89D-2 |
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E. PALOU, Center for Engineering Education, Univ. de las Americas, Puebla, Cholula, Puebla, 72820, Mexico and A. Lopez-Malo, Dept. de Ingeniería Química y Alimentos, Univ. de las Américas-Puebla, Santa Catarina Mártir, Cholula, Puebla, 72820, Mexico. The inactivation or inhibition pattern of microorganisms exposed to lethal or inhibitory agents or environments can be described by a dose-response curve. Antimicrobial activities of extracts from several plants and spices used as flavoring agents in foods have been recognized for many years. However, data on the effect of extracts in combination with other factors on mold growth is scarce. Additionally, there are no models to predict performance when natural preservatives are used in combination with other factors. The objective of this research was to evaluate at selected aw (0.94, 0.91, or 0.86) and pH 3.5 the effects of different concentrations of selected cinnamon extracts (alcoholic extract or ethyl acetate extract) on Aspergillus flavus and A. niger radial growth rate and to model mold response using the Fermi function parameters (Pc and k). Solid media formulated with every factor combination was inoculated with 103 spores/ml, and incubated at 27ºC up to 30 days. Periodically during incubation, mold colony diameter was measured to determine radial growth rate. Important differences in Pc and k were observed among aw, type of extract and molds. Pc decreased as aw decreased and varied from 186 ppm (A. flavus, aw 0.94, alcoholic extract) to 108 ppm (A. niger, aw 0.86, alcoholic extract). A large Pc value represents less effect on radial growth rate; thus higher concentrations are needed to inhibit growth. Increasing antimicrobial concentration at aw 0.86 had a dramatic effect on A. flavus and A. niger radial growth rate since k values were smaller than for higher aw. Fermi function adequately describes dose-response curves for tested extracts, and could be used to evaluate critical antimicrobial concentrations (Pc,), as well as to model flat or very sharp (with the k values) inhibition patterns.
Session 89D, Food Microbiology: Antimicrobial effects on foodborne microorganisms
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |