## 1 Introduction  
Since the 18 th century, when [PERSON] (1707-1778) first described the genus _Allium_, more than 1200 _Allium_ species have been categorized under Alliaceae. The primary _Allium_ species in Taiwan include _A. fistulosum_, _A. sativum_, _A. cepa_, _A. escalonicum_, and _A. tuberosum_, and they are critical vegetables and seasonings in some of the world's most popular dishes. In 1844, [PERSON] (1820-1864) extracted a pungent substance from garlic and named it \"allyl\", the Latin name for garlic [1]. Later, scholars studied this substance and discovered that it was a sulfur compound containing allicin. Among the types of _Allium_, garlic (_A. sativum_ L.) is the most commonly used seasoning in Asia. It has various biological properties such as antioxidant, anticancer, and bacteriostatic effects. When fresh garlic is placed in an environment with high temperature and high humidity for 15 to 90 days, it ages into natural black garlic (BG) with a sweet and sour taste and without the pungency of fresh garlic [2]. The sweet and sour taste of BG originates from its fructose and amino acids, whereas its black color is mainly caused by the Maillard reaction involving fructose, glucose, and amino acids [3]. During the aging process, allicinis rapidly transformed into various organic sulfur components. Compared with the S-allycysteine, S-allymercaptocysteine, and N(alpha)-fructosyl arginine in fresh garlic, those in BG are more beneficial to the human body [4]. Scholars have argued that aged BG does not have the pungent smell of allicin and has stronger biological activities such as antioxidant activity [5; 6; 7; 8], anticancer capacity, ability to reduce obesity, anti-inflammatory ability, antiallergy ability, liver protection, and dyslipidemia alleviation [9]. [PERSON] et al. [10] compared the biological activities and antioxidant activity of fresh garlic extract and the extract of BG aged at 70 \({}^{\circ}\)C and 90% humidity, discovering that the total phenol content of the BG extract is 2.5-fold greater than that of the fresh garlic extract, and the superoxide dismutase (SOD) activity of the BG extract is nearly 10-fold greater than that of fresh garlic. In addition, the crude lipid, crude protein, and total sugar content were discovered to be higher in BG than in fresh garlic in another study, with the BG extract containing various free amino acids [8]. When garlic is heated and aged, its pH decreases; furthermore, its polyphenol content and antioxidant activity increase substantially [11]. [PERSON] et al. [12] investigated the aging of fresh garlic into BG at temperatures of 60, 70, 80, and 90 \({}^{\circ}\)C and discovered that during heat treatment at different temperatures, contents of water, amino acids, and allicin progressively were reduced, whereas total phenols, total acid, and browning intensity were elevated. An aging temperature of 70 \({}^{\circ}\)C was concluded to be the most conducive to aging because BG formed at this temperature had outstanding quality and flavor. Animal tests found that in mice, anti-free radicals from BG extract were more efficient than those from fresh garlic extract [13]. Additionally, compared with fresh garlic, BG was more effective at improving the metabolic capacity of mice and strengthening their cardiovascular activity [14]. In our previous study, we discovered that through its own enzymatic reactions, garlic aged in a high-temperature and highly humid environment turned into darker, more tender, and sweeter BG [15]. Aged BG naturally has a higher antioxidant activity than fresh garlic. Through the aging process under high temperature and humidity, allicin is decomposed into various usable compounds, including a water-soluble sulfur-containing amino acid compound (S-allycysteine) that substantially increases the SOD activity and total phenol content.