## 3 Results and Discussion
### Effect of Ultrasound and Microwave Extraction on the Physicochemical Properties of the Extract  
The values of color parameters (Table 3) in the extracts obtained using ultrasound, microwaves and water baths ranged from 19.33 to 20.86 for L*, from 1.97 to 3.38 for a* and from 2.99 to 3.95 for b*. The value of the L* color parameter was close to the value of acai pulp obtained in a study conducted by [PERSON] [1]. Furthermore, in a study performed by [PERSON] and [PERSON] [46], similar values of the a* (1.6-2.1) and b* (1.0-2.6) color parameters of acai pulp were noted, while the L* color parameter (33.4-35.1) was significantly higher. The pH (Table 3) of the extracts obtained by microwaves and ultrasound extractions was in the range of 5.36-5.52. The highest pH value was observed for the water bath extract obtained at 25 \({}^{\circ}\)C for 25 min. Color and pH value differences between extracts may occur due to the different amounts of TPC, TF and TA in the tested samples. [PERSON] [47] showed a correlation between color levels and increased antioxidant activity, using the example of cold-brewed coffee extraction. Effect of Extraction Conditions on Correlation Coefficients between Antioxidant Activity, pH, Color and Content of Phenolic Compounds, Anthocyanins, and Flavonoids  
Flavonoid content (Table 4) was positively correlated with the antioxidant activity measured by DPPH and ABTS methods (\(p\leq 0.001\)) and negatively correlated (\(p\leq 0.001\)) with the antioxidant activity measured by FRAP analysis. This negative correlation probably relates to the mechanism of FRAP reaction and to flavonoids' Fe\({}^{2+}\) chelating properties [48]. TPC content was positively correlated (\(p\leq 0.001\)) with antioxidant activity measured with the use of DPPH and ABTS radicals. [PERSON] [49]  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Temp** & **Extraction** & **Time** & **L *(D65)** & _a *(D65)_ & _b *(D65)_ & **pH** \\ \hline \multirow{4}{*}{25} & water bath & 25 & 19.61 (0.02) b  & 1.97 (0.14) d  & 3.95 (0.11) a  & 5.52 (0.01) a  \\ \cline{2-6}  & ultrasound & 25 & 19.36 (0.01) c  & 3.38 (0.07) a  & 3.90 (0.03) a  & 5.39 (0.01) b  \\ \cline{2-6}  & ultrasound & 25 & 19.39 (0.03) c  & 3.15 (0.06) ab  & 3.79 (0.07) a  & 5.39 (0.01) b  \\ \cline{2-6}  & ultrasound & 45 & 20.86 (0.19 a  & 3.06 (0.09) b  & 3.19 (0.06) b  & 5.39 (0.02) b  \\ \cline{2-6}  & microwave & 3.16 & 19.45 (0.02) b  & 2.23 (0.17) c  & 3.89 (0.14) a  & 5.43 (0.04) b  \\ \cline{2-6}  & microwave & 4.33 & 19.45 (0.02) b  & 2.50 (0.04) c  & 3.79 (0.03) a  & 5.42 (0.01) b  \\ \hline \multirow{4}{*}{45} & water bath & 25 & 19.53 (0.02) b  & 2.12 (0.13) b  & 3.55 (0.01) b  & 5.40 (0.01) ab  \\ \cline{2-6}  & ultrasound & 25 & 19.56 (0.03) b  & 2.17 (0.05) b  & 3.80 (0.08) a  & 5.44 (0.02) a  \\ \cline{2-6}  & 45 & 19.75 (0.21) b  & 2.26 (0.12) b  & 3.66 (0.15) ab  \\ \cline{2-6}  & 2 & 19.33 (0.02) c  & 2.37 (0.10) b  & 3.73 (0.09) ab  & 5.43 (0.03) a  \\ \cline{2-6}  & microwave & 3.16 & 19.43 (0.02) c  & 2.74 (0.04) a  & 3.81 (0.04) a  & 5.36 (0.02) b  \\ \cline{2-6}  & 4.33 & 19.53 (0.12) b  & 3.03 (0.14) a [FOOTNOTE:a]Footnote a: b, c, d obtained similar results (\(p\leq 0.01\)) in research analyzing guava fruit extracts. Additionally, [PERSON] [50] showed a positive correlation between TPC and DPPH in honey. A negative correlation (\(p\leq 0.05\)) was also observed between the total content of phenolic compounds and the a* color parameter, which is responsible for the red color. The analyses did not show any significant correlation between the content of phenolic compounds in the extracts and the L* (brightness), b* (yellowness) and pH of the extract. Nonetheless, the content of anthocyanins was negatively correlated (\(p\leq 0.001\)) with the antioxidative activity measured by DPPH and ABTS methods. In turn, a positive correlation (\(p\leq 0.01\)) was noted between the content of anthocyanins and the antioxidant activity measured by the FRAP method.