# Influence of Ozone on the Biochemical Composition of Birch Sap
## 3 Results
### Physicochemical Analysis  
Variation of pH and titratable acidity of birch sap. Active acidity and titratable acidity were studied in parallel during the study. The two concepts are interrelated and each of these quantities describes the quality of the product. The parameter of acidity can be used to judge the suitability of the process for processing the product. pH is important to evaluate the ability of microorganisms to be established in sap. Titratable acidity determines the total acid concentration in the sap and also better predicts the effect of acid on taste than pH. Figure 8 shows the change of active acidity pH (A) and titratable acidity (B) of birch sap during storage. The active acidity pH (Figure 8A) of fresh birch sap was found to be about 6.20, and a pH value of 6.10-6.49 was recorded after ozonation. The titratable acidity value of fresh birch sap (Figure 8B) was 0.007 g 100 mL\({}^{-1}\), and immediately after ozonation, it was 0.00413-0.00817 g 100 mL\({}^{-1}\). According to the study data (Figure 8A), no significant differences were observed between the control group and those treated with ozone (Dunnett's test, \(p<0.05\)) and between the samples (Tukey HSD test \(p<0.05\)) both immediately after treatment and during storage at 2 \({}^{\circ}\)C and 20 \({}^{\circ}\)C. However, there was a visible change over time: after seven days at 2 \({}^{\circ}\)C the average decrease in active acidity was 8.7-20%, and after five days at 20 \({}^{\circ}\)C it was 12.5-31.3%. After storage for seven days at 2 \({}^{\circ}\)C or five days at 20 \({}^{\circ}\)C, the pH values dropped; the pH of fresh sap was 5.56 and 4.88, while for ozonated sap it was 5.19-5.63 and 4.45-5.34, respectively. It can be seen that at 20 \({}^{\circ}\)C the pH dropped faster. Assessing the mean values of the titratable acidity (Figure 8B), it was found that, after ozonation of birch sap, the titratable acidity was significantly affected after 5 min and after 30 min of ozonation according to both a Dunnett's test compared to the control group (\(p<0.05\)) and a [PERSON]'s HSD test comparing all samples (\(p<0.05\)). The acid content in these cases was 40.5% and 41.0% lower than in fresh sap. After 10 min of ozonation, a  
Figure 8: Variation of pH (**A**) and titratable acidity (**B**) of birch sap during storage: 1 (control)—non-ozonated sap (initial); 2—gap ozonated for 5 min; 3—gap ozonated for 10 min; 4—gap ozonated for 15 min; 5—gap ozonated for 20 min; 6—gap ozonated for 25 min; 7—gap ozonated for 30 min. Significant differences (\(p<0.05\)) were found according to a Tukey HSD test (marked in lowercase) and [PERSON] tests (marked with an asterisk \({}^{***}\)) (\(n=6\)). significant (Tukey HSD test \(p<0.05\)) increase in tittatable acidity was observed, which was about 14%. The acidity of the other ozonated samples (4, 5, and 6) varied minimally. After seven days of sap storage at 2 \({}^{\circ}\)C, a significant difference was found between the control group and groups 2 and 3 ([PERSON]'s test, \(p<0.05\)). Compared to the Tukey HSD test (\(p<0.05\)), ozonation had a significant effect on the sap, which was treated in both No. 2 and 3 ozonation rates. After five days at 20 \({}^{\circ}\)C, a significant difference was seen for treatment 7 when the sap was treated for 30 min ([PERSON]'s test and [PERSON]'s HSD test, \(p<0.05\)). From the study data, it can be observed that the tittatable acidity varies greatly between days. This may be related to the fact that the acid content increases during the storage of the sap, and the rate of change depends on the storage temperature. As mentioned earlier, fresh sap must be transparent, but when comparing the tittatable acidity indicators with the color indicators, it can be seen that the color change is not yet visually identifiable with increasing acidity indicators. Total soluble solids, electrical conductivity, and other components change in birch sap. The components accumulated in the sap are important indicators of quality.