Turbidimetric studies on sinapic acid — rapeseed protein interaction

✍ Scribed by Schwenke, K. D. ;Dąbrowski, K.

• Book ID: 102214914
• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 385 KB
• Volume: 34
• Category: Article
• ISSN: 0027-769X
• DOI: 10.1002/food.19900340616

✦ Synopsis

Abstract

The interaction of sinapic acid (SA) with the two main protein fractions from rapeseed, the 11 S globulin and the 2 S protein fraction (napin), was studied by means of turbimetry. The turbidity maximum (solubility minimum) of the 11 S globulin was shifted from pH 6.3 to pH 5.4–5.7 by an excess of SA (mass ratio 1:1). Titration of the 11 S globulin with SA at constant pH (4.0, 4.5, 5.0) pointed to an excess binding of SA to the protein without a clear stoichiometric ratio. Napin did not show a significant turbidimetric effect by SA at room temperature. The presence of SA changed, however, the heat induced aggregation of napin. The decrease of turbidity pointed to a drop of the size of aggregated particles by SA. These findings are discussed as the results of combined non‐covalent actions of SA to the proteins. Electrostatic interactions must play a certain role but not the dominant one.