The term Dry Sterilisation Process, DSP, denotes a dry aseptic sterilisation process. It is used for instance in the beverage industry during cold aseptic filling of beverages (juices, waters, UHT-milk, ...) into plastic bottles made from PET or HDPE, and also for some applications in the pharmaceutical industry. Sterilization (or sterilisation) is the elimination of all transmissible agents (such as bacteria, prions and viruses) from a surface or piece of equipment. ... A brick of French UHT milk Ultra-high temperature processing (or UHT) is the partial sterilization of food by heating it for a short time, around 1-2 seconds, at a temperature significantly above 100°C, typically 135-140°C. The high temperature reduces the processing time, which reduces the... Polyethylene terephthalate (aka. ... Polyethylene or polyethene is a thermoplastic commodity heavily used in consumer products (over 60M tons are produced worldwide every year). ...

In cold aseptic filling the sterile or near-sterile product is filled into a bottle which has to be sterilised prior to bottling to avoid product contamination. Caused by the heat-sensitive plastic material, the sterilisation process must not heat the bottles. Therefore chemical sterilisation processes are used for this purpose. The Dry Sterilisation Process uses an aqueous solution of hydrogen peroxide (H₂O₂) with a concentration of 30...35% to achieve the germ-killing effect. Hydrogen peroxide (H2O2) is a clear liquid, slightly more viscous than water, that has strong oxidizing properties and is therefore a powerful bleaching agent that has found use as a disinfectant, as an oxidizer, and in rocketry (particularly in high concentrations as high test peroxide (HTP)) as a monopropellant and...

At first the bottles are placed into a sterilisation chamber. This chamber is designed to be a vacuum chamber and is evacuated by vacuum pumps down to the low vacuum range. A certain amount of aqueous solution of hydrogen peroxide is now delivered to an evaporator and abruptly evaporated. Driven only by the pressure difference between the hydrogen peroxide vapor inside the evaporator and the evacuated sterilisation chamber, the vapor flows through an appropriate piping into the sterilisation chamber. The vapor is strongly expanding when it enters the chamber, undercooled thereby and instantaneously condensing. The forming condensate layer is covering all surfaces inside the sterilisation chamber, all inner and outer bottle surfaces and all surfaces of the chamber itself. For other uses, see vacuum cleaner and Vacuum (musical group). ... A vacuum pump is a pump that removes gas to leave behind a partial vacuum (of varying quality, depending on the pump). ... For other uses, see vacuum cleaner and Vacuum (musical group). ... Evaporation is the process whereby atoms or molecules in a liquid state (or solid state if the substance sublimes) gain sufficient energy to enter the gaseous state. ... Vapor (US English) or vapour (British English) is the gaseous state of matter. ... Condensation in the case of aerosol particles is when vapor is either condensing or evaporating from the particles. ...

The heat of vaporization, released by the phase change from gaseous to liquid, heats the forming condensate layer in such a way, that most of the hydrogen peroxide molecules are thermally dissociated thereby. The resulting free radicals, particularly the oxygen atoms, are immediately killing all the germs adhered to the surfaces already during the condensation. In contrast to other sterilisation processes the killing of the germs occurs instantaneously without any need for residence time. The standard enthalpy change of vaporization is a physical property of substances. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ... In chemistry, homolysis is chemical bond dissociation of a neutral molecule generating two free radicals. ... In chemistry, radicals (often refered to as free radicals) are atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ...

The condensate layer is removed from the sterilisation chamber and all bottle surfaces immidiately after the condensation. This is performed only by means of appropriate vacuum pumps which reduce the pressure inside the sterilisation chamber below 1 Torr. The condensate is rapidly re-evaporating when the decreasing chamber pressure reaches the condensates vapor pressure and the forming vapor is removed from the chamber by the vacuum pumps. This re-evaporation effects a total drying of the bottles and the surfaces inside of the sterilisation chamber and completely removes all hydrogen peroxide. The vapor pressure is the pressure (if the vapor is mixed with other gases, the partial pressure) of a vapor (this vapour being formed from molecules/atoms escaping from a liquid/solid). ...

Prior to deloading of the bottles from the sterilisation chamber, the chamber is vented to ambient pressure with sterile air to avoid recontamination of the sterile bottles.

The complete process time amounts to 6 seconds. Using the common reference germs for hydrogen peroxide sterilisation processes, endospores of different strains of bacillus subtilis and bacillus stearothermophilus, the Dry Sterilisation Process easily achieves kill rates of 10⁶...10⁸ (log6...log8) in count reduction tests and also in end point tests. An endospore is any spore that is produced within an organism (usually a bacterium). ... Binomial name Bacillus subtilis Ehrenberg, 1835 Bacillus subtilis is a catalase-positive bacterium that is commonly found in soil, belonging to the genus Bacillus. ...

The sterilised items leave the sterilisation chamber in a completely dry state. Only the surface temperature of the items is slightly increased by a few degrees (10°...15°) during the sterilisation process. Therefore, the process is particularly useful for the sterilisation of heat sensitive items like plastic bottles. It is also useful for applications which require high kill rates and short process times.