Analysis of the mechanisms and efficiency of Taxifolin encapsulation in whey proteins via thermomechanical mixing and spray drying

Abstract

Taxifolin (TXL) is a minor bioactive compound from the polyphenol class that may significantly impact human metabolism when included in food products. However, its application is limited by a bitter taste and low bioavailability. We hypothesized that encapsulating TXL in whey proteins using thermomechanical mixing or spray drying could effectively mask its bitterness and enhance bioavailability. Computational simulations indicated that each molecule of β-lactoglobulin (β-Lg) and α-lactalbumin (α-La) can bind at least one TXL molecule. Consequently, experiments used an equimolar ratio of whey proteins to TXL (1:1). Thermomechanical stirring of liquid whey protein concentrate (WPC) at 80 ± 2 °C followed by lyophilisation formed protein aggregates up to 160 μm in size, incorporating large TXL crystals. Encapsulation efficiency was 63 ± 3 %, and the bitter flavour remained unmasked. In contrast, encapsulation via spray drying achieved up to 71 ± 2 % efficiency at an inlet air temperature of 150 °C. The resulting WPC microcapsules, up to 30 μm in size, did not contain large TXL crystals, and bitterness was fully masked. This aligns with the observed reduction in TXL's antioxidant activity. After disrupting WPC microcapsules with ethanol, antioxidant activity of the polyphenol was nearly fully restored. These findings suggest that when such microcapsules are ingested with food, the antioxidant activity of TXL will be expressed in the intestine following proteins breakdown. The results may support the development of novel food products containing whey proteins with encapsulated TXL.

Keywords: Antioxidant activity; Microcapsules; Molecular modeling; Polyphenols; Taxifolin crystals; Α-Lactalbumin; Β-Lactoglobulin.

Graphical abstract

Fig. 1

Models of the tertiary structure of whey protein molecules β-Lg (A), α-La (B) and the spatial structure of the TXL molecule (C).

Fig. 2

A model of the β-Lg-TXL molecular system (A). The mutual arrangement model of the amino acid residues within the hydrophobic barrel of the β-Lg molecule and the TXL molecule during their interaction (B).

Fig. 3

Model of the tertiary structure of the α-La molecule with hydrophobic clusters (A). Model of the mutual arrangement of nonpolar amino acid residues of hydrophobic cluster 2 of α-LA molecule and TXL molecule during their interaction (B).

Fig. 4

Scanning electron microscopy of lyophilised WPC obtained after thermomechanical stirring of the liquid concentrate in pure form (A) and with TXL (B).

Fig. 5

Efficiency of TXL encapsulation into whey proteins by spray drying at different inlet air temperatures. Error bars represent the standard deviation (SD) of the mean (n = 3). Different letters of the upper indices represent the difference at p < 0.05.

Fig. 6

Fluorescence emission intensity of dry WPC obtained by spray drying at different temperature regimes with encapsulated or added TXL (% of fluorescence intensity of pure WPC).

Fig. 7

Scanning electron microscopy of TXL-encapsulated WPC obtained by spray drying at 130 °C (A), 150 °C (B), and 170 °C (C).

Fig. 8

Particle size distribution of pure and TXL-encapsulated WPC obtained by spray drying at different temperature regimes.