## 3 Results and Discussion
0.05) higher than in conventional garlic (G). The heat treatment processes applied to garlic resulted in a significant (\(p\)! 0.05) increase in the level of soluble solids in black garlic to an average of 48.77 \(\pm\) 4.71 \({}^{\circ}\)Brix (total for BG and EBG), while the increase in the content of reducing sugars was significantly higher in organic black garlic than in conventional black garlic. The results of our research coincide with those obtained by other authors. In fresh, unprocessed garlic, [PERSON] et al. (2019) [93] showed the content of soluble solids at the level of 40.47%, and during thermal processing of garlic (60 \({}^{\circ}\)C temperature and 90% relative humidity), increase in the amount of these compounds depended on the time of heat treatment. During the first 13 days of aging, they found no change in the content of soluble solids, but after 32 and 45 days of garlic processing, they showed a significant increase in the level of these components (to 43.17% and 45.67%, respectively). Other authors showed the content of soluble solids in fresh garlic in the range of 37.33-40.50% and their increase directly proportional to the temperature (72 \({}^{\circ}\)C, 75 \({}^{\circ}\)C and 78 \({}^{\circ}\)C) and time of garlic processing (up to 33 days) at a relative humidity of about 90%, up to 50.33%. In addition, these authors showed that at the end of heat treatment carried out at 78 \({}^{\circ}\)C and 75 \({}^{\circ}\)C, the content of soluble solids was lower (44.00% and 45.25%, respectively) in whole garlic heads than in peeled garlic cloves subjected to the same processing conditions (45.33% and 47.5%, respectively) [68]. In addition, [PERSON] et al. (2019) [93] also showed statistically significant differences in the level of these compounds in the three studied varieties: Chinese Spring, California White and Spanish Roja, both in fresh material (30.5%, 40.67% and 43.5%, respectively) and in black garlic produced from them (42.5%, 48.6% and 55.75%, respectively) during a 34-day heat treatment (72 \({}^{\circ}\)C, 90% humidity), which suggests that not only the conditions of the black garlic production process, but also the genotypic and environmental conditions, including the method of cultivation, determine the amount of compounds in the raw material and the changes in their content during the processes applied. Taking into account the obtained results for all analysed garlic samples, a statistically significant (\(p\)! 0.05) correlation was found between the total reducing sugars and total soluble solids (\({}^{\circ}\)Brix), (R\({}^{2}\) = 0.97), which means that with an increased in the content of reducing sugars, the content of soluble solids increases and this relationship was practically complete. During heat treatment leading to the production of black garlic, the pH level also changes significantly. According to the studies (Table 1), the average pH of fresh, unprocessed garlic was 6.26 \(\pm\) 0.09 (total for G and EG), while in black garlic it decreased significantly (\(p\)! 0.05) to an average of 3.69 \(\pm\) 0.36 (total for BG and EBG), with the lowest value in organic black garlic (3.43). Our research is confirmed in the studies by other authors, who showed the pH of fresh garlic at the level of 6.13 and a decrease in this parameter to a value of approx. 4.00 under the influence of heat treatment (90 days, 55 \({}^{\circ}\)C, 80% relative humidity) [79]. [PERSON] et al. (2016) [68] reported that the pH of fresh, unprocessed garlic heads (5.93 \(\pm\) 0.01) and cloves (6.31 \(\pm\) 0.07) under the influence of the aging process carried out during 33 days (90% relative humidity) was significantly reduced (to 3.49 \(\pm\) 0.06 and 3.52 \(\pm\) 0.03, respectively, for black garlic heads and cloves), depending on the temperature applied. At a higher temperature, the pH was lower. Additionally, [PERSON] et al.