A Comprehensive Review on Physical Modifications of Plant Proteins: Mechanism, Influencing Factors, Structural and Functional Properties

Plant proteins have received increasing attention from food researchers with the growing demand for plant proteins and the emphasis on healthy food and "clean labeling". However, due to their complex and dense structure and greater susceptibility to external factors, plant proteins exhibit poor functional properties, which are not conducive to processing and application in the food industry. Currently, physical modifications of plant proteins have been increasingly reported to improve their functional properties. To the best of our knowledge, there is a lack of a comprehensive review that systematically sorts out and summarizes the physical modification of plant proteins. Therefore, this review mainly summarizes the mechanisms and influencing factors of physical modifications in plant proteins. Furthermore, this review also summarizes and discusses the effects of physical modifications on the structural and functional properties (solubility, emulsifying, foaming, and gel properties) of plant proteins. Finally, the challenges and the future perspectives on the physical modifications of plant proteins are also summarized. Currently, physical modifications of plant protein are mainly ultrasound and high pressure, followed by cold plasma. Ultrasound, high pressure, cold plasma, and pulsed electric field techniques can be affected by more factors due to the complexity of the equipment. The spectroscopy results confirm that physical modifications play a crucial role in improving the structural properties of plant proteins, including secondary and tertiary structure as well as surface hydrophobicity. In addition, physical modifications have been shown to have a positive effect in improving the functional properties of plant proteins, including solubility, emulsifying, foaming, and gel properties.