Dear colleagues and researchers
I have a question about the microbiological analysis of food products. Is there any way that we can remove the effect of an antibacterial agent such as natamycin on a product and then perform a microbial test? On the other hand, can antimicrobial agents be inactivated in the product before the microbial analysis?
Please note that on an industrial scale, we cannot produce the product once with and once without the preservative.
Ultraviolet light deactivates the Natamycin structure, it may be experimented. But efficacy of other antimicrobial agents can not be precisely calculated as the broken-down structure may still have some antimicrobial potent.
Dear Mehdi Mohammadian
Yes, insofar as possible, it is necessary to neutralize the preservatives present in a product prior to conducting microbiological tests for the count or absence of objectionable microorganisms. In general terms to all preservatives, for this purpose, there are three approaches that can be combined with each other:
1) Sample dilution, as long as it is not over-diluted to lose sensitivity in microorganism counts
2) Preservative removal by Filtration
3) Neutralization: The incorporation of neutralizing agents in first dilution is widely applied in the microbiological tests of pharmaceutical products, the most used neutralizers are lecithin and polysorbate 20 or 80. In the market, you can find a dehydrated culture medium based on TSB that contains lecithin and one must add posisorbate 20 before sterilizing.
Although I cannot give specific information for natamycin, I recommend that you start designing your microbiological assay based on this information.
Good luck.
As Mariana suggested, the simplest means is aqueous dilution. Have you tried that? Try to use such mechanical methods 1st, nonionic surfactants such as Polysorbates can inhibit some microbes. As natamycin (Pimaricin) is is so poorly soluble in water, surfactants might make it more available. Polysorbates are used in pharma and cosmetic testing as the smaller subset of microbes of concern are not though to be susceptible.
UV is silly - jt does not penetrate foods and, even if it did, would impact microorganisms that might be present.
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