Date of Award
Doctor of Philosophy
Joseph G. Sebranek
Several listeriosis outbreaks linked to the consumption of food products have occurred in the last two decades. Post-processing contamination of frankfurters with L. monocytogenes after cooking or before packaging is one such major concern for the food industry and has become an important food safety issue for meat processors.;The hypothesis for this study was that surface dipping of frankfurters with chemical preservatives or their combinations will inhibit L. monocytogenes growth on frankfurters with the degree of inhibition dependent upon temperature.;Phase I of this study was an evaluation of different anti-microbials for effectiveness. Surface dipping solutions of organic acids, e.g. sodium diacetate (SD), sodium lactate (SL), potassium sorbate (PS) and potassium benzoate (PB), were used singly or in combinations at 6% total concentration to control L. monocytogenes growth on inoculated (105 CFU/g) vacuum-packaged frankfurters stored at 4.4°C for 14 days. The maximum population density of L. monocytogenes was decreased in SD, SD/PB and SD/SL/PB treatment groups compared with the others in Phase I. In Phase II these three treatments were investigated in more detail at different concentrations (3.0% and 6%) and storage temperatures (-2.2°C, 1.1°C, 4.4°C, 10.0°C and 12.8°C) for up to 90 days. The growth of L. monocytogenes was significantly decreased when stored at lower temperature (-2.2 and 1.1°C) compared with the other temperatures. Surface treatments with 6% SD, 6% SL/SD/PB, 3% SD/PB and 6% SD/PB effectively inhibited L. monocytogenes growth at 1.1°C compared with the control group, and the treatment 6% SD was the most effective. The 6% SD/PB treatment increased meaty flavor score, and the 3% SL/SD/PB decreased smoke flavor score of the frankfurters (P < 0.05) as assessed by sensory panels, however, no sensory difference was observed in saltiness, sourness and pepper flavors among surface-treated non-inoculated frankfurters. The SL/SD/PB treatment at either 3 or 6% significantly increased the lightness (L*) and decreased the redness (a*) color values for frankfurters compared with the control group. Storage time longer than two months also significantly increased L* value and decreased a* value.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
Lu, Zheng, "Inhibition of Listeria monocytogenes on frankfurters treated with organic acid salts " (2004). Retrospective Theses and Dissertations. 1182.