Pressurized steam, sterilization method

The most widely used sterilization method ia the food industry is moist heat. The heat is usually suppHed by high pressure steam, but because most foods already contain moisture the role of steam is to heat the food to the required temperature. The cooking and sterilization processes can frequendy be combined into one. The food may be sealed into impervious containers of glass, metal, or plastic film and undergo terminal sterilization, or it may be presterilized in batches or in a continuous operation and then filled into a presterilized container. The latter process is called sterile filling. 

Steam sterilization is at presenzt the most used method [2.15] for freeze drying plants. It requires a temperature of +121 °C for 10 to 30 min, and thus the plant must be pressure-tight up to 2.5 bar. 

UHT milk differs from pasteurized milk mainly in the heat treatment employed for sterilization. Usually UHT milk is heated at 130° to 150°C for 2 to 8 seconds and is then aseptically packaged. In the final heating stage, steam is injected directly into the milk, or the milk is infused into a steam chamber, followed by flash evaporation to remove added water (steam). An alternative procedure, the indirect method, involves heating milk across a stainless steel barrier, using high-pressure steam as the heating medium (Mehta 1980). 

For many years, pressurized steam(autoclaving) at 120 °C for 30 minutes has been the basic method for sterilizing instruments and decontaminating materials. When autoclaving is not possible, as is the case with lensed instruments and materials containing plastic and rubber, ethylene oxide— diluted with either fluorocarbon or carbon dioxide to diminish explosive hazard—was used at 440-1200 mg/L at 45-60 °C with 30-60% relative humidity. The higher concentrations have been used to increase penetration. 

This is certainly the most widely used and most versatile moist-heat sterilization method. Accordingly, it is widely used not only for sterilization of pharmaceutical products but also for laboratory and hospital sterilization and for the treatment of medical devices. Nonetheless, it has significant limitations, especially in pharmaceutical use, which are described later. The sterilizing medium is obviously pure pressurized saturated steam. The word saturated means that the steam is in thermodynamic equilibrium with its liquid form (water) at the temperature being considered. 

An appropriate partial pressure of air (sterilized by filtration) is maintained in the chamber during every phase of the process, to compensate for the overpressure inside the containers. Various methods for controlling the total chamber pressure (steam + air) can be used. With computerized process controllers, it is also possible to correlate at any time during each phase the air partial pressure to the average of the solution temperatures of two or more reference containers. 

Sterilization by moist heat usually involves the use of steam at temperatures in the range 121-134°C, and while alternative strategies are available for the processing of products unstable at these high temperatures, they rarely offer the same degree of sterility assurance and should be avoided if at all possible. The elevated temperatures generally associated with moist heat sterilization methods can only be achieved by the generation of steam under pressure. 

Equipment where necessary should be properly sterilized before use, preferably by pressurized dry steam. Other methods can be accepted if steam sterilization cannot be used because of the nature of the equipment. It is important not to... 

Steam sterilization (autoclaving) is performed under high steam pressure at relatively low temperature (125-130°C). However, if the polymer is subjected to attack by water vapor, this method cannot be employed. PVC, polyacetals, PE (low-density variety), and polyamides belong to this category. 

The most reliable method for the sterilization of culture media and culture solutions has proved to be that of treatment with superheated steam in an autoclave (superheated steam sterilizer) at 121 C, which corresponds to 1 bar over atmospheric pressure, for 20 to 30 minutes. The operating conditions quoted by the manufacturer must be observed when using an autoclave. 

Steam sterilization—Treatment method for infectious waste using saturated steam within a pressurized vessel such as an autoclave. 

Four common types of sterilisation are in use today gas, irradiation, steam autoclave and dry heat. The two first types of sterilisation are also called low-temperature steriUsation methods, applied to single-use products and the last two types, high-temperature sterilisation methods, applied to reusable products. Many sterilisers use saturated steam under pressure, but this method is not always practical. High temperatures damage many plastics and other synthetic materials. These materials require low-temperature sterilisation. Gas (ethylene oxide, EtO) and radiation are such sterilants. 

The most convenient way to disinfect work areas and materials, equipment, and instruments is through the use of chemical agents. Use of chemical disinfection is often necessary because pressurized steam, the most reliable method of sterilization, is not feasible for disinfecting large spaces, surfaces, and large items of equipment. Moreover, high temperatures and moisture can damage delicate instruments, particularly those with optical and electronic components. 

Several methods are used to sterilize medical devices including ethylene oxide, steam under pressure, dry heat, and gamma irradiation. In recent years. E-beam sterilization has become an increasingly popular method for the sterilization of medical plastics. E-beam sterilization offers a lower cost alternative to the more common gamma and ETO sterilization techniques. In selecting a thermoplastic resin for use in medical devices it is important to consider the effects of the sterilization method on the physical and optical properties of the material. Previously a smdy was performed to determine the effects of gamma sterilization on thermoplastic resins used in medical devices In the present work, a similar study was performed after E-beam sterilization. 

The medium is then sterilized to eliminate all living organisms in the vessel.,The most common method of sterilization is by moist heat (steam under pressure) in an autoclave. Generally, the autoclave is operated at approximately 15 psi at 121°C. The time of sterilization depends on the nature of the material, the type of container, and the volume. For example, test tubes of liquid media can be sterilized in 15 to 20 minutes at 121 °C. 

The design of the drying chamber is dictated by the chosen method of sterilization. If steam is used, it has to be a pressure vessel engineered and manufactured... 

Steriliziykni by saturated steam under pressure is the classical time-proven and most economical method of inactivation of microorganisms. When a requirement for sterility arises for a new type of medical device or pharmaceutical product, steam should always be given first consideration. This is because,... 

One of the most important performance criteria for medical applications is that of autoclaving. This is a common method to sterilize instruments and devices that uses a combination of high pressure and steam. In an aggressive cyclic environment such as this, retention of impact properties and optical properties is important. Another essential sterilization technology that is less severe than autoclaving is the use of ethylene oxide, against which blends and alloys must display chemical resistance. 

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