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FAQ's: Sound Science behind Charm's novaLUM and PocketSwabs

Why is Charm the leader in ATP Sanitation Monitoring?

Charm Sciences has been in the luminescence business since the early nineties. Since then, we have revolutionized how ATP Sanitation Programs are implemented by continually developed technology, instrumentation and swab devices. In a state-of-the-art environment, Charm manufactures instruments and swabs, and designs our own firmware and software. Committed to the highest quality standards Charm Sciences is firmly committed to providing unique testing solutions that maximize brand protection, quality and value to the customer, and ultimately to the consumer.

What is ATP?

atp-moleculeATP, or adenosine triphosphate, is a high-energy molecule that is used by living cells as their primary source of energy to drive cell chemistry. Animal, plant, bacterial, yeast, and mold cells produce and break down ATP in order to drive a number of biological processes including muscle contraction, photosynthesis, and the creation of different proteins. ATP may be cellular (e.g., within viable or dead microbial cells) and extra-cellular (free ATP).


Do all foods contain ATP?

Most foods will contain some naturally occurring ATP. However, the act of processing or cooking may reduce the levels of ATP.


What is RLU?

RLU stands for Relative Light Unit. All luminometers capture the light readings by measuring photo output with photodiode or photomultiplier tubes (PMT). RLU output varies between luminometer manufacturers based on detection system, the effective bandwidth used to accumulate the photon count, the speed of counting and internal calibrations. Charm uses a PMT system (novaLUM).


Can I compare RLU counts to CFU plate counts?

The Charm PocketSwab test, run on the novaLUM analyzer, will detect total ATP present on a food-processing surface. It does not differentiate between the ATP stemming from microbial cells and the ATP from organic matter, e.g., food residue left on the surface due to inadequate cleaning and sanitation procedures. Direct comparison of the RLU count from the novaLUM to Colony Forming Units (CFU) is impractical unless correlating to direct single cell suspensions. However, high CFUs often correlate with high RLU on the novaLUM/PocketSwab Plus. The presence of ATP on the surface indicates that it has not been adequately cleaned.


What is a biofilm?

A biofilm is a population of microorganisms attached to a solid surface. A biofilm population can include bacteria, fungi, yeasts, protozoa, and other microorganisms. A biofilm forms when bacteria attach to wet or dry surfaces, and begin to excrete a polyschharide glue-like substance. Biofilms can adversely affect both product and equipment. For example, biofilms are well known for causing the clogging and corrosion of membranes, filters, water systems and water contamination. In a food processing facility, the presence of a biofilm can lead to poor product quality and/or lost product due to contamination from the biofilm.


What if I have a biofilm?

The PocketSwab Plus contains an agent capable of cutting through a biofilm and exposing the underlying cells. If a biofilm has developed, it will most likely trigger an elevated RLU count.


What areas should be swabbed?

Food contact areas, and hard to clean areas should be the main focus of ATP swabbing programs. Food contact areas include both direct and indirect food contact surfaces. Direct contact areas will be those surfaces where if there is any residue present it may contaminate the product. No further microbial kill steps, such as pasteurization or washing (as in produce), will be encountered after contact with these surfaces. Indirect contact areas are those from which condensate, splashed product, dust, or liquid has the potential to be dropped, drained, or drawn into the product. A few examples of hard to clean areas may include filler heads, O-rings, nozzles, and areas with irregularly shaped surfaces, corners, grooves and cracks.


What is the proper swabbing technique?

Swab an area that is 4 inches by 4 inches square (or 10 cm by 10 cm). Hold the swab at approximately a 30-degree angle to the surface. Apply pressure to the swab tip and be sure to continuously roll the swab so that the entire swab tip comes in contact with the surface. If the surface you are swabbing does not have an area that is 4 inches by 4 inches (100 cm2), such as a gasket, then swab as much of the surface as possible. To prevent contamination of the swab, avoid touching the swab tip with your hand or anything else except the surface that is being swabbed. Once the swab has been activated, it should be read in the novaLUM within 60 seconds..


How should the PocketSwabs be stored?

Store PocketSwabs at room temperatures (2-25°C). The expiration date will be 1 year from date of manufacture.


Does the surface have to be dry before I can swab?

