Advances in Vacuum Microwave Drying for Berries: Processing, Quality, and Future Perspectives for Sustainable Fruit...

Berries are valued for their vibrant color, delicate texture, and high levels of bioactive compounds; however, their soft tissues and high moisture content make them highly perishable, resulting in rapid postharvest deterioration and limited storage stability. Drying is a practical approach to extend their shelf life, although many conventional drying techniques expose berries to prolonged heating and oxygen, which leads to flavor loss, pigment degradation, and structural collapse. Vacuum microwave drying (VMD) is considered an advanced drying technology that unites rapid volumetric microwave heating with low-pressure dehydration to achieve high-quality dried fruits in a fraction of the time required by conventional drying methods. This review provides a comprehensive analysis of recent progress in the application of VMD to berry processing, focusing on the effects of microwave power, vacuum pressure, product temperature, and pretreatments on drying kinetics, nutrient retention, and microstructural quality. Comparative studies demonstrated that VMD produces berries with superior color, texture, and rehydration ability, comparable to or even better than those obtained by freeze drying, while consuming substantially less energy. Despite its potential, industrial adoption remains limited by challenges in energy distribution, microwave penetration depth, and process scalability. Recent studies increasingly emphasize the potential of hybrid drying strategies and enhanced process control as promising directions to improve the reliability and efficiency of VMD applications. Therefore, VMD represents a promising technology that bridges scientific innovation and industrial practice, offering an efficient and low-energy pathway toward the production of high-value dried fruits with improved nutritional quality and sensory attributes.