Abstract:

To investigate the effects of drying temperature and oxygen content on modified atmosphere-drying characteristics
of carrots, a modified atmosphere dryer was used in this study, in which N2 was used as a drying medium to replace partial
air. The results showed that increasing drying temperature could shorten the drying time significantly. As the oxygen content
decreased from 20.9% to 5%, the mass transfer coefficient remained the same, yet the heat transfer coefficient increased
by about 0.5%; as drying temperature and oxygen content decreased, the carotenoid content increased, and the oxidative
degradation of carotenoid could be restrained when the oxygen content of drying medium was as low as 5%. With the drying
temperatures ranging from 40 to 60℃, the color difference values at 5% and 10% oxygen contents were obviously lower
than that at 15% and 20.9% oxygen contents, which indicates that modified atmosphere drying at low oxygen content could
preserve product color effectively. Therefore, the modified atmosphere drying of carrots is beneficial to obtain high quality
of dried products.

Key words: modified atmosphere drying, carrot, drying characteristics