ACTIVE MAP OF READY-TO-EAT LETTUCE: INTERPLAY BETWEEN FOOD QUALITY AND SAFETY (THE QUAFETY APPROACH)

Abstract

Oxidative enzymatic browning of cut edges and microbial spoilage are the two major causes of deterioration of ready-to-eat lettuce. Furthermore, we have demonstrated that these two processes are interrelated and the presence of spoilage pseudomonad bacteria on cut lettuce surface hastens the accumulation of phenolics and enhances browning, presumably as part of the host defense response. Preventing browning by heat treatment promoted bacterial growth and tissue maceration of Pectobacterium-inoculated lettuce core discs. The red-colored phenolic oxidation products have been isolated from cut lettuce and are currently under investigation. Modified atmosphere packaging (MAP) is used to preserve the quality of fresh-cut lettuce by inhibiting both the oxidative browning and the growth of microbial populations. Flushing the packages with a gas mix of desired composition (active MAP) expedites the achievement of favorable atmosphere conditions improving the product quality preservation. At the same time, the active MAP favored the survival of Salmonella on lettuce leaves, possibly due to the elimination of its natural antagonists. Atmosphere modification does not ensure microbiological safety of ready-to-eat lettuce and must be supported by appropriate sanitation practices. Washing with active chlorine followed by potable water rinsing did not taint shredded lettuce with unacceptable level of disinfection byproducts but produced wastewater heavily contaminated with trihalomethanes. The comprehensive approach to quality and safety of ready to eat fresh products is the basis of the EU FP7 QUAFETY project.