A calibration-free, non-invasive, and accurate total viable count detection method based on tunable diode laser absorption spectroscopy combined with most probable number counting

Total viable count (TVC), as an important indicator in the microbiological detection. A calibration-free, noninvasive, and accurate TVC detection method was developed using the most probable number (MPN) method and tunable diode laser absorption spectroscopy (TDLAS). In the experiment, a tunable distributed feedback (DFB) laser with a center wavelength of 4989.97 cm-1 was used to measure CO2 emitted from the microorganisms in a sealed culture bottle. Then, the thresholds of negative and positive culture bottles in the MPN-TDLAS method were established by the features of the Staphylococcus aureus (S. aureus) growth curve. The experimental results revealed that the MPN-TDLAS method has a good correlation (R2 = 0.99) with the TVC of the ISO:4833:2013 standard plate counting method, and the result of the quality control (QC) sample was satisfactory (Z-score was less than 2), which demonstrated that this method is well-suited for food microbiology testing applications.