Location: Quality & Safety Assessment Research2012 Annual Report
1a. Objectives (from AD-416):
1. Develop methods and instruments to identify food safety hazards throughout various stages of poultry and egg production and processing. 2. Detect and characterize foodborne pathogens, toxins, and bacterial threat agents with rapid optical methods. 3. Develop and evaluate detection methods for foodborne pathogens and toxins with nanotechnology.
1b. Approach (from AD-416):
Various optical (imaging) methods will be used for detecting intentional and unintentional contaminants and bacterial pathogens of food products. A real-time in-line hyperspectral imaging system will be used to rapidly detect diseased and contaminated broiler carcasses in processing plants. A monochromatic imaging system will be used for detecting cracks in table and hatching eggs. Hyperspectral microscopic imaging system, Raman imaging instrument and Fourier transform infrared spectrometer will be used to detect biofilms and foreign materials on the surfaces of food processing equipment. Visible/near-infrared hyperspectral imaging systems will be used to rapidly detect and characterize foodborne pathogens associated with poultry products and bacterial threat agents. Nanotechnology will be used for detection of foodborne pathogens and toxins. Collaboration with ARS Environmental Microbial and Food Safety Laboratory, BARC, FSIS, AMS, and the University of Georgia Nano Science and Engineering Center will be used to enhance the research.
3. Progress Report:
Improved automatic lighting for egg crack detection: Previously developed egg hairline crack detection system suffered from lower intensity candling lights that were only manually controlled in a few zones. The lighting system was totally upgraded to include higher-intensity, white light-emitting diodes (LEDs) and a custom-designed and developed programmable control board that used the existing camera system as part of feedback control. The result was automatic light control that allowed uniform illumination for all eggs in the crack detection system. Classification of Shiga Toxin producing Escherichia Coli (STEC) other than non-escherichia coli. O157 with hyperspectral microscope imaging: Non-O157 STEC serotypes (O26, O45, O103, O111, O121 and O145) have been recently recognized in an outbreak to cause human illness due to their toxicity. A hyperspectral microscope imaging method was developed to identify these pathogenic bacteria from the optical properties (spectral signatures) of the bacterial cells in micro-colony samples. The acousto-optic tunable filters-based hyperspectral microscope imaging method was able to identify STEC serotypes with several different classification algorithms. Salmonella detection with Surface Enhanced Raman Spectroscopy (SERS) with silver particle encapsulated biopolymer nanosubstrate: A nano-colloidal substrate developed from silver particle encapsulated biopolymer was tested for Salmonella detection with SERS. To confirm uniformity and reproducibility of the nanosubstrates, optical properties of the substrate plasma were measured with ultra-violet, visible spectroscopy, and hyperspectral microscopy. The biopolymer nanosubstrate has a longer shelf-life and generated stable SERS signals from Salmonella and enabled the differentiation of Salmonella serotypes Typhimurium and Enteritidis. Nanobiosensor for food toxin detection with DNA aptamers: Aptamers are single-stranded oligonucleotides generated from in vitro selection and have high affinities to their targets, which can be small molecules, proteins, virus, or cells. The protocol for detecting a single ricin protein based on these DNA aptamers was developed with a modified atomic-force microscope and the binding affinity of the aptamer to ricin was identified. The affinity was slightly higher than that with an antibody, which means aptamers could replace antibody as sensing agents. The methods will be used in further nanobiosensor development.
1. Differentiating non-O157 STEC serogroups in pure culture and from ground beef on agar media. A hyperspectral imaging technique was developed to detect and differentiate the Shiga Toxin-Producing Escherichia coli (STEC) serogroups other than E. coli O157 on Rainbow agar plates. These non-O157 STEC (O26, O111, O45, O121, O103, and O145) are known as the “big six”. A number of different classification techniques were developed to distinguish these E. coli colonies on spread plates of pure and mixed cultures. The classification models were tested on inoculated ground beef to measure the performance of the imaging technique. The average sensitivity and specificity was 95% and 92%, respectively. Test results obtained from these studies showed the potential of the imaging technique for rapid screening of STEC positive colonies to ensure that the correct colonies were selected for further confirmatory techniques.
Sundaram, J., Park, B., Yoon, S.C., Hinton Jr, A., Windham, W.R., Lawrence, K.C. 2012. Classification and structural analysis of live and dead salmonella cells using fourier transform infrared (FT-IR) spectroscopy and principle component analysis (PCA). Journal of Agricultural and Food Chemistry. 60(4):991-1004.