## 3 Results and Discussion
(2016) [64] noted significant decreases in the pH of fresh garlic (6.42) during heat treatment (45 days under different thermal conditions), to a pH of about 5.00 (45 \({}^{\circ}\)C) and up to approx. 3.05 (85 \({}^{\circ}\)C). Those studies suggest that both the higher temperature of garlic heat treatment and the longer duration of its use lead to a lower pH in the processed product. As indicated by the literature, the low pH of black garlic ensures its relatively long shelf life and high microbiological stability. A pH below 4.2 significantly reduces proliferation of anaerobic bacteria and growth of microorganisms responsible for food poisoning, and the high temperature accompanying the process of obtaining black garlic destroys the spores of bacteria and fungi, reducing food spoilage [98]. According to the literature, a low pH is usually accompanied by high acidity, mainly due to the high content of organic acids. [PERSON] et al. (2012) [70] showed a significant increase in the acidity of fresh garlic (4.6 g/kg) during heat treatment to 33.63 g/kg, 37.5 g/kg, 30.96 g/kg and 36.37 g/kg at 60 \({}^{\circ}\)C, 70 \({}^{\circ}\)C, 80 \({}^{\circ}\)C and 90 \({}^{\circ}\)C, respectively. The increased content of organic acids in black garlic not only determines the microbiological stability and taste qualities (giving the product a characteristic sweet and sour taste), but also facilitates hydrolysis of proteins and polysaccharides [99]. The many times higher acidity of black garlic compared to white garlic is due both to the high consumption of amino groups of amino acids during the Maillard reaction, as well as to the production of short-chain carboxylic acids as a result of degradation of dicarbonyl compounds and Amadori products [100,101]. The increasing number of products of the Maillard reaction, resultant from oxidation of aldehyde groups in aldoses, leads to an increase in the content of organic acids, resulting in a decrease in pH [77, 78, 79, 102, 103, 104]. Thus, the lower pH and higher acidity of black garlic are also closely related to the browning reactions. The obtained test results for all analysed garlic samples showed a statistically significant (_p_ < 0.05) correlation between the soluble solids content (\({}^{\circ}\)Brix) and the pH (R\({}^{2}\) = 0.96), which means that with the increase in soluble solids content, the pH of the tested samples decreased and it was practically complete. The literature lacks information on the comparison of bioactive content (phenolic acids, flavonoids and total polyphenols) and antioxidant activity in black garlic from conventional and organic cultivation. Therefore, in this paper, the content of phenolic compounds and antioxidant activity of white and black, organic and conventional garlic were studied and the results are presented in Table 2.  
The average content of the sum of the determined phenolic acids in the test samples of white garlic (G and EG) was 49.01 \(\pm\) 6.21 mg/100 g d.m. White garlic from organic cultivation (EG) was characterised by a significantly (_p_ < 0.05) higher content of these components (54.66 \(\pm\) 0.07 mg/100 g d.m.) than white garlic from conventional cultivation (43.35 \(\pm\) 0.63 mg/100 g d.m.). The dominant phenolic acids in white garlic, both conventional (G) and organic (EG), were derivatives of hydroxycinnamic acid (34.06 mg/100 g d.m. and 42.52 mg/100 g d.m., respectively), and the most abundant acids were p-coumaric acid (20.66 \(\pm\) 0.49 mg/100 g d.m. in G and 23.80 \(\pm\) 0.06 mg/100 g d.m. in EG) and gallic acid (9.29 \(\pm\) 0.10 mg/100 g d.m. in G and 12.14 \(\pm\) 0.01 mg/100 g d.m. in EG). The results obtained differed significantly from those in the literature, whose authors report fresh garlic's greatest share of caffeic acid, followed by ferulic, vanillin and p-hydroxybenzoate acid [8].