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Applied and Environmental Microbiology, September 2007, p. 5580-5586, Vol. 73, No. 17
0099-2240/07/$08.00+0     doi:10.1128/AEM.00351-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Antimicrobial Activity of Aroma Compounds against Saccharomyces cerevisiae and Improvement of Microbiological Stability of Soft Drinks as Assessed by Logistic Regression

Nicoletta Belletti,¹ Sylvain Sado Kamdem,¹ Francesca Patrignani,¹ Rosalba Lanciotti,¹ Alessandro Covelli,² and Fausto Gardini^1*

Dipartimento di Scienze degli Alimenti, Università degli Studi di Bologna, Sede di Cesena, Piazza G. Goidanich, 60, 47023 Cesena, Italy,¹ Flavourint, Via Roma, 8, 24040 Madone, Italy²

Received 13 February 2007/ Accepted 27 June 2007

The combined effects of a mild heat treatment (55°C) and the presence of three aroma compounds [citron essential oil, citral, and (E)-2-hexenal] on the spoilage of noncarbonated beverages inoculated with different amounts of a Saccharomyces cerevisiae strain were evaluated. The results, expressed as growth/no growth, were elaborated using a logistic regression in order to assess the probability of beverage spoilage as a function of thermal treatment length, concentration of flavoring agents, and yeast inoculum. The logit models obtained for the three substances were extremely precise. The thermal treatment alone, even if prolonged for 20 min, was not able to prevent yeast growth. However, the presence of increasing concentrations of aroma compounds improved the stability of the products. The inhibiting effect of the compounds was enhanced by a prolonged thermal treatment. In fact, it influenced the vapor pressure of the molecules, which can easily interact within microbial membranes when they are in gaseous form. (E)-2-Hexenal showed a threshold level, related to initial inoculum and thermal treatment length, over which yeast growth was rapidly inhibited. Concentrations over 100 ppm of citral and thermal treatment longer than 16 min allowed a 90% probability of stability for bottles inoculated with 10⁵ CFU/bottle. Citron gave the most interesting responses: beverages with 500 ppm of essential oil needed only 3 min of treatment to prevent yeast growth. In this framework, the logistic regression proved to be an important tool to study alternative hurdle strategies for the stabilization of noncarbonated beverages.

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* Corresponding author. Mailing address: Dipartimento di Scienze degli Alimenti, Università degli Studi di Bologna, Sede di Cesena, Piazza G. Goidanich, 60, 47023 Cesena, Italy. Phone: 390547636132. Fax: 390547382348. E-mail: fausto.gardini{at}unibo.it

Published ahead of print on 6 July 2007.

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Applied and Environmental Microbiology, September 2007, p. 5580-5586, Vol. 73, No. 17
0099-2240/07/$08.00+0     doi:10.1128/AEM.00351-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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