Validation of predictive growth models describing superatmospheric oxygen effects on Pseudomonas fluorescens and Listeria innocua on fresh-cut lettuce

• Published in: International journal of food microbiology Vol. 111; no. 1; pp. 48 - 58
• Main Authors: Geysen, S., Escalona, V.H., Verlinden, B.E., Aertsen, A., Geeraerd, A.H., Michiels, C.W., Van Impe, J.F., Nicolaï, B.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-2006; Elsevier
• Subjects: aerobes; bacterial contamination; Biological and medical sciences; Carbon Dioxide; Consumer Product Safety; Fluorescence; fluorescent dyes; food contamination; Food industries; Food Microbiology; food packaging; Food Packaging - methods; food pathogens; food storage; Fresh-cut butterhead lettuce; fresh-cut foods; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; genes; green fluorescent protein (GFP); head lettuce; inoculum density; Kinetics; lactic acid bacteria; Lactuca - microbiology; Lactuca sativa var. capitata; Listeria - growth & development; Listeria innocua; mathematical models; microbial growth; Model validation; Models, Biological; Modified atmosphere; modified atmosphere packaging; oxygen; Oxygen - pharmacology; plate count; predictive microbiology; Pseudomonaceae; Pseudomonas fluorescens; Pseudomonas fluorescens - growth & development; storage temperature; Superatmospheric oxygen; Temperature; Time Factors; virulence; Superatmospheric oxygen; Model validation; Carbon dioxide; Fresh-cut butterhead lettuce; Pseudomonas fluorescens; Modified atmosphere; Listeria innocua; Pseudomonadales; Validation; Oxygen; Vegetables; Growth; Lettuce; Bacteria; Pseudomonadaceae; Models
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2006.04.044

Two microbial growth models predicting the growth of
Pseudomonas fluorescens and
Listeria innocua at superatmospheric oxygen and carbon dioxide concentrations at 7 °C were validated on fresh-cut butterhead lettuce. Cut lettuce was inoculated with the same strain of
L. innocua as the in vitro experiments. The
P. fluorescens strain was tagged with a gene encoding green fluorescent protein (GFP) in order to distinguish the inoculated strain from contaminating
Pseudomonaceae. Also growth of aerobic mesophilic and lactic acid bacteria was monitored during the experiments. The suggested
P. fluorescens model was appropriate to predict growth on cut lettuce.
L. innocua on the other hand, grew considerably slower under in vivo circumstances than predicted. CO
2 had a growth promoting effect on
L. innocua growing on cut lettuce, whereas in vitro an inhibiting effect was observed. Validation parameters are calculated and hypotheses to explain the discrepancy between predicted and observed growth of
L. innocua are provided.