Inactivation of Bacillus subtilis spores in soybean milk by radio-frequency flash heating

An apparatus to pasteurize soybean milk using radio-frequency flash heating (RF-FH) was developed. An electrode surface was covered with a 50-μm thick Teflon film, and 28 MHz RF-FH was applied to soybean milk flowing through the electrode.A four-logarithm-order reduction of Bacillus subtilis spores was realized in the soybean milk by RF-FH at up to 115 °C for 0.4 s.Fouling of the electrode surface by the protein from the soybean milk became a problem with high-electric-field AC (HEF-AC) continuous treatment. When the electrode surface was covered with a Teflon film, there was no fouling. Tofu was produced experimentally using RF-FH processed soybean milk and conventionally heated soybean milk. Comparative studies revealed that the tofu made by RF-FH processing had higher gel strength than the tofu made by conventional heating.