Thanks a lot for your help Shazia....
Of course, it looks very helpful....
Best wishes....
What is the purpose of using DMSO? Would appreciate if you can enlighten me..
Shazia could you share with me your paper on using alkali to make starch more soluble?
Yong Kuen Ho asked what the purpose of DMSO was. DMSO is a hydrogen bond acceptor, but not a donor. So, at high concentration it disrupts the associations between different polymer chains in the starch, thus making it easier to dissolve. DMSO also favors the starch forming its 'V' form which involves single strands of starch complexed with a polar molecule, such as DMSO. Native starches, in plants, tend to form A (cereal) or B (potato for example) amylose domains. These are both double helical and there for tend to form molecular 'knots' that again restrict dissolution.
I think there is a paper by Rollings (1980s) which talked about the forming of these complex starch structures.
Hello
Now I have another question, if we have dissolved starch (native) in our solution and we want to separate this starch by precipitation, what is your suggestion. I know with ethanol it is possible but I want to use water, do you think is it possible with adding acid sulfuric to water? and ahat is the best PH for this?
As mentioned above, one of the method to obtain water soluble starch is alkali treatment. I mixed starch in isopropanol.aqueous media with NaOH (NaOH:AGU=2,2 mol/mol) and mixed 4 h in 40C. I leaved slurry and filtred it next day. Starch was water soluble (very low viscosity of 2wt % solution). In alkali treatment starch undergoes alkali hydrolisis, so the the Mw is lower after treatment. Meybe you schould search for some physical and mechanical methods? Please paste this link journal.pan.olsztyn.pl/fd.php?f=1190 into common browser or title: PHYSICAL AND CHEMICAL MODIFICATION OF POTATO STARCH TO OBTAIN RESISTANT
STARCH PREPARATIONS (it is in pdf format and i have problem with it copying)
There is a small trick to do it. Warm the water a little and then add starch little by little. You will find that your starch dissolve easily.
Generally warm/hot water causes starch gelatinization not solubilization. Gelatinization breaks down intramolecular bonds in starch granules leading to swell in warm water (water can diffuse into granules). Swollen granules cause increse of viscosity. I have found this article where results showed both dissolution and gelatinization (in NMMO solvent) http://pubs.acs.org/doi/abs/10.1021/bm200390a. Gelatinization depends on e.g. type of starch (amylose/amylopectin ratio), water in starch granules, pH etc.
Swapnil Patil, what type of starch did you disolve (gelatinized?)?
P.S I found one more article about soluble starch http://www.sciencedirect.com/science/article/pii/S0268005X0200036X
"According to K.H. Meyer (Koll, Z. 101, 1942), for colloidal solutions the better way is compare it to substances totally saturated by water than to real solutions in phisicochemical meaning, where substances are completely divided into particles surrounded by solvent. Even in the case of very small concentrations the network structure remains. " (Gunter Tegge, "Stärke und Stärkederivate")
Starch granules start to swell in rised temperature (pasting temperature), and granules volume are increased, depending on starch type. For example volume of potato starch increases about 1000 times, and for corn starch about 25 times. Soluble starch has shorter chains (by alkali, acid hydrolisis or oxidative agent treatment). so its formulo can be the same or can have alcoxide group starch-O-Na+ in place of starch-OH) There are many starch derivatives with functional groups or its graft-copolymers which are watersoluble.
Please can anyone help me with the molecular weight of potato starch dextrin
Hello, instead of precipitating the starch using ethanol, after dissolution in DMSO, is it a good idea to dialyze the DMSO out using water?
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