Classification of Food Colours

Anthocyanins are most stable in acidic conditions (pH 1–3), where they exist predominantly as the flavylium cation, which imparts a bright red color. As the pH increases, anthocyanins undergo structural changes that reduce their stability and alter their color:

• Acidic (pH 1–3): Red and most stable (flavylium cation)
• Slightly acidic to neutral (pH 4–6): Purple; stability decreases
• Neutral (around pH 7): Blue-violet; less stable
• Alkaline (pH > 7): Blue to greenish, followed by rapid degradation and loss of color