1a. Objectives (from AD-416):
The overall goal of this project is to enhance seafood safety, with special emphasis on catfish, through the development of new technologies and new original scientific information. The specific objectives are as follows: 1. Develop and validate models to simulate pathogen behavior under both growth and inactivation conditions. 2. Develop and validate non-thermal and advanced thermal intervention technologies to inactivate pathogens and spoilage microorganisms in raw and ready-to-eat seafood and aquaculture products, in particular, catfish. 3. Define the impact of non-thermal and advanced thermal intervention technologies on food quality and chemistry. It is expected that Objective 1 will contribute to the overall goal of this project through the development of new robust foodborne pathogen growth models that will aid regulatory agencies in their risk assessments and science-based policy decisions. Objectives 2 and 3 will contribute through the development of intervention technologies, which at the same time will enhance, or at the minimum, preserve the original product quality.
1b. Approach (from AD-416):
The incidence of foodborne illness associated with the consumption of contaminated seafood is disproportionately high. This project constitutes a comprehensive research effort to enhance seafood safety, with special emphasis on catfish. This will be accomplished through: 1) developing robust foodborne pathogen growth models to aid risk assessors in regulatory agencies in science-based policy decisions, 2) developing effective intervention technologies, and 3) enhance or, at the minimum, preserve seafood-quality. Intervention technologies to be investigated include flash pasteurization, pulsed and ultraviolet light, and ionizing (gamma) irradiation, electrolyzed water, modified atmosphere packaging, and GRAS food additives, etc. These interventions will be combined to obtain incremental improvements in microbial inactivation, the so-called hurdle to maximize foodborne pathogen inactivation. Food quality evaluation, studies will be conducted on the seafood subjected to various intervention methods to identify those technologies, which in addition to being effective in inactivating pathogens, are simultaneously neutral or even improve product quality.
3. Progress Report:
Seafood is responsible for more cases of foodborne illness when adjusted for per capita consumption than beef, poultry, or produce. A study to determine the incidence of heavy metals, banned antibiotics, and foodborne pathogens in catfish nuggets sold in the northeast United States was completed by researchers at Wyndmoor, PA in cooperation with scientists at Delaware State University and Cheyney University. This research is now in press in the Journal of Food Processing and Technology as part of a catfish special edition. In cooperative research between ARS researchers in Wyndmoor, PA and Mississippi State University the growth of foodborne pathogens in seafood including non-O157: H7 shigatoxin producing Escherichia coli (non-O157:H7 STECs) in catfish fillet meat at refrigeration and abuse temperatures (5, 10, 15, 22 and 30 degrees C) was evaluated. A predictive model was developed to describe the growth of non-O157:H7 STECs in catfish fillet meat. In addition, the thermal inactivation kinetics (thermal d and z-values) for the non non-O157:H7 STECs suspended in catfish fillet meat were determined. Radiation (gamma) inactivation kinetics for six non-O157:H7 serovars, as well as three O157:H7 isolates, propagated under acid resistant and tolerant conditions were determined. The results showed that radiation doses needed to inactivate E. coli O157:H7 could also inactivate non-O157:H7 serovars. This completed research fills a gap in the field of thermal and non-thermal processing as well as predictive microbiology. In cooperative research with scientists from the Residue Chemistry and Predictive Microbiology Research Unit in Wyndmoor, PA the use of flash (steam) pasteurization in combination with edible antimicrobial films was evaluated for inactivation of Listeria spp. Flash pasteurization along with edible films were able to inactivate 99.99% of Listeria on shrimp (Objective 2). Researchers at Wyndmoor, PA, in collaboration with scientists at Edinboro Universty of Pennsylvania determined the effect of ionizing radiation on lipid oxidation, color, mutagenicity, and clastogenicity of frozen crawfish tail meat. Ionizing (gamma) radiation had no effect on frozen crawfish tail meat chemistry or quality. This will help the US FDA evaluate a petition to allow irradiation of crustaceans in the United States.
1. Growth modeling of non-O157:H7 shiga-toxin producing Escherichia coli in catfish fillet meat. Due to contamination of water in much of the world, it is not unusual for finfish to be contaminated with foodborne pathogens, including non-O157:H7 shiga-toxin producing Escherichia coli (non-O157 STEC), and consumption of those contaminated fish cause foodborne illness in many countries. Fish may be stored at refrigeration or ambient temperatures prior to preparation and consumption. In this study, ARS researchers at Wyndmoor, Pennsylvania in cooperation with researchers at Mississippi State University determined the growth potential of a multi-isolate cocktail of non-O157:H7 serovars in catfish fillet meat at various storage temperatures. There was no STEC growth at 4 degrees C. However, the STECs were able to grow at 10, 15, 20 and 30 degrees C in a temperature dependent manner, with higher growth rate associated with higher temperature. Growth curves constructed using ComBase DMfit provided a good statistical fit to the observed data, resulting in a high correlation coefficient. The results of this study provide information to risk assessors regarding the growth potential of the STECs on seafood using catfish as a model system. The growth potentials of Salmonella spp. on raw tuna meat at different temperatures (including abuse temperature at 8-22 degrees C) also were established using similar methodology mentioned above. These data may enhance the safety of raw fish consumption.
2. Gamma radiation inactivation of O157:H7 and non-O157:H7 shigatoxin producing Escherichia coli in foods. Shigatoxin producing Escherichia coli (STEC) cause foodborne illnesses on a worldwide basis through contamination of many food types. Ionizing (gamma) radiation is a technology which is used on a global basis to improve the safety and shelf-life of foods. In this study the ability of gamma radiation to inactivate non-O157:H7 serovars and O15:H7 serovars suspended in catfish fillet meat at refrigeration temperature (4 degrees C) were compared by ARS researchers at Wyndmoor, Pennsylvania. The radiation doses needed to inactivate the non-O157:H7 STECs were similar to those needed to inactivate O157:H7. The results of this study provide information to risk assessors regarding the radiation doses needed to inactivate a wide variety of STEC serovars in seafood.
3. Irradiation of crustaceans. Seafood, when adjusted for per capita consumption, caused more foodborne illness outbreaks than meat, poultry, or produce. Ionizing (gamma) radiation is a technology which is used on a global basis to improve the safety and shelf-life of foods. In a study conducted by ARS researchers at Wyndmoor, Pennsylvania in cooperation with scientists at Edinboro University of Pennsylvania crawfish tail meat and raw shrimp were individually quick frozen and then gamma irradiated to a dose of 10 kGy. The color, fat rancidity, and the ability of irradiated crawfish and shrimp meat to damage DNA in human and bacterial cells was examined. Gamma radiation had no effect on the quality of crawfish tail or shrimp meat. No adverse effects in bacterial or human cells were observed. This research will help the US FDA evaluate a petition to allow irradiation of crustaceans in the United States.
Pang, Y., Sheen, S., Zhou, S., Liu, L.S., Yam, K. 2013. Antimicrobial effect of allyl isothiocyanate and modified atmosphere on Pseudomonas aeruginosa in fresh catfish fillet under abuse temperatures. Journal of Food Science. Volume 78(4)M555-M559.