Antimicrobial efficacy of natural extract against and in "Piel de Sapo" melon juice.

Background: The minimal inhibitory concentration (MIC) of an aqueous extract of with reported functional properties (PLX) was determined on two strains of () belonging to serogroups commonly associated with foodborne illnesses ( O157:H7 ATCC 700728 and O111 isolate 172) in vegetable products and two control strains for antimicrobial tests assays ( ATCC 25922 and - ATCC 29212).

Results: Mean MIC values at standard pH (7.4) in broth for the strains tested ranged from 4,444 µg/ml (35ºC) to 1,250 µg/ml (10ºC) and to 182 µg/ml (4ºC). At pH 5.5, conditions resembling those of melon juice, MIC was about 2 times higher at 35 and 10ºC compared with 4ºC. The MIC of was similar or slightly lower than those of at the conditions tested. In melon juice fortified with PLX (2,500 µg/ml, maximum sensorial acceptable limit), the three strains of maintained their viability although none showed growth potential after 4 days at 4ºC.

Conclusions: PLX could be added to melon juice to control O157:H7 and O111 during refrigerated storage, reducing the risk of microbiological contamination in this food.