88D-16 |
Mold growth in milk sweet as affected by water activity, pH and potassium sorbate |
S. M. ALZAMORA1, C. Char, S. N. Guerrero, and H. H. L. González. (1) Dept. of Industry - Natural and Exact Sciences School, University of Buenos Aires, Ciudad Universitaria, Buenos Aires, 1428, Argentina
Xerophilic mold growth represents a severe problem in concentrated foods since aw is not sufficiently low to prevent them from growing. In particular, "dulce de leche" (milk sweet) is a typical Argentine sweet spread prepared from milk concentrated by evaporation to about 70%w/w total solids (aw The objective of this research was to evaluate the effect of aw (0.75; 0.80 or 0.85), pH (5.9 or 5.5) and potassium sorbate (0 or 1,000 ppm) on the growth response of Penicillium simplicissimum, Aspergillus fumigatus and Eurotium chevalieri in milk sweet stored at room temperature. The mixture of milk and additives was evaporated to different total solids to obtain "dulce de leche" with aw 0.75, 0.80 or 0.85 ("natural" pH @ 5.9). For some experiments, the pH of the final product was adjusted with citric acid to 5.5 and/or 1,000 ppm potassium sorbate were added. The different "dulces de leche" were poured into Petri dishes, inoculated with 10 mL of each mold conidia suspension (@ 1.2 ´ 107 conidia/ml) and incubated at 30ºC. Time to growth and mold colony diameter were recorded as a function of incubation time. In those systems formulated with the preservative, no growth was detected after at least 120 days storage. In the systems where growth was observed (in general systems without sorbate), the mold behavior was not affected by the pH value, while the lag times increased to different degrees as aw decreased depending on the specific mold assayed. These results show the important role of potassium sorbate to inhibit the mold growth when hot filling is not adequate and/or the product is stored at room temperature for long periods of time.
Session 88D, Food Microbiology: General
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