Studies on self‐assembly interactions of proteins and octenyl succinic anhydrate (OSA)‐modified depolymerized waxy rice starch using rheological principles

Abstract

ABSTRACTDynamic tests (23 °C, pH ∼ 7.0) yielding relaxation times, λ, as a function of frequency and polymer concentration were performed to assess self‐assembly characteristics of biopolymers in aqueous solution. Reduction of λ‐values (slope) up to a critical frequency value (CFV) helps characterize structure formation. Proteins and octenyl succinic anhydrate (OSA)‐modified depolymerized waxy rice starch (DWxRc) show a well‐defined λ‐slope at all concentrations. Except for whey protein isolate (WPI, 0.184 g/L) and 7% OSA‐modified DWxRc (1.84 g/L), the λ‐values of the solutions are comparable (P > 0.05), indicating similar structures. Self‐assembly interaction of α‐lactalbumin (3.68 g/L) with OSA‐modified polysaccharides is observed with 18.4 g/L of 7% OSA‐modified DWxRc (CFV of 0.08 Hz), while WPI (3.68 g/L) exhibits self‐assembly with all polysaccharides and concentrations. Transmission electron microscopy (TEM) of electrostatically precipitated proteins alone or in combination with OSA‐modified polysaccharides confirms that λ−slope and CFV values relate to shape, size, and shear stability of the assembled structures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43603.