## 3 Results and Discussion
These differences can be caused by many factors, ranging from species and variety differences, to environmental differences, such as growing and harvest conditions, climate, season, agricultural practices and cultivation systems [84]. As a result of applied heat treatment processes, the content of phenolic acids in BG significantly increased (to 80.67 \(\pm\) 6.94 mg/100 g d.m. on average in BG and EBG), and the highest content of these bioactive compounds was found in organic black garlic (87.00 \(\pm\) 0.41 mg/100 g d.m.). The available literature confirms the upward trend in the content of phenolic acids observed in our study. Authors show a 4-8-fold increase in the content of these compounds during heat treatment of black garlic [55, 64, 68, 73, 77]. In the study by [PERSON] et al., (2013) [55] hydroxycinnamic acid derivatives predominated in black garlic at various stages of its processing, just as in this study, which found that in conventional (BG) and organic (EGB) black garlic they accounted for 82.5% and 81.1% of all phenolic acids, respectively. As in fresh garlic, the dominant acid was p-coumaric acid (26.64 \(\pm\) 0.47 mg/100 g d.m. in BG and 28.03 \(\pm\) 0.12 mg/100 g d.m. in EBG). The second place was occupied by chlorogenic acid (respectively, 21.56 \(\pm\) 0.53 mg/100 g d.m. in BG and 25.29 \(\pm\) 0.52 mg/100 g d.m. in EBG). The results of our study are consistent with those of other authors, who also showed the highest proportion of p-coumaric and o-coumaric acids out of all phenolic acids in black garlic, as well as their largest (14-fold) increase during its heat treatment [55]. The phenolic acid present in the lowest concentration in both white and black garlic was ferulic acid. Its average content in white garlic (G and EG) was only 0.71 \(\pm\) 0.06 mg/100 g d.m., and in black garlic (BG and EBG) it was 0.66 \(\pm\) 0.09 mg/100 g d.m. Similar results were obtained by [PERSON] et al. (2017) [74] without statistically significant changes in the content of ferulic acid in the process of black garlic production. The literature lacks information on the comparison of the composition and proportion of phenolic acids in conventional and organic black garlic, and the existing data on changes in the content of these compounds during heat treatment of black garlic are insufficient and diverse. As suggested by some authors, the differences in the share of individual phenolic acids at different stages of heat treatment most likely result from different mechanisms of their synthesis and metabolism during fermentation processes [55] and the conditions of the process itself. According to other authors, a several, and even many times higher, content of phenolic acids in black garlic (compared to unprocessed garlic) is due to their easier release from the tissue matrix under the influence of a high temperature which damages cell walls and vacuoles, and to the high stability of these chemical forms as compared with other phenolic substances. For the same reason, there is also an increase in the level of other phenolic compounds, e.g., flavonoids, during long-term heat treatment of black garlic (at a high temperature and humidity) [55; 84; 105; 106; 107]. As shown in Table 2, the tested samples had a significant (\(p\) < 0.05) variation in flavonoid content. White organic garlic EG showed a significantly higher (43.13 \(\pm\) 0.20 mg/100 g d.m.) flavonoid content than white garlic from conventional cultivation system G (37.75 \(\pm\) 0.54 mg/100 g d.m.). During the 45-day heat treatment of garlic (at 70 \({}^{\circ}\)C and 80% relative humidity), there was a significant (\(p\) < 0.05) increase in the content of flavonoids (62.94 \(\pm\) 5.65 mg/100 g d.m. on average in BG and EBG), with their highest concentration observed in organic black garlic EBG (68.08 \(\pm\) 0.46 mg/100 g d.m.). The results obtained in this study coincide with the results of other authors who showed an 1-5-fold increase in the content of these compounds, depending on the time and conditions of the aging process of black garlic [55; 73; 57].