Curly protein nanofibril systems for improving thermal stability and copigmentation of hibiscus anthocyanins

Anthocyanins are attractive natural colorants for clean-label food applications; however, their widespread use is limited by poor thermal stability. Protein nanofibrils have recently emerged as promising natural stabilizers because of their high surface area and ability to interact with anthocyanins through non-covalent interactions. This study investigated the copigmentation potential of curly protein nanofibrils prepared from pea, rice and whey protein isolates to enhance the thermal stability of anthocyanins extracted from Hibiscus sabdariffa.

Copigmentation significantly improved anthocyanin color stability in all nanofibril systems, although the extent of stabilization depended on protein source and fibrillation time. Curly rice protein nanofibrils prepared after 48 h exhibited the greatest bathochromic shift (4 nm) and hyperchromic effect (40.32%). Thermal degradation analysis showed that 48 h curly whey protein nanofibrils provided the highest thermal protection, with the greatest activation energy (91.48 kJ mol^-1) and the lowest degradation rate constant (0.14 × 10^-3 L·mg^-1·min^-1), whereas the highest z-value (65.77 K) was observed for 48 h curly rice protein nanofibrils. Fourier transform infrared spectroscopy and fluorescence analyses confirmed strong molecular interactions between anthocyanins and protein nanofibrils, indicating effective stabilization through non-covalent binding.

Curly protein nanofibrils effectively enhanced the thermal stability of hibiscus anthocyanins, with whey and rice protein nanofibrils showing the greatest stabilization potential. These findings demonstrate that curly protein nanofibrils are promising natural copigmentation agents for improving anthocyanin stability and support their application in clean-label food systems requiring enhanced color stability. © 2026 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.