Effect of Radio Frequency Cold Plasma on Blueberries Hot Air Drying: Characteristic Curves and Quality Assessments

Abstract

ABSTRACT Hot air drying (HAD) is an important processing method for blueberries, which is of great significance for extending their shelf life, reducing postharvest losses, and increasing added value. However, the surface of blueberries is covered with a waxy layer, leading to long drying times and severe loss of nutrients; pretreatment is generally considered a necessary approach to improve the efficiency of HAD of blueberries. Cold plasma (CP) is a promising non‐thermal pretreatment these years, but radio frequency cold plasma (RFCP) has not yet been applied to drying pretreatment. This study compared RFCP with four traditional pretreatments (blanching, ultrasound, freeze–thaw, alkaline solution) on blueberry HAD. Results showed that RFCP pretreatment achieved the highest effective moisture diffusivity ( D eff = 4.59 × 10 −10 m 2 /s) and the shortest drying time (50% reduction vs. control), outperforming all other pretreatments (which reduced drying time by only 8%–17%). RFCP also yielded the best color preservation (Δ E closest to fresh), the highest rehydration ratio, and the greatest retention of anthocyanins (+86.3% vs. control) and total phenolics (+46.3% vs. control), surpassing BL, UL, FT, and AS. These findings demonstrate that RFCP is a green and efficient non‐thermal pretreatment that outperforms traditional methods by simultaneously enhancing drying efficiency and preserving nutritional quality, offering a promising alternative for the processing of berries with waxy layers.