Understanding the ABCs of ATP testing and key factors to consider

These judgment calls usually need to be made quickly and under tight schedules. Therefore, it’s critical to have a hygiene monitoring and testing program that can be relied on to provide timely results that are accurate and precise.

Food companies typically rely on a combination of three types of testing:

Visual, Micro or ATP​

The first is visual inspection, which is simply reviewing the production environment based on human sight.

While such a process may seem basic and antiquated, it remains a helpful way to get a big-picture view about the effectiveness of cleaning and it can quickly identify areas needing attention.

Still, visual testing has obvious limitations because microorganisms cannot be seen by the naked eye. In addition, there often are surfaces on production equipment that can’t be visually inspected and may be dirty or contaminated.

Microbiological testing, on the other extreme, involves surfaces being swabbed and samples taken to specialized testing locations for processing and analysis.

While microbiological testing can help identify specific organisms present in the manufacturing environment, it commonly requires days to produce results. It also does not provide information about non-microbial organic residues present in the environment.

As in many industries, time is money in food production. While testing occurs, products may need to be held, reducing shelf-time and sales. If food is released and contamination is found, the company may find itself in a recall or withdrawal situation.

ATP testing, the third type, bridges the gap between the instant but imperfect human eye and the thorough yet time-consuming microbiological test.

ATP (adenosine triphosphate) is a molecule found in every cell of living organisms and testing systems work to detect organic matter residues from areas in a production environment that are considered cleaned.

In moments, they determine the amount of ATP,​ which is proportional to the amount of organic matter present in those surfaces and therefore indicative of the level of cleanliness.

Sanitation and plant managers of food production facilities must interpret the results and determine whether cleaning was effective enough for their manufacturing to commence, or if re-cleaning and re-testing is necessary before that can happen.

While ATP tests can’t distinguish between organic matter residues and microorganisms, or identify specific organisms, they provide enough information about the sanitary conditions of a food handling facility to take corrective action and avoid product withdrawals or recalls, adverse publicity or even injuries caused to the consuming public.

There are multiple ATP testing systems commercially available and while they all measure the same parameters for a similar purpose, there are important differences between the technologies.

Different devices​

Here are four factors to investigate before making a decision on an ATP testing kit:

1) Rugged Composition – ​Manufacturers need an ATP testing system that is robust and tolerant to a range of environmental conditions that can be found in a food processing plant, including temperatures ranging from cold to hot, variations in humidity, vibration from equipment or the shock of being accidentally bumped or dropped.

 2) Consistent Results – ​The results a system produces must be accurate and precise enough to give consistent readings across technicians and execution timing. Regardless if there was a 5-second or a 60-second delay between the swabbing and the activation of a test, the results should be consistent. A system has to be tolerant to exhibit similar readings when used by various technicians who may have different work speeds, agility or levels of experience.

3) Accuracy and Precision –​ With an accurate system, if the individual swabbed a surface with a level of ATP similar to that of a surface with a known quantity of ATP present (e.g., using an ATP control), the two swabs would reflect very similar results. With a precise ATP testing system, if a sample was collected from a surface and the swab was measured twice, a person would get nearly the same result both times.

4) Sensitive Light Detection –​ATP-based systems rely on detecting light emitted from the ATP present in microorganisms and organic matter when subjected to an enzymatic luminescent reaction, therefore must detect and measure very low levels 
of light.

As food processing surfaces become cleaner – for instance after re-cleaning – less ATP is present, so less light would be generated for measurement. As continuous improvement increases the cleanliness of a facility, even smaller levels of contamination have to be detected. Therefore, an ATP testing system must have a technology capable of detecting extremely limited amounts of light to alert organizations to very low levels of contamination.

The 3M Clean-Trace Hygiene Monitoring and Management System uses photomultiplier technology. A photomultiplier can detect, in a second, a single photon – the smallest unit of light.

Photodiode technology, used in some ATP systems, is unable to detect anything less than 10,000 photons per second.

To compensate for its inability to detect extremely low levels of light, the ATP’s swab chemistry of photodiode-based tests artificially amplify light to be visible in the more limited range of detection. This artificial amplification process generates a quick burst of light, during which time the ATP test results must be read.

If a delay occurs between swabbing and measuring the swab results, and the test is not read within a short timeframe, the accuracy and precision of results from photodiodes can become unreliable.

At the end of the day, it’s about the beginning of the day. Sanitation and plant managers are on the hook to make an important decision about production, and the cleanliness and sanitation of their production environment is paramount in that process.

By leveraging correct processes and technologies for ATP testing they can have greater degrees of confidence than ever before.