## 3 Results
### Ascorbic Acid Content  
The content of ascorbic acid in the obtained juices ranged from 29 to 36 mg/100 g and was at the level described in the literature (17-53 mg/100 g) [2; 16]. Degradation of ascorbic acid may take place under the influence of asorbinase or peroxidase. Other factors affecting oxidation are light, pH value, oxygen and the presence of metal ions. Furthermore, ascorbic acid is thermolabile [35]. Subjecting the mash to thermal, enzymatic and enzymatic treatment assisted by vacuum had no impact on the content of ascorbic acid in the juice in comparison to the sample obtained from the untreated mash (Figure 2). As indicated in the references, the effect of thermal or enzymatic treatment on the level of ascorbic acid content in the juice is ambiguous. In the case of barberry fruits, a beneficial effect of heat treatment of the mash on the content of ascorbic acid in the juice was noted. This may be due to the inactivation of oxidative enzymes. No such effect has been observed for enzymatic treatment [22]. In turn, [PERSON] et al. [36] examining the impact of enzymatic treatment for blueberry, black currant and raspberry marsh on ascorbic acid content in juice found an increase in the case of blueberry and raspberry and no effect in black currant. A similar effect for black currant was noted by [PERSON] et al. [11]. [PERSON] and [PERSON] [35] indicate that the profile of phenolic compounds can have a protective function in relation to vitamin C oxidation. They point out that quercetin had the greatest protective effect, followed by dihydroquercetin, kaempfer, quercetin, chlorogenic acid and p-coumaric acid. The results presented in Table 1 indicate that some of these compounds are present in the profile. They may have a stabilizing effect on the content of ascorbic acid in thermal or enzymatic treatment. The protective effect is generally attributed to the metal chelating properties. During mash treatment, the oxidation of ascorbic acid may also be related to an enzymatic reaction. Ascorbate oxidase is the major enzyme responsible for this process. This enzyme contributes to the oxidation of ascorbic acid in the presence of oxygen. Enzyme activity can occur both during pectinolysis or penehating the mash to 80 \({}^{\circ}\)C (15 min) during thermal treatment. Deaeration of the mash in the first 10 min during enzymatic treatment may also be insufficient to inhibit oxidative changes. Thus, as a result of pectinolysis and heat treatment, the content of ascorbic acid in the juice did not increase, but a stabilizing effect was only achieved compared to the control sample. The ultrasonic or thermosonic treatment of the mash caused a 20% decrease in ascorbic acid content in the juice in comparison to samples from the untreated mash (Figure 2). In the case of sonication, most studies are related to juice preservation. Similarly to enzymatic or thermal treatment, the influence of ultrasound on ascorbic acid stability is ambiguous. In the case of orange, watermelon and mango, there was a decrease from 5 to 32%, while for guava, grapefruit and apple there was an increase from 8% to 34% [37; 38; 39; 40; 41; 42; 43]. [PERSON] and [PERSON] [42] found that ascorbic acid degradation can be caused by sonolysis. They suggest that ascorbic acid can react with free radicals generated during cavitation. [PERSON] et al. [43] indicate that the partial deaeration of the mash (caused by ultrasound) may be one of the factors that cause the increased intensity of free radical generation. Additionally, non-inactivated enzymes in the sonicated mash may have an impact on ascorbic acid degradation in the tested samples. Hence, losses of ascorbic acid in juices obtained from mash after sonication or thermosonication may result from two overlapping effects: oxidation and sonolysis. In the case of thermosonication (despite the process being carried out at elevated temperatures), ascorbic acid content in the tested juices was not found to be higher (Figure 2). [PERSON] et al.