Validation of radio frequency assisted traditional thermal processing for pasteurization of powdered infant formula milk

Abstract This study validated the radio frequency assisted traditional thermal processing (RF assisted-TTP) for pasteurization of low-moisture foods. Powdered infant formula milk (PIFM) with water activity of 0.22 ± 0.01 was selected as a low-moisture food model. The cold spot during the RF heating of PIFM was found to be the center of top layer in a tray containing 312 g of PIFM. The PIFM was inoculated with Cronobacter sakazakii and 12 g inoculated sample packed in a plastic bag was placed at the pre-determined cold spot. The sample was treated until the cold spot reached 65 °C in a 6-kW, 27.12-MHz RF heating system and the sample tray was transferred to a hot air oven set at 65 °C for various holding times. Based on the microbial inactivation during holding time, D-value at 65 °C was determined. After 21 h oven holding, a 5-log reduction of C. sakazakii was achieved. The sample was also thermally treated in the same oven without any RF pre-heating. The quality analysis results indicated that both RF assisted-TTP and TTP had no significant effect on color, solubility, digestibility, and wettability, while significant changes were observed on water activity, moisture content, POV and TBArs after both treatments. Come-up time to heat up sample to 65 °C in RF system and oven was approximately 10 min and 5 h, respectively. RF assisted-TTP is more suitable for pasteurization of PIFM than TTP due to lower lipid oxidation and much shorter overall processing time. Thus, RF may provide a potential as an effective emerging technology for pasteurizing while maintaining the quality of PIFM.