# Bioactive Vitamin C Content from Natural Selected Fruit Juices
## 3 Results and Discussion
### Vitamin C Content in Juices Stored in Plastic Containers  
The citrus juice richest in vitamin C in plastic containers was grapefruit juice (34.50-22.00 mg/100 g), followed by mandarin-chemetine (23.00-5.60 mg/100 g) (Figure 4a,b). [PERSON] investigated which factors affected the vitamin C contents of citrus fruits [53]. In this research, the most important were thermal processing, types of containers, handling, and storage. Therefore, it is very important to point out the influence of each factor on the vitamin C content not only in citrus fruits but also in other fruits, e.g., in organic fruits available to consumers. Vitamin C content in grapefruit citrus juice stored in plastic packaging in the refrigerator (t\({}_{1}=4\)\({}^{\circ}\)C) after the 1 st day is greatly reduced (\(-6.9\%\)). In the coming days, the decline is even greater from the 2 nd day to the 7 th day, i.e., \(-8.41\%\) and \(-18.84\%\) (Figure 4a), respectively. The results showed that grapefruit juice, when stored in a plastic container and after three weeks at t\({}_{1}=4\)\({}^{\circ}\)C, led to the ascorbic acid content decreased to 35.1%. According to [PERSON] and others [45], regarding packing material, vitamin C in fruit juice was less stable when stored in plastic bottles. In plastic containers, vitamin C content in grapefruit juice at storage temperature t\({}_{2}=23\)\({}^{\circ}\)C was as follows: 1 st day: \(-11.59\%\); 2 nd day: \(-14.49\%\); 3 rd day: \(-18.84\%\); 7 th day: \(-21.74\%\) (Figure 4a). Immediately after the 1 st day, the decrease in vitamin C is 8.4% larger in the juice stored in the plastic packaging than in glass. The vitamin C content of grapefruit juice decreased more in glass containers than in plastic containers at the storage temperatures observed (t\({}_{1}=4\)\({}^{\circ}\)C, t\({}_{2}=23\)\({}^{\circ}\)C). [PERSON] and [PERSON]'s [81] analyses have confirmed that citrus fruit juice exposed to higher temperatures for extended periods lost its vitamin activity and became deteriorated. When storing grapefruit juice in the freezer at t\({}_{3}=-18\)\({}^{\circ}\)C in plastic containers, the degradation of vitamin C content was almost the same as in glass containers (Figure 4a). The biggest deviation between vitamin C contents was recorded after the 2 nd day when the decrease of vitamin C in the juice stored in the glass container was 2% higher than the content of vitamin C in the juice stored in the plastic container. Vitamin C content in grapefruit juice at freezing storage temperature in plastic packaging was as follows: 1 st day: \(-13.04\%\); 2 nd day: \(-15.94\%\); 3 rd day: \(-19.71\%\); 7 th day: \(-23.19\%\) (Figure 4a). High storage temperatures caused an increase in ascorbic acid degradation, while low temperatures caused a decrease in the rate of degradation [82; 83]. Vitamin C content in the storage of mandarin-clementine juice in the refrigerator (t\({}_{1}\) = 4 \({}^{\circ}\)C) in plastic packaging materials decreased as follows: 1 st day: \(-\)17.39%; 2 nd day: \(-\)23.91%; 3 rd day: \(-\)39.13%; 7 th day: \(-\)48.70% (Figure 4b). The most significant difference (6.52%) between the value of vitamin C in plastic and glass packaging was recorded after the 1 st day of storage. The results demonstrated that the ascorbic acid content was reduced to 52.39% after three weeks at t\({}_{1}\) = 4 \({}^{\circ}\)C in a plastic container in which the juice was stored. On the 1 st and 2 nd days, the vitamin C content in mandarin juice at storage temperature t\({}_{2}\) = 23 \({}^{\circ}\)C in plastic containers decreased by \(-\)22.17% and \(-\)23.91%, respectively (Figure 4b). After the 7 th day, the vitamin C content in plastic storage packaging materials decreased by 56.52%. Our results confirmed the claim made by [PERSON] et al. [84]. According to  
Figure 4: The vitamin C content in fruit juices in different temperatures in plastic containers: (**a**) grape-fruit, (**b**) mandarin-clementine, (**c**) late peach, (**d**) winter apple, (**e**) winter pear, (**f**) autumn plum. [PERSON] et al.