Encapsulant-bioactives interactions impact on physico-chemical properties of concentrated dispersions

All-natural wheat gliadin-gum arabic nanocarriers for encapsulation and delivery of grape by-products phenolics obtained through different extraction procedures

Grape pomace (GP), the major winery by-product, is still rich in phenolic compounds, scarcely applied in food systems due to physicochemical instability issues. This work aimed at fabricating gliadin (G)-based nanoparticles through antisolvent precipitation, for delivery of GP extracts, investigating different extraction strategies with ethanol/water solution (70:30 v/v). Interestingly, the fabricated nanoparticles were characterized by a nanometric size range with hydraulic diameter values around 100 nm and ζ-potential of 18-22 mV. The addition of gum arabic (GA), at the optimized G/GA ratio 1:1, improved particle stability and encapsulation efficiency of GP polyphenols. The two-step extraction of GP in the G-rich solvent retrieved from G extraction, as evidenced by total phenolics (1.24 times higher than the two separately obtained extracts G/GP10:10), HPLC-PDA analysis, encapsulation efficiency (62.9% in terms of epicatechin), and simulated digestion (95.6% release of epicatechin), represented the most promising approach to obtain G nanoparticles for efficient delivery of GP extracts.

Bioactives and extracts affect the physico-chemical properties of concentrated whey protein isolate dispersions

Non-covalent complexation interactions are known to occur between bioactive compounds and proteins. While formulating with these components can have positive outcomes such as stabilization of colors and actives, it can also result in changes to the structures and physical properties of proteins, affecting product functionality and sensory attributes. Previous experiments reported measurable changes in the physico-chemical properties of whey protein isolate (WPI) dispersions upon formulation with Aronia berry extract, ascribing changes to protein-polyphenol (PP) interactions in the systems. Pure gallotannin, beet extract, and cranberry extract, providing a diverse variety structures and sizes, were selected for further experimentation and comparison with the effects of Aronia extract. Concentrated dispersions with varying WPI:sucrose ratios, formulated with several bioactives contents from multiple different sources were analyzed to identify the effects of different bioactives on physico-chemical properties of dispersions. Dispersions formulated with cranberry extract demonstrated the largest increases in surface tensions, viscosities, and particle sizes, while those formulated with beet extract were the least affected by the presence of bioactives, suggesting that different bioactives and extracts had varying propensities for complexation interactions with WPI, despite their relatively low levels of addition (0, 0.5, and 1%).

Graphical Abstract

Effects of Aronia polyphenols on the physico-chemical properties of whey, soy, and pea protein isolate dispersions

Abstract

Bioactive compounds including polyphenols (PP) have been observed to naturally form non-covalent complexation interactions with proteins under mild pH and temperature conditions, affecting protein structures and functionality. Previously, addition of Aronia berry PP to liquid dispersions containing whey protein isolate (WPI) and sucrose was found to alter characteristics including viscosity, surface tension, and particle sizes, with changes being attributed to protein-PP interactions. In this study we aimed to investigate whether Aronia PP would interact with soy and pea protein isolates (SPI and PPI, respectively) to a similar extent as with WPI in liquid protein-sucrose-PP mixtures. We hypothesized that formulations containing PPI (comprised of larger proteins) and hydrolyzed SPI (containing more carboxyl groups) may exhibit increased viscosities and decreased aggregate sizes due to enhanced protein-PP interactions. Concentrated liquid dispersions of varied ratios of protein to sucrose contents, containing different protein isolates (WPI, SPI, and PPI), and varied Aronia PP concentrations were formulated, and physical properties were evaluated to elucidate the effects of PP addition. PP addition altered physical characteristics differently depending on the protein isolate used, with changes attributed to protein-PP interactions. SPI and PPI appeared to have higher propensities for PP interactions and exhibited more extensive shifts in physical properties than WPI formulations. These findings may be useful for practical applications such as formulating products containing fruit and proteins to obtain desirable sensory attributes.

Graphical abstract