Inactivation of Salmonella enterica and Listeria monocytogenes in cantaloupe puree by high hydrostatic pressure with/without added ascorbic acid

The objective of this research was to evaluate and develop a method for inactivation of Salmonella enterica and Listeria monocytogenes in cantaloupe puree (CP) by high hydrostatic pressure (HHP). Cantaloupe being the most netted varieties of melons presents a greater risk of pathogen transmission. Freshly prepared CP with or without 0.1% ascorbic acid (AA) was inoculated with a bacterial cocktail composed of a three serotype mixture of S. enterica (S. Poona, S. Newport H1275 and S. Stanley H0558) and a mixture of three strains of L. monocytogenes (Scott A, 43256 and 51742) to a population of ca. 10(8) CFU/g. Double sealed and double bagged inoculated CP (ca. 5 g) were pressure treated at 300,400 and 500 MPa at 8 degrees C and 15 degrees C for 5 min. Data indicated increased inactivation of both Salmonella and Listeria spp. with higher pressure. Log reduction for CP at 300 MPa, 8 degrees C for 5 min was 2.4 +/- 0.2 and 1.6 +/- 0.5 log CFU/g for Salmonella and Listeria, respectively. Survivability of the pathogens was significantly compromised at 400 MPa and 8 degrees C, inactivating 4.5 +/- 0.3 log CFU/g of Salmonella and 3.0 +/- 0.4 log CFU/g of Listeria spp. Complete inactivation of the pathogens in the puree (log reduction >6.7 log CFU/g), with or without AA, was achieved when the pressure was further increased to 500 MPa, except that for Listeria containing no AA at 8 degrees C. Listeria presented higher resistance to pressure treatment compared to Salmonella spp. Initial temperatures (8 and 15 degrees C) had no significant influence on Salmonella log reductions. Log reduction of pathogens increased but not significantly with increase of temperature. AA did not show any significant antimicrobial activity. Viable counts were about 0.2-0.4 log CFU/g less in presence of 0.1% AA. These data validate that HHP can be used as an effective method for decontamination of cantaloupe puree. Published by Elsevier B.V.