High-pressure processing alters stability of anthocyanin–catechin complexes

Researchers found that while HPP promotes the formation of anthocyanin–catechin complexes, it simultaneously reduces their thermal and light stability by decreasing the proportion of dominant conformations.

Anthocyanins are natural pigments abundant in fruits, vegetables, tea, and wine, prized for their vivid colors and health benefits including antioxidant, anti-inflammatory, and cardioprotective properties. Yet their poor stability under heat and light has long hindered food applications. Copigmentation—complex formation between anthocyanins and polyphenols such as catechins—enhances both stability and color intensity through π-π stacking and hydrogen bonding. However, structural outcomes depend strongly on pH: anthocyanins exist mainly as stable cations in highly acidic solutions and as less stable hemiketals at milder pH. High-pressure processing, which preserves food without heat, is known to accelerate anthocyanin–polyphenol reactions, but its effects on complex conformations and stability remained poorly understood. Due to these challenges, there is a pressing need to clarify how HPP influences the molecular structures and stability of copigmentation complexes.

A study (DOI: 10.48130/fia-0025-0025) published in Food Innovation and Advances on 26 June 2025 by Hui Zou & Yilun Chen’s team, Shandong Agricultural University, provides critical understanding of how food processing conditions impact anthocyanin stability, offering guidance for designing products that retain both nutritional and sensory quality.

To systematically examine the effects of HPP on anthocyanin–catechin copigmentation, researchers measured solution absorbance under varying pH values, molecular ratios, and pressure levels, while subjecting the complexes to thermal and light treatments. Absorbance ratios were used to normalize initial differences caused by accelerated reaction rates under HPP, enabling a clear comparison of stability across conditions. Thermal stability tests revealed that at pH 1.5, complexes maintained consistent absorbance at pressures of 0.1–300 MPa, but stability declined sharply at 500 MPa, particularly at a 1:1 molar ratio with extended pressurization, indicating disruption of weak interactions. At pH 3.6, overall absorbance was lower due to conversion of red flavonoid cations into colorless hemiketals, and although the effect of 500 MPa was less pronounced than at pH 1.5, it still reduced stability. Light stability tests showed that at pH 1.5, absorbance decreased slightly over time, while at pH 3.6, significant decreases were observed at a 1:1 molar ratio and fluctuating trends appeared at 10:1, suggesting complex interactions between light exposure, pH, and molecular ratios. Conformational searches and molecular dynamics simulations demonstrated that pressure altered structural distributions: dominant π-π stacking conformations present at lower pressures disappeared at 500 MPa, replaced by more diverse but less stable structures. Binding energy analysis confirmed that high pressure reduced the dominance of the most stable clusters, with proportions dropping from over 40% to around 20% at 500 MPa. Weak interaction analysis indicated that van der Waals forces dominated, but at high pressure hydrogen bonding became more prominent as intermolecular distances compressed. Finally, excitation energy calculations showed that increased pressure generally lowered light stability, particularly at 500 MPa where dominant conformations were lost. Collectively, the methods revealed that HPP accelerates copigmentation but simultaneously increases structural diversity, reduces dominant conformations, and compromises both thermal and light stability.

The study suggests that HPP can enhance color development initially, but long-term stability may be compromised due to the formation of structurally diverse, less stable complexes. Food manufacturers aiming to preserve anthocyanin-rich products such as juices, jams, and wines should consider combining HPP with optimized pH control, molecular ratios, and protective additives to balance color intensity with durability.

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References

DOI

10.48130/fia-0025-0025

Original Source URL

https://doi.org/10.48130/fia-0025-0025

Funding information

This work was supported by the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (CAAS-ASTIP-IVFCAAS, IVF-JCKJ202514).

About Food Innovation and Advances

Food is essential to life and relevant to human health. The rapidly increasing global population presents a major challenge to supply abundant, safe, and healthy food into the future. The open access journal Food Innovation and Advances (e-ISSN 2836-774X), published by Maximum Academic Press in association with China Agricultural University, Zhejiang University and Shenyang Agricultural University, publishes high-quality research results related to innovations and advances in food science and technology. The journal will strive to contribute to food sustainability in the present and future.

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