In general, aerobic mesophilic count and total yeast and mold count
inozonated pears were lower than in untreated pears over the storage
period, confirming the ozone microbicidal capacity as one of the most
potent known sanitizers [9]. There was rapid growth of aerobic
mesophiliconly in non-zonatedpears (Table 2). Growth of filamentous
fungi and yeasts occurred only from day 9 of storage in non-ozonated
pears, which was coincidentally accompanied by a decrease in the
aerobic mesophilic count and probably a result from the decrease in
pH (Figure 4). The pH of non-ozonated pears at the beginning of the
storage period was 5.4 and after 13 days decreased to 4.3. This trend is
observed in microbial counts because, in favorable conditions, bacteria
grow more rapidly than fungi. Besides, microorganisms generally grow
between pH 6.6 and 7.5, but fungi and yeasts are less demanding and
pH below 4.0 favors their growth [31]. The inactivation/inhibition of
micro-organism development by ozone through the oxidation of vital
cell components is a complex process in which the gas acts on parts of
the membrane and the cell wall, such as unsaturated fatty acids,
glycoproteins and glycolipids, as well as elements of the cell content
[22,32,33].