Chemical composition and biological potential of garlic by-products

Garlic is a vegetable from the Allium genus that has been valued for its medicinal properties since ancient times. Today, alongside traditional white garlic, increasing attention is being given to black garlic (produced through the thermal processing of white garlic at a specific temperature and relative humidity), a food with equally beneficial properties and rich nutritional value that is associated with numerous health benefits and a valuable nutritional composition. During the thermal processing of garlic, valuable by-products are formed, characterized by a high content of phenolic compounds, which are known for their exceptional biological properties, particularly their antioxidant and antimicrobial activity. The aim of this research was to determine and compare the chemical composition and biological potential of extracts from white and black garlic by-products. Extracts were prepared using microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE). The total phenolic content (TPC) of the extracts was determined using the Folin-Ciocalteu method, while specific phenolic compounds were identified using the HPLC method. The antioxidant potential was evaluated using FRAP, ORAC, and DPPH methods, and the antimicrobial activity was assessed by determining minimal inhibitory and bactericidal concentration. The results indicate a high TPC, with rutin identified as the dominant flavonoid, and a good biological potential for all tested extracts. Extracts from black and white garlic by-products exhibited similar antimicrobial activity against all tested microorganisms, with better activity observed against Gram-positive species, particularly Listeria monocytogenes. The extract from white garlic by-products obtained through microwave-assisted extraction demonstrated the highest antioxidant activity as measured by the DPPH (43.38%) and ORAC (39.02 mM TE/L) methods, along with the highest total phenolic content (60.10 mg GAE/g), indicating its exceptional potential for application in the food industry as a natural alternative to synthetic additives.