# Cold plasma-induced ovalbumin amyloid fibrils: Morphological characteristics and stability on astaxanthin-loaded high internal phase emulsions

## TL;DR

Cold plasma treatment creates ovalbumin fibrils that stabilize emulsions with astaxanthin, showing better performance under various conditions.

## Contribution

This study introduces cold plasma as a novel method to rapidly form ovalbumin amyloid fibrils for stabilizing high internal phase emulsions.

## Key findings

- Cold plasma treatment accelerates ovalbumin fibrillization, forming short worm-like fibrils within 10 minutes.
- HIPEs stabilized by 10-minute fibrils show higher oil fraction, ionic and thermal stability, and better astaxanthin retention.
- HIPEs stabilized by 24-hour fibrils exhibit improved stability under freeze-thaw cycles and centrifugation.

## Abstract

The morphological characteristics of cold plasma (CP)-induced ovalbumin (OVA) amyloid fibrils (OAFs) and their ability to stabilize astaxanthin-loaded high internal phase emulsions (HIPEs) were investigated. The results indicated that CP treatment significantly accelerated OVA fibrillization by inducing its globular structure unfolding and polypeptide cleavage, leading to the rapid formation of short, worm-like fibrils within 10 min of fibrillation. Compared to untreated OVA, which had a diameter of 18.65 ± 6.47 nm, the length of OVA worm-like fibrils progressively increased from 69.17 ± 23.84 nm (10 min) to 114.94 ± 38.04 nm (8 h) before decreasing to 92.24 ± 36.22 nm (24 h). The ability of OVA to stabilize HIPEs was significantly improved following fibrillation. Notably, the shorter fibrils of OAFs-10 min and OAFs-24 h exhibited superior stability in HIPEs compared to the longer fibril of OAFs-8 h. The reason may be ascribed to the robust interface adsorption ability of OAFs-10 min and OAFs-24 h with shorter length, generating a dense and thick interfacial layer in the oil/water emulsion (maximum 11.57 ± 1.98 %), as confirmed by confocal laser scanning microscopy (CLSM) imaging and interface protein adsorption analysis (maximum 31.61 ± 2.49 %), thereby preventing droplet coalescence. Additionally, HIPEs stabilized by OAFs-10 min exhibited a higher oil fraction (82.5 %), superior ionic (1200 mM) and thermal stability (100 °C), and greater astaxanthin retention (91.55 ± 1.97 %, 1200 mM) compared to those stabilized by other OAFs. Meanwhile, HIPEs stabilized by OAFs-24 h exhibited enhanced stability under freeze-thaw cycles and centrifugation, with centrifugal stability constant (Ke) of 16.18 ± 4.78 %.

•The morphological polymorphism of CP-induced OAFs for stabilizing HIPEs was investigated.•HIPEs stabilized by OAFs-10 min exhibited higher oil fractions, enhanced ionic and thermal stability•HIPEs stabilized by OAFs-10 min exhibited better astaxanthin retention compared to HIPEs prepared by other OAFs.•HIPEs encapsulated by OAFs-24 h displayed improved freeze-thaw cycles and centrifugation stability.

The morphological polymorphism of CP-induced OAFs for stabilizing HIPEs was investigated.

HIPEs stabilized by OAFs-10 min exhibited higher oil fractions, enhanced ionic and thermal stability

HIPEs stabilized by OAFs-10 min exhibited better astaxanthin retention compared to HIPEs prepared by other OAFs.

HIPEs encapsulated by OAFs-24 h displayed improved freeze-thaw cycles and centrifugation stability.