Inactivation Kinetics of Listeria innocua in Skim Milk in a Continuous Flow Processing System

Abstract

Thermal inactivation of List&z innocua in raw skim milk determined under continuous flow conditions was compared to results from the capillary tube method at 65, 68, and 70°C. A laboratory scale pasteurizer (LSP) was used to generate kinetic data under isothermal, continuousflow conditions. Inactivation was monitored by sampling at various locations along the hold tubes. DC,.,=+, D,,-and D,,m-values for L. innocua Ml were 11.5, 3.5, and 1.6 set, respectively, when iletermined by the LSP system and 16.5, 3.9, 1.5 set, respectively, when determined by the capillary tube method. Decimal reduction times for the two methods were predicted to be coincident at 69°C. Z,-values for the capillary tube and LSP systems were significantly different. The data suggest that the mechanism of thermal destruction may be different between batch and continuous flow processes.

Study of butter fat content in milk on the inactivation of Listeria innocua ATCC 51742 by thermo-sonication

“…Although the dairy industry is most concerned about the presence of L. monocytogenes in products such as cheese, other Available online at www.sciencedirect.com Innovative Food Science and Emerging Technologies 9 (2008) 176 -185 www.elsevier.com/locate/ifset sources of this microorganism are frankfurters and sliced meats (Yousef & Carlstrom, 2003). Listeria innocua, used as a surrogate of L. monocytogenes for microbiological studies, has shown similar behavior against heat and radiation in different media (Zapico et al, 1999), and a very high resistance to thermal treatment in skim milk (Fairchild et al, 1994) and to electric pulses (Picart, Dumay, & Cheftel, 2002). The use of sound waves in liquid media to disrupt cells, either alone (sonication), or in combination with heat (thermo-sonication), is an alternative approach to the inactivation of such bacteria.…”

“…Even the mode of thermal treatment batch or continuous, has a different mechanism of inactivation in cells. Although the supplied heat is the same, cells do not receive the same physical effects in batch mode, as compared to continuous processes such as pressure and shear forces (Fairchild, Swartzel, & Foegeding, 1994).…”

Autofluorescence and green fluorescent protein-derived fluorescence in Listeria innocua

“…Extensive research has been performed to validate L. innocua as a non-pathogenic surrogate of the food-borne pathogen L. monocytogenes [14,25,26]. Fairchild and Foegeding [17] reported L. innocua M1 to be an appropriate candidate for thermal inactivation of L. monocytogenes. However, the current method for the evaluation of L. innocua growth performance as a surrogate is based on colony counts which is time consuming (48 h) and has a relatively low limit of detection [26,27].…”

“…Listeria innocua M1, resistant to streptomycin (250 mg L -1 ) and rifampicin (50 mg L -1 ) both generated by selective enrichment [17], was originally obtained from Dr. P.M. Foegeding (Department of Food Science, North Carolina State University, Raleigh, NC) and used in this study as a final host of transformation with pSB2019 containing gfp3 [18].…”

Quantitative Evaluation of Thermal Inactivation Kinetics of Free-Floating Versus Surface-Attached Listeria innocua Cells

“…Previous studies of thermal inactivation of L. innocua (under static conditions) by the capillary tube method in skim milk (Fairchild et al 1994), in which linear microbial kinetics is assumed, gave a relatively low z value, i.e., 4.8°C. In the present research, a z value of 9°C was obtained (Table 1).…”