Hot water sterilisation

The overkill process is often used in daily practice and is based on the principle that the process should be sufficiently powerful to reduce a severe contamination with a very thermo-resistant organism, i.e. circa 10 spores of Geobacillus stearothermophilus, to the SAL 10 . The standard process for steam or hot water sterilisation in the... 

The Z-value is a measure for the change in resistance of the micro-organism following the change in temperature. Therefore, the Z-value should always be mentioned in the notation of the F-value. For steam and hot-water sterilisation, usually a Z-value of 10 °C is used. 

Hot water sterilisers are also called hot water (immersion) autoclaves. In these sterilisers, hot distilled water, freshly filled in the stainless steel steriliser bath and heated in a sanitary heat exchanger is pumped around inside the autoclave and is continuously and with high flow sprayed top down over the load to be sterilised. The hot water autoclave contains a mixture of water and air before and during the sterilisation process no vacuum phase is used (see Fig. 30.5). 

Fig. 30.5 Schematic representation of a hot water steriliser. Source Recepteerkunde 2009, KNMP...

With continued filtration, the bacteria count on the membranes increases exponentially. Regular sterilization of the polishing loop is recommended to avoid biofouling. Commercially available external pressurized UF modules can withstand both hydrogen peroxide and hot water up to 98°C for the sterilization. Hot water sterilisation is preferred as it does not introduce any chemical into the polishing loop, and it provides a quicker rinse up time compared to hydrogen peroxide. It is important to control the ion exchange resin leach-ables in the UF feed water. The presence of such leachables can result in severe flux decline in polysulfone UF modules (Maki et al., 1992). 

Other, more recently developed, uses include microwave oven parts, transparent pipelines, chemical plant pumps and coffee machine hot water dispensers. One exceptional use has been to produce, by an extrusion moulding process, very large rollers for textile finishing for use where cast nylons cannot meet the specification. Also of growing interest are medical equipment applications that may be repeatedly steam-sterilised at 134°C, filtration membranes and cartridges for ink-jet printers. 

The direct sterilisation of particulafe solid foods in a gas-solid fluidized bed was proposed as long ago as 1968 by Lawrence et al. (1968) who sterilised wheat flour in steam-air mixtures at the pilot scale. However, Jowitt (1977) described an atmospheric pressure process for fhe sferilisation of canned foods in which the cans are immersed in a fluidized bed of inert particles. This has a number of advantages compared to the conventional retorting process using pressurised steam or hot water ... 

Borosilicate glass ampoules of 100 mL were used for the preparation of the reference solutions they were washed with hot water, rinsed with ultrapure water, soaked during 24 h with 5% nitric acid solution and rinsed again with ultrapure water. The ampoules were then stoppered and sterilised at 180°C during 45 min. Blank tests performed in water in contact during 7 days with the ampoules did not reveal any chemical or microbiological contamination. The ampoules were not conditioned with the solutions they would contain in order to avoid bacterial contamination [14]. 

Sanitisation means disinfection for reducing microbial contamination down to an acceptable level, whereas sterilisation implies the inactivation of all microorganisms. Cleaning always precedes sanitisation. When a membrane system (membrane elements, pressure vessels and piping) has been infected by bacteria or mould, the system requires chemical sanitisation. Hot water sanitisation is used in pharmaceutical membrane systems. 

Classical sterilisation techniques using an autoclave and saturated steam under pressure, hot water or dry heat are practical and reliable. Other reliable sterilisation methods include membrane filtration, ionising radiatirm sterilisation (gamma and electron-beam radiation) and gas sterilisation (ethylene oxide, formaldehyde). Sterilisation equipment (autoclaves, membrane filters, and other sterilisers) is often used in industrial manufacturing, in preparation in pharmacies, and in other healthcare establishments. Standard sterilisation processes are described in the Ph. Eur., in other current Pharmacopoeias, in ISO standards and National guidelines. 

Steam sterilisation (heating in an autoclave) steam sterilisation or sterilisation with hot water in a closed container, minimum 15 min at 121 °C (Fo = 15). TTie humid heat denamres proteins and DNA of micro-organisms. 

Also empty sterile bottles must contain some water for injections (and be closed under vacuum) before they can be sterilised by steam or hot water. Without water inside only radiation or heat sterilisation is effective to sterilise an empty, washed and dried container. 

During the sterilisation of aqueous solutions by steam or hot water, the temperature within the closed containers (ampoule, vial, bottle or bag) lags behind the temperature within the steriliser chamber, and during cooling the opposite happens. Both effects are shown in Fig. 30.6. 

Because of the fundamental difference between sterilisation of finished medicinal products and medical devices (temperature-controlled hot water process vs. -pressure-controlled steam process), both processes have their own validation directive. Most countries have then-own National legislation and standards on sterilisation and validation. International ISO standards are always useful or are implemented and commented in the own country for steam sterilisation see [6]. 

Dissolve phytomenadione in Solutol HS 15 heated to about 60 °C and add slowly the warm water. The sterilisation can be done by heat at 120 °C or by filtration. After the ampoules have been heat-sterilized, they should be shaken for a short time, while they are still hot, to eliminate any separation of the phases that may have occurred. 

A 1.25% solution of Difco Bacto-agar is made up in hot distilled water and sterilised by autoclaving. The agar sets on cooling and must be melted in a boiling water bath and cooled to 44°C before use. 

The feed water passes upwards through a series of narrow, vertical chambers B, C, D, E, separated by thin, metallic walls from the hot, sterilised water, and enters the boiler F at a high temperature. Here it... 

The characteristics of polyamides depend very much on the composition. They are generally wear-resistant and all forms are hygroscopic. This absorption of water (plastifying effect) significantly changes the properties of polyamides. The thermal resistance of most polyamides is high. They can be sterilised by steam or gamma radiation polyamide 6.6 can even be sterilised by hot air. 

The principle of steam sterilisation for medical devices, pharmaceutical products and utensils is based on heat transfer by hot condensing steam under pressure. The steam condenses in the autoclave to pure water, releasing at that moment its heat content. This is a very effective means of heat transfer. Furthermore, the mechanism of inactivation by saturated steam (denaturation of proteins) is also very effective. Therefore, steam sterilisatirai in an autoclave is the preferred method for medical devices, utensils and some pharmaceutical products. It is of critical importance that the steam in a steam autoclave is completely saturated and not superheated, because only then the sterilisation is effective. For the details of steam sterilisation reference is made to other textbooks and guidance, such as [4,5]. The pressure of saturated steam at different temperatures is shown in Table 30.2. 

PET Higher clarity Better oxygen barrier Better impact properties Worse water barrier properties Unsuitable for hot fill and sterilisation Higher price... 

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