Abstract:

The effect of vacuum microwave drying conditions on the main carotenoids in pumpkin slices were investigated by
high performance liquid chromatography atmospheric with a C30 column and diode array detection coupled with atmospheric
pressure chemical ionization-tandem mass spectrometry (C30-HPLC-DAD-(APCI) MS/MS) technique. The results showed
that the total carotenoid content of vacuum microwave dried pumpkin was significantly (P < 0.05) higher than that of the
hot air dried one. Microwave intensity had the most evident influence on the carotenoids in pumpkin, followed by vacuum
degree and the thickness of pumpkin slices. By increasing microwave intensity, total carotenoid content was significantly
decreased, whereas it was increased by increasing either vacuum degree or slice thickness. Meanwhile, the contents of
α-, β- carotene and lutein decreased with the increase in microwave intensity, but increased with the increase in vacuum
degree or slice thickness. The contents of all β-carotene cis-isomers decreased with the increase in vacuum degree, but they did not
change significantly with the increase in slice thickness. These results collectively indicate that increasing vacuum degree or slice
thickness is beneficial to retain carotenoids, but too high microwave intensity results in decreased content of carotenoids.

Key words: pumpkin slices, vacuum microwave drying, carotenoids