MAP does not protect against S. enterica on lettuce: The use of appropriate sanitation practices to prevent contamination remains the major measure

Oxidative enzymatic browning of cut edges and microbial spoilage caused by bacterial genera Erwinia and Pseudomonas are two major deterioration causes in ready - to - eat lettuce. Furthermore, the presence of spoilage bacteria on cut surface enhances browning severity. Modified atmosphere packaging (MAP) is commonly used to preserve the quality of minimally processed lettuce by inhibiting the oxidative browning and the growth of microbial populations. Initial displacement of air with a gas mixture of desired composition (active MAP) reduces the time needed to generation of modified atmosphere thereby improving the quality of the product. Sensory test demonstrated the superior quality of the produce in active MAP over the passive one in terms of appearance, taste and odor. The present work examined the effects of MAP on indigenous microbial populations and the survival of inoculated Salmonella enterica on the surface of the lettuce. Leaves of romaine lettuce washed with 200 ppm chlorine were inoculated with S. enterica serotype Typhimurium or not inoculated and packaged in one of the three systems: (a) passive MAP in 35 - ?m low-density polyethylene bags having OTR 5700 cm3 m-2 day-1 bar-1 and WVTR 2.9 g m-2 day-1; (b) active MAP in the same bags with an initial gas mixture of 10% O2, 10% CO2, and 80% N2; and (c) control without MAP. Active MAP reduced aerobic plate counts of non-inoculated leaves compared to control, showing inhibitory effect towards indigenous lettuce microflora, but not towards Salmonella. Moreover, it even favoured the survival of the pathogen, possibly due to the elimination of its natural antagonists. Passive MAP effects were less pronounced. Our findings demonstrate that, despite its effects against indigenous microflora, active MAP does not protect against S. enterica on lettuce. The use of appropriate sanitation practices to prevent contamination remains the major measure for ensuring the microbiological safety of ready-to eat products. Original title, full list of authors, and source ACTIVE MAP OF READY - TO - EAT ROMAINE LETTUCE: EFFICIENT AGAINST BROWNING AND MICROBIAL SPOILAGE, BUT NOT AGAINST SALMONELLA ON THE LEAF SURFACE Rodov, V.(*), Horev, B., Sela, S., Vinokur, Y., Pinto, R., and Richard, G. vrodov@agri.gov.il ARO ? The Volcani Center, Bet Dagan, Israel CA MA 2013, XI International Controlled & Modified Atmosphere Research Conference, Trani (Italy), 3-7 June 2013, http://www.cama2013.org/ The picture is by detrasdelosalimentos.es Key wordsPoscosecha?? ?postcosecha?? ?postharvest?? ?na-oes?? ??? ??? ???????? ????? ??? ?post-r?colte?? ????? ?? ??????????? ??? ?na-oogst?? ?post-raccolta?? ?Obr?bka po?? ?p?s-colheita?? ????????????????? ?hasat sonras??? ??? ?Ernte?? ????????????????? ????? ????????????? ?postcollita?? ?poskliz?ov頠 ????? ??? ??? ??? ?nakon branja?? ?pozberov頠 ??? ?obdelovanje zemlje po?? ?post-colleita?? ?????? ??????? ?pascapanen?? ??il?onn postharvest?? ??????? ?p?c ra?as?? ?derliaus apdirbimas po?? ?lepas tuai?? ??? ?? ???????? ?post-recoltare?? ??????? ??????? ???????????????????? ?????????????? ?????????????????? ?sau thu ho?ch?? ?????????????????? ?zangemva kwenkathi yokuvuna lettuce??? blaarslaai??? ??????? ????? laktuko??? laitue?????? ?????????? ???? ???????? sla??? lattuga??? sa?ata??? alface??? ?????-???????? marul??? ????????