The beneficial effect of citric and ascorbic acid on the phenolic browning reaction in stored artichoke ( Cynara scolymus L.) heads

Abstract

Independent of the plant growing season artichoke heads stored at low temperature in closed polyethylene bags showed, with time, an increase in phenolics, especially caffeic acid. After 2 or 4 weeks, dependent on the storage temperature, the phenolic content decreased again while the pattern of changes in the phenolic level proved to be dependent on the harvesting period. Parallel with the increase in phenolic content, PAL activity increased but PPO activity remained almost constant or even decreased. Both citric and ascorbic acid were effective in improving the quality, as well as the shelf life, of the stored artichoke heads and by using either of the acids, an important delay of browning reaction could be noticed in the treated plant material. In order to better understand the nature of the important browning reaction in stored artichoke heads, the effects of citric and ascorbic acid on the phenolic metabolism, the PAL and PPO activity as well as on the iron/5- O-caffeoylquinic acid (IUPAC numbering) complexes, have been studied and the results obtained are discussed.