The interaction of Penicillium expansum Link, Colletotrichum acutatum, and Botrytis cinerea Pers.:Fr. with Listeria monocytogenes on osmotically dehydrated apple slices was evaluated. In mineral analyses of the slices, the calcium content of the peel and flesh tissues increased by 4- and 11-fold, respectively, when processed in 2% CaCl2. These slices also exhibited less decay by P. expansum, C. acutatum, and B. cinerea. Inoculation of slices with P. expansum resulted in a decrease in the pH of the flesh tissue at the infection site, while the pHs of slices infected with C. acutatum and B. cinerea increased and remained stable, respectively. Total mold population increased in wounds inoculated with P. expansum or C. acutatum. The presence of L. monocytogenes in the wounds did not significantly affect mold growth. The association of P. expansum and L. monocytogenes on apple slices resulted in a decrease in the bacterial population, whereas L. monocytogenes survived when slices were inoculated with C. acutatum. When associated with B. cinerea, there was a fourfold decrease in the L. monocytogenes population when slices were treated with 2% CaCl2. The total aerobic population was not significantly affected by the type of microorganism added to the wounds or by the osmotic treatment. These data show that osmotic dehydration with 2% CaCl2 combined with 20% sucrose limits decay of apple slices and does not promote bacterial or total aerobic population growth.

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