Garlic processing for bioactive transformation and recovery: aging, emerging technologies, extraction, isolation, and...

The health-promoting potential of garlic stems largely from organosulfur compounds (OSCs), phenolics, and flavonoids that drive its antioxidant, anti-inflammatory, and antimicrobial activities. However, key bioactive precursors such as alliin and allicin are chemically unstable, limiting the direct use of fresh garlic in functional food and nutraceutical development. To overcome this, various aging and processing techniques, most notably those used to produce black garlic, have been developed to convert these labile compounds into more stable, bioavailable derivatives, creating value-added products with enhanced functional properties. This review synthesizes current research on the biochemical transformations that occur during garlic aging and treatment, emphasizing the way different processing technologies influence the extent of compound conversion while preserving bioactivity. It critically examines extraction and purification strategies to maximize the recovery of bioactive compounds from aged or treated garlic, as well as recent advances in the extraction, isolation, and analytical characterization of these phytochemicals. Furthermore, previous studies demonstrated that garlic processing alters its phytochemical composition, with higher levels of certain compounds (such as SAC, phenolics, and flavonoids) and lower levels of other unstable compounds (such as alliin and thiosulfinates). The changes are influenced by the type of garlic, heat, pH, moisture, and processing time. While the application of conventional and emerging extraction methods can enhance bioactive recovery, limited kinetic studies, process standardization, and solvent usage remain important challenges. Future studies are needed to investigate time-dependent studies, process standardization, green extraction, bioaccessibility, pilot-scale validation, techno-economic analysis, and environmental assessment for the development of functional and nutraceutical products from garlic.