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Title: SERS Technique for Rapid Bacterial Screening

item Chao, Kuanglin - Kevin Chao
item Kim, Moon

Submitted to: ASABE Food Processing Automation Conference
Publication Type: Proceedings
Publication Acceptance Date: 6/17/2008
Publication Date: 6/28/2008
Citation: Chao, K., Kim, M.S., Liu, Y. 2008. Sers technique for rapid bacterial screening. ASABE Food Processing Automation Conference, June 28-29, 2008, Providence, Rhode Island.

Interpretive Summary: Rapid, accurate, and preferably routine methods for the identification of foodborne bacteria are increasingly important due to public health concerns and to economic loss from unexpected foodborne outbreaks, such as E. coli contaminated spinach and L. monocytogenes tainted ham / turkey products. This study provides simple procedures to produce silver colloids and assess their quality, to prepare bacterial cultures for SERS analysis, and to analyze the SERS spectra for the differentiation of E. coli, Listeria, and Salmonella. These procedures avoid the need to perform processes of labeling, purifying, separating, drying, or washing the bacterial samples, and also are advantageous in using small volumes of bacteria cultures and silver colloid and in requiring only about 20 minutes for bacteria-colloid mixture preparation and SERS measurement. Results from this study suggest that colloidal silver SERS technique can be used in routine and rapid screening for E. coli, Listeria and Salmonella bacteria. The SERS technique for screening of the presence of bacteria presented can be useful to food processing engineering, regulatory government agencies, and food processing industries.

Technical Abstract: This study reports the feasibility of citrate-reduced colloidal silver SERS for differentiating E. coli, Listeria, and Salmonella. FT-Raman and SERS spectra of both silver colloids and colloid-K3PO4 mixtures were collected and analyzed to evaluate the reproducibility and stability of silver colloids fabricated in a batch-production process. The results suggest that the reproducibility of the colloids over the batch process is high and that their binding effectiveness remains consistent over a 60-day storage period. Two specific SERS bands at 712 and 390 cm-1 were identified and used to develop simple 2-band ratios for differentiating E. coli-, Listeria-, and Salmonella-colloid mixtures with a 100% success. These results indicate that colloidal silver SERS technique may be a practical alternative method suitable for routine and rapid screening of E. coli, Listeria, and Salmonella bacteria.