# Influence of Ozone on the Biochemical Composition of Birch Sap
## 3 Results
### Changes in the Color of Birch Sap  
When choosing the ozonation range, it is very important to take into account the qualitative indicators. As is known, during storage, if the sap is not completely frozen, there are changes in composition--that is, fermentation of the sap takes place. The higher the temperature, the faster these changes occur. At the same time, the color coordinates of the dyes change. Figures 6 and 7 show changes in birch sap hue angle (_h_) and chrome (_C_) during storage. Color is an important indicator and affects its attractiveness. Figure 6: Changes in the chroma \(C\) of birch sap during storage: 1 (control)—untreated sap (initial); 2—sap ozonated for 5 min; 3—sap ozonated for 10 min; 4—sap ozonated for 15 min; 5—sap ozonated for 20 min; 6—sap ozonated for 25 min; 7—sap ozonated for 30 min. Dunnett tests treat one group as a control (No. 1) and compare all other groups against it. A significant difference between the control group and the other treatment groups is denoted by an asterisk “_\"\"_”. Tukey HSD test was used for the comparison of processing methods (marked in lowercase). The mean difference is significant at the 0.05 level (_n_ = 18). The \(L^{*}\), \(a^{*}\), and \(b^{*}\) values of all treated sap samples did not differ significantly (\(p\)! 0.05) from the control. The rate of treatment did not affect the color of the birch sap. Figure 6 shows the changes in chroma of sap samples immediately after treatment, as well as sap samples stored at 2 \({}^{\circ}\)C and 20 \({}^{\circ}\)C. The chroma of the sap samples immediately after ozone treatment (Nos. 2-7) ranged from 0.78 to 0.60 NBS units, while the initial fresh sap chroma was 0.79 \(\pm\) 0.04 NBS units. At 2 \({}^{\circ}\)C (day 7), the hue angle value of ozone-treated sap samples (Nos. 2-7) varied by 0.85-0.69 \({}^{\circ}\)C on average, and at 20 \({}^{\circ}\)C (day 5) by 0.93-0.71 \({}^{\circ}\)C. Untreated sap samples stored at 20 \({}^{\circ}\)C (No. 1) had the highest hue angle value and averaged 0.72 \(\pm\) 0.06 \({}^{\circ}\)C.  
Statistically significant differences (Tukey HSD test, \(p\)! 0.05) were recorded immediately after treatment between untreated sap and samples 4, 5, and 7, which were treated. After seven days, we assessed the differences between untreated sap samples and all ozone-treated samples (Nos. 2-7). After five days, we assessed the differences between treatments 1-3 and 7 and treatments 4, 5, and 6. Comparing the control group with the treatment groups (Dunnett's tests, \(p\)! 0.05), it was found that, immediately after ozonation, ozone had a significant effect on the chroma in sap samples treated for 15, 20, or 30 min. After seven days, a statistically significant difference between the chroma of the untreated and treated sap emerged. After five days, when the temperature was higher, a significant difference from the control group was found in group 4 (15 min). Changes in the hue angle \(h\) of birch sap are shown in Figure 7. Based on the results and a comparison of the ozone-treated samples at different intervals with the control group, the value of hue angle increased in the range of 2.1-4.7%. The difference in hue angle value between the treated samples stored for seven days and the control group is 2.3-4.9%. After five days of storage, the difference is in the range of 0.6-3.9%. The data averages and letter differences between samples in Figure 7 show a significant difference at the 5% level of significance (\(p\)! 0.05) using the Tukey HSD test. The control  
Figure 7: Changes in the hue angle of birch sap \(h^{\circ}\) during storage: 1 (control)—untreated 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. Dunnett tests treat one group as the control (No. 1) and compare all other groups against it. A significant difference between the control group and the other treatment groups is denoted by an asterisk “**”.