Thermal degradation of anthocyanins with particular reference to the 3‐glycosides of cyanidin. II. The anaerobic degradation of cyanidin‐3‐rutinoside at 100 °C and pH 3.0 in the presence of sodium sulphite

A mechanism is proposed for the degradation of cyanidin‐3‐rutinoside in the presence of sulphite involving the reversible formation of a 1:1 anthocyaninbisulphite complex which was shown to be stable under the conditions employed. Degradation of the anthocyanin may still take place because of the existence of the cationic and pseudobase forms of the pigment in solution at 100 °C. Although the commercial value of sulphite as a stabiliser for the anthocyanins in canned red fruits appears to be severely limited by its effect in decolourising the pigments and increasing the rate of corrosion of the cans, a possible use for the reagent in stabilising the anthocyanins during extraction from plant tissues is suggested.