Abstract
As a functional polysaccharide, inulin was carboxymethylated and it formed nanocomplexes with bovine serum albumin (BSA). The success of obtaining carboxymethyl inulin (CMI) was confirmed by a combination of Fourier transform Infrared (FT-IR), Raman spectroscopy, gel permeation chromatography (GPC), and titration. The effects of pH and ionic strength on the formation of CMI/BSA nanocomplexes were investigated. Our results showed that the formation of complex coacervate (pHφ1) and dissolution of CMI/BSA insoluble complexes (pHφ2) appeared in pH near 4.85 and 2.00 respectively. FT-IR and Raman data confirmed the existence of electrostatic interaction and hydrogen bonding between CMI and BSA. The isothermal titration calorimetry (ITC) results suggested that the process of complex formation was spontaneous and exothermic. The complexation was dominated by enthalpy changes (∆Η < 0, ∆S < 0) at pH 4.00, while it was contributed by enthalpic and entropic changes (∆Η < 0, ∆S > 0) at pH 2.60. Irregularly shaped insoluble complexes and globular soluble nanocomplexes (about 150 nm) were observed in CMI/BSA complexes at pH 4.00 and 2.60 while using optical microscopy and atomic force microscopy, respectively. The sodium chloride suppression effect on CMI/BSA complexes was confirmed by the decrease of incipient pH for soluble complex formation (or pHc) and pHφ1 under different sodium chloride concentrations. This research presents a new functional system with the potential for delivering bioactive food ingredients.
Highlights
Polysaccharides and proteins are biopolymers that are commonly used in food processing.Generally speaking, polysaccharides can be used to stabilize emulsions and suspensions, as well as to improve the thickening and gelling properties of food products
Could interact with bovine serum albumin (BSA) to form high turbidity complexes, which can be explained by the models that were proposed by Overbeek, Veis, Dubin, and Tainaka
A similar tendency in turbidity spectra was observed in carboxymethyl inulin (CMI)/BSA and pectin/BSA complexes, suggesting that the type of substituent groups
Summary
Polysaccharides and proteins are biopolymers that are commonly used in food processing. As the simultaneous addition of polysaccharides and oppositely charged proteins in certain specific pH ranges can induce electrostatic interaction and cause either soluble or insoluble complex formation, which can be used to enhance the quality of food, and participate in nutraceuticals and flavors delivery, increasing interest arises for the understanding of phenomena that are associated with these charge-charge interactions [4,5,6,7,8,9,10,11,12,13]. CMI is an anionic polysaccharide that is suitable for the complex formation with cationic protein as a type of functional biopolymer complexes for food ingredients, fat replacers, package, and drug delivery [42,43]. The complexes formation of CMI and bovine serum albumin (BSA, functional globular protein for human body) induced by electrostatic interaction were investigated.
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