No, the surface does not have to be dry in order to obtain valid swab results. The surface can be either wet or dry. The swab tip is premoistened with a biofilm breaking buffer to facilitate removing any ATP from a dry surface.


How often should critical and regular test sites be swabbed?

Critical test sites should be swabbed on a daily basis or anytime prior to start-up. If a failure is generated immediate corrective action should be taken and the area re-swabbed until a passing result can be obtained. Corrective action steps may include and additional water rinsing of the entire area or a complete re-cleaning if necessary.


How should I customize the novaLUM with our specific swabbing sites?

The novaLUM is designed for use with novaLINK software. novaLINK allows you to quickly and easily organize test locations into groups called “Sampling Plans”. Each location is associated with a surface type (e.g., Stainless Steel, Rubber, or Plastic), and each plan, location or surface can have its own pass/fail limit. The test operator can see these location names, surface types and limits on the novaLUM display and know exactly what piece of equipment or area should be swabbed. The organization of Plans is at the discretion of the user and may be modified at any time.


What are limits?

The limit is the cutoff RLU value between a passing and a failing result. Any number below the limit will pass and any number above the limit will fail. Please call us directly for guidance on limits.


Should swabbing be completed before or after the application of sanitizer?

Swabbing can be done before or after the application of the sanitizer; it will not make a difference as long as:

1) there is no ATP present
2) the sanitizer is at proper concentration, and
3) the minimum contact time recommended by the manufacturer has been observed.

Of course the surface should be completely clean before the sanitizer is even applied. This allows for a true reading of whether the equipment surface has been properly and effectively cleaned.

It is standard practice in most food plants especially with CIP systems to swab after adding sanitizer giving the passing count on the surface so there is not opportunity for recontaminating the surface prior to production of the food product. Some organisms thrive in central sanitizer systems and swabbing after adding sanitizer would detect any problems. Swabbing after the  application of sanitizer is acceptable so long as sanitizer dosage strengths, and application time are sufficient. The surface does NOT have to be dry prior to swabbing.


Will sanitizers or soap interfere with my swab counts?

Sanitizers when diluted and used in concentrations recommended by the manufacturer, will not cause interference in swab counts.  Additionally, soap will not interfere with readings. ATP that is being carried by soap but is still on the surface being swabbed will give a count due to the ATP. If the sanitizer concentration is greater than the EPA recommended ppm there may be a count on the Charm PocketSwab as the surface is not safe for production of a food product. Excessive sanitizer on the surface can cause “pitting” which will be harboring points for bacteria, off-flavors in the finished product, money wasted as you can not sanitize dirt, and the possibility of bacteria mutating and becoming resistant to the sanitizer.


Will direct sunlight affect swab counts?

Sunlight can affect swab results for all ATP detection systems. Activating and counting the swab in direct sunlight can cause increased RLU results. Charm manufactures a dedicated swab specifically for ‘outdoor’ use, the FieldSwab™, which has applications for example, truck washing, grain storage areas, and fresh cut produce harvesting equipment.


How do I know that the novaLUM and swabs are functioning properly?

To ensure that tests and the novaLUM are functioning properly, run a positive and negative control, See Controls & Maintenance section. If either the positive or negative control is out of range contact the Technical Service department of Charm Sciences by phone at (978) 687-9200 or email at


All ATP systems the same?

No. There are 2 main detector groups - photodiode based and photomultiplier (PMT) based. Photodiodes are silicon chips and inexpensive, however they lack sensitivity and are subject to temperature fluctuation, performance drops as temperature cools (like refrigerated plants). Photomultiplier’s (PMT) are more expensive but have the sensitivity needed to detect levels of soil that affect product quality and safety. Charm uses a photomultipler (PMT) detector.


There is conflicting information on ATP systems on the market today, Why?

Much of it is contracted data disguised as science. There are a number of sponsored "papers". Charm Sciences encourages independent evaluations of our technology, by the customer, as it provides a realistic assessment of how test(s) will perform in a plant setting. At customer’s request, Charm will make available in-house comparative data.



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Contact Charm

Charm Sciences, Inc.
659 Andover Street
Lawrence, MA 01843

phone-icon 1.978.687.9200 
phone-icon 1.800.343.2170