Preservation nightmare

So we made this  serum for a client.
Was a simple water, niacinamide, hyalauronic acid, aloe Vera, hexapeptide 8 with a carbomer formula. Customer didn’t want to use parabens so we used Benzyl Alcohol and Dehydroacetic Acid as preservative. Stability and microbiologically tested it and all was fine.

a year and half later we have found that after a year, it turns brown. Turns out it’s Mould and yeast (waiting for full microbiogy report). Completely stooped as this has never happened before.

tested all the raw materials and everything seemed to be fine but have my doubts about the dried aloe Vera. We are using the 200x aloe Vera dry powder at 0.5 percent and I think it’s the culprit because we have  had issues with preserving it for longer than six months with the above preservative in another formula we were testing recently. Starts off all ok and after about three months the preservation system just fails because of it. 

now we have added dm dm hydantoin at 0.3 to the above  Benzyl Alcohol and Dehydroacetic Acid at 0.8 percent . will wait and see what happens after a challenge test 
. Any comments on this ? 

also tried the above preservative (Benzyl Alcohol and Dehydroacetic Acid at 0.8 percent with urea at 0.3 percent - again let’s wait and see. Any comments on this combination ? 

HOWEVER- we have another product - a facial mist -  which is totally water based with glycerin and witch hazel and aloe Vera (0.1 percent) and parfum.... and we have preserved that with phenoxyethanol 0.4 percent and urea 0.4 percent.  and we did test it perpetually last year every month for microbiology compliance for 6 months. But now I’m VERY SCARED whether it will remain preserved for a whole year because of the aloe Vera - which is a total nightmare to preserve -

can someone throw any light on blends of preservatives here ?

example
- above facial mist
-phenoxyethanol 0.4 percent and urea 0.4 ; do you think it’s fine or needs additions or over kill? 

Or if we use 
- DM DM Hydantoin enough on its own at 0.3 percent if we use that ? What other preservative works better with this ? Phenoxyethanol? 

Can’t find literature on which blends work best for very aqueous formulations (and with pesky ingredients such as this aloe Vera)

help please ! 

Comments

  • MarkBroussardMarkBroussard Member, Professional Chemist
    What is your final product pH?  Are you using a pre-neutralized carbomer or are you neutralizing the carbomer with one of the usual suspects?

    From what you have written, it would appear that perhaps your final product pH is above 6.0?  If so, that may be part of your problem.

    It would also help immensely if you added a chelating agent, plus a pH adjustment to below 6.0, if feasible.  Or, switch to a low-pH activating carbomer ... Ultrez 21 or 30, I forget which one starts gelling at pH 4.0
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • GuntherGunther Member

    a year and half later we have found that after a year, it turns brown.  
    Was the product marketed without a previous challenge test?

    Try making a test formulation preserved with high levels of parabens to see if the brown thing is the preservative failing, or actually oxidation or degradation.
  • Gunther said:

    a year and half later we have found that after a year, it turns brown.  
    Was the product marketed without a previous challenge test?

    Try making a test formulation preserved with high levels of parabens to see if the brown thing is the preservative failing, or actually oxidation or degradation.

  • It was a small batch made for there give aways. It was challenge tested which is why we are stumped. pH is 5.5. Cheating agent is EDTA. Carbomer is ELT 20 which needs to be neutralized via TEA 
  • MarkBroussardMarkBroussard Member, Professional Chemist
    Did you check to see if there was a pH drift to higher levels over time?
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • No pH drift as such for the one in question.

    However this is a good point. Because we made approx 20 samples over time (all over a year ago) which thankfully were still lying around. One sample which is VERY brown in colour has a pH of 8 as of today. The rest have same pH. 

    Very strange. Can’t remember how that happens. 

    What can we add in an aqeous formula so that pH doesn’t drift ? Never done this before. Sodium Glutanate ? What would you recommend ? Thank you for your help and comments thus far. 
  • MarkBroussardMarkBroussard Member, Professional Chemist
    A solution to your problem would be to use a high molecular weight Hyaluronic Acid as your gelling agent/thickener as opposed to carbomer or switch to a pre-neutralized carbomer or perhaps one of the Seppic gelling polymers.  That would allow you to eliminate the carbomer and the TEA which would simplify your manufacturing process and eliminate the potential for pH drift.


    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    See website for details www.desertinbloomcosmeticslab.com
  • Bill_TogeBill_Toge Member, Professional Chemist
    aloe vera is terrible for going brown, especially at high temperatures
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • MaxMax Member
    Hello, in term of preservative why not using something like Kathon, not the most friendly one but works everytime. as for the pH, would it be possible to use a buffer?
  • PerryPerry Administrator, Professional Chemist
    Another solution is to use an Aloe Vera extract which is a 1% solution in something like propylene glycol. 
  • ozgirlozgirl Member, PCF student
    The Benzyl Alcohol and Dehydroacetic acid preservative does discolour over time to give a yellow colour. Also definitely keep your pH below 6 for this preservative.
  • vjayvjay Member
    The Benzyl Alcohol and Dehydroacetic acid preservative does discolour over time to give a yellow colour. Also definitely keep your pH below 6 for this preservative. 

    need to change the preservative system and do the challenge test again
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