Application of natural antimicrobials for food preservation
“THE NATURAL ALTERNATIVE - antimicrobial compounds derived from nature as
an alternative to synthetic preservatives in food”
Antimicrobials from microorganisms:
 Many microbes as part of their defence mechanism produce chemicals which inhibit
the growth of other microbial species (that is definition of antimicrobial).
“Bacteriocins” are antimicrobial proteins which have a great potential these are
produced by both gram negative and gram positive bacteria. And these compounds
are also produced by lactic acid bacteria they are referred as “lantibiotics” and an
interesting area for food manufacturers. Lactic acid bacteria are generally harmless to
food as they cause detectable food spoilage only when they are in very large number
and they are part of products like cheese and fermented meat. So the ability of
bacterial strain that produce Bacteriocins and lantibiotics can be safely exploited, to
produce these antimicrobials i.e. Bacteriocins and lantibiotics by using the bacteria in
starter cultures or even ending them to certain foods. A very important thing is that
these lantibiotics are not used as therapeutic agent so there is no issue of developing
antibiotic resistance.
 “Nisin” is most important bacteriocin in food preservation is commercially used now
days. It is a stable polypeptide compound produced by some strains of “Lactobacillus
lactis”. It is also approved safe by USA and many other countries.
 Other bacteriocins of special interest include “pediocin”, a stable protein produced by
strains of “Pediococcus acidilactici”. This antimicrobial is generally regarded as safe
(GRAS).
What is role of thimerosal in vaccines? Why are some vaccines noted to be
"thimerosal-free" while some are "thimerosal-reduced"? What is the
difference between "thimerosal-free" and "preservative-free"?
“Thimerosal” is a preservative that has been used in some vaccines since the 1930's.The
concentrations which found in vaccines, these concentrations meet the standard set by the
United States Pharmacopeia; that is, it kills the specified challenge organisms and help to
prevent the growth of the challenge fungi. Since the use of thimerosal, it has a long record of
safe and effective use preventing bacterial and fungal contamination of vaccines. And also
that it establishes no ill effects other than minor local reactions at the site of injection i.e. are
a mild swelling or inflammation.
When Thimerosal is added at the end of the manufacturing process it acts as a preservative to
prevent bacterial or fungal growth in the event that if the vaccine is accidentally
contaminated, which can happen because of the repeated puncture of multi-dose vials. When
thimerosal is used as preservative in vaccines, its concentrations in vaccines is up to 0.01%
(50 micrograms thimerosal per 0.5 mL dose or 25 micrograms mercury per 0.5 mL dose). In
some cases, thimerosal is used during the manufacturing process and is present in small
amounts in the final vaccine (1 micrograms mercury or less per dose).
The term "preservative-free" indicates that no preservative (thimerosal or anything else) is
used in the vaccine; however, traces used during the manufacturing process may be present in
the final formulation. For example, some vaccines may be preservative-free but may contain
traces of thimerosal.
Likewise, the term "thimerosal-reduced" usually indicates that thimerosal is not added as a
vaccine preservative, but trace amounts (1 micrograms mercury per dose or less) may remain
from use in the manufacturing process. Such trace amounts are not felt to be clinically
significant, nor would they result in exposure exceeding any federal guideline for mercury
exposure. Vaccines may be termed "thimerosal-free" if no thimerosal can be measured; i.e.,
thimerosal content is below the limit of detection.