Manufacturing facilities for dairy products, brewed beverages, and processed foods are hygienically maintained generally using clean-in-place (CIP) method. Back in the mid-20th century, cleaning of food processing equipments required disassembly before cleaning. Equipments, particularly tanks, pipes, and fillers must be designed in a way removal and draining of process effluents such as waste solids and steam condensate can be facilitated.
With CIP, food processing equipments can maintain high levels of hygiene without the need for disassembly prior to cleaning and sanitation. This ensures that the equipment is hygienically ready for the next production run while lessening the downtime. Circulating detergent and sanitizing solutions at the correct temperature and time ensures total control and maximum effectiveness of the sanitation process. Detergent solutions should ideally be fresh because some of them can support the growth of microorganisms (not exceeding 48 h).
The counterpart of CIP is Clean-out-of-place (COP). As the name suggests, COP is a cleaning system that requires disassembly of food processing equipments and production tools to an external area. COP is mainly utilized for small equipments such as fittings and tank vents, and/or parts that CIP cannot efficiently clean.
Over COP, CIP is favored because there is no need for equipment disassembly, less time-consuming, and less labor intensive.
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Specialized knowledge of pipe flow, sanitation, processing operations, and process control are necessary for the design and installation of CIP systems in big food processing plants.
Here is how CIP is done.
PERFORMING CLEAN-IN-PLACE
In essence, the CIP system is a chemical cleaning procedure. In this method, all soiled surfaces are brought into close contact with the chemical solution. To do this, cleaning, rinsing, and sanitizing solutions are introduced down the same piping path as the product. Water and aqueous cleaning solutions can more easily penetrate equipment crevices with the addition of surface-active materials. Such materials significantly lowers the water’s surface tension.
The process of CIP can be divided into 6 parts:
- Pre-rinsing with cold (soft) water.
- Alkali washing supplemented with sodium hypochlorite (bleach)
- Intermediate water rinse.
- Acid rinse.
- Final water rinse.
- Rinse with sanitizing solution or flushing with hot water.
Pre-rinsing prepares the equipment for cleaning and sanitation. This removes residue and partially eliminates fats. Alkali washing uses caustic soda or sodium hydroxide (NaOH) as the main detergent (in most CIP systems) with pH between 0.5 and 4.0%. The intermediate water rinse uses water to remove residual caustic from the previous step. Acid rinse uses concentrated, low-foam liquid acid. This is ideal if the soil is predominantly mineral.
Final water rinse flushes residual cleaning agents. In most cases, the final rinse water is recovered to be used as a pre-rinse solution for the next cleaning cycle. Recovery of rinse water is a popular CIP option because there is little possibility of system contamination due to soil redeposition. To prevent soil redeposition in multi-use systems where the cleaning agents are recycled, a rather complex CIP design and a thorough understanding of the clean-in-place (CIP) circuit are necessary.
Rinsing with sanitizing solution helps destroy microorganisms before commencing production. Ammonium compounds, anionic acids, iodophores, chlorine-based sanitizers, and peroxyacetic acid/hydrogen peroxide are a few of the frequently used sanitizers. Most CIP systems use chlorine or bleach because it is economical and very effective.
EFFECTIVITY OF CLEAN-IN-PLACE
The effectiveness of the cleaning agents depends on several factors. With higher temperature, the cleaning efficiency increase. The added energy in the form of heat forces molecules to move faster, thus accelerating the chemical reaction. Furthermore, the elevated temperature lowers the viscosity of adhering soils, which allows for faster removal. Clean-in-place (CIP) systems typically function between 140°F (60°C) and 180°F (82.2°C).
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At an appropriate concentration, the cleaning agent possesses better a surface binding capacity. The most popular alkaline cleanser used in CIP is sodium hydroxide (NaOH), often at concentrations between 1 and 5%. Caustic alkali is effective in removing proteins and carbohydrates. The contact time of the cleaning solution also affects efficiency. Sufficient contact time is necessary to allow appropriate contact of the chemical with the surface.
With pH meters, redox potential meters, and optical density meters, one may determine the concentration of cleaning chemicals and organic effluents. Pressure drop readings in the pipeline can be used to estimate the level of surface contamination.
The characteristic of the equipment to clean also affects effectivity of CIP. Foods like cream, yogurt, and fruit pulps, which are very viscous fluids or semi-solids, make it difficult to clean and rinse equipment. Pigging, a cleaning procedure utilized in the chemical and oil industries, has been proposed for cleaning such challenging food pipes. This way, the viscous material is removed from the pipeline using a magnet-equipped plug (pig), before flushing and water and CIP.
The entire system must be automated for clean-in-place to be effective. In conjunction with on-line sensors for temperature, level, flow rate, pressure, and valve position, microprocessor controllers (PLC) are employed.
CIP FREQUENCY
Cleaning frequency varies depending on the materials being processed. And the dedication of the management to good hygiene also matters.
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From a microbiological perspective, an earlier microbiological assessment of a product might provide insight into the frequency of cleaning required in a certain facility. Usually, after a processing period, food equipment needs to be cleaned every day. However, cleaning also depends on how frequently products are changed when different food products are processed in the same equipment. The necessary automation and valves must also function reliably if CIP is used.
There are some food products that are less vulnerable to microbial growth. If this is the case, CIP every after production may not be required. This is true for acidic products such as carbonated soda and vinegar. Facilities that produce dairy products, on the other hand, need regular CIP because these products are more susceptible to against microbial contamination.
References:
Y. Motarjemi, H. Lelieveld (2014). Food Safety Management: A Practical Guide for the Food Industry. Academic Press.
B. Ray (2005). Fundamental Food Microbiology (3rd edition). CRC Press.
A. Demirci, M. Ngadi (2012). Microbial Decontamination in the Food Industry. Woodhead Publishing.
G. Saravacos, A. Kostaropoulos (2016). Handbook of Food Processing Equipment (2nd edition). Springer.
