Introduction - Production of protein isolates
6 important questions on Introduction - Production of protein isolates
Which parts are separated by separation by size?
- Cream
- Casein micelles
- Whey proteins
- Lactose/salts
- Solvent
Which parts are separation by size fractionation of milk?
- Whole milk --> cream
- Skimmed milk --> caseins
UF
- Whey protein --> lactose
- WPC-35
- WPC-50
- WPC-65
- WPC-80
- WPI-95
What happens in separation based on solubility? And how is it different for whey proteins and caseins?
- Whey proteins (globular)
- Soluble at ~pH 4.6 (pI)
- up to ~30 g/L
- Caseins (random coil)
- Precipitate
- at ~pH 4.6
- at natural pH after removal of k-casein (by rennet)
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What are different kinds of casein isolates and how are they isolated?
- Rennet casein --> precipitation induced by: rennet - removal of k-casein
- Acid casein --> precipitation induced by acidification (to pH 4.6)
- Na/K-caseinate --> precipitation induced by acidification (to pH 4.6) and readjustment to pH 6.8 (solubilise again) with NaOH or KOH
- Micellar casein --> ultra- or microfiltration
In soy 2 major proteins are present: glycinin and conglycinin. The SDS-PAGE shows the protein composition of 2 protein isolates made from soy. Why is the protein composition different for each isolate?
- Differences in pH during extraction or precipitation will result in differences in protein composition
- Which proteins are present in the final isolate, depends on the pH used and the solubility at the pI of the proteins
Differences in isolation methods of proteins result in:
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