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Although the antimicrobial activity of some spices and herbs is documented, the normal amounts added to foods for flavor is not sufficient to completely inhibit microbial growth. The antimicrobial activity varies widely, depending on the type of spice or herb, test medium, and microorganism. For these reasons, spice antimicrobials should not be considered as a primary preservative method (6). However, the addition of herbs and spices can be expected to aid in preserving foods held at refrigeration temperatures, at which the multiplication of microorganisms is slow.Zaika (20) has given an excellent summary of the antimicrobial effectiveness of spices and herbs. A partial listing of this summary is as follows.
- Microorganisms differ in their resistance to a given spice or herb.
- A given microorganism differs in its resistance to various spices and herbs.
- Bacteria are more resistant than fungi.
- The effect on spores may be different than that on vegetative cells.
- Gram-negative bacteria are more resistant than gram-positive bacteria.
- The effect of a spice or herb may be inhibitory or germicidal.
- Spices and herbs harbor microbial contaminants.
- Spices and herbs may serve as substrates for microbial growth and toxin production.
- Amounts of spices and herbs added to foods are generally too low to prevent spoilage by microorganisms.
- Active components of spices / herbs at low concentrations may interact synergistically with other factors (NaCl, acids, preservatives) to increase preservative effect.
- Nutrients present in spices / herbs may stimulate growth and/or biochemical activities of microorganisms.