## 3 Results and Discussion
### Kyna  
The content of kynureic acid was measured in raw potatoes, potato slices before and after blanching, the water remaining after blanching, and potato crisps. Such analysis has not been conducted so far. In their studies, [PERSON] et al. [6; 9] determined KYNA content  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Technological Parameters**} & \multicolumn{2}{c}{**FIC**} & \multicolumn{2}{c}{**BI (\(\lambda\) = 360)**} & \multicolumn{2}{c}{**BI (\(\lambda\) = 420)**} \\ \hline
**Blanching** & **Blanching** & **Frying** & & & & & & \\
**Temperature** & **Time** & **Temperature** & **Ismena** & **Provita** & **Ismena** & **Provita** & **Ismena** & **Provita** \\ (°C) & **(min)** & **(°C)** & & & & & & \\ \hline - & - & 155 & 33.06 \(\pm\) 1.97 d & 11.14 \(\pm\) 1.33 kc & 0.52 \(\pm\) 0.04 c & 1.26 \(\pm\) 0.07 b & 0.17 \(\pm\) 0.00 b & 0.22 \(\pm\) 0.04 b \\ - & -  
in various food products, including potatoes. However, the research was performed on potatoes with yellow and white flesh. In the current research, it was shown that the content of kynure acid in Provita, a purple flesh potato cultivar, was higher (almost three times) than in _cv._ Ismena tubers, similar to the content of other bioactive compounds (Table 7). The content of kynure acid in yellow flesh potato tubers differed depending on the potato variety [9]. The KYNA content in potatoes from the _cv._ Ismena variety (0.226 \(\mathrm{\SIUnitSymbolMicro g}\)/g) determined in the experiment was average in relation to the potato cultivars previously reported by [PERSON] et al. [9]. In the current study, it was found that the slicing process resulted in a reduction of KYNA content in Ismena but not Provita potato slices. Thermal treatment, i.e., blanching, caused additional losses in the content of this compound in potato slices of both cultivars--almost by half. Moreover, it was demonstrated that the loss of kynure acid during the blanching of potato slices is temperature dependent. The effect of blanching on the content of kynure acid has not been directly demonstrated by researchers so far. It was shown that the cooking of whole tubers in boiling water did not change the content of this acid in potatoes [6]. It was shown that kynure acid was also present in the water after blanching, which confirms the good solubility of this compound in the aqueous medium. However, the content of KYNA in water after blanching, regardless of the temperature used, was at a similar level. The frying process also affected the content of kynure acid in potato crisps. This is confirmed by the research of [PERSON] et al. [9], who analyzed the content of kynure acid in raw material and finished products. It was found that potato crisps had a lower content of kynure acid compared to raw potatoes. It can be assumed that the use of a high-temperature process, i.e., frying, affected the content of this acid in the finished product. Recently, kynure acid has drawn attention due to its involvement in fat metabolism. [PERSON] et al. [10] demonstrated that kynure acid improves the metabolic consequences of a high-fat diet (HFD). It was proven that kynure acid had a role in the significant reduction of body weight and decrease of subcutaneous/inguinal white and visceral/epidydmal white adipose tissues of mice that were treated with HFD containing 34.9 \(\mathrm{\SIUnitSymbolMicro g}\)% fat, which corresponds to the content of fat in crisps. Moreover, lower serum triglyceride level and improved glucose homeostasis were found [10]. All these effects were attributed to the activation of G protein-coupled receptor 35 (GPR35) by kynure acid [10; 32]. Similar results were reported by [PERSON] et al. [12]. Intriguing properties of kynure acid were reported by [PERSON] et al. [33], who found that kynure acid treatment results in a better functional recovery of injured ischemic-reperfusion tissue, probably due to tissue repairing and con