Is it true that herbs and spices prevent antimicrobial growth in foods they're added to?

A growing body of research suggests they can. However, the amounts normally added to foods is insufficient to completely inhibit microbial growth. Further, antimicrobial activity varies, depending on the food, microorganism, and herb or spice. As such, herbs and spices shouldn't be used as a primary means of preserving a food. Nevertheless, herbs and spices may aid in preserving foods at refrigeration temperatures since microbes grow slowly under those conditions.
 
Source(s):
Hospitality Institute of Technology and Management "Antimicrobial Effects of Spices and Herbs"