This organic acid inhibits molds but not yeasts. It occurs in some foods as a result of natural processing. It is present in Swiss cheese at concentration up to 1%, where it is produced by the bacterium Propionibacterim shermanii (Beuchat 2000). Since, yeast are typically unaffected, the acid can be added to bread dough without interfering with leavening (Ranun 1999).
In the food industry, propionic acid is often used as a sodium or calcium salt (Ray 2001). Propionates are used primarily to inhibit molds in bakery goods. In addition to their antimycotic properties, propionates will inhibit Bacillus mesntericus, the rope causing bacterium. Propionates are also used in a limited extent to inhibit mold growth in processed cheese.
The antifungal activity of propionic acid is weak compared to the other organic acids. Therefore, propionates must be used in relatively high concentrations to be effective. As with other organic acids, the pH value of the food to be preserved affects antimicrobial activity. Because of its low dissociation constant, propionic acid is active in a pH range similar to that of sorbic acid (Eckland 1990).
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