Transport phenomena and their effect on microstructure of frozen fruits and vegetables

Background: Fresh fruits and vegetables have a short shelf life. Freezing offers a solution to their long-term preservation. However, transport phenomena during freezing of fruits and vegetables pose significant changes in microstructure, affecting quality stability, shelf-life extension, and market value. Therefore, information on the microstructure of frozen fruits and vegetables is very critical for process design and quality control. Scope and approach: In this review, transport phenomena and their effect on the microstructure of frozen fruits and vegetables are considered at the cell level. The effect of cell structure, freezing rates, and heat and mass transfer characteristics on the texture of cellular tissues are presented. Emerging techniques for controlling ice crystal growth are also discussed. Key findings and conclusions: The quality of frozen fruits and vegetables is hinged on the microstructure stability, which is highly dependent on phase change processes and the size of ice crystals. The proportion and characteristics of cellular water, heat and mass transfer parameters, freezing rate and thermal property of cells are considered as the main drivers for moisture migration and ice crystal formation. To produce frozen fruits and vegetables with high quality, more insightful study and accurate understanding of transport phenomena in cellular space and their corresponding effects on the microstructure is necessary. It is hoped that this review should provide critical information on preserving the microstructure and quality of fruits and vegetables as affected by moisture migration for future studies.