IAFP 2009 Program Book and Abstract Book - AB83

Purpose: The purpose of this study was to develop data that demonstrates how L. monocytogenes grows on foods that were previously frozen and then thawed and held at refrigeration temperatures, such as on a salad bar. Methods: Twelve strains of refrigeration temperature-adapted L. monocytogenes were used to inoculate four frozen food samples: corn, green peas, cooked crab meat, and cooked shrimp. Growth of L. monocytogenes was monitored at four different temperatures (4, 8, 12 and 20°C) using the plate count method with PALCAM agar. In addition, aerobic plate counts on non-inoculated samples and informal sensory analysis on inoculated samples and non-inoculated samples were conducted at the same time at all temperatures, to observe the relationship between product spoilage and growth of L. monocytogenes. Results: Lag phase and exponential growth rates were calculated for all conditions using the Gompertz model. L. monocytogenes tended to grow faster on corn and green peas than on crab meat and shrimp at 4, 8 and 12 °C during storage. All samples showed low initial aerobic plate counts, but counts on corn, green peas, and shrimp increased rapidly at all temperatures. Significance: The data developed can possibly be used by FDA to develop guidance on enforcement criteria and possibly in the Food Code on how to handle these types of foods. P1-59 Adaptation of the Lateral Flow Immunochromatographic Hand-held System for the Detection of Staphylococcal enterotoxin B (SEB) or Staphylococcal enterotoxin C (SEC) in Commercial Infant Formulas, Baby Foods, Milk and Milk Products JOYCE M. NJOROGE, MaryAnn Principato, Robert L. Jones, Jr. and Thomas Boyle FDA, Laurel, MD, USA Introduction: Rapid, sensitive, and specific methods have been developed to detect either SEB or SEC contamination in a variety of dairy products. Further, methods were developed to extract and detect SEB in baby foods, which were texturally complex and varied with respect to ingredients and colors. Purpose: The purpose of this study was to provide adaptive techniques that are fast and easy to use for the qualitative detection of toxin in wide variety of foods used by a large and sensitive group, such as infants and very young children. Methods: Two lateral flow immunochromatographic assay devices (LFDs), developed by the Department of Defense for the detection of environmental contamination with SEB or SEC, were adapted for use in a variety of infant formulas and foods, milk and popular commercial dairy products. Three concentrations of SEB or SEC (5 µg/ml, 500 ng/ml, and 5 ng/ ml) were used. 1 ml volume of toxin or Phosphate buffered saline (PBS) was added to the food matrices. The semi-solid food matrices were mixed thoroughly following the addition of 19 mls PBS. All samples were incubated for 2 h at 4°C, then centrifuged (1500 × g 20 min). One-hundred fifty µl of the supernatant was applied to the lateral flow devices. Results: Once the product wicked onto the strip, either toxin was easily detectable as far as 5 ng/ml. 2% milk and milkbased infant formula, wicked easily into the lateral flow devices strips. Soy-based formulas, chocolate milk, and ice creams required dilution to wick into the LFDs. There were no discernable differences in the ability to detect the three concentrations of either toxin regardless of color, texture or the type of ingredient used to make the ice-cream or the baby foods. The inability to detect the last dose in baby foods may have been a function of the degree to which the sample was diluted in order to induce sample flow onto the strip. SEC was not tested with baby food items. Significance: The lateral flow immunochromatographic device is fast, accurate, and adaptable to a wide variety of food matrices. The ease of use and assay, coupled with simpler extraction strategies, would permit rapid and reliable detection of SEC or SEB in these foods. P1-60 Inactivation of Escherichia coli O157:H7, L. monocytogenes, Salmonella enterica and Shigella flexneri DSC on Iceberg Lettuce (Lactuca sativa) by X-ray BARAKAT S. MAHMOUD and Gary R. Bachman Mississippi State University, Pascagoula, MS, USA Introduction: Vegetables are an important part of healthy eating. However, vegetables, including iceberg lettuce, have been associated with many foodborne outbreaks. X-ray technology is a promising non-thermal method of reducing pathogenic and spoilage bacteria on food. Purpose: The purpose of this investigation was to study: (a) efficacy of X-ray doses (0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 1.5 and 2.0 kGy) against inoculated E. coli O157:H7, L. monocytogenes, Salmonella enterica and Shigella flexneri on iceberg lettuce, and, (b) the effect of X-ray treatment on the quality and shelf life of iceberg lettuce during storage at 4°C. Methods: 100 µl of each targeted organism was spotted onto the surface (10 cm2) of lettuce leaves (approximately 9 log ml-1) separately, after which the leaves were air dried and treated with X-ray at 22°C and 55% relative humidity. Surviving bacterial populations were evaluated using a non-selective medium (Tryptic Soy Agar) with the appropriate selective medium overlay for each organism; for E. coli O157:H7 (CT-SMAC agar), for L. monocytogenes (MOA), and for Salmonella enterica and Shigella flexneri (XLD). Results: More than 5 log CFU reduction (recommended by FDA) of E. coli O157:H7, L. monocytogenes, Salmonella enterica and Shigella flexneri was achieved with 2.0 kGy X-ray. Treatment with X-ray significantly reduced the initial microflora on iceberg lettuce and kept them significantly (P 0.05) change the green color of iceberg lettuce. Significance: These results showed that X-ray treatment significantly reduced selected pathogens and inherent microorganisms on iceberg lettuce, which suggests a good alternative to other technologies for the fresh produce industry. Abstract Book — 83 Poster

IAFP 2009 Program Book and Abstract Book

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