'CLEAN' - what does it mean?
An attempt to clarify the terms used
Terms such as sanitary, aseptic, sterile and clean are widely used, but there appears to be no universally accepted definition.
In the food industry, terms such as 'Cleaning In Place' or 'Sterilising In Place' are generally used. Unfortunately there is no clear definition as to the exact meaning of term such as 'sanitary', 'sterile' or 'clean'. Courtesy of Johnson Pump, we present you at least an attempt to clarify the terms used.
Sanitary:
means 'visually' or 'superficially' clean. It would be expected to achieve a sanitary condition on pumps by circulation of cleaning media and manual stripdown/auto-claving. After cleaning the pumps/system could be subject to swab tests to verify.
Aseptic:
by definition this means 'free from micro-organisms that could cause disease', but now more generally it means 'free from all extraneous organisms' i.e. only those that are wanted are present.
Sterile:
means 'the complete absence of living organisms' - 'biologically clean'. Would be achieved by steam circulation and could be subject to biological tests to verify (finished products can be terminally sterilised).
Clean:
as in 'clean area' would be an area that has been sterilised.
These conditions are achieved by procedures ranging from manual strip down and cleaning of component parts (possibly supported by auto-claving) to CIP (Cleaning In Place) or SIP (Sterilising In Place, sometimes also referred to as Steaming In Place or Steaming Through). It is not uncommon to find a combination of procedures being used to achieve the required environment for processing. For example a particular piece of equipment may be subject to manual strip down and cleaning whilst the rest of the plant undergoes CIP or, CIP could be followed by SIP to achieve the required environment for processing to continue.
With the increase in the use of biotechnology and aseptic processing methods an increasing number of plants will be subject to cleaning by CIP and SIP methods.
Typical CIP (Cleaning In Place)
Different processors or processes have different expectations of CIP. One may require that following CIP most product is washed away and that the pump is visually clean or only small traces of product are still apparent whilst to another, following CIP, it is required that the pump is 100% micro-biologically clean. There are, of course, various degrees within these two extremes.
CIP systems are extensively used in the food and pharmaceutical industries in conjunction with the processing of a wide range of products. However, the use of CIP is not restricted to these industries alone and in recent years the chemical, electronics and photographic industries have introduced similar procedures. CIP relies on the circulation of fluid through the system at velocity and temperature. Velocity is required to generate turbulence in order to dislodge debris whilst temperature is required for the fluids to clean effectively. Velocity can range between 1 to 3 meters/second but is most commonly in the range 1.5 to 1.8 meters/second, the velocity depending on, amongst other things, the pumped product, the process and the system to be cleaned. Generally, during CIP, the process pressure needs to be matched or exceeded to ensure that product debris is dislodged.
In most PD (positive displacement) pump mechanisms, pressure influences slip (internal leakage) and therefore adds to the effectiveness of cleaning by increasing velocity in slip paths. A centrifugal pump is often used to circulate the cleaning fluids as the required velocity is often beyond the scope of, or cannot be cost effectively achieved by, the process pump.
The following CIP regime is typical for a system used for food processing:
Step 1 Pre-rinse:
Cold water - 5 minutes - removes product debris.
Step 2 Detergent wash:
Normally sodium hydroxide (Caustic) alkaline based 30 to 45 minutes - 75°C to 95°C - removes carbohydrates, proteins, fats.
Step 3 Rinse:
Cold water - 5 minutes - removes detergent residues.
Step 4 Acid wash:
Nitric or phosphoric acid - 15 to 30 minutes - 60°C removes mineral salt residues and neutralises.
Step 5 Final rinse:
Cold water - 5 minutes - removes acid residues.
Cycle times, temperatures, fluids and concentrations of fluids used will vary depending on the product, process and system. Further, additional washes may be introduced.
