VATIS UPDATE Article

Jie Shao and other researchers from Zhejiang Normal University, China, and Umeå University, Sweden, have developed an instrument based on tunable diode laser absorption spectroscopy (TDLAS) to assess bacterial growth of various types of samples under a variety of conditions. TDLAS enables fast, accurate and noninvasive measurement of bacteria levels in food, blood supplies and other products derived from living matter. The researchers’ basic setup involved a tunable diode laser as the light source, beam shaping optics, a sample to be investigated, receiving optics and one or more detectors.

The emission wavelength of the laser was tuned over a characteristic absorption line transition of the species within the gas being assessed, causing a reduction of the measured signal intensity, which the researchers used to determine gas concentration. When the wavelength is rapidly tuned across the transition in a specific manner, it can be combined with a modulation technique called wavelength modulation (WM), which enhances the sensitivity of the TDLAS technique. By applying WM-TDLAS to transparent containers of organic substances such as food items or medical samples, bacterial growth can be quickly and accurately evaluated.

Micro-organism growth is driven by many factors, which make it difficult to accurately estimate the amount of bacteria within food containers or blood samples at any given time. A better understanding of the growth process of micro-organisms could help reduce food waste and prevent sickness. Within the medical realm, the ability to assess the quality of blood samples quickly and accurately could mean that a larger percentage of blood could be directly tested for bacteria, reducing the risk of bacterial blood contamination.