Anthocyanin Structural Types and Stability: Implications for Natural Colorant Applications in Food Systems

Anthocyanins are promising natural food colorants because of their vibrant hues and health benefits, which have prompted recent research efforts. Although various techniques have been developed to externally stabilize anthocyanins and preserve their color and stability during food processing and storage, the impact of their molecular structure on stability within food matrices remains insufficiently explored. This review summarizes the stability of anthocyanins in relation to their structural diversity, transformations, and environmental factors. Features such as hydroxylation, methoxylation, glycosylation, acylation, and related structures like 3-deoxyanthocyanidins, pyranoanthocyanins, and polymeric pigments are examined concerning hydration, oxidation, and chromophore stability. The mechanisms involved include electronic effects, steric hindrance, molecular rigidity, co-pigmentation, and interactions with the food matrix. The color of anthocyanins is highly pH-dependent, transitioning from red in acidic conditions to blue or colorless at neutral and alkaline pH, reflecting underlying structural transformations of the chromophore. Food-processing conditions, including pH changes, heat treatment, light exposure, and interactions with complex matrices, have a significant influence on the stability behavior of these compounds. The structure–property relationships are outlined to guide the use of different anthocyanins in diverse food systems: acidic beverages, neutral products, heat-processed foods, and novel applications. This review provides a fundamental understanding of anthocyanin stability and establishes a scientific basis for utilizing various anthocyanins in current food applications.