We have received several questions related to ATP Testing (Kikkoman A3), such as "Can we measure the number of bacteria and viruses?" and "Do the measured values correlate with the number of bacteria (CFU)?" Therefore, in this article we will look in depth at the correlation between the 2 units RLU and the CFU unit.
1. The concepts of ATP, the RLU unit and the CFU unit
1.1. The concept of ATP
- What are ATP, ADP, AMP?: ATP (adenosine triphosphate) is a molecule that is present in the metabolism of all living organisms. ADP (adenosine diphosphate) and AMP (adenosine monophosphate) are produced from ATP when there is fermentation or heat treatment.
- Measuring ATP is a rapid ATP testing method used by food and beverage processors to quickly assess the cleanliness of a surface or a liquid sample from places such as a CIP system. The result displayed after an ATP test is expressed in RLU units.
- ATP Monitoring is used in food and beverage facilities to confirm that the presence of ATP is removed or minimized by effective sanitation processes. ATP monitoring prevents cross-contamination, ensures product integrity, can improve product shelf life, protects brand reputation and complies with GMP standards and HACCP requirements.
1.2. The RLU unit
- RLU is short for Relative Light Unit (Relative Light Unit) and is the unit of measurement used in bioluminescence. ATP meters are used to measure and quantify light with RLU output. Because manufacturers use different sensor technologies and algorithms to count photons, RLU readings will vary depending on the technology of each manufacturer. However, because the ATP bioluminescence reaction is linear , the more ATP there is, the more light there will be.
1.3. The CFU unit
- CFU is short for Colony Forming Units which is called the colony forming unit. It is an index for evaluating; estimating the number of viable fungal or bacterial cells in a given sample.
- Each colony is considered to have grown from a single colony forming unit separately. To determine CFU in practice, bacteria must be cultured, and the cells that are capable of multiplying, that is, living cells, must be counted.
2. The difference between the RLU unit and the CFU unit (ATP amount ≠ countable number of bacteria)
- The index values obtained through ATP Measurement Testing (Kikkoman A3) indicate the total amount of ATP + ADP + AMP. The ATP molecules in most of the places being tested come not only from bacteria but also from organic soiling such as food residue and human perspiration. Therefore, the total amount of ATP + ADP + AMP obtained from the sample is displayed as a measured value in RLU units.
- As we explained in the section "The difference between bacterial testing and ATP testing (Kikkoman A3)", any organic matter left over, including food residues, can lead to the growth of bacteria over a short period of time. However, bacterial testing may miss monitoring such latent risks.
- Please see the values measured using our Lumitester Smart and LuciPac A3 as a chart of the number of bacteria (CFU/ml, on the vertical axis) versus the amount of luminescence (RLU, on the horizontal axis).
- Focus on the part marked in green. The ATP measurement method with Lumitester & LuciPac shows high luminescence, but no bacteria were detected. This means that the number of bacteria is very low, but organic soiling such as food residue is still present. Organic residues left on the surface can create the growth of bacteria in a short time, posing a risk of contamination and foodborne illness.
- From a hygiene point of view, that also means that body fluids such as saliva, nasal mucus, blood and other organic soiling may remain because of incomplete sanitation and insufficient measures to prevent infectious diseases.
- The most ideal ATP measurement method should be performed after sanitation, but before applying disinfectant. Because disinfectant is less effective when residue remains on the surface, it is best to remove all ATP before the disinfection step. At some facilities, testing after sanitation is not possible. In these cases, testing after disinfection is acceptable.
* Customers can refer to detailed information about the Lumitester Smart ATP meter and the Lucipac A3 swabs at the following link:
https://pacificlab.vn/vi/shops/group/may-atp-kiem-tra-ve-sinh-be-mat/