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Results •Bacteria were detected at 10 3 cells/g in un- injected controls, but none were Salmonella sp. •Salmonella recovery from injected controls exceeded 95%, and varied <1% •Recovery from the microwaved nuggets ranged from 10 2 to 10 6 cells/gm, and the values were highly variable compared to the unheated controls. •Heated recoveries of Salmonella from nuggets are given in Fig. 1. Conclusions •Microwave cooking of frozen, raw, breaded chicken nuggets will not totally remove viable Salmonella that may be present in the raw food. •This is important because a small amount of Salmonella can cause serious sickness. Abstract The presence of potentially pathogenic Salmonella sp. in raw chicken is recognized as a possible health hazard. It is commonly believed that frozen chicken nuggets are precooked, when in fact most frozen nuggets and strips are raw. The objective of this study was to measure survival of Salmonella in chicken nuggets cooked in a microwave. Frozen nuggets were injected with 10 7 cells of Salmonella, an amount which has been associated with previous salmonellosis outbreaks from eating undercooked chicken. A 1300 watt microwave was used, and injected-nuggets were heated (3 at a time) at the highest power for 30, 60 and 120 seconds. Salmonella were recovered from individual nuggets by homogenization with sterile buffer, followed by plate counts using nutrient agar. Controls included unheated, injected nuggets, as well as un-injected nuggets. Bacteria were detected at 10 3 /g in un-injected, unheated nuggets, but none were Salmonella sp. Cell recovery exceeded over 95% in unheated controls, and values differed less than 1% among replicates. While Salmonella levels were reduced in injected-nuggets at each heating time, the reduction from the initial 10 7 level ranged from 10 6 to 10 2 Salmonella cells recovered. The highly variable results from the microwave- heated samples could be the result of uneven heating frequently observed when foods are cooked in the microwave. Even low concentrations of Salmonella in foods can be problematic, and the suggested preparation protocols for chicken nuggets need to be reviewed to assure food safety. Introduction •Salmonellosis is caused by the bacterium Salmonella. •This gram negative rod is very common in poultry products. •Improper preparation of foods that are potential carriers of this bacterium can lead to infection. •There are over 40,000 cases of Salmonellosis and 600 of these lead to death annually in the United States. •The main symptoms are diarrhea and fever. In fact, it may take some infected individuals several months to fully recover (Center for Disease Control, 2004). •Not all chicken nugget products are precooked. This public misconception has lead to a series of Salmonellosis outbreaks in British Columbia, Canada (MacDougall et AL. 2004). Literature •Baron, E.J., Peterson, C.R and Finegold S.M. 1994 Barely and Scotts Diagnostic Microbiology Mosby. St. Louis Missouri •Benson, Harold J. Microbiological applications : laboratory manual in general microbiology. 8th ed., short version. Boston : McGraw-Hill, c2002. •Center For Disease Control Division of Bacterial and Mycotic Diseases. Salmonella 2004 <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/salmonellosis_g.htm#What%20is %20salmonellosis> •Doyle, M. Beuchat, L and Montville. Food Microbiology. (Herndon VA: ASM Press, 2001), 91-169. •MacDougall et AL. 2004. Frozen Chicken Nuggets and Strips-A Newly Identified Risk Factor for Salmonella Heidelberg Infection in British Columbia, Canada. Journal of Food Protection 67: 1111-1115 Resistance of Salmonella in Frozen Chicken Nuggets to Microwave Cooking Ryan C. Shaw and Carolyn F. Mathur, Department of Biological Sciences, York College of PA Methods Fig. 1. Recovered Salmonella cells/nugget injected with 10 7 cells/nugget. Average recoveries ranged from 10^6 to 10^2 cells Salmonella when heated at 30, 60 and 120 seconds (see groups 2, 3 and 4 respectively in Table 1). Table 1. Experimental Design ________________________________________________ 10 7 cells Nugget Groups b Salmonella Injected 0(s) a 30(s) 60(s) 120(s) 1 + + 2 + + 3 + + 4 + + 5 - + 6 - + _____________________________________________________________ ____ a seconds heated at maximum setting b n = 3 per group ►Salmonella preparation Salmonella (ATCC 14028) was grown ON in nutrient broth at 37 0 C and quantified by a standard plate count method. The amount injected in each nugget contained 10 7 bacteria in 0.4 ml suspension. ►Sample treatments and processing The experimental treatments are given in Table 1. Each nugget (3 per treatment) was injected with Salmonella, arranged equidistantly in a sterile glass beaker in the microwave, and heated (1300 watts) for either 30, 60 or 120 seconds. After heating, nuggets were analyzed individually for the presence of viable Salmonella. Each nugget was cut into 6 smaller pieces, homogenized with 40mL of sterile buffer for 5 minutes (to achieve a relatively homogeneous suspension), and quantified by serial dilutions and plate counts. Objective: To determine if Salmonella survives in uncooked breaded chicken nuggets prepared in a microwave Discussion •The highly variable results from the microwave-heated samples could be the result of uneven heating frequently observed when foods are cooked in the microwave. ► Controls •Salmonella-injected, unheated nuggets (group 1) were evaluated to determine the sensitivity of the recovery method. •Both heated and unheated, un-injected nuggets (groups 5 and 6) were processed to detect any bacteria present, and suspicious isolates were checked to determine if they were Salmonella. .
