88D-19 |
Ultrasound and natural antimicrobials: inactivation of Saccharomyces cerevisiae by the combined treatment |
S. N. GUERRERO1, S. M. Alzamora1, and M. Tognon. (1) Laboratorio de Microbiología de Tecnologías Emergentes, Universidad de Buenos Aires, Departamento de Industrias. Ciudad Universitaria . Nuñez, Buenos Aires, 1428, Argentina The employment of ultrasonic waves represents an emerging preservation factor for obtaining minimally processed foods. It can be employed in conjunction with other hurdles to enhance food stability. The objective of this research was to study the inactivation of Saccharomyces cerevisiae by the combined action of ultrasound, mild heat treatment(45°C) and addition of cinnamon oil or low weight chitosan on viable cells suspended in Sabouroud broth. In a previous study the minimal inhibitory concentrations of cinnamon oils and chitosan were determined in order to select sublethal levels for the combined method. The ultrasonic treatments were carried out in a double-wall cylindrical vessel connected to a water bath to attain 45.0°C . Ultrasound at 20 kHz and 95.2 micrometers of wave amplitude was applied with a 13 mm-diameter probe as soon as 5 mL culture was inoculated into the vessel containing Sabouroud broth with Chinese or Ceylan cinnamon oils (50,100, 150 and 200 ppm)or low weight chitosan (1000 ppm). Samples were taken at preset intervals during 30 minutes determining viable yeast number .Different mathematical models , including among others the modified Gompertz model, were fitted to the yeast inactivation curves obtaining the characteristic parameters. Saccharomyces cerevisiae survival curves during ultrasonic treatment at 45°C combined with the addition of the natural antimicrobials were sigmoid while inactivation with only ultrasonic treatment followed a first-order kinetics. For the combined treatment, the modified Gompertz model was suitable for describing the yeast behavior. The analysis of the biological parameters showed that the chitosan was the most effective of the assayed antimicrobials. Preincubation of the inoculated system with chitosan prior to the ultrasonic treatment caused more yeast inactivation. The use of ultrasound and natural antimicrobials was effective against S. cerevisiae survival.
Session 88D, Food Microbiology: General
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