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Cleaning and sanitising

Objective

In the food, drink and milk industry, the processing equipment and production facilities are cleaned and sanitised periodically, also in line with legal requirements. The frequency of doing this can vary considerably according to the products and processes. The aim of cleaning and sanitisation is to remove product remnants, other contaminants and microbes from the foregoing process run. The conditions and frequency are selected so as not to contradict any legal requirements.

Field of application

Whole of the food industry.

Techniques, methods and equipment

Before starting the cleaning process, equipment is emptied as far as possible. Cleaning and sanitising can be carried out in various ways. Traditionally, it has been corned out manually. “Cleaning In Place” (CIP), wash-in-place (WIP) and, clean out of place (COP) are all expressions used for different modes of cleaning.

COP is used when several of the machine's components need to be dismantled, usually before the manual or automated cleaning of the machine is started. The dismantled components will then be cleaned separately outside the machine, hence COP. Forming machines are examples of this and components like augers, pistons and forming plates seals all have to be dismantled/disassembled before cleaning these components, as well as the rest of the machine. Another example is a piston filler with rotary valves: The valves have to be dismantled and manually cleaned while an automatic system cleans the rest of the machine. High-pressure jet cleaning, using gels and foaming can all be done manually or automatically. The individual cleaning method is an appropriate combination of cleaning factors such as solvent (water), temperature of cleaning solution, cleaning agents (i.e. chemicals) and mechanical forces. Manual cleaning means that the equipment to be cleaned is taken apart and manually cleaned (brushed) in a cleaning solution. Only mild conditions, with regard to temperature and cleaning agents, can be used.

CIP is used especially for closed process equipment and tanks, either stationary or mobil (i.e. for small process units). The cleaning solution is pumped through the equipment and distributed by sprayers in vessels, tanks and reactors. The cleaning programme is mostly run automatically. The following steps can be distinguished: pre-rinse with water, circulation with a cleaning solution, intermediate rinse, disinfection, and final rinse with water. In automatic CIP-systems, the final rinse-water is often re-used for pre-rinsing or may be recycled/re-used in the process.
In CIP-cleaning, high temperatures (up to 90˚C) are used, together with strong cleaning agents. The CIP systems used for open systems like freezers are almost automatic, except for some dry clean-up and opening of hatches. Temperatures here are normally below 50˚C and the pressure is 10 to 15 bar. ('Medium pressure systems`). In high pressure jet-cleaning, water is sprayed at the surface to be cleaned at a pressure of about 40 to 65 bar. Cleaning agents are injected in the water, at moderate temperatures up to 60°C.
An important part of the cleaning action takes place due to mechanical effects. In foam cleaning, a foaming cleaning solution is sprayed on the surface to be cleaned. The foam adheres to the surface. It stays about 10 to 20 minutes on the surface and is then rinsed away with water. Foaming can be done both manually and automatically. Besides the foam cleaning there is also a technique using “gel”.
High-pressure jet cleaning and foam cleaning are generally applied for open equipment, walls and floors. In some cases, cleaning is done using only hot water, however, cleaning agents are normally used in the food, drink and milk industry. Cleaning agents are alkalis (sodium and potassium hydroxide, metasilicate, sodium carbonate), acids (nitric acid, phosphoric acid, citric acid, gluconic acid), composed cleaning agents containing chelating agents (EDTA, NTA, phosphates, polyphosphates, phosphonates), surface-active agents, and/or enzymes.
For disinfections (sanitisation) various sanitisers can be used, such as hypochlorites, iodophors, hydrogen peroxide, peracetic acid and quaternary ammonium compounds (QACs). In some cases, cleaning is done using only hot water, however, this depends on the nature of the product and process. Cleaning agents are delivered in bags (powdered cleaning agents), drums or sometimes bulk tankers. All required safety precautions need to be taken into consideration when handling and storing cleaning agents.

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