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Advisor(s)
Abstract(s)
Acidification of foods with organic acids, either by fermentation or by intentional addition, is an important
and common mechanism for controlling foodborne pathogens in a diversity of food products. The objective
of this work was to study thermal inactivation of Listeria innocua, an acid tolerant microorganism, at 52.5,
60.0 and 65.0 °C, at different pH values (4.5, 6.0 and 7.5), using three types of acid (lactic, acetic and
hydrochloric) and three different plating media (Tryptic Soy Agar with 0.6% yeast extract—TSAYE; TSAYE plus
5% NaCl—TSAYE+5%NaCl; and Palcam Agar with selective supplement—Palcam Agar), according to a 34
factorial experimental design. Survival data experimentally obtained were fitted with a Gompertz-inspired
model and kinetic parameters (shoulder, maximum inactivation rate—kmax, and tail) were estimated for all
conditions considered. The influence of temperature, pH, type of acid and enumeration media on kinetic
parameters was assessed. Results showed that, with the exception of the type of acid, all the remaining
factors and their combinations significantly affected the shoulder period and kmax. In relation to tail,
temperature and recovery media were the affectable factors. It was concluded that the survival of this
bacteria is higher when combining low temperature with neutral pH, and when TSAYE is the enumeration
medium. Bigelow-inspired models were successfully developed and describe accurately the temperature and
pH effects on the kinetic parameters.
Description
Keywords
Listeria innocua Thermal inactivation pH Type of acid Recovery media
Citation
"International Journal of Food Microbiology". ISSN 0168-1605. 133: 1-2 (2009) 121–128
Publisher
Elsevier