The bottom of the plant is the drains, and the drain design and maintenance are critical, Dr. Kornacki elaborates. “Some places have exposed finished product lines over drains, and the drains are not appropriately trapped,” he laments. “Or finished product is often near an open sump. I have also seen processing equipment, such as a slicer, located over an open sump. The sump provided a bioaerosol source that was seeding the slicer with microorganisms.”
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Explore This IssueOctober/November 2019
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The top of the plant is the heating, ventilation, and air conditioning (HVAC) system, Dr. Kornacki continues. “HVAC systems are all too often designed without an appropriate microbiological filter located after the cooling coils, catch pans and fan chamber, all of which are frequently contaminated,” he says. “These systems are often sources to the general environment of low and injured microbial populations.”
The top of the “sandwich” is also the roof, and if it leaks, product can be contaminated by water and bird droppings, Dr. Kornacki relates. “Birds are well known sources of both Salmonella and Listeria, which can enter the plant by this vector,” he notes.
So many things in the middle of the “sandwich” can be problematic in food processing, Dr. Kornacki emphasizes.
For starters, finished product is vulnerable to environmental contamination from the plant, and negative air pressure can bring contaminants into the plant from outside or from raw processing areas, he says.
“Besides vulnerability from the top of the building, if, for example, plant employees do not have captive shoes, they wear their work shoes home and back, and can then track pathogens in from their farms or gardens,” he relates.
Moreover, some maintenance personnel seem to live above the rules designed to minimize cross contamination, Dr. Kornacki continues. “They may carry tools from a raw ingredient area to a post processing area,” he points out. “Well-managed facilities should have separate dedicated tools for their raw or finished product areas. Some maintenance employees will fail to sanitize tools before and after use, which should be done.”
And, if forklifts aren’t segregated into specific, restricted areas based upon the principles of hygienic zoning, they can be another source for environmental cross contamination in the facility, Dr. Kornacki adds.
“This principle also applies to areas where electric forklifts are charged,” he says. “Common charging areas for raw and finished areas of the plant will also be a source of cross contamination in the facility. Moreover, floor scrubbers are sources of bioaerosols and can be sources of environmental and even food product contamination. They should not be used near exposed product or active finished product processing lines.”
Major sources of product contamination are structures just adjacent to product zones that can slough or vibrate into the plant such as flanges on rotary valves, Dr. Kornacki notes, adding that metal to metal and metal to plastic areas on product slicers can be another problem.
Cleaning, namely the removal of soil that protects microbes, and sanitization, which is the killing of microbes, should both be verified, Dr. Kornacki advises. “Some plants do ATP (adenosine triphosphate) swabs on equipment after cleaning and before sanitation, which is a part of cleaning verification, but they don’t take pre-operational microbiological swab samples for sanitation verification,” he mentions. “A finished product contact surface subjected to a cleaning regime, but ineffectively sanitized, can be a source of product contamination.”
The Road to This Work
Dr. Kornacki completed all of his studies at the University of Wisconsin, where he earned a BS in bacteriology, an MS in food science with a microbiology option, and a PhD in food science with a microbiology option. He says he was inspired to pursue a career in food microbiology while enrolled in an undergraduate food bacteriology course taught by the iconic Robert Deibel, PhD, founder of Deibel Laboratories.