Interim cleaning is carried out between different product runs to reduce or eliminate the hazards and organoleptic properties from the first product being transferred to the subsequent product. 

It also covers the cleaning of a production line prior to planned breaks, for example operative’s lunch breaks or shift changes.  This is most likely to happen across all lines (unless break times are staggered).

As the interim clean will be undertaken during the production day, there will likely be a number of constraints that need to be taken note.  These include:

• Time - it is likely that production will need to recommence asap.
• Limited dismantling of equipment - time, or the availability of engineering support, may well preclude the thorough dismantling of equipment to access all surfaces.
• Cleaning with production staff will probably be less effective than their hygiene operative colleagues.  This has implications on their health and safety and may lead to the selection of milder, less caustic or acidic cleaning and disinfection materials.
• Minimum use of water - if the area to be cleaned is a high hygiene, ready-to-eat (RTE) food manufacturing area, or an area used to manufacture dry foods, the use of water as a cleaning agent may either be not allowed or have to be limited.
• Minimum space - it is likely that adjacent process lines will be in production during the cleaning process.  Whilst this is not best practice it may be unavoidable and as such, food products on adjacent lines must be protected from cleaning aerosols.

Note: Interim cleaning is different from general housekeeping, which is designed to keep food production areas free of debris for primarily operative health and safety reasons.

Objectives and risks

The objectives of the interim clean must first be defined. These may include: the removal of a hazard such as microbial pathogens or allergens, the removal of food soils likely to create brand protection issues, such as meat species (e.g. pork in a beef product) or meat residues (e.g. meat in a vegetarian product) or the removal of food soils that may cause organoleptic issues in subsequent products e.g. highly flavoured or coloured ingredients.

The objectives of the clean will determine both the design of the interim clean (e.g. rinsing only, detergent clean, detergent and disinfectant clean), whether it requires validation and how it is monitored and verified to demonstrate its effectiveness. 

If the interim clean objective is to control allergens or pathogens, the clean will have to be validated to meet best practice and retailer requirements.  Validation is undertaken to demonstrate that under worst case scenarios (e.g. hardest soil to remove, most difficult area to clean, lowest acceptable chemical concentrations, temperatures and contact times) allergen or pathogen levels are reduced to the limit of detections of allergen or pathogen detection methods.

For many interim cleans, the major monitor of success is visual cleanliness of the line.  If the line is not visually clean, the use of additional cleanliness testing is not appropriate.  Visual cleanliness may be acceptable in meeting the objective of an organoleptic clean.  If visually clean, the use of ATP or protein based, rapid hygiene tests are useful to ensure a high level of cleaning has been achieved.  The removal of brand protection issues and hazards should also be periodically verified by the use of appropriate test kits, e.g. lateral flow strips for allergens or microbiological sampling for pathogens.