Effectiveness of superheated steam for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, Salmonella Enteritidis phage type 30, and Listeria monocytogenes on almonds and pistachios

This study was undertaken to evaluate the effectiveness of superheated steam (SHS) on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, Salmonella Enteritidis phage type (PT) 30 and Listeria monocytogenes on almonds and in-shell pistachios and to determine the effect of superheated steam heating on quality by measuring color and texture changes. Almonds and in-shell pistachios inoculated with four foodborne pathogens were treated with saturated steam (SS) at 100 degrees C and SHS at 125, 150, 175, and 200 degrees C for various times. Exposure of almonds and pistachios to SHS for 15 or 30 s at 200 degrees C achieved >5 log reductions among all tested pathogens without causing significant changes in color values or texture parameters (P>0.05). For both almonds and pistachios, add and peroxide values (PV) following SS and SHS treatment for up to 15 s and 30 s, respectively, were within the acceptable range (PV < 1.0 meq/kg). These results show that thermal application of 200 degrees C SHS treatment for 15 s and 30 s did not affect the quality of almonds and pistachios, respectively. Therefore, SHS treatment is a very promising alternative technology for the tree nuts industry by improving inactivation of foodborne pathogens on almonds and pistachios while simultaneously reducing processing time. (C) 2016 Elsevier B.V. All rights reserved.