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Acid value of creams and emulsions - Is there a way to calculate it theoretically?
Hello,
I have a questions of acid value (KOHmg/g) of ready emulsion or cream.
Can it be calculated and settled theoretically limits according to the values of raw materials used in a formulation?
Or the acid value could only be measured at initial point of product analysis and we can`t rely on the acid value indicated at specifications of raw materials (oils, fats) ?
Can the acid value be the reliable criteria evaluating the ageing of emulsion?Thank you
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3 Replies
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Theoretically, the final acid value can be calculated from the acid values of the used triglyceride oils/butters and their respective amounts.However, the apparent acid value of an emulsion depends on the pH. You’d have to set the pH to very acidic prior to extraction of free fatty acids followed by titration thereof. It might be faster if you had some fancy equipment such as RP-HPLC at hand…Theoretically, you could do a reverse titration (saponification with excess base and titrate back with an acid) with the emulsion if you had the value of the fresh sample to compare with an older/rancid one (of the same batch). Depends a bit on the ingredients, though.It’s not used to evaluate ageing of emulsions and might not be your best choice given the presence of water and antioxidants (hydrolysis without rancidity). Acid values are only an indicator for old oils or oils going rancid due to some correlation but they don’t give any direct indication of rancidity.A better value regarding rancidity is the peroxide value. In practical terms, several different values are usually used to gauge oils and fats. -
Dear Pharma,
thank you so much for so detailed explanation! You really helped. Have a beautiful day!
Again.. me only can thank once more Perry for this wonderful place with smart and amazing people here! Chemist corner is a treasure among the cosmetic chemists. -
You’re welcome 🙂
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