Typical SIP (Sterilising In Place)
Sometimes referred to as 'Steaming Through' or 'Steaming In Place'. Equipment components may need sterilising, i.e. heating to high temperature (up to 140°C) to kill organisms still remaining on the surface of the equipment. In the past this has been done by physically dismantling equipment, taking to an autoclave (a sterilising machine), sterilising, removing and bagging, re-assembling and then running. A long, costly process which represents all sorts of problems to personnel and can cause much accidental damage. The trend now is to pass steam through the system and to sterilise the internal surfaces without dismantling. It is important to steam through for a period long enough for the coldest part of the system to reach the temperature required for the time period required to kill off the organisms.
A pre-requisite for equipment which can be successfully SIP’D is one that can be CIP’D. Any product remaining after cleaning could insulate that area from the temperature thus allowing some organisms to survive and so contaminate any subsequent product being processed.
Sterilising of the system is carried out to kill off, or make inert, any micro-organisms or their spores that may be remaining on the surface after cleaning. With food products this is often done during the cooking process and so the product is sterilised rather than the system. However, new packaging techniques (flexible packaging i.e. wax paper cartons) do require system sterilisation.
Many pharmaceutical and some other products can be damaged by sterilisation and so it is normal for the system to be sterilised before use rather than the product itself.
A typical SIP regime for a pharmaceutical process is:
Step 1 Pre-rinse:
Cold water - 5 minutes - removes any debris.
Step 2 Sterilisation:
Steam condensate - 30 minutes - 121°C to 140°C kills off any remaining micro-organisms and spores.
Step 3 Nitrogen Purge:
Nitrogen - 5 minutes - ambient - gives inert atmosphere.
Step 4 Solvent flush:
Acetone, toluene, isopropyl alcohol - 5 minutes - ambient dries system out.
These steps may be done more than once before use.
Aseptic and bio-technological processing
Typical aseptic process
An aseptic process, or part of a process, is one that requires the avoidance of the ingress of micro-organisms into a process which might contaminate the product. Typically processing of foods into aseptic containers, of fermentation processes where a stray organism could spoil the fermentation. In food processing a typical example is the processing of low acid foods containing particulate matter. A typical system would comprise a feed pump to transfer product, usually at a constant flow rate, to a heat exchanger where the product is heated to 120°C to 140°C. The heat exchanger is connected to a product cooler by a holding tube the length of which, combined with the flow rate of product, determines the cooking time.
To avoid vaporisation of the product the pressure in the holding tube must be maintained above the vapour pressure of the product, normally at 3 to 4 bar. For products free of particulate matter this can be achieved with a valve or homogeniser but if particulate matter is included then a pump is used. This pump is referred to as the back pressure pump and is often the same size as the feed pump but running slightly slower thus creating a back pressure.
When the product passes from the holding tube all the micro-organisms should have been killed so the system down stream from the holding tubes must be aseptic. The pumps employed as both the feed and back pressure pumps are generally rotary lobe pumps.
Typical bio-technological process
A bio-technological process is one that utilises fermentation to produce useful products. Biotechnology has existed for hundreds of years in the form of brewing. Over the last 50 years products such as penicillin, vitamin B12 and citric acid have also been produced by this method.
Recently, however, the advent of genetic engineering has allowed manufactures to transfer foreign DNA into bacteria, yeast’s, etc., to cause them to produce products that they would not normally produce and then to clone large quantities of that micro-organism. he most widely used bacteria is Escherichia Coli (E.Coli). The possibilities of bio-technologically produced products is limitless - from antibodies to plastics - providing it is of organic origin.
A biotech process is normally divided into 2 distinct areas - fermentation and product recovery (often referred to as downstream processing).
Fermentation is basically the same in all types of production, though there are many different types of fermenters. It is the addition of nutrients, a carbon source (nutrients can contain carbon in the form of carbohydrate), water and normally oxygen, to a micro-organism under controlled conditions, to produce products, byproducts and heat. The mode of production, however, can vary greatly. The product may be produced during the growth phase of the micro-organism (primary metabolite) or produced within the micro-organism (intracellular) or excreted by the micro-organism (extra cellular). The product may be made in a batch mode or as a continuous process or combinations of the two. The product recovery also varies considerably from one product to another, utilising such procedures as cell disruption, centrifugation, precipiation filtration, ultra filtration, chromatography and electrophoresis.
Courtesy of:Johnson Pump
www.johnson-pump.com
