Challenges of dry hazelnut shell surface for radio frequency pasteurization of inshell hazelnuts

Thermal inactivation kinetics (D and z values) of Salmonella Enterococcus faecium in fresh hazelnut shell kernel were determined. Aluminum pouches containing either 1.5 g powder or 2 ground inoculated with bacterium at their original water activities (aw-shell = 0.91 ± 0.01, aw-kernel 0.93 0.01) isothermally treated a thermal death time (TDT) sandwich 55, 60, 65, 70 75 °C for determining D values. A single layer inshell hazelnuts one nut located the center (cold spot) tray was subjected to hot air assisted radio frequency (HARF) heating 6-kW 27.12-MHz RF system temperature ~75 10, 15 20 min. The log-linear model fits survival data both E. well. D-values bacteria higher than those shell. Higher demonstrated that it is suitable surrogate kernel. There large variation between calculated (based on F-value) experimental log reductions Salmonella. Only 1.0 0.1 reduction achieved after min HARF heating. Because pasteurization simultaneous drying process, F-value methodology could not give an accurate reliable lethality prediction due increased resistance caused by moisture loss. Around increase spraying 0.1% buffered peptone (BPW) same treatment condition. While activity top surface where 0.17 0.01 before treatment. This very dry major factor deviation from observed microbial this study. creates challenge pathogens other nuts similar structure. An efficient protocol needs be developed optimized combining disinfectants/salt solution process conditions enhance food safety quality hazelnuts. study provides valuable information direction industry improving