## 3 Results and Discussion
### Bioactive Properties
#### 3.4.2 TPC and TFC  
The phenolic and flavonoid content of fresh and dried quince fruits shown in Table 3. Fresh fruits had the highest TPC and TFC of 259.68 \(\pm\) 23.26 mg GEA/100 g DM and 40.17 \(\pm\) 0.48 mg EPI/100 g DM, respectively. Freeze drying preserved a high content of phenolic compounds (233.56 \(\pm\) 5.96 mg GEA/100 g DM), which were only about 10% less in freeze-dried samples than in fresh fruit. Similarly, convection drying at 40 \({}^{\circ}\)C preserved a relatively high content of polyphenols (205.87 \(\pm\) 12.90 mg GEA/100 g DM). Significantly, the lowest TPC was found for quintec dried at 60 \({}^{\circ}\)C (141.79 \(\pm\) 9.83 mg GEA/100 g DM). Sublimation drying also preserved a high content of flavonoids (36.79 \(\pm\) 0.74 mg EPI/100 g DM), the loss of which, compared to fresh fruit, was about 11%. The amount of these compounds was significantly lower in convection-dried samples at 40 \({}^{\circ}\)C (25.99 \(\pm\) 0.21 mg EPI/100 g DM) and 60 \({}^{\circ}\)C (22.41 \(\pm\) 0.70 mg EPI/100 g DM). Figure 3: Tannin content of quintec samples. Fresh—fresh fruit; Freeze-Dried—freeze-dried fruit; Conv-40—convection-dried fruit at 40 \({}^{\circ}\)C; Conv-60—convection-dried fruit at 60 \({}^{\circ}\)C. Values with the same letter are not significantly different at \(p<0.05\) ([PERSON]’s post hoc test). The present study did not investigate the qualitative composition of bioactive compounds, focusing on their quantity and change during the selected method or drying parameters. However, the available literature shows quince fruits' qualitative composition of polyphenols or flavonoids. They contain important phenolic compounds, including 3-O--claviloylquinic acid (chlorogenic acid), 4-O--clavoylquinic acid (crypto chlorogenic acid), 5-O--clavoylquinic acid (neochlorogenic acid), and 3,5--diclavoylquinic acid. The dominant flavonoids in the fruit of _C. oblonga_ are epigallocatechin and rutin, with catechins and quercetin present in lower concentrations. In addition, lucenin, vicenin, stelarin, and apigenin were also found [37]. The importance of flavonoids in quince was proven in a study by [PERSON] et al. [38]. Using hyperlipidemic rat models, researchers studied the effects of total flavonoids from _C. oblonga_ (from the leaves and fruit) on blood lipid levels and antioxidant potential. They demonstrated that total quince flavonoids can effectively regulate lipid metabolism and scavenge oxygen free radicals, indicating their potential value in preventing and treating hyperlipidemia. In general, freeze drying helps protect the product's quality characteristics, since a low temperature reduces the likelihood of degradation of many sensitive compounds, such as polyphenols and flavonoids [5]. For example, in a study by [PERSON] et al. [39] on Japanese quince, they also found that freeze drying allows for high content of bioactive compounds, including polyphenols, whose loss was only slightly more than 4% compared to the polyphenic extract before drying. A study by [PERSON] et al. [40], evaluating the effect of freeze drying on the phenolic compound content of selected tropical fruits, showed that freeze-dried melon had only about 11% fewer polyphenols than fresh fruit. The same study showed just over 20% loss of phenolic compounds in freeze-dried mango and carambola compared to fresh counterparts and as much as a 40-50% reduction in TPC in melon and watermelon after freeze drying. On the other hand, in the [PERSON] et al. [41] study, the TPC of freeze-dried groundnut fruit was significantly higher (more than 40%) than that of fresh fruit. The authors explain this increase by the higher extractability of polyphenols into the extraction solvent due to the mild microstructural changes induced by the formation of ice crystals during freeze drying and higher rehydration with solvent due to the porous structure obtained. In addition, drying can change the fractional contribution of free and bound phenolic compounds [41]. A study by [PERSON] et al.