Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2016
Publication Date: 7/11/2016
Citation: Mukhopadhyay, S., Sokorai, K.J., Ukuku, D.O., Fan, X., Juneja, V.K., Sites, J.E., Cassidy, J.M. 2016. Inactivation of Salmonella enterica and Listeria monocytogenes in cantaloupe puree by high hydrostatic pressure with/without added ascorbic acid. International Journal of Food Microbiology. 235:77-84. doi: 10.1016/j.ijfoodmicro.2016.07.007.

Interpretive Summary: Production, consumption and trade of cantaloupe fruit increased in recent years due to its nutritive value, taste, texture and versatility. Due to the increased consumption outbreaks related to cantaloupe has also increased. Since cantaloupe melons grow at ground level, their outer skins can be contaminated with pathogenic bacteria. Since 1990, more than twenty-five outbreaks have been linked to cantaloupes which caused many people ill and even death. Most of these outbreaks are caused by bacteria known as Listeria monocytogenes and Salmonella. These outbreaks highlight the need for effective decontamination methods to ensure the safety of cantaloupe and cantaloupe products such as puree. Thermal treatment is not an appropriate method for decontamination since cantaloupe is very heat sensitive. Therefore the purpose of present study was to evaluate and develop a nonthermal method to ensure safety and extend shelf life of cantaloupe product such as puree.

Technical Abstract: 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 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. 108 CFU/g. Double sealed and double bagged inoculated CP (ca. 5 g) were pressure treated at 300, 400 and 500 MPa at 8 deg C and 15 deg 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 deg 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 deg 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, were achieved when the pressure was further increased to 500 MPa, except that for Listeria containing no AA at 8 deg C. Listeria presented higher resistance to pressure treatment compared to Salmonella spp. Initial temperatures (8 and 15 deg C) had only minor influence on Salmonella log reductions. Log reduction of pathogens increased but not significantly with increase of temperature. AA exhibited mild antimicrobial activity. Viable counts were about 0.2-0.4 log CFU/g lower in presence of 0.1% AA. These data validate that HHP can be used as an effective method for decontamination of cantaloupes puree.