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Difference of Ascorbic acid (AA) dissolved or precipitated in Glycerol?

Referring to pat US20110008445A1

Solution 1

At 25C, AA was dissolved in glycerol and alcohol (subsequently removed by distillation).
The AA was measured using scattered light (JIS K0101 using formazine as ref).

5 µm sized particles of AA were found to be dissolved in the glycerol.

Solution 1a

Solution 1 was aged at 28C for 10 days.

10% AA remained dissolved
90% AA precipitated

25 µm sized particles of AA were found to be suspended in the glycerol.

Solution 1b

Solution 1 was aged at 15C for 10 days.

10% AA remained dissolved
90% precipitated

80 µm sized particles of AA were found to be suspended in the glycerol.

Analysis

A key aspect of the experiment focusses on AA being in two different states:
Dissolved and Precipitated

The implication is that the AA is somehow different, otherwise why mention dissolved and precipitation?

Also, the AA was initially dissolved in glycerol and alcohol.

Therefore the AA was

  1. Dissolved in Glycerol and Alcohol
  2. Dissolved in Glycerol
  3. Precipitated and suspended in Glycerol

Question

Does Ascorbic Acid remain in its usable form, in all three scenarios?

('Usable' relates to applying this concept, of dissolving the AA in Glycerol and Alcohol, as a precursor to AA encapsulation in lecithin emulsion).

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  • $\begingroup$ My short answer is yes. L-Ascorbic acid is stable, in mostly neutral and basic conditions. And, I assure that the particle sizes are given in $\pu{\mu m}$ (See abstract of the patent application and SEM figures). $\endgroup$ – Mathew Mahindaratne May 20 at 22:45
  • $\begingroup$ Thanks for that @Mathew Mahindaratne. With the 1000's of words, confirmation of units was missed :( I've ordered glycerine, a high shear (rotor stator) homogeniser & am now tracking down a high HLB ester supplier - not easy in small qty. Will be using de-oiled sunflower lecithin powder & fine milled ascorbic acid. Will prototype a contact sonificator, as bath method is poor - I have a spare head :) Probably a month to get together. Do you want to put your answer up confirming that the ascorbic acid remains usable when dissolved in glycerine - and await potential disagreement :) Thanks again... $\endgroup$ – Marco-UandL May 21 at 21:34
  • $\begingroup$ Could you separate the patent text and your commentary in the question? Otherwise, it is hard to read, and I don't expect anyone to go and read the actual patent. $\endgroup$ – Karsten Theis May 23 at 17:36
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    $\begingroup$ @Karsten Theis - Thanks for taking the time on my question. Hopefully it is now easier to understand. I think that we already have the answer, but it was worth the effort to present the question with greater clarity. This experience will no doubt help with future questions :) $\endgroup$ – Marco-UandL May 24 at 14:11
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To acknowledge OP's request, I am putting this as my answer:

What OP's initially referring to (US20110008445A1) was a patent application. Since it was a 2011 application, I searched for the patent and found it (Ref.1). It's abstract states that:

A Suspension of ascorbic acid in glycerol or in glycerol comprising diglycerol, in which the content of ascorbic acid is 13% by mass or greater, and further in which 8 to 12% by mass of the ascorbic acid is dissolved in glycerol or in glycerol comprising diglycerol, and the rest of ascorbic acid is precipitated in the form of microcrystals having a particle diameter of $\pu{25 \mu m}$ or smaller and is uniformly dispersed in the suspension. The suspension of ascorbic acid in glycerol is useful as a base material for cosmetics containing ascorbic acid which exhibits excellent feel in the use (spreadability and Smooth feel on application to the skin).

The patent described the preparation of ascorbic acid suspentions in alcohol or glycerol. Based on my knowledge in ascorbic acid, all forms of suspensions contain ascorbic acid in in its usable form. However, one should be aware that ascorbic acid tends to have browning effect due to slow formation of related furan derivative on long standing (Ref.2).

References:

  1. Mikiharu Okumura, Takanori Ohta, “Suspension of Ascorbic Acid in Glycerin and Process for Production Thereof,” United States Patent 2012, 8,211,472 B2 (https://patentimages.storage.googleapis.com/62/29/bf/f95fde91d869cd/US8211472.pdf).
  2. T. Lalikainen, M. A. Joslyn, C. O. Chichester, “Browning Reactions, Mechanism of Browning of Ascorbic Acid-Citric Acid-Glycine Systems,” J. Agric. Food Chem. 1958, 6(2), 135–139 (DOI: 10.1021/jf60084a011).
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  • $\begingroup$ Thanks for that answer & additional research. I will set aside some samples in a fridge and cupboard to monitor any colour change over time. I found a supply of Sucrose Stearate that can be tested as an aid to emulsifying lecithin. In the intervening period, other options will be procured. Thanks again for your time :) $\endgroup$ – Marco-UandL May 22 at 20:33
  • $\begingroup$ Good. I'm sure it stays same for long lime. Good luck on your work though. :-) $\endgroup$ – Mathew Mahindaratne May 22 at 20:53

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