Fractionating Soybean Storage Proteins Using Ca2+ and NaHSO3

Individual soybean storage proteins have been identified as having nutraceutical properties, especially β-conglycinin. Several methods to fractionate soy proteins on industrial scales have been published, but there are no commercial products of fractionated soy proteins. The present study addresses...

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Bibliographic Details
Published in:Journal of food science 2006-09, Vol.71 (7), p.C413-C424
Main Authors: Deak, N.A, Murphy, P.A, Johnson, L.A
Format: Article
Language:English
Subjects:
Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts
beta-conglycinin
Biological and medical sciences
CaCl2
calcium
calcium chloride
cations
chemical composition
contaminants
Food industries
fractionation
Fruit and vegetable industries
functional foods
Fundamental and applied biological sciences. Psychology
glycinin
plant proteins
protein
protein fractionation
protein subunits
sodium bisulfite
sodium chloride
soy protein
soybeans
sulfur dioxide
yields
β-conglycinin
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Summary:Individual soybean storage proteins have been identified as having nutraceutical properties, especially β-conglycinin. Several methods to fractionate soy proteins on industrial scales have been published, but there are no commercial products of fractionated soy proteins. The present study addresses this problem by using calcium salts to achieve glycinin-rich and β-conglycinin-rich fractions in high yields and purities. A well-known 3-step fractionation procedure that uses SO2, NaCl, and pH adjustments was evaluated with CaCl2 as a substitute for NaCl. Calcium was effective in precipitating residual glycinin, after precipitating a glycinin-rich fraction, into an intermediate fraction at 5 to 10 mM CaCl2 and pH 6.4, eliminating the contaminant glycinin from the β-conglycinin-rich fraction. Purities of 100% β-conglycinin with unique subunit compositions were obtained after prior precipitation of the glycinin-rich and intermediate fractions. The use of 5 mM SO2 in combination with 5 mM CaCl2 in a 2-step fractionation procedure produced the highest purities in the glycinin-rich (85.2%) and β-conglycinin-rich (80.9%) fractions. The glycinin in the glycinin-rich fraction had a unique acidic (62.6%) to basic (37.4%) subunit distribution. The β-conglycinin-rich fraction was approximately evenly distributed among the β-conglycinin subunits (30.9%, 35.8%, and 33.3%, for α', α, and β subunits, respectively). Solids yields and protein yields, as well as purities and subunit compositions, were highly affected by pH and SO2 and CaCl2 concentrations.
ISSN:0022-1147
1750-3841
DOI:10.1111/j.1750-3841.2006.00132.x