I wanted to extract oat proteins from whole oat flour. The extraction technique is base-acid method simply. I tried 2 different temperatures as 25º C and 50º C. In both temperatures, after NaOH addition and stirring, I centrifuged and collected supernatant for protein precipitation. When I add %20 citric acid solution, its color turned white and it was obvious that the proteins had started to precipitate. However, as the pH decreased, the solution became denser and became gel-like. I cannot centrifuge it like this. The proteins do not precipitate but remain suspended. I request your support in this regard.
I would suggest to test an extraction using Oat bran, instead of that Oat Flour.
Thank you for your answer Dear Vernon. It is very valuable for me to get information from someone like you.
Gelatinization of the starch was enhanced at acidic pH and caused starch suspensions in the solution. Because starch has a polyhydroxy structure, it is negatively charged in a strongly alkaline environment, which breaks the hydrogen bonds between starches and turns the double helix of starch into a single helix. This enhances the solubility and further acidification makes the oxidated starch complex insoluble again.
If you are looking for a specific protein try to use iso-electric precipitation...Enzyme-assisted extraction to get rid of complex starch molecules by amylase treatment or protease treatment to convert the hydrophobic oat proteins into their soluble polypeptide counterparts may also be beneficial...The fat composition would also be problematic during alkaline extraction. Oxidated lipids penetrate to the medium and could be co eluted which may cause some suspension trouble..Thus defeating process prior to protein extraction may ease the work and is traditionally applied in vegetal protein extraction employing soxhlet apparatus.
Besides protein families in oats possess hydrophobic structures which tend to be aggregated during the acidification process again causing gelatinization. Prolamins and glutenins in oat flour may be the other usual suspects of the mentioned drawback. Organic solvent precipitation can also be tried in order to establish a phase separation between proteins and other insoluble molecules.
Here are links to the numerous publications specific to this topic of which hopefully you may find an accurate answer to your question...
https://typeset.io/search/what-are-the-best-methods-for-oat-protein-extraction-8jhqzm9ot5?q=what+are+the+best+methods+for+oat+protein+extraction%3F
Good luck...İEA