Elucidating polymorphic nanofibril - anthocyanin interactions through multimodal physicochemical analysis and AFM imaging for the design of stable food colorants

Introduction The stability of natural food pigments such as anthocyanins remains a key challenge for their application in food systems. Methods Here, we investigated the potential use of protein nanofibrils as scaffolds to enhance anthocyanin stability, using Hibiscus sabdariffa extracts copigmented with pea and whey protein nanofibrils of distinct morphologies (linear and curly). Copigmented systems were systematically characterized through thermal, spectral, and nanoscale imaging analyses. Results and Discussion Linear nanofibrils provided a more favorable environment for anthocyanin binding than curly fibrils, with pea nanofibrils inducing stronger spectral shifts, whereas whey nanofibrils offered superior pigment stabilization and thermal resistance. Atomic Force Microscopy (AFM) revealed that copigmentation induced distinct morphological rearrangements of the nanofibrils, underscoring the critical role of fibril polymorphism in pigment–protein interactions. These findings establish nanofibrillated proteins as versatile scaffolds for stabilizing natural pigments and providing a mechanistic framework for designing more stable and functional food colorant systems.