###### Abstract  
The aim of this study was to evaluate the bioactive and physicochemical properties of white and black garlic (_Allium sativum_ L.) from conventional and organic cultivation. Both white conventional (G) and organic (EG) garlic were processed during 45 days heat treatment at 70 \({}^{\circ}\)C temperature and 80% relative humidity. In black garlic (BG) samples the content of soluble solids, total reducing sugars, total polyphenol as well as antioxidant activity significantly (\(p<0.05\)) increased (by about 33.5%, 60.5%, 118.4%, 125.8%, respectively), while a pH significantly (\(p<0.05\)) decreased (by about 41.1%) as compared to white garlic samples. The study showed significant differences between colour of white and black garlic, both in the \(L^{*}\)\(u^{*}\)\(b^{*}\) and RGB colour space, especially in the case of the \(L^{*}\) parameter, indicating that the colour of garlic changed from white to dark brown or black during the thermal processing. All organic garlic samples had improved bioactive ingredients and antioxidant activity compared to conventional garlic for both fresh (unprocessed) and heat-treated black garlic. The production of black garlic, especially organic (EBG), allows one to obtain a product with higher amount of bioactive compounds, which can be widely used in the design of health-promoting functional food. black garlic; _Alllium_; \({}^{\circ}\)Brix; reducing sugars; polyphenols; antioxidant activity; \(L^{*}\)\(u^{*}\)\(b^{*}\) colour space; organic food +
Footnote †: journal: Applied Sciences  
as a natural antibiotic and shows strong bactericidal properties, effectively fighting infectious bacteria infecting, among others, skin, mouth, gastrointestinal, respiratory, and urinary tract [24; 25]. Stimulating production of bile and accelerating intestinal peristalsis, it has a beneficial effect on the functioning of the digestive system. Fighting the bacteria _Heliobacter pylori_, which are the cause of indigestion and even stomach cancer, garlic has a good effect on the entire digestive tract [25; 26; 27]. Garlic also has an immunomodulatory effect by stimulating the activity of natural killer cells and macrophage phagocytosis, activating the response of lymphocytes to myogens and cytokines [28; 29], as well as improves the elasticity of arteries and lowers blood pressure [30; 31; 32]. It effectively lowers cholesterol and triglycerides. Given the above, garlic can be helpful in preventing heart attacks, strokes, and other diseases of the cardiovascular system [33; 34; 35]. It is also known for its antidiabetic [36; 37; 38], anti-inflammatory, anti-rheumatic [39], and even anti-cancer properties, associated with a strong antiproliferative and proapoptotic effect on various cancer cells [40; 41; 42; 43; 44]. Garlic also exhibits outstanding antioxidant abilities, is a strong free radical scavenger, interrupts free radical reactions, and supports the action of endogenous antioxidative enzymes, increasing the body's ability to fight free radicals and, thus, is extremely effective in preventing many civilizational diseases [45; 46; 47; 48]. The versatile health effects and physiological properties of garlic, widely documented in the literature, are attributed to the variety of bioactive compounds, mainly polyphenic substances with strong antioxidant properties [3; 4; 6; 13; 47; 49; 50; 51; 52; 53; 54; 55]. The organosulphuric compounds naturally collected in garlic include: colourless and odourless allin (s-allyl-l-cysteine sulphoxide), \(\gamma\)-glutamyl-s-allyl-cysteine (GSAC), and their derivatives, formed during mechanical damage of garlic cloves.