###### Abstract
During cutting, crushing, chopping, biting, and various technological procedures (including heat treatment), under the influence of the released vacuolar enzyme (allinase), various derivatives of sulphuric compounds of allinin hydrolys to allicin are formed, including sulphides (DAS), disulphides (DADS), diallyl trisulphides (DATS), S-allyl-cysteine (SAC), and ajoenes, which determine both the bioactive properties and sensory qualities of garlic (taste and smell) [56; 57; 58; 59; 60; 61]. They give fresh garlic its typical sharp taste and aroma. Natural, baked, dried, marinated, in the form of cloves, flakes, powder, or oil, it gives the dishes a distinct and intense aroma, without which many of them would lose their specific character. Its taste and aroma make it a rather controversial spice. For some it is an indispensable ingredient, while others do not tolerate its characteristic aroma [13]. In addition to bad breath or body odour, excessive consumption of raw unprocessed garlic can cause burning in the oesophag, nausea, vomiting, diarrhoea, indigestion, abdominal and stomach pain, and even ulceration of the stomach wall or intestines [62]. Despite a wide range of its health-promoting properties, fresh garlic consumption is declining, with the exception of China and India [63], and new methods of its processing are being sought to eliminate unpleasant odour, improve sensory properties, and even strengthen its beneficial health-promoting and therapeutic properties. Thermal processing is widely applied in food production to obtain a greater range of colours and flavours, as well as improve the texture, digestibility, nutritional and health-promoting value of food products [64; 65]. Depending on the type (cooking, baking, frying, or microwaving), intensity and time of its use, food processing modifies the structure, composition and mutual proportions of bioactive compounds. It changes their bioavailability, thereby affecting the physiological effects of plants [33; 35; 46; 65; 66]. The exact origin of black garlic is not fully known. Most sources attribute it to the cultures of the Far East, i.e., today's China, Japan and Korea, where, even now, its production is greatest. Black garlic is a product of heat treatment carried out in the range of temperature between 60 \({}^{\circ}\)C and 90 \({}^{\circ}\)C and humidity conditions of 70-90% for a different but relatively long time (usually 60-90 days) [60; 64; 67; 68; 69; 70]. During this time, garlic acquires a new colour and loses its characteristic smell and sharp taste. Not only sensory characteristics of garlic change, but also its nutritional and health-promoting properties. By changes in, among others, the water content, the texture of garlic becomes more jelly-like, rubbery and greasy, making black garlic softer and stickier [8; 60; 64; 70; 71]. As a result of enzymatic and non-enzymatic browning, caramelization and oxidation of phenolic compounds, garlic changes colour from white to brown and eventually becomes black. It also acquires a completely different taste and aroma [72,73]. The increasing content of organic acids decrease significantly the pH of black garlic [64,67,68,69,64]. In addition, the content of reducing sugars (mainly fructose) produced in the hydrolysis of polysaccharides which are present in fresh garlic increases many times [70,71,74,75,76]. During the producing of black garlic the amount of the Maillard products increase, ultimately leading to the sweet and sour taste of raw garlic, with a hint of prunes, apricot and vanilla [8,67,77,78,79]. At the same time, volatile organosulfphuric compounds present in fresh garlic, including allicin, responsible for the irritating, sharp taste and aroma of garlic, are converted into stable, soluble and odourless substances with strong antioxidant properties such as S-allyl-L-cysteine (SAC), sulphides (DAD), disulphides (DADS), trisulphides (DATS), diallyl (DAS), dithines and apoenes [14,60,64,77].