## 1 Introduction
Technological processes, depending on type and intensity, affect the properties, activity, and bioavailability of compounds contained in fruits and vegetables, bringing about changes in their concentration, activity, and structure [39]. The most common methods of garlic processing include heat treatment (cooking, baking, frying, or microwaving), which may change the properties of the dietary fiber, its quantity and proportions of its fractions, cause loss of vitamins and other biologically active compounds, and reduce the content of natural antioxidants [19; 33; 34]. Thermal treatment, depending on its type and duration, may modify the composition and mutual proportions, as well as the bioavailability of bioactive compounds, e.g., organosulfuric or polyphenic compounds, thus influencing the physiological effects of garlic consumption in the body [33; 34; 39]. Therefore, new methods of garlic processing, production technologies, and industrial processes are constantly being searched for, which, on one hand, will allow to eliminate the unpleasant and irritating smell, and on other will improve the palatability and organoleptic characteristics and help obtain a better quality product, securing or even enhancing the beneficial properties of this nutritious plant. An example of such a process is the garlic fermentation process leading to the production of black garlic--a product characterized by completely different physicochemical, sensory, culinary, nutritional, dietary, and health-promoting properties than raw garlic [36; 37; 40; 41; 42; 43; 44]. In recent years, black garlic has been gaining ever more interest from both consumers and scientists, and thanks to its incomparably better health-promoting properties than those of other processed products and raw garlic, it is now considered the healthiest food product of natural origin and classified as a functional food of the \"Superfood\" kind. The process of producing black garlic, known from antiquity, comes from Asia and has been part of Korean, Japanese, and Thai cuisine for centuries. Over a dozen years ago was introduced to Europe, where it enjoys a constantly growing consumer interest. Black garlic is produced by long-lasting fermentation processes of whole heads or cloves kept under controlled conditions of high temperature (60-90 \({}^{\circ}\)C) and humidity (70-90%) for a period of several to over a many weeks(usually 30-90 days). This process takes place without the participation of microorganisms (bacteria and fungi), and without the addition of preservatives, but only under the influence of enzymes naturally occurring in the raw material, as a result of natural reactions and biochemical changes of the compounds present in garlic [36; 37; 40; 41; 42; 43; 44; 45]. During this long-term heat treatment, garlic undergoes enzymatic and non-enzymatic browning reactions, e.g., oxidation, caramelization and Maillard reactions, which radically change the physicochemical, organoleptic, sensory, and bioactive properties of garlic [46; 47]. As a result of fermentation processes, unstable organosulfur compounds present in raw garlic are transformed into stable, water-soluble substances, the most important of which is S-allycysteine, displaying very high antioxidant activity. For this reason, black garlic exhibits many times higher antioxidant potential than raw garlic [44; 46; 47]. As the temperature of the fermentation process increases, so does the intensity of the production of browning reaction products, including Amadori and Heyns compounds, which are important intermediates in the Maillard reaction that can further generate various thermal treatment products [40; 46; 47]. Since, as a result of the reaction of glucose or fructose with amino acids, changes in the sugar content occur, the fructose content increases significantly, thus leading to the characteristic sweetness of black garlic. As a result, it loses its sharp, irritating, characteristic garlic flavor and aroma.