P1-68 Validation of Radio Frequency Dielectric Heating (RFDH) System for Destruction of Cronobacter sakazakii and Salmonella spp. in Nonfat Dry Milk (NDM)

Monday, July 29, 2013
Exhibit Hall (Charlotte Convention Center)
Minto Michael, Kansas State University, Manhattan, KS
Randall Phebus, Kansas State University, Manhattan, KS
Harshavardhan Thippareddi, University of Nebraska-Lincoln, Lincoln, NE
Jeyamkondan Subbiah, University of Nebraska-Lincoln, Lincoln, NE
Sohan Birla, University of Nebraska-Lincoln, Lincoln, NE
Karen Schmidt, Kansas State University, Manhattan, KS
Introduction: Cronobacter sakazakii and Salmonella spp. have been associated with human illnesses from consumption of contaminated nonfat dry milk (NDM), a key ingredient in powdered infant formula and many other foods. C. sakazakii and Salmonella spp. have been reported to survive spray drying if milk is contaminated after pasteurization.

Purpose: Determine the thermal processing parameters (D- and z-values) for C. sakazakii and Salmonella spp. in NDM and validate radiofrequency dielectric heating (RFDH) system for decontamination of NDM.

Methods: High-heat (HH) and low-heat (LH) NDM were separately inoculated with a 5-strain cocktail of either C. sakazakii or Salmonella spp., transferred to thermal death time (TDT) disks and held at 75, 80, 85 or 90°C for 0 to 80 min. Surviving populations of the organisms were determined by plating on tryptic soy agar. Three replications were conducted and linear regression was used to determine the D- and the z-values. The inoculated NDM was heated using an RFDH system and held at specific temperatures in a convection oven to validate the RFDH system. 

Results: The D-values of C. sakazakii or Salmonella spp. were similar within the HH- or LH-NDM at respective temperatures using TDT disks and RFDH combined with convection oven used for the holding period; except for Salmonella spp. in HH-NDM at 85°C. D-values of C. sakazakii and Salmonella spp. varied from 23.00 to 26.25 min at 75°C, 7.52 to 13.75 min at 80°C, 6.03 to 8.68 min at 85°C, and 3.05 to 5.82 min at 90°C. The z-values of C. sakazakii or Salmonella spp. in HH- or LH-NDM were similar using TDT disks and RFDH. 

Significance: Radio frequency heating can be used as a post-process lethality treatment for NDM prior to the packaging; however, the effect of RFDH on the functional properties of NDM should be evaluated to enhance adoption by the dry milk industry.