sour milk

[sososo]

I noticed that sour milk gives a harder soap than regular milk. So, everytime when I use milk in a recipe, I keep the milk at room temperature for 3-4 days. Then, of course in the freezer before I use it.
Do you notice this too? Do you have an explanation for this?

 

[lsg]

I imagine it is the lactic acid in the sour milk.

 

[sososo]

I imagine it is the lactic acid in the sour milk.

Oh, now I understand:
latic acid + lye = sodium lactate

And, as we know, sodium lactate has the property to make a hard soap.

Thank you.

 

[lsg]

I don't know about that. "Sodium Lactate is naturally derived from the fermentation of Lactic Acid."

http://www.newdirectionsaromatics.com/sodium-lactate-preservative-p-1813.html

 

[DeeAnna]

Well, hmmm, I beg to differ with NDA. Lactic acid, not sodium lactate, is created by fermenting sugars or starches.

Sodium lactate is the simple salt created by reacting lactic acid with a base that contains sodium (NaOH will do nicely). This is an acid-base reaction, not a fermentation reaction.

You can ferment cane or beet sugar, cornstarch, potatoes, molasses, etc. to get lactic acid, by the way. The sugar or starch doesn't have to come from milk, although it can (yogurt, cream cheese, or truly soured milk all contain lactic acid).

If you react lactic acid with a base that contributes potassium (KOH, for example) you will end up with potassium lactate instead. So I wonder what soured milk or yogurt would contribute to a KOH (soft or liquid) soap that a non-fermented milk would not.

 

[lsg]

I am no expert, that's for sure, but these sites seem to say that the process starts with lactic acid that is then neutralized with caustic soda.

http://www.sodium-lactate.com/


http://www.food-info.net/uk/e/e325.htm

 

[cm4bleenmb]

I'm confused. (But I'm used to it. LOL) Are you saying that by dissolving a little salt into the soured milk/dairy product, it would create sodium lactate from the lactic acid, which would help make your soap harder?

Well, hmmm, I beg to differ with NDA. Lactic acid, not sodium lactate, is created by fermenting sugars or starches.

Sodium lactate is the simple salt created by reacting lactic acid with a base that contains sodium (NaOH will do nicely). This is an acid-base reaction, not a fermentation reaction.

You can ferment cane or beet sugar, cornstarch, potatoes, molasses, etc. to get lactic acid, by the way. The sugar or starch doesn't have to come from milk, although it can (yogurt, cream cheese, or truly soured milk all contain lactic acid).

If you react lactic acid with a base that contributes potassium (KOH, for example) you will end up with potassium lactate instead. So I wonder what soured milk or yogurt would contribute to a KOH (soft or liquid) soap that a non-fermented milk would not.

 

[lsg]

No, the way I think it works is lactic acid is used to produce sodium lactate. Naturally soured milk contains lactic acid. Lactic acid is taken through a chemical process to make sodium lactate, but according to the articles I have read, lactic acid occurs naturally through a fermentation process.

 

[Lin]

I'm confused. (But I'm used to it. LOL) Are you saying that by dissolving a little salt into the soured milk/dairy product, it would create sodium lactate from the lactic acid, which would help make your soap harder?

salt is NaCl (sodium chloride), NaOH (sodium hydroxide) is lye.

 

[shunt2011]

I use buttermilk in my soap quite frequently. If I don't have store bought I add lemon juice to milk or 1/2 and 1/2. It make a wonderful soap.

 

[paillo]

Buttermilk is my favorite non-vegan milk in soap. Hard, white bars and high in lactic acid, which, as I understand it, has gentle exfoliating qualities at the quantities used in soap. I use lactic acid facial peels, love them for the exfoliation and smoothing out pigmentation. I'm no chemist, but DeeAnna and others, would be interesting to hear your take on the different qualities/benefits of different milks in soap.

 

[neeners]

hmm....sounds like i'll have to use some of my kefir to make some soap!

btw, whey makes a really creamy soap too, to all who make cheese at home.....

 

[DeeAnna]

"...the process starts with lactic acid that is then neutralized with caustic soda...."

Yep, there ya go!

"...Are you saying that by dissolving a little salt into the soured milk/dairy product, it would create sodium lactate..."

You got the "sodium" part right, but that's not the whole story.

Table salt (sodium chloride, NaCl) is a "salt", using the specific chemistry sense of the word "salt". If you put table salt with lactic acid, you are not likely to get much if any sodium lactate, so table salt won't work.

You need a "base" to convert an "acid" into what chemists call a "salt". Many salts can be made from an acid, but in this case we want to turn an acid into a sodium salt.

Sodium hydroxide (NaOH, the "lye" we use to make soap) is a base that contains the sodium we're looking for. So, as Lin pointed out, the base "sodium hydroxide" is what you would mix with "lactic acid" to get the salt "sodium lactate".

 

[boyago]

"...the process starts with lactic acid that is then neutralized with caustic soda...."

Sodium hydroxide (NaOH, the "lye" we use to make soap) is a base that contains the sodium we're looking for. So, as Lin pointed out, the base "sodium hydroxide" is what you would mix with "lactic acid" to get the salt "sodium lactate".

and as I understand it, the lactic acid is what breaks down/spoils the milk. Is the conversion of lactic acid to Sodium lactate what keeps the soap from turning into a moldy sour milky wad of funk?

Also is there enough lactic acid in dairy that I should adjust my NaOH to compensate? Soapcalc does have a milk fat option for calculation. Butter milk has 4grams per cup would I enter that there to keep my lye working?

I am so going to dig my chem class next term!

 

[sososo]

I think next time I will try to use pickles brine instead water - it also contains lactic acid.

 

[boyago]

I think next time I will try to use pickles brine instead water - it also contains lactic acid.

Hopefully people with stronger chemical knowledge than me will chime in but the acid will neutralize some of the NaOH and you'd have to compensate to still have enough to make soap. I don't know how you'd do that.

Plus you'd smell like dill so there's that.

 

[sososo]

Hopefully people with stronger chemical knowledge than me will chime in but the acid will neutralize some of the NaOH and you'd have to compensate to still have enough to make soap. I don't know how you'd do that.

I will use a low SF (maybe 0% SF)

Plus you'd smell like dill so there's that.

I don't think so. When i used neem oil I notice that the soap didn't keep that terrible smell more than 4 or 5 days. Also for lard, sesame oil and other smelling oils.

 

[seven]

Hmmm, i beg to differ as far as neem oil. I was using a small percentage (2%), and the neem smell is def still there. It's been curing for 18 days. The smell is dissipating, but certainly not as fast as 4-5 days.

 

[cm4bleenmb]

So the simple take-away from this is that soured dairy products will help to make your soap harder? I love you guys.

 

[sososo]

Hmmm, i beg to differ as far as neem oil. I was using a small percentage (2%), and the neem smell is def still there. It's been curing for 18 days. The smell is dissipating, but certainly not as fast as 4-5 days.

I used 5% neem (strong rotten onion smell!) and after 4-5 days the soap was ok. (gelled soap)