today from ABB Pressure Systems AB. The plant can have a through-put of 300 to 6000 litres per hour at 600 MPa pressure depending on the size of the press. The processing cost at 600 MPa is between 3 to 20 pence per litre depending on production capacity. Processing at 900 MPa instead of 600 MPa will increase the cost 50%, while prolonging the processing time from 3 minutes to 6 minutes at 600 MPa, i.e. introducing a hold time, increases the cost 100%. Pressure is thus cheaper than time. The food is prepacked in flexible material and loaded into the high pressure vessel. Pure water is used as pressure transmitting medium. The pressure is increased to the value required. After decompression the food is ready for distribution.     

Pressure stability of insulin: A fourier transform infrared spectroscopy study

High hydrostatic pressure can induce partially unfolded protein conformations that are highly aggregation prone under conditions that normally favour the native state. We investigated the pressure stability of insulin at pH 2 with Fourier transform infrared spectroscopy. We do not observe any cooperative change up to 13 kbar. All spectral changes in the amide I area are fully reversible and are assumed to arise from the elastic effect of pressure, which causes no conformational changes. Moreover, insulin has no higher temperature-induced aggregation tendency when pressure pre-treated.     

The Influence of High Pressure on the Formation of Diketopiperazines And Pyroglutamate in Peptides and Peptide Esters

The effects of pressurization on several short chain peptides were examined. Leucylleucine methyl ester was rapidly degraded under pressure at 60 °C. Results were comparable to the pressure induced degradation of aspartame, meaning that the ester bond is largely high pressure sensitive: The structure of such peptides is consequently modified. Glutamine in model systems underwent cyclization to pyroglutamate under pressure only at conditions unrealistic for industrial purposes: 50 °C, pH 9, and holding times exceeding 30 min. No cyclization of peptides with glutamine at the C-terminus was observed.     

Changes in Volatile Aromatic Compounds of Strawberry Puree Treated by High-pressure During Storage

The changes in volatile flavor components and lipoxygenase and peroxidase enzymatic activity of Cilady strawberry puree during high pressure processing (400 MPa/20 °C/20 min) and storage at 4 °C were evaluated. High pressure processing maintains the original aromatic distribution, but after thirty days of storage an increase in some volatile compounds was observed. After high pressure treatment and storage, a residual lipoxygenase activity was observed, which could explain some slight changes of volatile compounds. On the other hand, the peroxidase was clearly inactivated by high pressure treatment.     

Influence of Synthesis and Composition conditions on Strength Characteristics of Synthetic Carbonado-Type Diamonds

Polycrystalline diamonds carbonado were synthesized under pressure 6.0-12.0 GPa. Ni-Cr-Mo alloy and pure Ni were used as the catalysts. The strength was tested by static compression technique according to GOST 9206-80. Diamond powders APK 4 with the grit size 500/400 and 400/315 were made by crushing of the bulk polycrystalline samples and this diamond powders were under investigation. Influences of the synthesis pressure and the chemical treatment on strength of diamond carbonado were studied.     

Effect of nitrogen pressure on the combustion synthesis of titanium nitride

Abstract

Titanium nitride, TiN, has attractive physical and chemical properties such as hardness, chemical stability and electrical conductivity. It is a typical material with a wide range of stoichiometry. It can be synthesised by high pressure combustion synthesis. The composition and microstructures can vary with the experimental conditions especially with thermal treatment and nitrogen pressure.