| Summary: | One of efforts of food diversification is used flour from tubers as a
supplement or substitution for wheat flour. Sweet potatoes are one of another.
The sweet potato tuber was change become different form as chips before drying
then crushed it into flour.
The drying process generally occurs in three periods. At the first time is
pre-heating, constant rate periods in the second, and the last time is falling rate
periods. Between constant and falling rate periods, there is critical moisture
content point (Mk). At this point there is not enough water on the surface to
maintain a water activity value of one. Moisture content decrease very slowly at
falling rate periods and require a long time to achieve moisture content we need
(about 7% wb for wheat flour). Dried chips ready for flouring when the critical
moisture content (Mk) was reached. The changing become smaller particles as
flour aims to accelerate the drying process, so the amount of heat energy we used
can be suppressed.
The determination of critical moisture content (Mk) is reached by
mathematical equation approach. Mathematical equations made from a constant
during falling rate and constant rate periods. This mathematical equation is
derived from observation of the material moisture content. The experiment was
made of different thickness of chips and two cultivars of sweet potato which were
yellow tuber and purple one.
The result is lower critical moisture content at the thicker chips. Drying
time is related with amount of heat energy that used to evaporate the water from
material. The best time to drying at the purple sweet potato is moisture content to
36% wb and thickness of chips 4 mm. For the purple, the best time to drying is
also at moisture content to 36% wb and thickness of chips 1 mm.
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