## 3 Results
### Results of Analytical Methods
#### 3.3.3 Results of Measurement of Water-Soluble Solid Content, pH Value, and Colour

Table 4: Results of the water-soluble solid content and pH value of treated Covington (dark orange) and Bonita (white) varieties of sweet potatoes after storage. For the Bonita (white-fleshed) variety, the untreated (C), apple pomace (AP), and chokeberry pomace (CP) samples had almost identical pH values (5.81-5.83), while the ascorbic acid (AA) and citric acid (CA) samples had lower pH values (5.36 and 4.45, respectively) (Table 4). During the storage period, the control and plant extract-treated samples exhibited a slight increase in pH (5.92, 5.85, and 5.90). Conversely, the pH values of the ascorbic acid (5.36) and citric acid (4.45) samples exhibited a decrease during storage, reaching 5.16 and 4.25, respectively. The treatment had a significant effect (F(4;10) = 34,105.970; \(p<0.001\)); the storage time had a significant effect (F(1;10) = 161.783; \(p<0.001\)), and their interaction was also significant (F(4;20) = 444.391; \(p<0.001\)). A similar trend was observed for the Covington variety. Conversely, the untreated sample exhibited an increase during storage, reaching 5.96, while the apple pomace (5.31) and chokeberry pomace (5.69) samples showed an increase (5.96, 5.92, and 5.72, respectively). Conversely, the ascorbic acid (4.85) and citric acid (4.42) samples exhibited lower initial pH values, which underwent a decline during storage (to 4.65 and 4.11, respectively). The treatment had a significant effect (F(4;10) = 76,643.667; \(p<0.001\)), while the storage time had a significant effect (F(1,10) = 998.756; \(p<0.001\)), and their interaction was also significant (F(4;20) = 5351.756; \(p<0.001\)). In summary, for both varieties, the pH values of the untreated (C), apple pomace (AP), and chokeberry pomace (CP) samples were higher than those of the ascorbic acid (AA)- and citric acid (CA)-treated samples. This difference can be attributed to the acidic treatments. A comparison of the various treatments in the Bonita (white-fleshed) samples revealed that the differences were less pronounced, and the changes during storage were less significant than in the Covington (dark-orange-fleshed) variety. The colour change was characterised using the \(\Delta\)E* values (Table 5). A comparison of the colour values on day 7 with their respective values and on day 0 for the Bonita (white-fleshed) variety was made. The difference was found to be noticeable for the untreated (C) and chokeberry pomace-treated (CP) samples, while it was very noticeable for the apple pomace (AP)-, ascorbic acid (AA)-, and citric acid (CA)-treated samples. On day 7, the difference was noticeable for the apple pomace (AP) and ascorbic acid (AA) samples, while it was very noticeable for the chokeberry pomace (CP) and citric acid (CA) samples compared to the untreated (C) sample. In light of these observations, it can be concluded that colour changes occurred during storage for all samples, both untreated and treated. On day 7, a comparison of the treated samples to the control revealed no significant differences among the treatments. However, a notable distinction emerges when day 7 values are compared with day 0 values for the treatment with chokeberry pomace extract (CP). This observation is further supported by the low browning index (BI) values of the samples treated with chokeberry pomace extract (CP). For the Covington (dark-orange-fleshed) variety, the \(\Delta\)E* values indicate that a noticeable colour difference was observed between day 0 and day 5 samples for both the untreated and treated samples. On day 5, a very noticeable colour difference was observed for the apple pomace (AP) sample compared to the untreated sample, while it was only noticeable for the chokeberry pomace (CP), ascorbic acid (AA), and citric acid (CA) samples. These findings suggest that all samples underwent colour changes during storage, yet no notable differences in browning index (BI) values were observed between treatments, in contrast to the Bonita variety.