In recent years, research on freeze-dried vegetables has expanded from single-process optimization to multiple dimensions, including nutritional mechanisms, composite technologies, quality control, and green low-carbon practices, forming a relatively systematic research framework and driving the industry towards high-quality development.
🔬 Process Innovation: From Basic to Composite
Research focus has shifted from traditional vacuum freeze-drying (FD) technology to composite processes aimed at energy saving and improved quality and efficiency.
• Combined Drying Technology: By coupling infrared radiation, microwaves, and pulsed jet beds, heat and mass transfer are enhanced during the sublimation stage, significantly shortening drying time and improving energy utilization efficiency.
• Process Optimization: For different vegetables (such as leafy greens, root vegetables, and mushrooms), the infrared absorption and penetration patterns are studied, and mathematical models are established to optimize drying conditions, providing a theoretical basis for industrial scale-up.
🌿 Nutritional Mechanisms: From Holistic to Precise
Research has delved into the changing patterns and regulatory mechanisms of specific nutrients, moving beyond simply assessing overall quality.
• Vitamin Retention: Studies show that freeze-drying retains heat-sensitive nutrients more efficiently than sun-drying. The vitamin C loss rate in freeze-dried vegetables can be controlled at a low level, while the loss rate in sun-drying is as high as 60%–80%.
• Active Substances and Color: Active substances such as polyphenols and carotenoids are better preserved under rapid freezing and appropriate drying conditions. Meanwhile, research has also focused on the oxidation problems caused by the porous structure during storage, providing optimization directions for packaging and storage.
💧 Quality Control: From Appearance to Protection
Addressing the challenges of freeze-dried products' hygroscopicity and quality degradation after rehydration, research has extended from single drying processes to comprehensive quality control.
• Hygroscopic Mechanism and Regulation: A systematic study of the hygroscopic characteristics of freeze-dried hawthorn, apples, and other products revealed that their porous structure leads to strong hygroscopicity. To address this issue, research explored edible coatings based on zein and combined them with electrospray coating technology to form a dense, water-resistant film on the surface of fruits and vegetables. This significantly reduced moisture absorption while effectively maintaining nutritional components and sensory quality.
🌍 Green and Low-Carbon: From Production to Certification
Under the "dual carbon" goal, green and low-carbon research on freeze-dried vegetables has become a new hot topic, aiming to quantify and reduce the environmental impact of the entire industry chain.
• Carbon Footprint Calculation: Taking freeze-dried kale powder as an example, existing research has accurately calculated the carbon footprint per unit product (e.g., approximately 11.67 kg of CO2 equivalent per kilogram of product) through life cycle assessment, providing the industry with quantifiable environmental indicators.
• Green Technology Integration: Research is extending to upstream links such as raw material planting, cold chain logistics, and energy structure. By optimizing green planting, energy-saving equipment, and intelligent management, a low-carbon processing model is being constructed to enhance the green competitiveness of products.
