## 3 Results and Discussion
### Impact of Ingredients and Processing Conditions on Phenolic Content and Antioxidant Activity
#### 3.3.3 Content of Phenolic Acids--UPLC Analysis  
The determination of content of phenolic acids was performed for sample revealing the highest antioxidant activity in DPPH assay. The assay was performed with the use of Waters ACQUITY UPLC Chromatogram. The study results were obtained for functional food product obtained with the following production parameters: 36% sm, 100 rpm, L/D = 20. Results are presented in Table 7.  
It is commonly known that oxidative stress is one of crucial factors leading to various disorders including cardiovascular, cancer or neurodegeneration. In order to avoid to high level of free radicals, organism developed various systems counteracting the negative impact of the reactive molecules [47]. Nevertheless, the external source of antioxidants and free radical scavengers is essential for maintenance balance in organism. The most important source of natural antioxidants are fruits and vegetables rich in secondary plant metabolites revealing high ability to scavenging free radicals. An example of the valuable fruit is blueberry riches in phytochemicals presented in [PERSON]'s et al. work [48]. The fruit is studied towards its pro-health properties from a long time. Considering the various activities, it was decided to use the fruit as additive to functional food products. Anthocyanins, phenolic acids (caffeic, chlorogenic, p-counaric and ferulic acids), flavonoids (mainly quercetin derivatives) and proanthocyanins have received the most attention among the phytochemicals found in blueberries [49]. The following phenolic acids were found in the samples: protocatechuic, p-OH-benzoic, vanillic, caffeic, syryngic, p-counaric, ferulic, synaptic and salicylic acids, according to the chromatographic analysis carried out by the authors. The study confirmed a high health-promoting activity based on free radical scavenging and high polyphenol content. The authors observed an increase in the total polyphenol content and antioxidant properties of the product with increasing fruit content. The most suitable for consumption are products enriched with 30% of blueberry which revealed above 90% ability to scavenge free radicals within few minutes. Additionally, the high content of polyphenols influences on the antioxidant activity but also support the fight against other negative factors leading to various disorders. Considering the fact that potato base did not reveal ability to scavenge free radicals (approx. 22%), the enrichment of the food products with fruits significantly improves their pro-health properties along with supplementation of valuable secondary plant metabolites. Significant feature of analyzed functional food samples is also lack of negative influence of production parameters (moisture and screw rotation speed) on antioxidant activity of samples with various \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{8}{c}{**Content of Phenolic Acids (ug/g)**} \\ \cline{2-10}  & **Protocatechuic** & **p-OH-Benzo** & **Vanillic** & **Caffeic** & **Syngic** & **p-Counaric** & **Ferulic** & **Synacic** & **Salicylic** \\ \hline Functional & \multirow{2}{*}{3.154 \(\pm\) 2.18} & \multirow{2}{*}{LOQ} & \multirow{2}{*}{1.151 \(\pm\) 0.21} & \multirow{2}{*}{81.09 \(\pm\) 8.75} & \multirow{2}{*}{11.288 \(\pm\) 1.67} & \multirow{2}{*}{2.719 \(\pm\) 0.35} & \multirow{2}{*}{9.1 \(\pm\) 0.279} & \multirow{2}{*}{3.466 \(\pm\) 0.14} & \multirow{2}{*}{0.307 \(\pm\) 0.04} \\ food sample & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Content of phenolic acids [ug/g] obtained using UPLC analysis. content of fruits. The results allow us to assume that these parameters will not have a destructive effect on the health-promoting properties of the tested products. According to [PERSON] et al.