Hot air-assisted radio frequency heating for stabilization of rice bran: Enzyme activity, phenolic content, antioxidant activity and microstructure

Effects of Radio Frequency Heating on the Stability and Antioxidant Properties of Rice Bran

“…In a previous study, 6 kW, 27.12 MHz RF for 200 g rice bran stabilization required 15 min [ 17 ], and 12 kW 27.12 MHz RF for 400 g rice bran stabilization required 6 min [ 19 ], respectively. Although the dielectric properties (ε′ and ε″) of rice bran at 27.12 MHZ were larger than 40.68 MHz [ 20 ], 1 kg rice bran at our 5 kW, 40.68 MHz RF heating system obtained a faster temperature increasing rate and less heating time ( Table 1 ).…”

“…Furthermore, similar results were obtained by Pradeep et al [ 9 ], indicating that an improper high temperature would cause the loss of antioxidants. Rice bran (400 g) stabilized by the hot air-assisted RF heating system (12 kW, 27.12 MHz) at high temperatures of 110–115 °C for 6 min had no significant change in protein, lipid, total tocotrienol and total tocopherol content and fatty acid composition, only reducing the free phenolic content of the rice bran [ 19 ]. The RF heating at 100 to 120 °C holding for 5 min for stabilization of rice bran had a negative impact on the yield, purity, foaming properties and solubility of the rice bran protein isolates, but it improved the absorption and emulsifying properties [ 18 ].…”

“…In a previous RF study, rice bran (400 g) was stabilized by a hot air-assisted RF heating system (12 kW, 27.12 MHz) at a low temperature of 100–105 °C for 15 min or at high temperature of 110–115 °C for 6 min without a significant effect on the protein, lipid, total tocotrienol, total tocopherol and fatty acid composition, but reducing the free phenolic content of the rice bran [ 19 ]. The dielectric properties (ε′ and ε″) of rice bran during RF heating were greatly influenced by the frequency, temperature and moisture content of the rice bran [ 20 ].…”

“…The dielectric properties (ε′ and ε″) of rice bran during RF heating were greatly influenced by the frequency, temperature and moisture content of the rice bran [ 20 ]. In addition, researchers have only selected 200 g [ 17 ] and 400 g [ 19 ] rice bran by applying 6 kW and 12 kW 27.12 MHz RF equipment, which still required 15 min and 6 min for rice stabilization, respectively.…”

Rice bran and its constituents: Introduction and potential food uses

“…Among the treatments, infrared radiation showed the greatest inactivation of lipase activity. Liao et al (2020) Hot air-assisted radio frequency heating The stabilisation method does not affect the tocol content in rice bran but better antioxidant activity than rice bran treated with extrusion. Asad et al (2021) Microwave heating Microwave treatments reduce the free fatty acid value that fits to the human consumption.…”