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It is essential to determine the cleanliness of food processing equipment and manufacturing areas before they are used for food production. Luminometers help processors monitor surfaces that may contaminate food products and compromise product safety and quality.
Visual assessment is commonly used to evaluate surface cleanliness, but it is subjective and unreliable. It needs to be combined with other testing methods (including luminometers) to ensure food contact surfaces are clean. Luminometers provide rapid, real-time data to help processors assess and validate the hygienic status of food contact surfaces.
Surface cleanliness can be evaluated in seconds using a luminometer to measure residual amounts of the chemical marker adenosine triphosphate (ATP). ATP is a compound found in all types of plant, animal and microbial cells.
The science behind the luminometer is based on the enzyme luciferase — the same enzyme that makes firefly tails glow at night. Residual ATP interacts with luciferase to generate light. This light is measured by the luminometer and is recorded in relative light units (RLU). The amount of light generated is directly proportional to the amount of ATP present — an indication of the total biological contamination level.
Visually clean surfaces are sampled using cotton or foam tipped swabs that have been moistened with water, a buffer or a solution that extracts ATP from microorganisms and food residue. Sample swabs are put back into swab tubes (which contain liquid luciferase to cause a reaction) and are then put in the luminometer for analysis.
Most swabs are analyzed onsite, but they remain stable for several hours before luciferase activation which allows greater flexibility in reading times. Once activated, swabs must be analyzed by the luminometer within 60 seconds or less.
There are also a number of commercial swabs available for food processors who require ATP testing for water or for allergens. The presence of ATP in water may indicate a loss in process control. Special swabs are used to detect ATP in clean-in-place (CIP) systems or in water quality assessments for food and beverage processing.
Commercial swabs to test allergens are a thousand times more sensitive than normal surface testing swabs and detect ATP common to allergenic foods (ex: egg, milk). The ATP detection levels are similar to protein-based allergen tests and indicate potential contamination.
Processors should follow the swabbing protocol outlined in manufacturers' instructions. However, there is common surface testing protocol:
Luminometers show RLU test results on a screen as either a number or a pass/warning/fail reading.
Numbers: Numbers are often considered superior, because they demonstrate the degree of sanitation effectiveness and provide measurable targets for continued sanitation improvement. As the processor's sanitation process improves, the luminometer test result number decreases.
Data management software is provided with most luminometers and provides several benefits:
For more information, email the CVO/Food Safety Knowledge Centre or call 204-795-8418 in Winnipeg.