studies on drying characteristics of bottle gourd
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Date
2014
Authors
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Publisher
MPUAT, Udaipur
Abstract
Although hot air drying is the simplest and economic method of drying foods,
certain problems such as cell collapse, structure changes in food due to local
hardening and unfavorable changes in colour, texture, flavour and nutritive value are
likely to occur in dehydrated bottle gourd therefore an attempt has been made for a
comparative study between tray drying and fluidized bed drying of bottle gourd slabs.
Locally available bottle gourd was used in the present study. Bottle gourd
were washed and further peeled manually. These peeled bottle gourds were cut into
different dimensions i.e. slab shape, as per the requirement of the investigation. bottle
gourds were cut into dimensions of 10 x 10 x 3 mm, 10 x 10 x 5 mm and 10 x 10 x 7
mm. The bottle gourd slabs were blanched for 2 min followed by dipping in 1% KMS
solution. Bottle gourd slabs were removed from the solution and put on wire mesh
tray to drain the excess of solution from them.
Whole slabs of 10 x 10 x 3 mm, 10 x 10 x 5 mm and 10 x 10 x 7 mm size were
subjected to tray drying and fluidized bed drying. Slabs were dried at 50˚C, 60˚C and
70˚C at a constant air velocity of 3m/s and 10m/s for tray drying and fluidized bed
drying respectively. The effect of process variables such as air temperature and size
along with air velocity were studied in tray and fluidized bed drying experiment.
The initial moisture content of bottle gourd was 16.48 g of water/g of dry
matter (94.28 % wb).The complete drying took place in the falling rate period .It was
inferred from the study that drying time was reduced as temperature increased for
bottle gourd slabs in tray dryer and fluidized bed dryer. The drying time was higher
for tray dryer compared with the fluidized bed dryer at all the temperature and size
level. The drying time was higher for slabs of 10×10×7 mm as compared to slabs of
10×10×5mm and the drying time of slabs of 10×10×5 mm was higher than the slabs
of 10×10×3mm, for all the three levels of drying air temperature. Drying time was
higher for slabs of 10×10×7 mm as compared to slabs of 10×10×3 mm in all the three
temperature and size levels for both tray drying and fluidized bed drying experiments.
Minimum drying time was observed for high air temperature 70˚C and for the small
slab size 10×10×3 mm in fluidized bed drying. Drying rate for slab of 10×10×7 mm
was lower compared with that of slabs of 10×10×5 mm and for slab 10×10×5 mm
was lower compared with of slabs of 10×10×3mm in all the three temperature levels
(50˚C, 60˚C and 70˚C) for both tray drying and fluidized bed drying experiments. The
drying rate is high for the slabs of 10×10×3mm at 70˚C for fluidized bed drying.
Moisture diffusivity for fluidized bed dryer at every size and every temperature level
is higher compared to tray dried product .Moisture diffusivity of bottle gourd slabs
dried under fluidized bed drying conditions was found in the range of 1.03 × 10-09
m2/s to 6.18 × 10-09 m2/s. and for the tray dryer the range of moisture diffusivity is
9.14 × 10-11 m2/s to 6.27 × 10-10 m2/s. Air temperature and thickness of slabs were
statistically found to have significant effect on moisture diffusivity of bottle gourd
slabs. Drying constant increased with increase in temperature for both tray dried and
fluidized bed dried samples. Page model gave better fit for both tray drying and
fluidized bed drying conditions. Among all the three mathematical models tested, the
Page model gave an excellent fit with experiment data of the fluidized bed drying.
Samples dried at high temperature and at small thickness 10×10×3 mm in fluidized
bed drying were of best quality in terms of water activity (0.318) compared with tray
drying. The color of fluidized bed dried product is good compare with tray dryer. The
color of fluidized bed dried product for 10×10×5 mm slab at 60˚C is best.
There was no significant difference in the carbohydrate content, fat content
and protein content of Bottle gourd slabs dried in fluidized bed dryer and tray dryer.
The fluidized dried product in fat (0.26 g), protein (1.27 g) and carbohydrate (3.79 g)
content manner found best comparatively to tray dried product. Sensory evaluation
show that the fluidized dried product was good in flavor, texture, color and overall
quality etc. compare with tray dryer.
Description
studies on drying characteristics of
bottle gourd
Keywords
Citation
Mattu and Champawat, 2014