Research Progress on the Degradation of and Preservation Techniques for Chlorophyll in Vegetables during Thermal Processing

Chlorophyll imparts a green color to vegetables and possesses antioxidant, antimicrobial, immunomodulatory, and anticancer functions. However, it is unstable during thermal processing and easily degraded, resulting in loss of its bioactivity, thereby affecting the color and nutritional quality of vegetables. In plants, chlorophyll is normally degraded by pheophorbide oxygenase and also oxidized and degraded by chlorophyll peroxidase in the presence of phenolic substances. During thermal processing, chlorophyll is degraded through enzymatic and non-enzymatic reactions, the latter including the destruction of cell structure and chemical degradation reactions caused by heating. Additionally, factors such as temperature, pH, oxygen concentration and processing methods influence chlorophyll degradation during thermal processing. Physical, chemical, and biological methods are currently employed to prevent the degradation of chlorophyll through various mechanisms such as inactivating enzymes, enhancing the stability of chlorophyll by metal ions, promoting the formation of chlorophyll aggregates, and improving antioxidant capacity. This paper summarizes recent research on the degradation pathways and kinetics of chlorophyll in vegetables during thermal processing, and reviews and analyzes the techniques used to preserve chlorophyll during thermal processing.