# Influence of Ozone on the Biochemical Composition of Birch Sap
## 4 Discussion
[69], in published studies of birch sap, the pH ranges from 5.5 to 8. The titratable acidity depended on the pH, i.e., the titratable acidity increased with decreasing active acidity. The titratable acidity increased during storage. Reviewing the values recorded in other studies, the titratable acidity in birch and maple sap was 0.50 and 0.70 mmol NaOH per liter of sap, respectively [5]. In our study, the TSS value of birch sap was about 0.57-0.63\({}^{\circ}\)Brix. This is lower than observed in another study where birch (_Betula pendula_ [PERSON] and _B. pubescens_ [PERSON]) sap contained about 0.7\({}^{\circ}\)Brix [60]. [PERSON] et al. [69] reported that the average soluble dry matter content of birch sap was 0.5-1.8\({}^{\circ}\)Brix. However, this may be due to differences in birch species and the area from which the sap was collected. The electrical conductivity of fresh birch sap increased during storage. This was confirmed by [PERSON] and [PERSON]'s [9] study of birch sap. Another study found a significantly higher specific conductivity, which contradicts our research. According to [PERSON] et al. [5], the electrical conductivity of Latvian birch (_Betula pendula_ [PERSON]) and maple (_Acer plantoides_ L.) sap is 629 and 967 S cm\({}^{-1}\), respectively, which characterizes the total mineral content as well as the acidity of the sap. It is generally considered that fresh birch sap intended for consumption can be stored for up to two months (0-2 \({}^{\circ}\)C). Although the titratable acidity and pH are most likely to change during storage at this temperature, the soluble solids content and the electrical conductivity are the least likely to change [70]. Comparing the physicochemical parameters of birch sap found in our study, in several cases, it was close to the results of other studies performed. However, it was confirmed that the sugar content and other parameters of the sap depend on the type of birch, habitat, and meteorological conditions [10; 71]. According to studies in the Russian Far East, these carbohydrates reach 0.9% at the beginning and end of the sap flow and rise to 1.3% in the middle [72]. [PERSON] et al. [73] found that the sugar content of silver birch sap ranged from 0.25% to 2.25%. According to [PERSON] et al. [74], who studied the composition of the sap of _Betula pendula_ [PERSON], _Betula pubescens_ [PERSON], and _Betula pendula_ var. _carelica_ Mercklin trees in Finland, glucose (2.5-4.7 g L\({}^{-1}\)), fructose (2.3-4.5 g L\({}^{-1}\)), sucrose (<0.7 g L\({}^{-1}\)), galactose (<0.05 g L\({}^{-1}\)), sugar alcohol myosinositol (trace), malic acid (0.1-0.7 g L\({}^{-1}\)), succinic acid (<0.1 g L\({}^{-1}\)), citric acid (<0.1 g L\({}^{-1}\)), phosphoric acid (<0.04 g L\({}^{-1}\)), and fumaric acid (traces)were detected. In southeastern Poland, _Betula pendula_ Roth sap was found to contain a significantly higher sugar content: 0.46 \(\pm\) 1.03% of carbohydrates, of which glucose is 0.93 \(\pm\) 0.39%, fructose is 1.21 \(\pm\) 0.49%, and sucrose is 0.32 \(\pm\) 0.24% [75]. Sap (_Betula pendula_ Roth, and _B. pubescens_ Ehrh. ), which is used for syrup production in Finland, had a maximum glucose and fructose concentration in late April or early May of 5-8 g L\({}^{-1}\)[76]. [PERSON] et al. [5] showed that silver birch sap contained mainly fructose (5.39 \(\pm\) 0.05 g 100g\({}^{-1}\)), glucose (4.46 \(\pm\) 0.04 g 100 g\({}^{-1}\)), and sucrose (0.58 \(\pm\) 0.01 g 100 g\({}^{-1}\)), and the average ascorbic acid concentration was only 3.2 mg L\({}^{-1}\). In Lithuania, birch sap contains on average 1.85% sugars, of which monosaccharides (1.46%) and sucrose (0.39%) are present [77]. There are no studies on the effects of ozone on the physicochemical parameters of birch sap. However, compared to changes in the parameters in other juices when exposed to ozone, in many cases, it is consistent with our results that ozone has minimal or no effect. For example, [PERSON] et al.