The study revealed that bioactivity of dried sour cherries is
better maintained by a low drying temperature, a short processing
time, and limited contact of the material with oxygen
present in the air. In this sense, vacuum–microwave drying is
much better than convective drying and competitive with
freeze drying. High power levels at the beginning of VMD
do not contribute to a high temperature of the dried material
because relatively large amounts of evaporating water require
lots of energy. In addition, the total drying time is reduced.
Therefore, it is recommended to dry sour cherries with a
possibly high microwave power if a certain critical temperature
level is not exceeded. When approaching this level, the
power of emitted microwaves should be immediately reduced
to the value that ensures the maintenance of a sufficiently low
temperature and provides a high bioactivity in the dried product.
This study revealed that VMD at 480 Wup to a moisture
content of ca. 1 kg/kg dm followed by drying at microwave
power reduced to 120 W ensured the highest content of
phenolic compounds, high antioxidant capacity, and attractive
color, which was compatible with anthocyanins content.
Additionally, this procedure had a positive influence on contents
of the compounds from the quercetin derivatives.
The study revealed that bioactivity of dried sour cherries isbetter maintained by a low drying temperature, a short processingtime, and limited contact of the material with oxygenpresent in the air. In this sense, vacuum–microwave drying ismuch better than convective drying and competitive withfreeze drying. High power levels at the beginning of VMDdo not contribute to a high temperature of the dried materialbecause relatively large amounts of evaporating water requirelots of energy. In addition, the total drying time is reduced.Therefore, it is recommended to dry sour cherries with apossibly high microwave power if a certain critical temperaturelevel is not exceeded. When approaching this level, thepower of emitted microwaves should be immediately reducedto the value that ensures the maintenance of a sufficiently lowtemperature and provides a high bioactivity in the dried product.This study revealed that VMD at 480 Wup to a moisturecontent of ca. 1 kg/kg dm followed by drying at microwavepower reduced to 120 W ensured the highest content ofphenolic compounds, high antioxidant capacity, and attractivecolor, which was compatible with anthocyanins content.Additionally, this procedure had a positive influence on contentsof the compounds from the quercetin derivatives.
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