Oil-in-Water Emulsion as a Model System to Study the Growth of Escherichia coli O157:H7 in a Heterogeneous Food System

Oil‐in‐water emulsions (hexadecane, minimal media M9], and Tween 20) were used as model system to study the growth of Escherichia coli O157:H7. Stationary‐phase cell density decreased as the hexadecane concentration was increased (0%, 5%, 20%, and 40% w/v]) and biphasic growth was observed in 40% emulsions supplemented with 0.4% glucose. Thin aggregate fimbriae (curli) were observed using SEM, and a greater percentage (Ps <0.001) of curli‐producing colonies were isolated from 40% emulsions. Heat resistance (55 °C) of emulsion‐grown cells was greater than broth‐grown cells, indicating that growth and physiology under heterogeneous conditions differ from cells grown in liquid.