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Proteins - Sources of proteins and protein isolation - soy

6 important questions on Proteins - Sources of proteins and protein isolation - soy

How can you get a soy protein concentrate?

The defated soy bean meal is is put in an aqueous solution at pH4-5.
Since the soy proteins are not very well soluble in this pH range, they will not go into solution.
It is centrifuges and the pellet will contain the proteins and insoluble carbohydrates.
The supernatant will have the soluble carbohydrates

How can you get a soy protein isolate?

The defatted soybean meal is put at pH8-9. The proteins and other soluble components will disolve into the water.
The non soluble carbohydrates are centrifuged out and will go into the pellet.
The pH is adjusted to the Iso Electric point of the proteins.
The protiens will parcipitate and you will have an you can centrifuge them out again.

How can the pH interval influence your isolation method?

This can give for soy beans a completely other composition of proteins.

In what do you need so solubelize and centrifuge your sample?

In a buffer with a higher concentration then the acid that might be in the sample. The same thing applies to the salt present in the sample.

Otherwise you might to a separation step at the wrong pH or charge.

Why are there different properties of the same type of proteins in from differnt souces?

This might be due to there protein itself. But it might also be due to the other compounds present in your isolate. For instance the left over starch or phenolic compunds.

For what is the free SH group in beta-lactoglobulin responsible?

Upon heating it can bind to one of the S in an S-S group. How you will have a new S that can bind to and other protein and this is how you get aggregation.