 Wide distribution in plant tissues; in fruits, vege and flowers.  Include flavonoids and related compounds  Classes of flavonoids i.Anthocyanins (in syllabus) ii.Flavones & Flavonols iii.Flavanals iv.Flavanones Water soluble pigments

 Flavonoids have a C6C3C6 skeleton-  consist of 2 benzene rings and a 3C chain that together with oxygen, forms part of the central ring. Structure

Anthocyanin structure

 6 common anthocyanidins  Cyanidin- strawberries  Delphinidin- plums, peaches, apple skins, figs  Pelargonidin- grapes, pomegranates, eggplant  Peonidin  Malvidin methyl derivatives  petunidin

 Red, blue and purple coloured pigments  Exist as glycosides (> stable). Usually 1 or 2 sugars are present.  Commonest sugars; glucose  Others; galactose, rhamnose or pentose sugar  Common position for sugars: C3 or C5  Anthocyanins with sugars = Glycones  Anthocyanin without sugars = Aglycones/ anthocyanidins ANTHOCYANINS

1.Leaching  Pigments can leach into processing fluid (eg. Canning fluid due to breakdown of cell wall & their water soluble nature  ~use < mature fruits for processing 2.Enzymatic degradation  Anthocyaninsugar + aglycone anthocyanase (slow) chalcone (pale yellow) Stability of pigments during processing

3.Colour changes due to pH of processing/ cooking water.  Red cabbage bluish coloured cabbage soft water +H (eg lime juice or vinegar) pH ~7 reddish cabbage  At pH 8 or >8 = greyish colour  At high pH = green colour

4.Contact with metal  Anthocyanin form greenish, blue, purplish and slate grey pigments with metals  Colour depends not only on particular anthocyanin but also metal ions  Anthocyanin anhydro bases form coloured compounds with metal like Fe and Al. The complexes form sometimes are very stable  Because of this, food contain anthocyanin processed in enamel-lines (lacquering inside metal can) rather than thin plate as it can degrade colour af anthocyanin