## 3 Results
### Results of Analytical Methods  
#### 3.3.1 Results of Measurement of Total Polyphenol Content  
The total polyphenol content of the Bonita (white flesh) cultivar was found to be similar (40.01-41.87 mg GAE/100 g) for samples prepared without treatment (C) and treated with apple pomace (AP) or chokeberry pomace (CP) extracts, as shown in Figure 4. In comparison, samples treated with citric acid (CA) or ascorbic acid (AA) solutions showed double values (80.69 mgGAE/100 g and 88.32 mgGAE/100 g). The treatment had a significant effect (F(4;10) = 202.909; \(p\) < 0.001). Following a week of storage, the polyphenol content of the untreated (C) and plant extract-treated (AP and CP) samples exhibited an approximate twofold increase, while the ascorbic acid (AA) treatment resulted in more than double the amount of polyphenolic compounds. The ascorbic acid treatment yielded the highest value (202.25 mgGAE/100 g). In contrast, the polyphenol content of the sample treated with the citric acid solution (CA) decreased (by 28.5%) and was only 57.65 mg GAE/100 g at the end of storage. The storage time had a significant effect (F(1;10) = 475.856; \(p<0.001\)). The increase in polyphenol content after storage was highest for the sample treated with the apple pomace extract (AP) (139%), followed by the sample treated with the ascorbic acid solution (AA) (129%), the untreated (C) sample (124%), and the sample treated with the chokeberry pomace extract (CP) (103%). The interaction of treatment and storage time had a significant effect (F(4;20) = 97.192; \(p<0.001\)). The Covington (orange flesh) variety exhibited a comparable trend to that of the Bonita variety. At the time of sample preparation, the polyphenol content of the untreated (C), apple pomace (AP), and chokeberry pomace (CP) extract-treated samples was nearly the same (44.31-46.27 mg GAE/100 g). These values were more than doubled for the sample soaked in the citric acid solution (CA) (94.94 mgGAE/100 g) and more than quadrupled for the sample soaked in the ascorbic acid solution (AA) (185.81 mgGAE/100 g). The treatment had a significant effect (F(4;10) = 283.850; \(p<0.001\))  
The results of the five-day storage experiment demonstrated a similar trend to that observed for the Bonita variety. The untreated (C) and plant extract-treated (AP, CP) samples exhibited an increase in polyphenol content of approximately two times (96.57-100.26 mg GAE/100 g), while the ascorbic acid (AA) treatment caused a smaller increase (230.55 mg GAE/100 g). The storage time had a significant effect (F(1;10) = 159.528; \(p<0.001\))  
The citric acid solution (CA) treatment exhibited a slight decrease (5.7%), while the remaining samples demonstrated a more prominent increase. This increase was most significant in the untreated (C) sample and the samples soaked with chokeberry extract (CP) (126% and 121%), followed by the sample treated with malic extract (AP) (109%) and the sample treated with the ascorbic acid solution (AA) (24%). The interaction of treatment and storage time had a significant effect (F(4;20) = 13.225; \(p<0.001\)). The ascorbic acid (AA) treatment resulted in the highest total polyphenol content in both varieties, primarily due to the protective effect of ascorbic acid in the treatment solution on polyphenolic compounds. A comparison of the two cultivars revealed comparable behaviours in the immediate aftermath of treatment and after storage, with similar changes in total polyphenol content. After examining 14 sweet potato varieties, it was found that the phenolic content of the yellow- and orange-fleshed varieties was  
Figure 4: Results of total polyphenol content of treated Covington (dark orange) and Bonita (white) varieties of sweet potatoes after storage. Each value is expressed as the mean \(\pm\) standard deviation. The presence of different letters indicates that the groups in question are significantly different. Higher case letter: comparison of treatment at the fixed storage time. Lower case letter: comparison of storage time at fixed treatments.