PhD

The present investigation entitled ‘Instant juice powders of cashew apple
(Anacardium occidentale L.) and pineapple (Ananas comosus (L.) Merr.)’ was carried
out in the Department of Processing Technology, College of Agriculture, Vellayani
during 2013-2016 to optimise the process parameters for micro encapsulation through
spray drying of cashew apple and pineapple juices, to evaluate the effect of drying on
physical, chemical and nutritional quality parameters of fruit powders, to formulate
blended fruit powder and to assess organoleptic quality, storage stability, economics
and consumer acceptability of the standardised formulations.
Fruit juice mixed with a carrier, maltodextrin or resistant dextrin in 80: 20,
70:30, 60:40, 50:50 and 40: 60 solid ratios were fed to co-current spray drier at inlet
temperatures of 150oC, 160oC, 170oC, 180oC, 190oC and 200oC for optimization of
drying parameters of cashew apple, pineapple and their equal blend independently.
Feed rate was varied to maintain the outlet temperature at 88 ± 2OC with 4 bar
atomization pressure and 2000 rpm blower capacity. Carrier resistant dextrin, juice
solid to carrier ratio of 40:60 and 160oC inlet temperature resulted in high recovery of
fine, coarse and bulked fruit powders. This combination recovered 72.09, 85.62 and
74.70 per cent of total solid content from juice carrier mix of cashew apple, pineapple
and their equal blend respectively of which 40.55, 47.06 and 42.02 per cent were from
cyclone.
Based on higher recovery percentages, five treatment combinations (150oC to
190oC with 40:60 ratio) from each carrier were selected and subjected to
physicochemical analysis. Resistant dextrin yielded fruit powders with low moisture,
dispersible solids, viscosity, angle of repose and with high per cent soluble solids,
lightness and hue angle, whereas maltodextrin yielded fruit powders with high total
soluble solids. Resistant dextrin lowered chromaticity of pineapple and blended juice
powder in contrast to the effect in cashew apple. Resistant dextrin produced pineapple
powder with low water activity while maltodextrin improved bulk density of cashew
apple and blended powder. Inlet temperature of 160oC yielded fruit powders with
higher bulk density whereas powder moisture and angle of repose were low at 190oC.
Drying at 160oC could decrease water activity and improve total soluble solids of
cashew apple powder whereas reduction in water activity and chromaticity along with
improvement of hue angle were observed in blended juice powders. Powders with
resistant dextrin had high glass transition temperature and low hygroscopicity. Powder
particles were spherical with 3 - 30 μm size and had occasional surface dents. None of
the treatment combinations influenced sinkability of powders.
Maltodextrin yielded fruit powders with high sugars and resistant dextrin
yielded cashew apple powder with high vitamin C. Carriers did not significantly
influence the energy value of fruit powders. Inlet temperature of 160 oC yielded
vitamin C rich powders from all fruits as well as β-carotene rich pineapple powder.
None of the treatment combinations influenced crude fibre, pH, total ash or titrable
acidity. Fruit powders with resistant dextrin dried at 160oC had superior scores in
sensory analysis.
Good quality fruit powders produced at 160oC using each carrier, when
subjected to a storage study for six months under four packaging atmospheres,
microbial growth was totally absent. Refrigerated storage could maintain vitamin C,
β-carotene, moisture content, titrable acidity, total phenol and high sensory
acceptability of fruit powders. Cost of production of fruit powders with carrier
resistant dextrin was comparatively less and highest consumer preference was for
pineapple powder.
Instant juice powders of cashew apple, pineapple and their equal blend produced
by spray drying at 160oC with resistant dextrin as carrier in 40:60 juice solid to carrier
ratio had optimum physical, chemical, nutritional and sensory qualities with six month
shelf stability under refrigeration. Further studies to improve shelf life of the product
in ambient temperature, exploration on nutraceutical functions and development of
spray drier for small scale industries with higher efficiency will be highly beneficial
for improving cost effectiveness and commercialization of the technology.