Air Quality in Production Facilities

The development and evolution of Food Safety Plans for each individual food production facility has included the implementation and the upgrading of environmental monitoring programs (EMP). The goal of an EMP is to gauge and monitor the presence of microorganisms within the manufacturing site. This includes the testing of food contact and non-food contact surfaces with particular focus on high traffic areas, niche harborage sites, worn structural sites and wet areas where condensation may have occurred. The sampling for a standard EMP predominantly focuses on surfaces (e.g. belts, floors, drains, floor-wall junctures, doors, posts, bins, pallets, etc.). In addition to testing surfaces in a standard EMP, it is pivotal to consider the role of air quality.

The management of air quality can mitigate the incidental introduction of yeast, mold and bacteria in the production stream or in finished product, post-processing but pre-packaging. Standard sanitation procedures are designed with the treatment of processing equipment and the physical area within the production area in mind. However, if there were a contamination event within an air handling system, re-introduction and contamination of the production area would occur while the air handling system is running. As such, insight into the quality of air and managing the direction of air flow is pivotal for Food Safety and Food Quality Plans at any manufacturing site. This is important insight to have as it can allow for the prevention of product contamination as well as allow for the troubleshooting and halting of any on-going contamination events associated with poor air quality due to microbial presence, first indicated by spoiled packages.

When considering air quality at a production facility, one of the first steps to take is to assess what the quality is. This can be performed several different ways, dependent on available resources. The two most popular and easiest to perform are Sedimentation and Impactor systems. Sedimentation applies to the natural downward settling of air particles over time. A petri dish containing agar and a medium consisting of nutrients beneficial to the target (i.e. yeast, mold, bacteria) is prepared and then placed at a location within the production facility. Due to natural gravitational forces, as mentioned, air particles will settle onto the petri dish. The Sedimentation method is very economical and can be performed very easily as it only requires preparation and placement of opened petri dishes at predetermined sites. However, this method is passive and relies on the settling of particles which occurs at a different rate from one collection event to the next. Larger particles would, of course, settle faster and thus there is a systematic bias as well. Additionally, it is impossible to calibrate amongst all events as the volume of air and settled particles is not consistent from event to event. The Impactor system method is more precise but requires the purchase or rental of specialized equipment. The Impactor system employs a mechanical sampler that uses a jet or vacuum to draw in air streams at a known rate and thus volume. The air that is mechanically collected is then directly applied onto a petri dish within the Impactor system. This allows for the operator to normalize across sampling events and standardize as to how much air volume is collected, based on the jet or vacuum setting. There are drawbacks for this approach which include the purchasing or rental of an Impactor system, manually moving the apparatus and finding room for placement on the production floor and cleaning of the unit to remove any chance of re-contamination from prior events. Despite the pros and cons of the Sedimentation and Impactor systems, both allow for the gleaning of air quality data, specifically if microorganisms are present and at what concentration. Following collection, the petri dish samples are incubated and the concentration of the target microorganism is enumerated.

In addition to measuring and observing the presence of microorganisms, additional steps can and should be taken to further minimize the potential for product contamination. This includes, but is not limited to, two approaches. The first approach is the use and upkeep of a proper HVAC (heating, ventilation and air conditioning) and filtration system for the air moving throughout the plant. The HVAC system allows for the management of temperature and humidity within the production facility as well as air flow direction and pressurization. By controlling the temperature and humidity, microbial growth is mitigated as long as the temperature is kept lower than that considered ideal for most microorganisms. In controlling the humidity, moisture control is in place. To this end, by managing the humidity and air moisture, reaching the dew point can be prevented or lowered. The dew point is a value at which moisture condenses out of the air from a gaseous state to a liquid state, and onto a surface. A decrease in available moisture is related to microbial viability and growth. Additionally, a high air moisture level can affect measurement techniques as a more dense moisture state would alter collection. The second approach to managing further spread and contamination of product is the use of air pressure gradients. Such gradients will prevent cross-contamination between the raw ingredient area, production area, packaging and warehouse storage. A gradient is established due to the kinetics of a higher air pressure state flowing into a lower air pressure state without any bi-directional flow. In applying this, one can take advantage of air flow directions to have air flowing outward from the room where post-processed product is being packaged and sealed, and toward other areas of the plant. This approach utilizes a positive air pressure condition, where all ambient air flows out of the room without reintroduction other than at the point of filtration and entering. Furthermore, this air pressure condition can be utilized such that air from within the plant flows backwards through the process flow to the point of raw ingredient storage. The air pressures of rooms throughout the facility are a function of a properly operating HVAC system. This air gradient direction will mitigate the contamination of airborne microorganisms from the raw ingredient areas into finished product solely from the air. While keeping the positive air pressure in mind, it is also important to investigate any potential for negative air pressure states for the facility. This is more frequently observed in older facilities with a large number of exhaust fans or less than ideal placement of an exhaust unit. A negative air pressure state would allow for any ambient air from outside the area to flow into the plant from the outside, introducing air containing water, dust, microorganisms and other debris. Any time that un-filtered air is introduced into the production area without prior filtration, the chance for contamination is increased.

Overall, it is important to understand the state of air flow and quality within each production facility. In measuring, at predetermined frequencies, the QA/QC staff can maintain a pulse on the presence of yeast, mold, and bacteria that are airborne and translocating throughout the facility. Furthermore, by understanding the management and flow of the air, preventive measures can be put in place (i.e. air flow gradients) to minimize product contamination. By minimizing product contamination, the goal of providing a safe and high quality product to the consumer is attained without the presence of harmful microorganisms or microorganisms that could lead to spoilage.

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