Microwave- and radio frequency-assisted two-step roasting of peanut kernels for enhanced heating efficiency and flavor

Peanuts continue to be processed using traditional, time-intensive methods, such as frying. This study explored microwave or radio frequency preheating combined with oven roasting to reduce processing time while maintaining product quality. Compared with dry-fried peanut kernel (DFPK) samples that take 18 min to reach 90 °C, microwave-preheated and oven-roasted peanut kernel (MWPK) samples reached 130 °C in 70 s, and radio frequency-preheated and oven-roasted peanut kernel (RFPK) samples reached 130 °C in 180 s. Sensory evaluation was used to optimize oven roasting conditions, with MWPK samples receiving higher scores than RFPK and DFPK samples. Volatile compound analysis, which was conducted using headspace solid-phase microextraction-gas chromatography-mass spectrometry, revealed 2,5-dimethyl-pyrazine and 2-ethyl-3-methyl-pyrazine as the primary aromatic compounds generated during the Maillard reaction. The optimal process involved 70 s of microwave preheating followed by oven roasting at 130 °C for 5 min. Overall, this process yielded high-quality peanut kernels while reducing processing time and energy consumption.