Anthocyanins are the pigment compounds responsible for red, purple and blue colours in many fruits and vegetables. Within each plant source, these pigment compounds vary in concentration, proportions, and chemical structure, all of which influence use for color in a food or beverage. The pH causes a bathochromatic shift typically from red to purple to blue, from low to high pH respectively, while heat and light degrade the pigments. The effects of these stresses vary by source namely with the structure of the anthocyanins present.
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Anthocyanins are synthesized within the plants from flavanol derived structures called anthocyanidins. Examples of anthocyanidins include: delphinidin (blue-red), pelargonidin (orange) and cyanidin (orange-red). These anthocyanidins are the building blocks which are further reduced, dehydroxylated and glycosylated within the plant to produce anthocyanins. Anthocyanins further vary in substitution patterns and glycosyl group(s), both of which affect their colour and stability.

Additionally, these pigments exhibit a reversible change in molecular structure as the pH of solutions change from acidic to basic. This change in structure is characterized by a shift in hue from red to purple to blue as the pH changes from acidic to basic. Anthocyanins can be blended together to enhance the visual appearance of the food or beverage product. They work well in several varieties of applications.

Pigments from vegetable sources typically contain more acylated anthocyanins than those from fruit sources, making them more stable. The structure possibilities and the variety of anthocyanins present form the characteristics of each anthocyanin colour. Anthocyanins also contain natural antioxidants.

Chemical Structure (Anthocyanins)

Figure 1: Anthocyanidin
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Figure 2: 3,5 Diglycoside Anthocyanin

anthocyanin anthocyanidin chemical compound structure diglycoside