Storage Studies on Spray Dried Camel Milk Powder
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Date
2021
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Publisher
ICAR-NDRI, KARNAL
Abstract
The demand for camel milk is rising throughout the world due to its therapeutic properties,
though its availability only in certain pockets is a major detriment to this. Drying has been used
to increase the shelf life of the milk and its easy transportation. Several attempts have been
made at freeze drying and spray drying of camel milk. Spray drying is preferred, as it is costeffective.
Earlier studies at our Institute optimized the process variables for spray drying of
camel milk. The current research aims to determine the storage stability of the developed spray
dried camel milk powder at different temperatures. Spray dried camel milk powder of
composition (1.42 ± 0.17% moisture, 26.80 ± 0.52% protein, 27.86 ± 0.14% fat, ash 8.04 ±
0.10%, and 35.84 ± 0.40% lactose) was packed in single layered aluminium pouches and stored
at 25, 37 and 45 ˚C. The moisture sorption isotherm was determined and monolayer moisture
content was calculated using BET and GAB models at different temperatures. The results
indicated that the equilibrium moisture content increased with water activity but reduced with
increase in storage temperature. Monolayer moisture content also decreased from 3.17% (25
˚C) to 2.60% (37 ˚C) and 1.63% (45 ˚C) by BET model. During the storage of 120 days, the
highest reduction in most of the reconstitutional properties (i.e., wettability, dispersibility,
solubility) was observed in the powder stored at 45 ˚C. The moisture content increased
significantly (P<0.05) to 2.95±0.21%, 2.67±0.07% and 2.39±0.34% at 25, 37 and 45 ˚C,
respectively. Dispersibility of the powder reduced significantly (P<0.05) from 67.83±0.44% at
zero day to 54.81±1.28, 50.95±0.84, 50.27±1.77% at 25, 37 and 45 ˚C, respectively.
Wettability of the powder sample at zero day was 3.67±0.15 sec at 60±2˚C water temperature
and increased significantly (P < 0.05) to 10.33±0.33, 13.17±0.44 and 18±1.15 sec with the
temperature of storage. The initial solubility (98.58±0.13%), reduced significantly (P<0.05) to
87.35±0.36%, 89.56±0.92% and 79.25±0.40% at 25, 37 and 45 ˚C, respectively. The zero day
microbial counts (total plate count - 2.18±0.06 log cfu/g, thermophilic spore count - 1.13±0.01
log cfu/g) increased significantly (P<0.05) to 3.19±0.04, 3.10±0.03, 3.07 ± 0.03 log cfu/g and
1.15±0.01, 1.47±0.01, 1.91±0.03 log cfu/g at 25, 37 and 45 ˚C, respectively. Coliform, yeast
and mold counts also followed this increasing trend during storage. Physical properties like
bulk density and flowability decreased on increasing storage temperature. Carr Index and
Hausner ratio increased significantly (P<0.05) to 14.96±0.96, 13.77±0.73 and 16.91±0.24, and
1.18±0.01, 1.16±0.01 and 1.21±0.00 at 25, 37 and 45 ˚C, respectively. It was evident that most
deterioration of powder occurred at 45 ˚C. Lower storage temperature resulted in increased
moisture content and water activity, resulting in reduced flowability and increase in number of
total plate counts. Major changes in the reconstitutional properties took place due to absorption
of moisture at low storage temperature and chemical changes due to melting of fat or state
transition of amorphous lactose at higher storage temperature. At all the temperatures, spray
dried camel milk powder was found to be stable and safe for human consumption till 120 days
of storage. The storage temperature of 25 ˚C was recommended for spray dried camel milk
powder, provided the packaging material used has lower water vapour transmission rate.