Factors influencing anthocyanin content in red cabbage (Brassica oleracea var capitata L f rubra (L) Thell)

In North and Central Italy an experiment was conducted for two consecutive years to optimise the anthocyanin yield of red cabbage. Two hybrids ('Roxy' and 'Gradur') were grown under a factorial combination of increasing rates of potassium sulphate (0, 50, 100 kg K ha(-1)) and superphosphate (0, 39, 78 kg P ha(-1)) applied before planting. Cabbages were transplanted at the beginning of August and harvested in winter. Anthocyanins were extracted from cabbage heads with HCl in methanol (1% v/v solution) and quantified by absorption spectrophotometry at 530 run. Results showed that red cabbage can give high yields of anthocyanins (more than 90 kg ha(-1)) which are characterised by strong acylation and therefore, presumably, by good stability. However, differences over sites and years were marked. In the first year, yields in North Italy were reduced by a heavy infection of soft rot disease. The choice of variety, linked to a different anthocyanin content in the heads, appeared to be the major factor for a successful crop. P and K fertilisation had only a small influence. On clay soils in Central Italy the highest rates of both elements had a negative effect on the anthocyanin concentration in cabbage heads. (C) 2002 Society of Chemical Industry.