T2-04 Determination of the Thermal Inactivation Kinetics of Escherichia coli, Salmonella enterica and Listeria monocytogenes in Fettuccine Alfredo

Monday, August 4, 2014: 9:15 AM
Room 203-204 (Indiana Convention Center)
Emefa Monu, University of Tennessee-Knoxville, Knoxville, TN
Malcond Valladares, University of Tennessee-Knoxville, Knoxville, TN
Doris D'Souza, University of Tennessee-Knoxville, Knoxville, TN
P. Michael Davidson, University of Tennessee-Knoxville, Knoxville, TN
Introduction: Several foodborne illness outbreaks have been linked to ready-to-eat foods, such as pasta dishes. Mild heat processing can be a reliable method of inactivating pathogens, but it is necessary to determine the thermal inactivation kinetics of pathogens in food systems to design efficient thermal processing methods.

Purpose: The objective of this study was to determine the thermal inactivation kinetics of selected pathogenic bacteria in a fully-cooked pasta with sauce. 

Methods: Five-strain cocktails of Escherichia coli O157:H7, non-O157:H7 E. coli, Salmonella enterica and Listeria monocytogenes were mixed with a commercial Alfredo sauce. Fettuccine noodle pieces (3.8 cm length) were mixed 1:1 (w/w) with the sauce and allowed to sit for 30 min before vacuum packaging in polyethylene-nylon bags. Bags were placed in a holder and submerged in a circulating water bath at 56, 58 or 60°C. Following heating for appropriate times, samples were placed in an ice-bath, blended with phosphate buffered saline, then serially diluted and spread-plated on tryptic soy agar plates. Survivors from triplicate experiments were enumerated after 24h at 37°C or 48h at 32°C (Listeria). D- and z-values were determined using a first-order model.

Results: For Salmonella, Listeria, E. coli O157 and non-O157, D-values (min) at 56°C were 3.75 ± 0.39, 7.58 ± 1.04, 7.66 ± 0.04 and 7.47 ± 0.40, at 58°C, 1.07 ± 0.06, 2.07 ± 0.06, 3.39 ± 0.14 and 5.03 ± 0.39, and at 60°C were 0.46 ± 0.01, 1.09 ± 0.32, 1.20 ± 0.19 and 1.28 ± 0.22 min, respectively. z-values for Salmonella, Listeria monocytogenes, E. coli O157 and non-O157 were 4.42 ± 0.33, 4.82 ± 0.74, 4.96 ± 0.42 and 5.20 ± 0.39°C, respectively.

Significance: These results show the difference in thermal inactivation kinetics of the selected pathogens in pasta with sauce. These data will be useful to the food industry in developing mild thermal treatments, such as microwave pasteurization, to produce safer consumer products.