Black garlic: A comparative review of maturation, nutritional composition, bioactive compounds, biological activity, and health effects

Black garlic is a processed garlic product obtained through controlled thermal aging under specific temperature and humidity conditions (maturation), which induces physicochemical and biochemical transformations. Compared with fresh garlic, black garlic exhibits improved sensory properties, including a sweeter taste, softer texture, and reduced pungency, together with enhanced functional properties. This review summarizes current knowledge on the effects of processing on the nutritional composition, bioactive compounds, and biological activities of black garlic. Thermal aging significantly modifies proximate composition by reducing moisture and increasing the relative concentrations of proteins, carbohydrates, minerals, and free sugars. The maturation process is also associated with increased levels of bioactive compounds such as S-allyl cysteine, phenolics, and flavonoids. Simultaneously, Maillard reactions lead to the formation of melanoidins and 5-hydroxymethylfurfural. These compositional changes have been associated with the increased antioxidant capacity of black garlic. Evidence from in vitro studies indicates that black garlic exhibits antioxidant, antimicrobial, and cytotoxic activities, whereas human clinical studies suggest potential benefits for endothelial function, inflammatory responses, immune modulation, and lipid metabolism. Overall, black garlic represents a promising functional food with potential applications in health promotion and disease prevention. However, further studies are needed to standardize processing conditions, clarify mechanisms of action, and confirm its long-term clinical efficacy and safety.