Modeling the microbial interaction and the death of Escherichia coli O157:H7 during the fermentation of Spanish-style green table olives

• Published in: Journal of food protection Vol. 66; no. 7; pp. 1166 - 1175
• Main Authors: Skandamis, P.N, Nychas, G.J.E
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 01.07.2003
• Subjects: acid production; acidification; bacterial contamination; Biological and medical sciences; Colony Count, Microbial; dynamic models; equations; Escherichia coli; Escherichia coli O157 - growth & development; Escherichia coli O157:H7; Fermentation; food contamination; Food industries; Food Microbiology; food pathogens; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; glucose; Glucose - metabolism; Hydrogen-Ion Concentration; Lactic Acid - metabolism; lactic acid bacteria; Lactobacillus - physiology; mathematical models; microbial competition; microbial growth; Models, Biological; nutrient availability; nutrient consumption; Olea - microbiology; olives; protonated acid; starter cultures; sucrose; Sucrose - metabolism; yeasts; Yeasts - physiology; Europe; Spain; Olive; Microorganism interrelationships; Fruit; Escherichia coli; Predictive microbiology; Bacteria; Fermentation; Modeling; Enterobacteriaceae
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-66.7.1166

A dynamic model was developed to describe the microbial interaction and the death of Escherichia coli O157:H7 during the fermentation of green table olives with two different starter cultures supplemented with different amounts of glucose and sucrose. The model consists of six differential equations including substrate (glucose or sucrose) consumption and product inhibition (protons and protonated lactic acid). Experimental data from a multifactorial experiment were used to fit the model, and the model was verified with independent data. Yeasts, which were the only competitors of starters, managed to reach levels equal to those of starters by the end of fermentation. The decrease in the level of Escherichia coli O157:H7 was proportional to the initial amounts of glucose and sucrose added. However, in the majority of cases, the death of the pathogen occurred in three successive phases, with a short mediate survival period. The production of lactic acid during fermentation seems to be the main factor governing the behavior of this pathogen under such stress conditions. Therefore, the death of E. coli was modeled with a differential equation that included the effects of pH, protonated lactic acid, and the protective effect of the substrate.