## 3 Results and Discussion
### Vitamin C, Total Polyphenols, and Antioxidant Activity Analysis of Fruit Juice Formulations
The AA reduction for rose-apple juices was found to be 63.5%, 67%, 69%, 69%, and 67.4% for AC1, AC2, AC3, AC4, and AC5 juices formulations, respectively. [PERSON] et al. [51] reported that ascorbic acid content of orange pasteurized juice was about 20% lower than a natural one. In this study, it is possible that the decrease in ascorbic acid content in mixed juices was, among other things, related to the pH value of these juices. According to [PERSON] et al. [52], the maximal degradation of ascorbic acid will occur at pH 4 and the minimal at pH 2. Mixed juices with higher rose juice content also had a higher DHAA content. Due to the low stability of DHAA, it can be expected that it may undergo an unfavourable and irreversible hydrolyse to 2,3-diketogulonic acid and other breakdown products, such as 2-furoic acid and 3-hydroxy-2-pyrone, in a short period of time [53]. The Folin-Ciocalteu method is usually used for determination of the total polyphenol content, but the reagent is nonspecific. The results of the determinations made by this method are affected by the presence of reducing sugars, aromatic amines, sulphur dioxide, ascorbic acid, organic acids, and other compounds, making the results often overstated. According to [PERSON] [54] and others and [PERSON] and others [55], this method is based on oxidation-reduction reactions (single electron transfer-SET), and can thus be considered as one of the methods for the determination of antioxidant activity. All juices are significant sources of polyphenols. The rose juice presented higher TPC content (272.93 mg GAE/100 mL) than the strawberry juice (44.64 mg GAE/100 mL) or the apple juice (42.69 mg GAE 100 mL). In a similar study conducted by [PERSON] et al. [49], the results for rose juice from _Rosa rugosa_ fruit were close to 200 mg GAE/100 mL. However, [PERSON] et al. [35] in their research on _Rosa rugosa_ fruit juices obtained a TPC content of 432.7 \(\pm\) 3.3 mg GAE/100 mL. In the research conducted by [PERSON] et al. [56], TPC was determined in apple juices at approximately 18.85 mg GAE/100 mL. This value was much lower than that obtained for the tested apple juice. According to [PERSON] et al. [57], the polyphenol content in apples and products obtained from them depends mainly on the variety used and the processing technology, and for fresh juices it is much higher because during storage the juices lose about 50-90% of their polyphenols content. Also, in strawberry juices different authors obtained different TPC results. The TPC determined by [PERSON] [58] for strawberry juice was 197.4 mg GAE/100 mL and that determined by [PERSON] and [PERSON] [59] was approximately 143 mg GAE/100 mL for strawberry juice prepared from strawberries of the Marmolada variety. The rose-strawberry juices presented TPC in the range of 164.40 \(\pm\) 2.04, 182.22 \(\pm\) 3.03, 215.89 \(\pm\) 3.07, 250.48 \(\pm\) 1.44, and 306.17 \(\pm\) 2.14 mg GAE/100 mL for AB1, AB2, AB3, AB4, and AB5 formulations, respectively. The rose-apple juices presented TPC in the range of 116.21 \(\pm\) 2.65, 155.42 \(\pm\) 3.02, 179.22 \(\pm\) 3.65, 199.43 \(\pm\) 3.21, and 230.87 \(\pm\) 2.98 mg GAE/100 mL for AC1, AC2, AC3, AC4, and AC5 formulations, respectively. The increase in the rose juice concentration resulted in the increase in the TPC content (_p_ < 0.05) in the mixed juices. The result may be related to the higher TPC content in rose juice, which is also confirmed by the results of other authors. Apple juices tested by [PERSON] and [PERSON] [41] had a polyphenol content of 71.1 mg GAE/100 mL, and the addition of rose nectar at 25% and 50% increased the polyphenol content to 224.7 and 378.8 mg GAE/100 mL, respectively. The addition of juices with rose fruits significantly affects the antioxidant activity of juices with strawberry and apple. Among single-ingredient juices, strawberry juice had lower antioxidant activity. This value was independent of the addition of rose juice.