When rehydrated, FD carrot slices retained the highest score for appearance; however the aroma/¯avor of
VMD carrot slices was preferred over those of FD
samples (Table 3). This may indicate that there is preferential retention of ¯avor volatiles in product treated
by VMD compared to FD. An evaluation of the eect
of VMD on volatile retention in food matrices is the
subject of on-going research. Color, appearance, texture, aroma/¯avor, and overall acceptability of AD
carrot slices were greatly improved when rehydrated.
No signi®cant dierences were found in texture and
overall acceptability among the rehydrated VMD, AD,
and FD samples.
Reliable cost estimates of VMD are dicult to arrive
at because very few commercial VMD systems are in
commercial use. VMD uses electricity rather than the
fossil fuels typically used for hot-air convection dryers.
In Canada, electricity costs are about four times that of
natural gas, the cheapest fossil fuel available. On the
other hand, VMD is typical two or three times as e-cient as convection food dryers in terms of water evaporated per unit energy. One study of energy, labor and
capital costs conducted by Durance and Liu (1996) on a
commercial pilot-scale drying operation indicated VMD
costs about 15% greater than convection drying. By
comparison, freeze drying costs have been reported up
to 400% that of conventional drying (Fellows, 1988).
These ®gures will of course vary widely depending upon
local energy, labor and ®xed costs.
When rehydrated, FD carrot slices retained the highest score for appearance; however the aroma/¯avor ofVMD carrot slices was preferred over those of FDsamples (Table 3). This may indicate that there is preferential retention of ¯avor volatiles in product treatedby VMD compared to FD. An evaluation of the eectof VMD on volatile retention in food matrices is thesubject of on-going research. Color, appearance, texture, aroma/¯avor, and overall acceptability of ADcarrot slices were greatly improved when rehydrated.No signi®cant dierences were found in texture andoverall acceptability among the rehydrated VMD, AD,and FD samples.Reliable cost estimates of VMD are dicult to arriveat because very few commercial VMD systems are incommercial use. VMD uses electricity rather than thefossil fuels typically used for hot-air convection dryers.In Canada, electricity costs are about four times that ofnatural gas, the cheapest fossil fuel available. On theother hand, VMD is typical two or three times as e-cient as convection food dryers in terms of water evaporated per unit energy. One study of energy, labor andcapital costs conducted by Durance and Liu (1996) on acommercial pilot-scale drying operation indicated VMDcosts about 15% greater than convection drying. Bycomparison, freeze drying costs have been reported upto 400% that of conventional drying (Fellows, 1988).These ®gures will of course vary widely depending uponlocal energy, labor and ®xed costs.
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