OPTICAL DETECTION OF FOOD SAFETY AND FOOD DEFENSE HAZARDS
Location: Quality and Safety Assessment Research Unit
Title: Acousto-optic tunable filter hyperspectral microscope imaging for identifying foodborne pathogens
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 10, 2012
Publication Date: N/A
Interpretive Summary: Although conventional microbiological methods for cell counting are accurate and still are the standard for foodborne pathogenic bacteria detection, this method is laborious and takes a long time to obtain final results, ranging from days to week. Therefore, a more sensitive, accurate and rapid detection method for foodborne pathogenic bacteria is needed for a practical use with a high accuracy for identification. Optical detection methods are promising to meet the above requirements for real-time, in-situ foodborne pathogen detection with a minimum sample preparation process. In order to understand optical properties of foodborne pathogenic bacteria, a hyperspectral microscope imaging system, which provides both spatial and spectral information of each cell, could be an effective tool. In this study, the preliminary results to obtain quality hyperspectral images and their spectral characteristics from pathogenic bacteria were reported. The outcome of this study will benefit food industry and regulatory agency for food safety inspection and evaluation.
Hyperspectral microscope imaging (HMI) method, which provides both spatial and spectral characteristics of samples, can be effective for foodborne pathogen detection. The acousto-optic tunable filter (AOTF)-based HMI method can be used to characterize spectral properties of biofilms formed by Salmonella enteritidis as well as Escherichia coli. The intensity of spectral imagery and the pattern of spectral distribution varied with system parameters (integration time and gain) of HMI system. The preliminary results demonstrated that optimum parameter values of the HMI system are important and the integration time must be no more than 250 ms for quality image acquisition from biofilm formed by S. enteritidis. Among the contiguous spectral imagery between 450 and 800 nm, the intensity of spectral images at 498, 522, 550 and 594 nm were distinctive for the biofilm; whereas, the intensity of spectral images at 546 nm was distinctive for E. coli. For more accurate comparison of intensity from spectral images, a calibration protocol, using neutral density filters and multiple exposures, needs to be developed to standardize hyperspectral microscope image acquisition. For the identification or classification of unknown food pathogen samples, ground truth regions-of-interest pixels need to be selected for “spectrally pure fingerprints” for the Salmonella and E. coli species.