Stability of carotenoids and carotenoid esters in pumpkin (Cucurbita maxima) slices during hot air drying

The levels of carotenoids and carotenoid esters in pumpkin (C. maxima) slices as affected by hot air drying (60–100 °C, 6–17 h) were assessed via an HPLC-MS/MS method. Among the 25 carotenoids and carotenoid esters identified in pumpkin flesh, xanthophyll diesters (including (all-E)-violaxanthin dipalmitate, lutein 3-O-myristate-3′-O-laurate, lutein 3-O-palmitate-3′-O-laurate, lutein 3-O-myristate-3′-O-palmitate, lutein 3-O-stearate-3′-O-myristate and lutein 3-O-stearate-3′-O-palmitate) accounted for 43% of the total carotenoids (853.6 ± 18.5 μg/g, dried weight). Dihydroxy xanthophylls, especially those containing 5,6-epoxy group, were more heat-labile than carotenes, while xanthophylls were less heat stable than their diester counterparts. The degradation rates (first-order reactions, R2 = 0.983–0.992) for lutein diesters (rate constant: 0.002–0.049 h−1) in pumpkin slices were only 10–20% of that for lutein (rate constant: 0.020–0.243 h−1) during hot air drying, and 76–98% of lutein diesters could be retained in the final dried products.