Ionic strength and hydrogen bonding effects on whey protein isolate–flaxseed gum coacervate rheology

Abstract

Whey protein isolate (WPI) was mixed with anionic flaxseed (Linum usitatissimum L.) gum (FG), and phase transition during coacervate formation was monitored. Effects of ionic strength and hydrogen bonding on coacervation of WPI‐FG system and corresponding rheological properties were investigated. During coacervate formation, structural transitions were confirmed by both turbidimetry and confocal laser scanning microscopy. Increasing ionic strength with sodium chloride (50 mM) decreased optical density (600 nm) at pHmax. Correspondingly, pHc and pHϕ1 decreased from pH 5.4 to 4.8 and from 5.0 to 4.6, respectively, while pHϕ2 increased from pH 1.8 to 2.4. Sodium chloride suppressed biopolymer electrostatic interactions and reduced coacervate formation. Adding urea (100 mM) shifted pHϕ1, pHmax, and pHϕ2 from 4.8, 3.8, and 1.8 to 5.0, 4.0, and 2.2, respectively, while pHc was unaffected. Optical density (600 nm) at pHmax (0.536) was lower than that of control in the absence of urea (0.617). This confirmed the role of hydrogen bonding during coacervate formation in the biopolymer system composed of WPI and FG. Dynamic shear behavior and viscoelasticity of collected coacervates were measured, and both shear‐thinning behavior and gel‐like properties were observed. Addition of sodium chloride and urea reduced ionic strength and hydrogen bonding, resulting in decreased WPI‐FG coacervate dynamic viscosity and viscoelasticity. The disturbed charge balance contributed to a loosely packed structure of coacervates which were less affected by altered hydrogen bonding. Findings obtained here will help to predict flaxseed gum behavior in protein‐based foods.

Effects of sodium alginate and locust bean gum on dough rheology and microstructures, and bread quality

“…However, the G ′ and G ″ values of WFL 0.6 + NaCl mixtures were obviously higher than those of WF + NaCl mixtures. These were in good accordance with the result of Liu et al (2020) that the G ′ and G ″ values of whey protein isolate‐flaxseed gum coacervates decreased after the addition of NaCl. This may be due to the electrostatic screening effects of NaCl that can weaken the gluten network structures formed by dough and AG.…”

“…As for the dough–AG mixtures, both hydrogen‐bonding and electrostatic interactions might be predominant between dough and AG. Generally, hydrogen‐bonding interactions might be weaker than electrostatic interactions (Liu et al, 2020). Thus, WFL 0.6 showed looser networks compared with WFA 0.6 .…”

“…Changes of A and R values in the presence of NaCl suggested possible electrostatic interactions between gluten and AG. The presence of NaCl can induce the charge screening effect that may weaken electrostatic interactions between AG and gluten molecules, which leads to a loosely packed gluten network (Liu et al, 2020).…”

In vitro antioxidant and antidiabetic activity of essential oils encapsulated in gelatin‐pectin particles against sugar, lipid and protein oxidation and amylase and glucosidase activity

“…Different studies have reported higher bioactivity for essential oils at acidic pH. Because, at low pH, essential oils are more hydrophobic and will be passed through the cell membranes easily (Liu et al., 2020). Gelatin‐pectin solutions dissolved in acetic acid solution display low Newtonian behavior.…”

Porous hydrogel composite with whey protein isolate and galactomannans of Leucaena leucocephala (subabul) seeds: Stability, rheological, thermal, and morphological characterization

“…Non‐starch polysaccharides like galactomannans have been used in food industries for stabilizing foams and emulsions through hydrogen bonds or hydrophobic interactions (Li & de Vries, 2018; Wijaya et al., 2019). The most prominent interactions between proteins and polysaccharides are electrostatic in nature and are formed between the positively charged group of proteins and the negatively charged anionic polysaccharides (Bertsch et al., 2019; Iqbal et al., 2019; Liu et al., 2020). Soluble complexes are formed between WPI and galactomannan at neutral pH with better foam stability due to the higher viscosity of the aqueous phase.…”