Investigation of the astringency-masking effect of ι-carrageenan on natural polyphenols and its differential mechanism at various concentrations

Abstract

The astringency of natural polyphenols affects consumers' acceptance for food, and it is urgent to find safe and effective astringency-masking substances. This study introduced ι-carrageenan (CA) as a novel astringency-masking agent and investigated its interaction mechanism using epigallocatechin gallate (EGCG) and β-casein (βCN) as model compounds. Sensory evaluation demonstrated that 0.3 % CA achieved a 56-80 % reduction in astringency intensity scores for four polyphenols, with masking efficacy exhibiting concentration-dependent enhancement. Through integrated analytical approaches including techniques such as multispectral analysis and isothermal titration calorimetry, we revealed concentration-dependent interference patterns in EGCG-βCN interactions. Three distinct mechanisms were elucidated: (1) Competitive binding with βCN to inhibit EGCG-induced protein precipitation; (2) Facilitation of βCN aggregation into higher molecular weight coacervates; (3) Formation of ternary EGCG-CA-βCN complexes. These findings highlight the potential of CA in the development of low astringency functional foods, providing the food industry with a new strategy for masking astringency.

Keywords: Astringency; Carrageenan; Epigallocatechin gallate; Molecular mechanism, β casein; Polyphenols.

Graphical abstract

Fig. 1

Volunteer sensory tests. (A) Heat map of an average abundance of astringency scores for 15 volunteers. Blue and red colors represent low and high abundance, respectively. (B-E) Astringency sensory scores of volunteers. The control group was treated with no CA. Error bars indicate standard error, and different letters indicate statistically significant differences between samples (p < 0.05). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Circular dichroism spectra (A-B) and secondary structure analysis (C—D) of βCN alone, in the presence of EGCG, CA, as well as in the presence of EGCG-CA complexes at different concentrations of CA (0.2, 0.4, and 0.8 g/L).

Fig. 3

(A-B)Fluorescence spectra of EGCG and βCN in the absence and presence of increasing concentrations of CA (0.0–1.2 g/L). (C—D)FT-IR spectra of βCN, CA, βCN-CA, βCN-EGCG and βCN-CA-EGCG. (E-F) SDS-PAGE electropherograms and β-casein precipitation indices of β-casein after different β-casein binding reactions: βCN with EGCG, CA, and EGCG-CA mixtures (EGCG+CA, 0.2, 0.4, 0.8 g/L). Error lines indicate standard errors and different letters indicate statistically significant differences between samples (p < 0.05).

Fig. 4

Thermal analysis plots for the titration of βCN by EGCG, CA, and EGCG+CA mixtures and the titration of CA by EGCG. (A-D) Heat release measurements; (G-H) molar enthalpy changes against EGCG-βCN, CA-βCN, EGCG+CA-βCN, and EGCG-CA ratios after peak integration.

Fig. 5

Structure and the ESP maps. (A) EGCG, (B) CA, (C) EGCG-CA-1, (D) EGCG-CA-2. (E-F) The electrostatic potential maps corresponding to the above structure.