Color, Carotenoids, and Peroxidase Degradation of Seed-Used Pumpkin Byproducts as Affected by Heat and Oxygen Content During Drying Process

The effects of heating temperatures (50, 60, and 70 °C) and oxygen contents (vacuum degrees of 10 Pa and 105 Pa) on the color, carotenoids, and peroxidase degradation of seed-used pumpkins’ byproducts (SUPBs) during drying processes were investigated. Changes of carotenoid monomer contents were analyzed as well. Overall, heating temperatures showed more significant effects on color and carotenoid contents of SUPBs than oxygen content. A higher b* value was desirable after drying process, and the highest b* value (61.62) was obtained under 50 °C (105 Pa). Meanwhile, both of total color difference and browning index were mainly influenced by b* value (p < 0.01). In addition, significant positive correlation between total carotenoid content and peroxidase enzyme activity was observed (R2 = 0.95*), and the highest retention ratios were both obtained at 60 °C (105 Pa). Among the four carotenoid monomers (lutein, α-carotene, β-carotene, and cryptoxanthin) measured, lutein was the most abundant one in SUPBs with a higher thermal stability, and α-carotene was significantly related to peroxidase enzyme activity (p < 0.05). All of total carotenoid content, lutein, α-carotene, β-carotene showed positive correlations with b* value, which indicated carotenoids might appropriately determine the yellow color of SUPB samples.