Green discolouration of processed artichokes: a defect caused by spoiler Pseudomonas strains

Despite food discolouration is a common microbial spoilage phenomenon, the uncommon green discoloration of processed artichokes was never reported. In this study, the progression of green discolouration in artichoke quarters was evaluated using an innovative non-destructive and contactless computer vision system method; after three days of cold storage an average green discoloured area of 46% was detected in artichokes inoculated with Pseudomonas strains isolated from spoiled samples. After 24 h of incubation in an undefined artichoke-based medium (AB), chlorogenic acid and di-caffeoylquinic acid concentrations were reduced by both viable cells of Pseudomonas spp. and cell-free supernatants of siderophore-producing Pseudomonas strains with an average value of 73% and 55%, respectively. Green discolouration of artichokes due to Pseudomonas contamination could be sustained by enzymatic oxidation of phenolic acids to quinones, and/or by the formation of metal-phenolic acids complexes mediated by siderophore release. This study highlights Pseudomonas spp. as a microbial group to be controlled during artichoke processing and the need to develop control strategies to avoid green discolouration.