Effects of Radio Frequency Roasting and Pressing Techniques on Peanut Oil Quality and Aroma

Peanuts undergo roasting to develop a distinctive aroma before undergoing controlled temperature pressing for peanut oil extraction. This study utilized 100°C hot air-assisted 5 kW radio frequency (HARF) equipment for peanut roasting. Subsequently, peanut oil extraction was conducted through cold pressing (CP) at 60°C and hot pressing (HP) at 120°C, with a comprehensive evaluation of their qualities and aromas. Analysis revealed that the surface temperatures of roasted peanuts were lower than their center temperatures, with center temperatures ranging from 120.6°C to 167.6°C for RF roasting durations of 4.5 to 10.5 min. As RF roasting time increased, acidity value, peroxide value, and malondialdehyde content significantly rose, reaching maximum values after 10.5 min, which evident charring on the peanut surface rendered them unsuitable for oil extraction. Aroma analysis via GC-IMS showed that peanuts roasted for 8.5 min exhibited volatile compounds similar to those found in commercial peanuts. Comparatively, 120°C HP yielded more oil than 60°C CP. Furthermore, GC-IMS analysis indicated that HP peanut oil contained more volatile compounds, contributing to a burnt odor and Maillard reaction, affecting both color and oxidation levels. Accelerated storage experiments at 65°C for duration of 24 days demonstrated a continuous increase in both acidity and peroxide values throughout the storage period."