In 2011, the increased public awareness of food pathogens contributed in large measure to the passage of the Food Safety & Modernization Act (FSMA), which put into place a far more rigorous set of regulations surrounding food safety than had ever existed. In recent years, equipment cleaning processes employed by the food and beverage industry have come under even more increased scrutiny. This is the result of the widespread publicity around pathogen outbreaks in commercially processed food, including E. coli found in Californian romaine lettuce in 2018, and the presence of Listeria in Blue Bell ice cream in 2015. A drive toward more efficient food production coupled with the increased awareness of food pathogens has led the food processing industry to shift its focus to the equipment cleaning processes—specifically cleaning equipment surfaces that come into direct contact with food.
Designing a Clean-in-Place System
There are two basic approaches used in cleaning food processing equipment. The first, clean-out-of-place (COP), is used for cleaning pieces of equipment and utensils that can be easily removed from the production line and disassembled for cleaning (e.g., beaters used in mixers). The second approach, called clean-in-place (CIP), is employed in aseptic and other processing operations where the interior surfaces of the food processing line, such as tanks and piping, cannot be easily reached and disassembled for cleaning. CIP cleaning is the more difficult of the two cleaning processes, and typically involves specialized CIP systems, employing fluid pumps and heaters.
In a CIP system, cleaning fluids are typically heated to increase their cleaning efficiency. Depending on the application, a few different cleaning agents may be used, including hypochlorites, peracetic acid, ozone-enriched water, and acid anionic. The cleaning fluid is circulated through the CIP system in a prescribed manner to regulate the flow, mixing, temperature, time, and mechanical force used with the cleaning agent to achieve maximum results.
Historically, steam-based heat exchangers were used to heat cleaning fluids used in CIP applications in the food and beverage industry. In recent years, the trend has been to use electric fluid heaters (often in-line types) that may be easily incorporated into CIP skids (see Figure 1). These electric fluid heaters provide the flexibility needed for designing into different types of CIP systems, and are ideally suited for lower process flows.
In selecting a fluid heater for CIP applications, there are several critical factors to consider, including:
- Sanitary Design
- Components such as the heating element, valves and gaskets, used in the construction of the heater eliminate possible locations for contaminants to thrive in the heater.
- Wetted surfaces in the heater should be constructed of 316L electropolished stainless steel, as it presents an extremely smooth surface to the cleaning fluid.
- Dead Leg Eliminating
- Eliminate any areas outside of the regular fluid flow path that could harbor pathogens.
- Non-threaded design fittings provide a smoother surface with few nooks and crannies.
- Fluid Drainability
- Cleaning fluids should be completely drained from the system after use.
- An input on the bottom of the heater should allow for complete gravity draining of the heater.
- Temperature Control
- Maintaining an accurate fluid temperature is essential for the efficiency of the cleaning process.
- Temperatures may fluctuate more readily in steam-powered heat exchangers than electrically powered fluid heaters, leading to inconsistent cleaning results.
While fluid heaters are at the heart of the clean-in-place process, there are other considerations to be taken into account when designing an ideal CIP system. First, engineer your system for efficient operations. Easy access to the cleaning equipment is also important, especially during FDA inspections.
Most important, though, is a CIP line that’s designed for maximum cleaning against microbial agents. With this in mind, use the proper tanks for the cleaning agents. Fluid tanks should have smooth and continuous welds, be self-draining, and their interior surfaces should be round or tubular, not flat, with no ledges or recesses that could harbor contaminants.
Then, identify and use the proper cleaning agents for your particular application. Hypochlorites are ideal for cleaning stainless steel surfaces that come into direct contact with food. Peracetic acid can be used against all microorganisms and may be applied with either cool or warm water. Acid (anionic) is an effective cleaning agent for removing hard water films or milk stone (found in dairy operations). Finally, ozone-enriched water kills microbes as effectively as chlorine without the hazardous side effects that come with chlorine’s use, and has been approved by the FDA for use on food contact surfaces.
Your CIP system must also be designed for the correct fluid flow rate to ensure cleaning “turbulence” and thorough cleaning results. The fluid flow rate through the CIP system’s process piping should be greater than or equal to 5 feet per second. The flow rate is a function of the pump size—ideally, it should be able to produce a flow rate that’s at least four times greater than that required during cleaning operations, so selecting the proper fluid pump for your CIP system is critical.
Finally, your CIP system needs to be engineered with the proper connections between the component pieces. Avoid creating lively dead areas that are outside of the cleaning agent process flow. These too are ideal locations for pathogen growth.
Even the most carefully designed CIP system will need to be monitored on an ongoing basis once it’s in use to ensure that it’s working as intended. “Automation” does not equal “automated process control.” Several items in the CIP system need to be checked on a regular basis, including cleaning chemical concentrations, pH levels, and pump/metering device performance. Also, check the water chemistry on a periodic basis. Hard water can precipitate on surfaces and clog holes, compromising fluid flow and coverage. A well-designed and well-maintained CIP system will ensure that your food-processing line is operating at maximum efficiency, and delivering results that will minimize the likelihood of food pathogen problems.