Editors’ note: This is part 2 of a two-part series on dry cleaning. Part 1, which published in the August/September 2021 issue of Food Quality & Safety, looked at the rationale for dry cleaning and the challenges that can accompany the process. Part 2, published here, focuses on solutions to these challenges.
We tend to think of dry cleaning in the food industry as being related only to those food plants that undertake dry/low water activity food and ingredient processing. But dry cleaning and sanitization can be a valuable option in the control of microbial hazards for any processing plant. Here, we look at solutions related to microbial control through controlled use of water, dry cleaning, and sanitization techniques.
Control Water at the Site of Personnel Entry
As discussed in the first article in this series, the water used to ensure personnel hygiene at the entry point to the production area can itself lead to the growth and spread of contamination. For dry food production, this risk could be minimized through a slight change to the personnel entry procedure; have personnel wear clean production area footwear and protective clothing after thorough hand washing and drying, followed by the use of a hand sanitizer immediately after entry to the food production area (see Figure 1).
Control Water Through Dry Cleaning
Fortunately, when it comes to controlling microbial growth and spread through the use of dry cleaning, there are plenty of methods available. This dry cleaning can be as simple as using a brush and dustpan or as complex as dry ice blasting. Dry cleaning methods include:
- Granular purging, scrubs, and blasting;
- Dry ice;
- Compressed air;
- Scourer pads;
- Brushing, scrubbing, and sweeping;
- Detail cleaning;
- Dry steam; and, if all else fails,
- Disassembly and removal for wet cleaning and drying.
While the use of these dry cleaning methods will limit microbial growth, all have the potential to spread contamination if used inappropriately. Figure 2 ranks most of the different cleaning methods in order of risk with regard to the spread of contamination.
Most dry cleaning methods are ranked at the lower end of this scale. Notable exceptions to this are the blasting of surfaces with inert granules, sugar, salt, or dry ice fragments and the use of compressed air.
Pigging. This method uses a specialist projectile (the “pig”) that is pushed or pulled through pipework to remove dry debris inside. The pig has a diameter slightly larger than the pipe, and this compact fit enables it to maintain full contact with the pipe and push most of the debris to waste or for recovery. Pigging is a gross contamination removal technique, and further cleaning of the pipes may be required.
Granular purging, scrubs, and blasting. This involves the use of inert granules, or food items such as salt and sugar, to provide an abrasive force for the removal of contamination from the inside surfaces of pipework or open surfaces. For pipework cleaning, care must be taken to select a purge material that will not affect the quality or safety of the product and/or that can be fully recovered or removed as part of the cleaning process.
Dry ice. This method uses carbon dioxide to form dry ice crystals that are then projected at high velocity onto an open surface, where they provide an inert abrasive force for the removal of contamination.