100A-24 |
Optimizing combinations of aW, pH and antimicrobial agent concentration in inhibiting Eurotium chevalieri growth in Dulce de Leche: Influence of inoculum size |
C. D. Char1, S. GUERRERO2, L. Gonzalez, and S. M. Alzamora. (1) Industry. Natural and Exact Sciences School, Buenos Aires University, Ciudad Universitaria, Nuñez, Buenos Aires, 1428, Argentina, (2) Department of Industry. Natural and Exact Sciences School, Buenos Aires University, Ciudad Universitaria, Nuñez, Buenos Aires, 1428, Argentina “Dulce de Leche” is a typical argentine sweet spread prepared from milk concentrated by evaporation to about 70 % w/w total solids (aW ranging from 0.80 to 0.85) at atmospheric pressure with added sucrose, glucose, and vanillin.Growth of Eurotium chevalieri, a xerophilic mold, represents a severe problem in this type of products with high sugar concentration. The objective of this research was to evaluate the effect of the inoculum size (representing different levels of environment contamination) and the antimicrobial agent concentration in the mold growth in Dulce de leche formulated with different aW and pH values and stored at room temperature during 90 days. Different “Dulces de Leche” prepared with selected water activity (aW 0.85 or 0.80), pH (6.0 or 5.5), and potassium sorbate concentration (0, 500, 1000, 1500 or 2000 ppm) were poured into sterile Petri dishes . The dishes were inoculated in one central point with Eurotium chevalieri conidia suspension(@ 2. 107 conidia/ml). The selected inoculum sizes were 2.0, 5.0, 7.5 or 10 µL. The dishes were incubated at 25°C. Each condition was evaluated by triplicated. Time to growth and mold colony diameter were recorded as function of time during 3 months. Logistic regression was used in order to obtain polynomial equations to mathematically model (probabilistic) Eurotium chevalieri growth-no growth interface. The probability of growth diminished as aW and inoculum size diminished and as antimicrobial agent concentration increased. The lag phase did not significantly change with the inoculum size while the mold growth rate was greatly affected. Potassium sorbate concentration significantly influenced both kinetic parameters. The applied model permitted to calculate Eurotium chevalieri probability of growth when inoculated in the formulated media and the levels of variables potassium sorbate concentration and inoculum size in the combination for a pre-established probability level of 0.1. This study contributed to optimize operation conditions in order to obtain a safer product when fails occur during the hot filling process or when the product is stored for a long period of time.
Session 100A, Food Microbiology: General II
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