# Physicochemical and Sensory Evaluation of Yanggaeng Treated with Roasted Guateman Coffee Extracts
## 3 Results and Discussion
### Antioxidative Properties of Yanggaeng  
Table 6 shows the TPC and DPPH free radical scavenging rates of the Yanggaeng samples. Coffee contains antioxidant compounds such as chlorogenic acid, hydroxycinnamic acid, melanoidins, and caffeine [38; 39]. The antioxidant activity of coffee varies significantly, depending on its origin, roasting level, and extraction method. The TPC of the Yanggaeng samples increased significantly with the addition of G compared with that of CON, irrespective of the roasting levels. In the L group, L2 sample showed a 1.46-fold increase in polyphenol content relative to that in the CON group. In the M group, the TPC values progressively increased with higher concentrations of G, reaching the highest value in the M6 sample (CON: 15.60 < M2: 20.18 < M4: 21.99 < M6: 22.79). Similarly, in group D, samples D4 and D6 exhibited 1.65-fold and 1.61-fold increases in TPC, respectively, compared to the CON group. The increase in total polyphenol content may be attributed to the enhanced extractability of polyphenic compounds. Roasting disrupts the cellular structure of coffee beans and reduces their moisture content, thereby improving the solubility of polyphenic compounds [40]. Furthermore, the thermal degradation of coffee  
components during roasting may produce low-molecular-weight phenolic derivatives, which are readily measurable in the TPC assay [41]. Notably, no significant differences in TPC were observed when different roasting levels were compared, suggesting that the concentration of coffee extract had a more pronounced effect on polyphenol content than the roasting degree itself.  
Regarding DPPH radical scavenging ability, Yanggaeng samples in group L did not show significant changes with varying concentrations of G. However, only the M6 and D6 samples demonstrated significantly higher DPPH radical scavenging activity, likely due to elevated polyphenol levels. Across all roasting levels, group D consistently exhibited the lowest DPPH radical scavenging ability at all concentrations. The roasting of coffee significantly affects the content and composition of antioxidants. Dark roasting generally results in lower levels of chlorogenic acid and total polyphenols owing to prolonged roasting [42]. During roasting, increased intensity initially elevates chlorogenic acid levels, but prolonged roasting leads to its degradation into compounds such as quinic acid, which influences the acidity and antioxidant activity [32; 33; 34]. Chlorogenic acid effectively reduces free radicals; thus, Yanggaeng prepared with lower levels of roasted coffee beans may exhibit a reduced DPPH radical scavenging activity. These findings are consistent with those of [PERSON] et al. [43], who reported a decrease in DPPH scavenging ability with increased roasting intensity for both espresso and drip coffee. Additionally, [PERSON] et al. found that the DPPH radical scavenging ability significantly decreased in the order of light, medium, city, and French roasts [44]. The antioxidant activity of Yanggaeng containing G was attributed to the presence of TPC, with the antioxidant activity diminishing as roasting intensity increased.