β-Caryophyllene-rich pepper essential oils suppress spoilage activity of Pseudomonas fluorescens KM06 in fresh-cut lettuce

Abstract Pseudomonas fluorescens are able to cause the biodeterioration process of fresh-cut lettuce via the indole-3-acetic acid (IAA)-dependent type III secretion system (TTSS). The application of pepper EOs of proven of anti-IAA and anti-TTSS activities into salad dressing can reduce the organoleptic deterioration of fresh-cut leafy vegetables during storage. In this work, the influence of black and white pepper EOs on IAA production and on TTSS gene expression in P. fluorescens KM06 was examined. The black and white pepper EOs and β-caryophyllene at concentrations below the sub-MICs altered (i.e., 78%, 94%, and 90%, respectively) the IAA production in a 72 h old culture of P. fluorescens KM06. All the test agents significantly reduced the mRNA levels of the TTSS gene (−0.106, −0.428, and −0.448 for black pepper EO, white pepper EO and β-caryophyllene, respectively) ( p in situ experiments, the supplementation of the salad dressing with sub-MIC doses of β-caryophyllene-rich white and black pepper EOs also markedly inhibited bacterial IAA production (by 81% and 73%, respectively) and the IAA-related TTSS gene expression (by −0.880 and −0.680, respectively) ( p