RSP wrote:
>> Hi all,
>> I am performing preservative challenge testing on various cosmetic
> products. I am running a test to determine if the Aspergillus niger
> recovered from failed challenge tests is in the form of vegetative mold
> or spores. I am heating my dilutions up to between 65-70 degrees
> Celcius and plating these dilutions and observing for growth. Is this
> temperature high enough to destroy all vegetative forms of the mold and
> only allow for the recovery of mold spores. The A. niger strain being
> used is the one called for by USP XXIII under preservative challenge
> testing, the ATCC strain number escapes me at this time.
>> Thanks
> Rick
Rich:
Rather than use this fungus (I've never heard of an A. niger
contaminated cosmetic), I'd look to the literature for a fungus that
actually casues problems in this regard. After finding such as fund
gus, I'd perfrom the necessary experiments to understadn the effect of
heat for that fungus. This is important since spores differ in a number
of factors, inclduing heat resistance.
Bottom line is that you should NOT rely on the USP. It was and is a
compendial method based on the best guess of folks with experience in
the field many years ago and directed at very specific applications, not
including cosmetics.
