Using the abbreviations QB for quinoidal base and \({\text{F}}{{\text{C}}^ + }\) for flavylium cation, state an equation to describe how pH affects the colour of anthocyanins.

Suggest why blueberries should not be stored in aluminium cans.

\({\text{quinoidal base}} + {{\text{H}}^ + } \rightleftharpoons {\text{flavylium cation}}/{\text{QB}} + {{\text{H}}^ + } \rightleftharpoons {\text{F}}{{\text{C}}^ + }\);

Accept \( \to \) instead of \( \rightleftharpoons \)

blueberries are acidic and \({{\text{H}}^ + }\) ions react with aluminium to form \({\text{A}}{{\text{l}}^{3 + }}\);

\({\text{A}}{{\text{l}}^{3 + }}\) ions form (deeply) coloured (coordination) complexes with anthocyanins;

fruit discoloured;

\({\text{A}}{{\text{l}}^{3 + }}\) cause health problems / \({\text{A}}{{\text{l}}^{3 + }}\) deposited in bones instead of \({\text{C}}{{\text{a}}^{2 + }}\);

Most candidates correctly compared structural features of EGCG and rosmarinic acid in (a), but poorly demonstrated the application of knowledge of the factors that affect the colour of anthocyanins. One G2 respondent wondered whether candidates need to know the colours of pigments. This is clearly stated in F.4.3

Most candidates correctly compared structural features of EGCG and rosmarinic acid in (a), but poorly demonstrated the application of knowledge of the factors that affect the colour of anthocyanins. One G2 respondent wondered whether candidates need to know the colours of pigments. This is clearly stated in F.4.3