[PhilGeis]

Yes the combination is safe enough.  A formaldehyde releaser (e.g. DMDM hydantion, Germall, Germal II) with parabens was the most common preservative system through the latter 2 decades of the last century.

You should add EDTA.

[PhilGeis]

Tho DMDM hydantoi is high and I’d prefer nbezoate or IPBC over sorbate,  there’s no obvious reason your combination should be not work if pH is ok..

[PhilGeis]

Add rinse off (esp. surfactant based) or leave on emuslion.

[PhilGeis]

PhilGeis said:

Please heed Graillotion’s comments.    The objective oif preservation per FDA and EU is to protect in use.   A preservative system good “enough for a few  months” is like not enough.

Is LIKELY not enough.  I’m not in high school.

[PhilGeis]

Please heed Graillotion’s comments.    The objective oif preservation per FDA and EU is to protect in use.   A preservative system good “enough for a few  months” is like not enough.

[PhilGeis]

Climatechangeanxiety said:

@PhilGeis ok, so then I’ll try Sodium Benzoate, seems to be the popular rec on this board! Separately, do you think my use of maltodextrin makes it a greater “bug food” source, therefore might I need to increase my percentage of preservative?

Thank you in advance for your expertise! 

Assume you mean Na benzoate with benzyl alcohol?  I’d add EDTA and would not be that concerned that maltodextrin is bug food as much as its effect on preservatives.   Cepacia can grow in distilled water.

[PhilGeis]

pH (via pKa) is a controlling factor for organic acids - benzoic and sorbic - efficacy.  In combination with some surfactants (incl those commonly used for shampoos etc.) , the effective benzoic acid pKa and pH range for efficacy for  is greatly increase - approaching neutrality.    This has not been observed fior sorbic acid.

[PhilGeis]

Is this for personal use?  Didn’t see 1-3 months self life mentioned.   Are you heating your “tap water” or is this cold process?
Reducing “bug food” is not going to mean you need less preservation.  The common contaminats of shampoos (esp. cepacia)  can grow quite well in distiled water.

I’ve seen some degree of synergism with benzyl alcohol and benzoate but you will need a chelator.  The cosmetic market has largely gravitated to benzoate over sorbate, esp. in the surfactant context.

Historically orgniac acids, with parabens, were the go-to preservatives.  The development of cold-process, surfactant-based shampoos back in the 1930’s found them  pretty useless, and the industry shifted to formaldehyde with L’Oreal’s Dopal and P&G’s Drene.

Is “eco-friendly” your marketing claim?

[PhilGeis]

Probably not - tap water typically includes pseudomonads - esp. P . aeruginosa.    Chloromethylisothiazolinone is the most commonly- used primary preservative in surfactant products.  Suggest use with Na benzoate and EDTA.   

[PhilGeis]

Please let us know how it works .

[PhilGeis]

Help me understand, please.  I understood your consideration that the product was “self-preserving” - why did you think that possible?  Is there unique chemistry?

Be aware the preservative test evaluates speed and extent of kill, not growth inhibition.

[PhilGeis]

I encourage folks to design a system that should work (theoretically effective against Gram -/+ and fungi) and then confirm it works vs these in challenge testing both as made and after ageing.  Passing a classic USP 51 (as EP or ISO) is not a guarantee.  Prrservatives help in manufcturing but are primarily intended (as specified by FDA and EU cosmetic directive) to protect consumers in use and USP is not validated fpr that.

[PhilGeis]

There is a reason every cosmetic product on the market includes preservatives.  
Why would you assume your product is uniquely “self-preserving.”

[PhilGeis]

Andraous said:

I am doing a chalenge test before using any preservative 

Why?

[PhilGeis]

Coke cola?  A single-use product in a pressurized, herrmetically-sealed vessel at a prohibitive pH?  Coke is clearly irrelevant.

Benzoic acid (Na benzoate) as preservative has a substantial Gram negative gap.  One need merely look at COSMETIC products now on the market to see its limited use - and virtually always as a secondary preservative.

Please - preservation is a serious effort.  Infections from contaminated cosmetics have resulted in blindness and even death.  If you don’t know the subject well, please do not offer casual suggestions.

[PhilGeis]

Sodium benzoate by itself is not adequate.   A simple check of cosmetic labels (not just for micellar water) shows virtually none using that option.  Pseudomonads eat benzoate.

[PhilGeis]

Try to other biugunaide 1st - polyaminopropyl biguanide.

[PhilGeis]

From the big company cosmetic experience, I’ll offer that it’s both acquisition and development - rarely acquisition only to block others.   Cosmeticss are so dynamic that first to market with a unique product/claim/compelling ad is much more of a win than slowing others - even if possible. 
As consumers are more convinced of extravagant claims when combined with extravagant precetag, technology cost is often not a barrier.  But advertising (even to puffery) is a factor in convincing without great technology.

[PhilGeis]

Another biguanide -  polyaminopropyl biguanide.

[PhilGeis]

Think EU cosm directive allows 0.1% with stipulation - “Not to be used in applications that may lead to exposure of the end-user’s lungs by inhalation.”
Are there other nonpermissive directives? 

[PhilGeis]

Concentration and formula dependent.  

[PhilGeis]

Irritation effect ? Is this from experience or heresay?  Glycols help but that still at minimum leaves a fungal gap. IPBC is any option - some use PHMB.

[PhilGeis]

Please work off water activity of the product, not percentage of any ingredient.   As a stand-alone agent of preservation, water activity should be less than 0.7.  As shown in the attached, you’ll need much greater levels for the polyols in aq. solution - e.g. >60% propanediol.  As pharma said, lesser levels may contribute but  please measure water activity of the product as the control element not their %. per se.   and be aware - lowering Aw will inhibit but not necessarilly kill - and may not contribute in  challenge test.

https://hal.archives-ouvertes.fr/hal-00301063/docuent
and
https://www.researchgate.net/publication/266083369_Optimization_of_cosmetic_preservation_Water_activity_reduction#fullTextFileContent

[PhilGeis]

count  yes - but “recognized pathogens” is not enough.  An y Gram negative bacteria?

[PhilGeis]

Formaldehyde releaser, organic acid if pH works.  Is context rinse off  or leave on?  Hot process?  How clean is your otameal nd what is package design?