It's important to know how microorganisms -- particularly pathogenic microbes -- grow under various conditions. Certain bacteria can cause food poisoning when eaten and bacterial growth in medical blood supplies, while rare, might necessitate discarding the blood. Now a group of researchers from Zhejiang Normal University in China and Umeå University in Sweden report a fast, accurate, and noninvasive technique for monitoring bacterial growth. They report the results in Applied Optics, a journal of The Optical Society (OSA).

Microorganism growth is driven by many factors, which make it far from easy to accurately estimate the amount of bacteria within food containers or blood samples at any given time.

To avoid the risk that any particular packaged food item will go bad and cause illness, it's given an unnecessarily short shelf life. In short, a better understanding of the growth process of microorganisms could reduce food waste and prevent people from being sickened by food poisoning -- or both.

Within the medical realm, it's critical to be able to assess the quality of blood samples quickly and accurately. Without this ability, samples might need to be discarded or, alternatively, result in or worsen illnesses. Although bacterial blood contamination is rare, it does occur and has led to deaths. A rapid screening method could mean that a larger percentage of blood could be directly tested for bacteria. 

"Microorganism growth is always associated with the production of carbon dioxide (CO2)," said Jie Shao, associate professor at the Institute of Information Optics, Zhejiang Normal University, Jinhua, China. "By assessing the level of CO2 within a given closed compartment -- bottle or bag -- it's possible to assess the microbial growth."

Several detection techniques are currently capable of rapid and accurate measurements of gas compositions. Those based on optical spectrometry are most appealing because they're noninvasive, boast high sensitivity, provide instant responses, and are potentially useful for assessment of bacterial growth. 

"A technique referred to as 'tunable diode laser absorption spectroscopy' (TDLAS) is particularly suitable because it combines all of these properties with an ease of use and low cost," Shao said.