Re: preservatives

January 15, 2004

>#1 When a preservative is used I understand that it extends

>the " shelf life " of the product.

When i think of the " shelf life " of a product, I think about how long

that product will be physically stable and sellable.

Quoting from the Principles of Preservation

http://health.groups.yahoo.com/group/Cosmeticinfo/files/Preservative_Info/Princi\

ples_of_Preservation.pdf

" A preservative is defined as a material that will prevent the growth

of or react with and destroy microorganisms that might damage the

product or create a health hazard by growing on or in the product. "

>Is there still a limit to that " shelf life " ?

In theory, there is always a self life for any man made product.

>Is there a recommended " use by " date?

A " use by date " is used in drugs. Over a period of time, the activity

of an active ingredient will change, hence the " use by date " .

>#2 If ,after I get some experience under my belt, I come up with a

>formula that I might like to sell how do I go about getting a

>challenge test done? Does a test need to be done on each batch?

A challenge test is the last thing that you do when creating a product.

If the product passes the challenge test, you should have to do it

again. An Aerobic Plate Count (APC) is run on every batch to make sure

that it is not contaminated.

Quoting from the Principles of Preservation

http://health.groups.yahoo.com/group/Cosmeticinfo/files/Preservative_Info/Princi\

ples_of_Preservation.pdf

" Preservative efficacy testing is an essential part of substantiating

the safety of a product. Most large personal care manufacturers have a

microbiology staff that performs preservative testing. Smaller

companies may use the services of an outside micro lab for testing. The

goal of efficacy testing is to determine, not only which preservative

system to use against the strains of microorganisms to which the

product may be exposed, but also that concentration of preservative

that will preserve the product during manufacturing and under use

conditions.

The microbiologist's most important procedure for testing if a sample

is contaminated is the Aerobic Plate Count or APC. The APC is used to

determine the number of viable organisms present in a sample. This is

carried out on agar plates that contain materials that support

microbial growth. Each colony is assumed to represent growth from a

single organism.

Preservative testing is often lengthy and time consuming. Therefore,

there are a number of fairly rapid screening methods that are used by

microbiologists. The most common of these is called the Minimum

Inhibitory Concentration or MIC test. This test determines the lowest

concentration of the preservative system that will retard microbial

growth. It uses inoculations of standard organisms that are

representative of both Gram-positive and Gram-negative bacteria, yeast

and mold.

In light of the previous discussion of all of the factors that may

influence the activity of a preservative, it is essential to test the

preservative system in the actual finished formulation. This is done by

means of an Adequacy of Preservation Challenge Test or Challenge Test.

For this test, the preservative is generally incorporated into a

product base and " challenged " or inoculated with a large number of

standard organisms along with various " house " organisms. " House "

organisms are organisms that have adapted to a particular product or

environment and whose metabolic activity is varied from the norm of its

particular strain. They are often unique to a manufacturing plant.

Assays are performed over a predetermined period of time, typically 4

to 8 weeks, sometimes with a rechallenge at 3 or 4 weeks. "

Maurice

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Maurice O. Hevey

Convergent Cosmetics, Inc.

http://www.ConvergentCosmetics.com

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January 15, 2004