Combined Effect of Drying Methods and Enzymatic Hydrolysis on Antioxidant Activity, ACE-Inhibitory and Functional Properties of Black Garlic

This study aimed to evaluate the combined effects of enzymatic hydrolysis and drying methods on functional attributes, nutritional contents, bioactive compounds and antioxidant capacity of black garlic ( Allium sativum L .). Three proteolytic enzymes with distinct protease activity namely Alcalase, Pepsin, and Flavorzyme were applied to five different drying treatments: sun drying (SDry), hot air drying (HDry), freeze drying (FDry), infrared-assisted freeze drying (IFDry) and pulsed vacuum drying (PVDry). This study demonstrated that Alcalase exhibited the highest proteolytic efficiency showing the highest degree of hydrolysis at 50.47% ( p  < 0.05), total soluble protein at 150.76 µg/mL ( p  < 0.05), and a significantly higher total sugar content ( p  < 0.05). Notably, PVDry preserved these parameters better than thermal methods, highlighting its efficacy in minimizing oxidative and thermal degradation. Enhanced levels of key amino acids including hydrophobic, aromatic, and sulfur-containing residues were linked to increased antioxidant, metal-chelating, nitric oxide scavenging, and ACE-inhibitory activities. PVDry-Alcalase treatments consistently showed the most pronounced functional improvements. Phenolic and flavonoid contents were also elevated in non-thermal drying combined with enzymatic hydrolysis, further enhancing radical scavenging capacities. This study demonstrates that integrating broad-specificity enzymatic hydrolysis with mild drying techniques strategically maximizes black garlic’s bioactive compound extraction and stability, underpinning its potential as a potent functional food ingredient. These findings provide a methodological framework for optimizing industrial black garlic production to improve health-promoting properties and product quality.