Home Cosmetic Science Talk Formulating Advanced Questions Preservative for rice powder product

  • Preservative for rice powder product

    Posted by talfoa on January 17, 2023 at 3:03 pm

    Hi guys!
    I need help with a formula which is an anhydrous powder mainly based on Oryza sativa rice starch.

    The main problem is the efficency of the preservative. 

    Despite it is anhydrous, the product is a shampoo powder and therefore water contamination can not be excluded and a preservative is reconmended due to the vegetal origin of the main ingredient.  However, i could not be able to find a suitable preservative system capable to let the product pass the challenge test, expecially for fungi. 
    I tryed with both liquid and solid (which i finely crushed) preservatives but i am not sure if it is possible to homogeneously disperse them in the powder and more problematic, if the preservatives are in general active in powder products. Creams and gel based on rice are ok and they pass the challenge test easily and therefore is not a problem of “too much food” for fungi and bacteria.

    So, this is the scenario. Some of you have any suggestion to how i can solve this? Any comment or experience would be extremely apreciated.

    Thank you in advanded!

    PhilGeis replied 2 months, 3 weeks ago 5 Members · 9 Replies
  • 9 Replies
  • PhilGeis

    January 17, 2023 at 3:40 pm

    The final product is an anhydrous powder?  How are you testing it for preservation, and what is bioburden of the rice starch?   
    Think you need to generate some in-use data - not only direct water contamination but taking up water from humid shower environment.

    Please drop the “too much food’ context - bacteria can grow in distilled water and fungi on basement walls.

  • talfoa

    January 18, 2023 at 8:57 am

    Many thanks Phil for the answer. Yes, the final product is an anhydrous powder. The challenge test is performed by an external lab so i don’t have control on this. To be honest, I am not an expert in the field but the rice starch is theoretically steril and also the external service reported that the product is not contaminated at the start of their analysis. Basically, after they inoculate bacteria and fungi the preservative is not able to reduce them. I added the maximum concentration allowed of the preservatives together with up 2 boosters.

    You are right, we already consider the well-known hygroscopicity of rice.

    So, now the general question is: How preservatives can act in anhydrous powder? This come from the fact that the corresponding cream formula is protected by the same preservative system tested for powder.

    Thank you! 

  • PhilGeis

    January 18, 2023 at 12:19 pm

    There is no challenge test that’s appropriate and applying aq. product standards is not appropriate.
    Your worry is growth of fungi - if its wet enough for bacteria, you haven’t a chance.  Get the lab to run AW (water activity) on product held at humidified conditions.
    What is the pres system you’ve tried?

  • talfoa

    January 18, 2023 at 4:21 pm

    I am really sorry but i don’t get the point of performing the AW under humidified conditions. The AW resulted so far (after 24h of conditioning) are 0.08 to 0.13. 
    So far i tested:
    Solid: Sodium benzoate+chlorphesin+decylene glycol

    liquid: Phenoxyethanol, Caprylyl, Glycol Decylene Glycol

  • PhilGeis

    January 18, 2023 at 5:27 pm

    Aw tells you the risk in use.  Your primary risk is humidity and fungi.  Packaging must protect vs. direct water addition.  

  • Ghita37

    January 21, 2023 at 9:28 pm

    Hello everyone/ 
    What preservative is best for a peel mask made of rice powder? 

    Many thanks 

  • DoctorBotanica

    February 6, 2023 at 2:51 am

    Slightly off topic, could essential oils theoretically help with the shelf life of the product and possibly act as a deterrent for contaminants? I used to make a rice powder for hair and after several years of being in the bathroom I haven’t detected any contaminants at least through sight and smell. I don’t have the resources to test it in a lab but would love to know what the scientific understanding is on this.

  • Budgie

    September 27, 2023 at 7:05 pm

    A few years ago I wanted to submit a formula with rice to my assessor and I was advised they couldn’t do an assessment because of something to do with certain bacteria/mould etc. They used to suggest a preservative system but for this there was nothing. I would love to find out if there is a PS that can tolerate rice in cosmetic formulas and pass the required tests.

    • PhilGeis

      September 28, 2023 at 8:39 am

      Can you offer any more detail? This sounds like a lot of BS for an officious assessor.

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