## 3 Results and Discussion
### The Antioxidant Activity of Soy Sauces  
Polyphenols have been associated with many health-benefiting properties. They act as antioxidants in chronic diseases and are positively related to cardiovascular events, osteoporosis, diabetes, and neurodegenerative diseases [40]. Many studies confirmed that some are associated with bitterness and astringency in many types of food, including soy sauces [41]. The results of the current study (Table 2) showed that higher total polyphenol content (GAE) was found in conventional soy sauces (\(p<0.05\)). The total flavonoid content ranged from 32.39 to 46.31 \(\upmu\)q quercetin/mL, with higher content observed for TS_O and KS_C. These values were generally lower compared to non-pasteurized soy sauces; for instance, Korean industrially prepared sauce contained 13.3 mg of GAE per ml (original units are converted to SI units here and in the whole paragraph). Nevertheless, the use of heat treatment (pasteurization) reduces the total polyphenol content of the final products. The temperature influenced this parameter; after application at 75 \({}^{\circ}\)C, the GAE content was 86% of the initial value, and after 100 \({}^{\circ}\)C, it was only 59% [42]. Similarly, several times higher content was observed for the traditional soy sauces fermented with _Monascus_, commercial  
Figure 3: The relative concentration of the different types of aroma compounds in soy sauces (without ethanol). or lab-cultivated red fungi. The total phenolic content in the products was 800.2 and 885.7 \(\upmu\)g gallic acid/mL, respectively [43]. Soybean as a raw material is the main source of polyphenols and flavonoids in shoyu sauce. The initial content of raw soy seeds depends on many factors. For example, black and brown soya seeds varieties contain a lot of total polyphenols, ranging from 4.94 to 6.22 mg of gallic acid equivalents/g, and can be an effective source of anthocyanins. The yellow seed variety has high total isoflav content (>3.6 mg/g), whereas the black seeds are rich in total daidezin (>2.0 mg/g) [44]. The fertilizers have a significant effect on the antioxidant activity and phenolic metabolites [45]. Germination and sprout formation are accompanied by a significant increase in total flavonoid content with antioxidant potential [46; 47]. Several studies indicated that fermentation processing increases the antioxidative potential of soybean products [48; 49; 50; 51]. A high concentration of polyphenols (>5 mg/g) was observed in tempeh-fermented soybean via the _R. oligosporus_ NRRL 5905 strain [52]. Moreover, during fermentation, the polyphenol glycosides are typically converted to their aglycone forms, which are significantly readily absorbed from the small intestine [4; 53]. Some of the polyphenols found in soy sauce are daidezin (0.20 mg/100 mL), glycitein (0.15 mg/100 mL), 6''-O-acetylycitin (0.15 mg/100 mL) [54], and genistin (0.75 mg/100 mL) and genistein (0.23 mg/100 mL) [55]. However, daidezin and genistein were not found in soy sauces available at the retail level in Australia and Indonesia [56]. Likewise, in dark soy sauces, daidezin and genistein were not detected [57]. Generally, soy sauce is regarded as a poor source of isoflav. The leading hypothesis is that during the fermentation, microorganisms can degrade them [56; 57]. Prolonged fermentation also leads to additional modifications to the polyphenols, and the presence of 6-hydroxygenistein, 8-hydroxygenistein, and genistein-7-tartaric acid ether [58] has been observed. When analyzing the antioxidant activity of the current study's sauce samples, a higher antioxidant activity was found in the system with the ABTS radical than with the DPPH radical (Table 2). The highest antioxidant activity was demonstrated for KS_C. The results are expressed as Trolox equivalent antioxidant capacity (TEAC). The lowest antioxidant activity of sauces was approx. 0.799 \(\upmu\)mol TE / mL (DPPH) and 11.50 \(\upmu\)mol TE/mL (ABTS) for TS_C. Generally, the Trolox equivalent antioxidant capacities of seasoning were low compared to other studies.