Homogenisation treatments

Liquid foodstuffs, for example milk products must be submitted to homogenisation treatment in order to improve their long-term physical stability ("shelf life"). The liquid is pumped at very high pressure by a multiplex reciprocating piston pump through the narrow clearances of a hydraulically controlled homogenisation valve (Fig. 1.4-4, C, bottom). 

In the presence of gaseous oxygen, pure or diluted with nitrogen or other inert gases, aluminium is very stable at a wide range of temperatures. As a consequence, alloys are fused and elaborated under the natural atmosphere of the casthouse. Heat treatments are normally carried out in furnaces under air up to temperatures in the order of 600 °C for durations of up to 24 hours in the case of homogenisation treatments. Heat treatment practices using controlled atmosphere are reserved for cases where very specific quality requirements must be met. 

Ladle metallurgy, the treatment of Hquid steel in the ladle, is a field in which several new processes, or new combinations of old processes, continue to be developed (19,20). The objectives often include one or more of the following on a given heat more efficient methods for alloy additions and control of final chemistry improved temperature and composition homogenisation inclusion flotation desulfurization and dephosphorization sulfide and oxide shape control and vacuum degassing, especially for hydrogen and carbon monoxide to make interstitial-free (IF) steels. Electric arcs are normally used to raise the temperature of the Hquid metal (ladle arc furnace). 

The ferritic steels may also undergo intercrystalline corrosion as a result of grain boundary carbide formation. In the normal softened state (treated i 800 C) the carbon is largely precipitated and the ferrite composition homogenised so that further heating at lower temperatures has no adverse effect. During solution treatment above 950 C, however, carbon is redissolved. Sensitisation can then occur at lower temperatures but the rate is so rapid that it can only be suppressed by very rapid cooling which is not practically feasible. Thus weld decay is very possible in service unless a remedial... 

Marine fouling leading to the local production of HjS increases crack growth rate, but what the effect is when combined with CP is uncertain. Some of the factors mentioned earlier in connection with other steel corrosion problems are important to sulphide stress-corrosion cracking, (SSCC), eg. compositions, particularly C which usefully can be reduced to below 0.05%, S, microstructure and segregation . Compositional homogenisation by heat treatment can be beneficial ", whilst the presence of Cu in the... 

Alloys are generally of the Al-Mg-Si type with additions of copper and chromium or manganese. Colour varies with the particular alloy and the film thickness. For optimum control of colour, the alloy must be carefully produced with strict attention to composition, homogenisation and heat-treatment, where appropriate, and the anodising conditions must be maintained within narrow limits. It is usual to arrange matters, preferably with automatic control, such that current density is held constant with rising... 

A widely used technique for cell disruption is high-pressure homogenisation. Shear forces generated in this treatment are sufficient to completely disrupt many types of cell. A common... 

The oranges were washed, chopped in a meat mincer and homogenised by a Fryma mill. Water (0.6 volumes) were added before the slurry was heat treated by steam injection at 100°C for 2 minutes. The enzyme treatment was carried out for 1 hour at 40°C with 10 lU/g slurry of PME and 25 pg enzyme protein/g slurry of the other enzymes for each of the enzymes. The gelated orange slurry were treated at 85°C for 3 minutes to inactivate the enzymes before the strength of the gel was measured by a SMS TeJrture Analyser TA-XT2 (Stable Micro Systems, XT. RA Dimensions, Operations Manual versions) by compression analysis using a flat cylinder (20 mm dia.) with a speed of 2 mm/s. The force to provide a 20% compression was recorded. 

Pretreatment of biological samples for surfactant analysis is usually straightforward and includes either homogenising with anhydrous sodium sulphate or freeze-drying. Below, the sample treatment methods for extraction and clean-up of non-ionic and anionic surfactants in biota that have been encountered in the literature are reviewed. 

Samples collected in field are usually preserved by freezing after dissecting into small pieces. Homogenisation and grinding to rupture cell membranes appear to be the most commonly used pre-treatment procedures for tissue matrices (e.g. fish muscle tissue) [38]. 

Whole rock analyses. The thoroughly homogenised whole rock samples were dissolved in a HF/HN03/HC104-solution and analysed for major and trace elements by emission spectroscopy (ICPES). The carbonate content was determined separately by treatment of the rock powder with HC1. Total organic carbon of the whole rock samples was determined by a Leco carbon analyzer. 

Sharma, R., Dalgleish, D.G. 1994. Effects of heat treatments on the incorporation of milk serum proteins into the fat globule membrane of homogenised milk. J. Dairy Res. 61, 375-384. 

In the solvent method the separation of the solubilised or dispersed material from the solvent phase can be explained by precipitation or phase change induced by solvent evaporation, addition of electrolyte, pH modification or heat treatment (Krochta and McHugh 1997). Such treatments can be adjusted to enhance film formation or specific properties. For composite emulsion-based films or coatings a lipid material and most likely a surfactant, is added to the solution, which is then heated above the lipid melting point and homogenised. The prepared solution is then applied on an appropriate support and the solvent evaporates. 

Samples, as taken, are often unsuitable for direct analytical measurement. These samples will require some pre-treatment. Sample pre-treatment is a term used to encompass a variety of sample preparation procedures, including pre-concentration, clean up, extraction, dissolution, digestion and homogenisation. 

Many cells are susceptible to the appreciable shearing forces that arise on repeated freezing and thawing, or to hypotonic buffers which cause cells to swell up, and in certain cases to lyse this is particularly the case for cells in soft plant and animal tissue. Such treatments only rarely lead to complete cell lysis, the exceptions to this being erythrocytes and reticulocytes which are lysed quantitatively under hypotonic conditions. Non-mechanical homogenisation is of particular relevance to cells like yeast which are refractory to other procedures. One of the simplest procedures for yeast, which can certainly not be described as gentle, is toluene-induced autolysis. This is carried out at room temperature and leads to permeabilisation of the cell walls this causes various hydrolases to be activated causing breakdown not only of the cell structure, but also (undesirably) of many sensitive proteins and nucleic acids in the cell. Consequently, this process is mainly of historical interest. 

The impact, which the introduction of intermediate quantities can have on the relevance list, is convincingly demonstrated by the treatment of the homogenisation characteristic for mixtures with density and viscosity differences, c.f [616] and section 3.4.2. 

The initial pH of the homogenised sample was 7.7 which was adjusted to 1.7 by addition of hydrochloric acid (Supra Pur, Merck) directly in the tank. The sample was further homogenised by circulating the water for one hour every six hours throughout the storage period, using a metal free magnetic pump. To allow colloidal material to flocculate, the sample was stored for 9 months before further treatment. 

The material was collected in the Rhine River, air-dried and further dried at 40 C for 48 h. About 40 kg were milled, homogenised and sieved to obtain particles of less than 250 pm size. The treatment was carried out following the Dutch norm NEN 5751. The material was bottled in brown glass bottles (1200 bottles each containing ca. 30 g). 

A pilot study on the heat sterilisation process of the sediment material was performed to evaluate the losses of CBs. From the results it was concluded that the heat treatment has to be carried out at ca. 120°C over a period of 2 h in order to have the least effect on the CB content. Immediately after sampling, the sediment was air-dried at 40°C over a period of several weeks with continuous churning up and removal of larger objects. The dried sediment was then sieved (pore size 2 mm) and jet-milled for a particle size of less than 125 pm and heat sterilised at 120 C for 2 h, homogenised in a 250 L multi-purpose mixer during semi-automatic filling of bottles. The material was finally packed in 4400 bottles, each one containing 40 g. 

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