Label-Free Detection of Bacteria in Fruit Juice

Rapid quantification of microbial contamination in fruit juice is highly desired for food safety control. Yet, the complex sample matrix and the diversity of bacterial contaminants present a great challenge. Employing the Flow NanoAnalyzer, a label-free approach for the detection of the bacterial population in fruit juice was reported. The weak autofluorescence of bacterial cells was used as a hallmark for the identification of bacteria. The sample pretreatment protocol was optimized to reduce fluorescence background, lyse residual plant cells and debris, and attain a good recovery of bacteria from juice samples. The as-developed method was successfully applied to the bacterial measurement of freshly made orange juice and apple juice purchased from grocery stores. This approach shows great potential in the microbial control analysis of other liquid drinks.

The bacterial concentrations measured by Flow NanoAnalyzer complimented those of the plate counter, with a correlation coefficient of 0.97. Morever, the experimental procedure, including sample pretreatment and result analysis, can be accomplished within one hour, which is far more efficient than the plate counting method. 

Anal. Chem., 2020, 92(3), 2393-2400.