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Applied and Environmental Microbiology, November 2009, p. 7060-7069, Vol. 75, No. 22
0099-2240/09/$08.00+0     doi:10.1128/AEM.01045-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Design of an Experimental Viscoelastic Food Model System for Studying Zygosaccharomyces bailii Spoilage in Acidic Sauces{triangledown}

L. Mertens,1,2 A. H. Geeraerd,1,3 T. D. T. Dang,1,4 A. Vermeulen,1,4 K. Serneels,1,2 E. Van Derlinden,1,2 A. M. Cappuyns,1,2 P. Moldenaers,5 J. Debevere,1,4 F. Devlieghere,1,4 and J. F. Van Impe1,2*

CPMF, Flemish Cluster Predictive Microbiology in Foods ,{dagger} ,{dagger} Chemical and Biochemical Process Technology and Control Section (BioTeC), Department of Chemical Engineering, Katholieke Universiteit Leuven, W. de Croylaan 46, B-3001 Leuven, Belgium,2 Division of Mechatronics, Biostatistics and Sensors (MeBioS), Department of Biosystems, Katholieke Universiteit Leuven, W. de Croylaan 42, B-3001 Leuven, Belgium,3 Laboratory of Food Microbiology and Food Preservation, Department of Food Safety and Food Quality, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium,4 Applied Rheology and Polymer Processing Division, Department of Chemical Engineering, Katholieke Universiteit Leuven, W. de Croylaan 46, B-3001 Leuven, Belgium5

Received 7 May 2009/ Accepted 9 August 2009

Within the field of predictive microbiology, the number of studies that quantify the effect of food structure on microbial behavior is very limited. This is mainly due to impracticalities related to the use of a nonliquid growth medium. In this study, an experimental food model system for studying yeast spoilage in acid sauces was developed by selecting a suitable thickening/gelling agent. In a first step, a variety of thickening/gelling agents was screened, with respect to the main physicochemical (pH, water activity, and acetic acid and sugar concentrations) and rheological (weak gel viscoelastic behavior and presence of a yield stress) characteristics of acid sauces. Second, the rheological behavior of the selected thickening/gelling agent, Carbopol 980, was extensively studied within the following range of conditions: pH 4.0 to 5.0, acetic acid concentration of 0 to 1.0% (vol/vol), glycerol concentration of 0 to 15% (wt/vol), and Carbopol concentration of 1.0 to 1.5% (wt/vol). Finally, the applicability of the model system was illustrated by performing growth experiments in microtiter plates for Zygosaccharomyces bailii at 0, 0.5, 1.0, and 1.5% (wt/vol) Carbopol, 5% (wt/vol) glycerol, 0% (vol/vol) acetic acid, and pH 5.0. A shift from planktonic growth to growth in colonies was observed when the Carbopol concentration increased from 0.5 to 1.0%. The applicability of the model system was illustrated by estimating µmax at 0.5% Carbopol from absorbance detection times.

* Corresponding author. Mailing address: Chemical and Biochemical Process Technology and Control Section (BioTeC), Katholieke Universiteit Leuven, W. de Croylaan 46, 3001 Leuven, Belgium. Phone: 32 16 32 14 66. Fax: 32 16 32 29 91. E-mail: jan.vanimpe{at}cit.kuleuven.be

{triangledown} Published ahead of print on 25 September 2009.

http://www.cpmf2.be/.

Applied and Environmental Microbiology, November 2009, p. 7060-7069, Vol. 75, No. 22
0099-2240/09/$08.00+0     doi:10.1128/AEM.01045-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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