Home Cosmetic Science Talk Formulating Does 20% sodium chloride in water need preservative?

  • Does 20% sodium chloride in water need preservative?

    Posted by abdullah on October 10, 2021 at 2:08 pm

    I usually make 20% sodium chloride in water in 180kg size and store it and use it in shampoo. So do i need to add preservative to this solution when i am storing it? 

    abdullah replied 2 years, 6 months ago 3 Members · 8 Replies
  • 8 Replies
  • PhilGeis

    Member
    October 10, 2021 at 5:03 pm

    20% is not prohibitive to microbial growth.

  • pharma

    Member
    October 10, 2021 at 6:15 pm

    +20% salt only allows growth of extreme halotolerant and extreme halophilic microbes (CLICK) which are usually only found in environments naturally very high in salt. Hence, there is a very high chance that you won’t have microbial growth (however, 20% salt doesn’t mean contaminating microbes will die in there) especially if you were to cool your batch or boil it before ‘canning’.

  • PhilGeis

    Member
    October 10, 2021 at 6:34 pm

    Moderate halophiles can grow up to 20% salt and halophiles are among the contaminants of many household and industrial products - minerals/salts themselves are often the source.
    Pharma makes a good point - they are heat sensitive.  Boil it and seal it - or take your chances.

  • pharma

    Member
    October 10, 2021 at 7:26 pm

    PhilGeis said:

    …are among the contaminants of many household and industrial products - minerals/salts themselves are often the source…

    Good you mention this, it completely skipped my mind. Totally makes sense especially regarding sea salt. Saline lakes and salt evaporation ponds are home to a plethora of ‘weird’ microbes such as halobacteria (hence the red colours) which aren’t found elsewhere… as it seems with the exception of the unsuspicious salt shaker in everyones kitchen. Hmm… in hindsight it sounds so obvious (*feeling stupid right now*).

  • PhilGeis

    Member
    October 10, 2021 at 11:54 pm

    Pharma - and worse - the damned things are so hard to culture, it takes forever to figure out the problem (discolor, clouding, slime) is microbial. 

  • abdullah

    Member
    October 11, 2021 at 3:14 am

    @Pharma @PhilGeis then what percentage of salt is prohibitive to microbial growth?

    Also does 35 g/100 ml solubility mean 35%?

  • PhilGeis

    Member
    October 11, 2021 at 10:28 am

    Not sure there is a limit or at that level concern is more potential than reality.
    Yup 35% by weight.

  • abdullah

    Member
    October 11, 2021 at 11:54 am

    @PhilGeis thanks

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