Effect of radio frequency-assisted hot-air drying on drying kinetics and quality of Sichuan pepper (Zanthoxylum bungeanum maxim.)

Abstract

Radio frequency (RF) is an efficient uniformity heating method that can be used for pasteurization. Information on how RF heating influences the physicochemical properties of agricultural product is limited. In this study, the effect of RF heating treatment combined with hot-air (HA) drying (50 °C, 55 °C and 60 °C) on the physicochemical properties of Sichuan pepper was assessed. Sichuan pepper was subjected to RF treatment combined with HA drying, and the performance was compared with HA drying alone (50 °C, 55 °C and 60 °C) in terms of drying kinetics, volatile components, non-volatile components (OH-α-sanshool, polyphenols and flavonoids) and antioxidant activity (ABTS and ferric reducing antioxidant power). RF heating had no negative effects on OH-α-sanshool for the 50 RF-HA group but it could significantly reduce the loss of polyphenols (12.27% at 55 °C, RF-HA group) and flavonoids (15.08% at 60 °C, RF-HA group). Compared with fresh Sichuan pepper, the 50 RF-HA group retained a similar aroma profile. RF heating treatment followed by HA drying is a prospective technique for obtaining high-quality dried Sichuan pepper.