Assessment of Total Phenolic Compounds, Antioxidant Capacity, β-Carotene Bioaccessibility, HMF Formation, and Color Degradation Kinetics in Pumpkin Pestils

Pestil, often known as fruit leather, is one of the most significant traditional foods manufactured and consumed throughout Türkiye. Due to its practical consumption, the availability of numerous nutrients, and the ability to meet energy requirements, pestil is recognized as a snack food. The aim of this study was to evaluate the bioaccessibility of total phenolic compounds (TPC), antioxidant capacity (AOC), and β-carotene in pumpkin pestils dried by hot air drying (HAD), vacuum drying (VCD), and microwave drying (MD) methods using an in vitro digestion model. Additionally, 5-hydroxymethylfurfural (HMF) formation and color degradation of pestils were evaluated. Changes in TPC and AOC were determined using spectrophotometric methods, whereas the detections of β-carotene and HMF were carried out with high performance liquid chromatography–photodiode array detector (HPLC–PDA). Significantly higher TPC (10.99–105.70%) and AOC (15.30–118.58%, 21.88–401.04% and 89.28–482.14%, in CUPRAC, FRAP, and DPPH assays, respectively) values were observed after drying (p<0.05). Moreover, it was observed that there were statistically significant increases in TPC and AOC values after digestion for all pumpkin pestils compared to undigested samples (p<0.05). Drying process resulted in lower β-carotene content (between 32.15–61.11%) in pumpkin pestils; however, it increased the percentage of bioaccessible β-carotene (max 62.16%) in the pestil samples. Compared to HD and VCD techniques, pumpkin pestils dried with MD exhibited significantly higher TPC, AOC and β-carotene content (p<0.05). All of the pumpkin pestils except those dried by MD at 180 W contain HMF below the Turkish Standards Institute legal limit of 50 mg/kg. L* value of pestils were described adequately to the zero- and first-order kinetic models while a* and b* values were only fitted to zero-order model. In conclusion, the findings obtained in this study pointed out that drying processes (especially by MD method) increased the bioaccessibility of TPC, AOC, and β-carotene.