Design, Development, and Optimization of a Hot Air–Assisted Continuous Infrared Dryer for Efficient Drying and Quality Retention of Broccoli

ABSTRACT

Broccoli is a highly nutritious vegetable, but it is susceptible to rapid deterioration due to its high moisture content. Although infrared‐assisted drying has shown promise, most studies have focused on batch systems with limited industrial applicability. Therefore, this study aimed to design, optimize, and evaluate a novel continuous hot‐air‐assisted infrared (HA‐IR) dryer for efficient broccoli drying while maintaining product quality and storage stability. Engineering properties of broccoli slices were determined to support dryer design and operation. The performance of tray drying, infrared drying, and HA‐IR drying was compared, and process parameters were optimized using response surface methodology. The optimized HA‐IR drying conditions significantly reduced drying time and energy consumption while improving moisture removal, vitamin C retention, and color quality. A continuous HA‐IR dryer was subsequently fabricated and evaluated, achieving 40% thermal efficiency, a final moisture content of 7.5%, a moisture diffusivity of 1.71 × 10 ⁻¹⁰  m ²  s ⁻¹ , and minimal color change under optimized operating conditions of a 20 cm lamp distance and a 2 rpm belt speed. In addition, pretreatment with 6‐benzylaminopurine at 10 ppm improved chlorophyll retention and color stability. Storage studies demonstrated that polypropylene packaging effectively maintained product quality for up to 60 days. This highlights the potential of the developed continuous HA‐IR drying system as an energy‐efficient and industrially applicable technology for broccoli preservation.