How Does Food Processing-Induced E/Z Isomerization Regulate Carotenoid Bioaccessibility? - From Food Matrix to Mixed...

Carotenoids are essential lipophilic antioxidants in plant-derived foods, and their health benefits are highly dependent on bioaccessibility. Although carotenoids naturally occur predominantly as all-E isomers in plant tissues, food processing can induce geometrical isomerization to generate Z-isomers with enhanced bioaccessibility. This review begins by describing the accumulation, structural stability, and release of carotenoids in dietary plants and outlining key analytical methods for their detection and characterization. It then systematically summarizes the effects of thermal processing (industrial thermal sterilization, domestic cooking, and thermal drying), non-thermal processing (mechanical treatment, high-pressure processing, pulsed electric fields, ultrasonication, irradiation, non-thermal drying), and ingredient addition on carotenoid release and isomerization. Furthermore, the regulatory role of processing-induced isomeric structural changes on carotenoid bioabsorption is critically discussed. Processing alters the spatial configuration of carotenoids via E/Z isomerization, reducing crystallinity and aggregation while enhancing micellization efficiency. Concurrently, processing disrupts the plant matrix, promoting the release of isomerized products, thereby improving bioaccessibility. The effects on isomerization degree and bioaccessibility vary with processing method and parameters: moderate processing favors Z-isomer formation, whereas excessive processing leads to degradation. Elucidating the mechanisms of processing-induced E/Z isomerization and its regulation on bioaccessibility provides a theoretical basis for the scientific processing of plant-derived foods and precision nutrition, offering new perspectives for integrating food processing technology and nutritional science.