A Review of the Current Knowledge of Thermal Stability of Anthocyanins and Approaches to Their Stabilization to Heat

Abstract

Anthocyanins are colored valuable biocompounds, of which extraction increases globally, although functional applications are restrained by their limited environmental stability. Temperature is a critical parameter of food industrial processing that impacts on the food matrix, particularly affecting heat-sensitive compounds such as anthocyanins. Due to the notable scientific progress in the field of thermal stability of anthocyanins, an analytical and synthetic integration of published data is required. This review focuses on the molecular mechanisms and the kinetic parameters of anthocyanin degradation during heating, both in extracts and real food matrices. Several kinetic models (Arrhenius, Eyring, Ball) of anthocyanin degradation were studied. Crude extracts deliver more thermally stable anthocyanins than purified ones. A different anthocyanin behavior pattern within real food products subjected to thermal processing has been observed due to interactions with some nutrients (proteins, polysaccharides). The most recent studies on the stabilization of anthocyanins by linkages to other molecules using classical and innovative methods are summarized. Ensuring appropriate thermal conditions for processing anthocyanin-rich food will allow a rational design for the future development of stable functional products, which retain these bioactive molecules and their functionalities to a great extent.

Complexation of Anthocyanin-Bound Blackcurrant Pectin and Whey Protein: Effect of pH and Heat Treatment

“…Applying heat caused the color of the MH mixtures to fade away. This is likely because the high heat (85 • C) can irreversibly change the structures of the ACNs by opening the pyrylium ring to form chalcones, which are colorless [25,47]. Further thermal degradation will then ensue, separating the ACNs from their sugar glycosyl molecules [25] and permanently disabling the ability of ACN to generate color.…”

“…Above pH 1, the equilibrium will shift to fewer flavylium cations due to the deprotonation of the pyrylium ring forming more quinoidal base ACN that is blue in color. In a slightly acidic medium, nucleophilic attack by water on the aglycone unit will occur forming a colorless ACN known as the carbinol pseudobase [25][26][27]. Due to the structure of ACN, it is believed that at different pH levels, ACN exhibits different biopolymer affinities where some reports have shown that flavylium cation binds more to biopolymers in comparison to carbinol pseudobase, especially when present at high concentration [16,[28][29][30].…”

“…It is well known that heating at temperatures >60 • C causes the unfolding of the globular WP and exposure of its hydrophobic and charged amino acids (AA) [31][32][33], which increase the binding sites for pectin-WP and ACN-WP interactions. Furthermore, heating can alter the structure of ACNs to chalcones, which can further develop into the derivatives of aldehyde or benzoic acid [25].…”

Why Black Flowers? An Extreme Environment and Molecular Perspective of Black Color Accumulation in the Ornamental and Food Crops

“…The most important issue of natural colorants is their low stability under high temperature ( Oancea, 2021 ). However, anthocyanins are comparatively more stable to heat stress ( Albuquerque et al, 2021 ).…”

“…The main anthocyanin structure contains 2-phenylbenzopyrylium heterocycle C-15 skeleton called anthocyanidin or aglycon. This skeleton contains ▬OCH3 or ▬OH groups ( Oancea, 2021 ). Presence of ▬OH group reduces stability and increases blue color, while the presence of ▬OCH3 groups elevates stability and redness ( Albuquerque et al, 2021 ).…”