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International Journal of Food Science and Nutrition Engineering 2014, 4(1): 15-19
DOI: 10.5923/j.food.20140401.03
Comparison of Physicochemical Properties of Spray-dried
Camel’s Milk and Cow's Milk Powder
Abdel Moneim E. Sulieman1,*, Osama M. Elamin2, Elamin A. Elkhalifa2, Loouis Laleye3
1Department of Biology, faculty of Science, University of Hail, Kingdom of Saudi Arabai
2Department of Food Science and Technology, Faculty of Engineering and Technology, University of Gezira, Wad-Medani, Sudan
3Department of Food Science, Faculty of Agriculture, University of Al-Ain, United Arab Emirates
Abstract In the present study, fresh raw camel and cow's milk were concentrated to 20-30% total solids, and then dried
using a pilot spray-dryer. The effect of direction of feed on physicochemical properties camel milk powders on
physicochemical characteristics of the various spray-dried milks were determined. Some of the examined parameters of spray
dried milks were affected, such as the water activity which had low values (0.154 - 0.208). Moreover, the degree of lightness
was affected by direction of feeding, where co-current feeding gave the highest degree of lightness (97.73), when compared
to counter current (93.82). The spray-drying samples also affected the solubility which recorded higher values of tested milk
powder samples. The flowability was affected by the direction of feeding; the co-current feeding gave high values, when
compared to counter-current feeding which gave less values (1.21-1.37). The yield was also affected, the spray-dried samples
gave (68.84-88.20). The chemical analysis indicated that moisture, protein, fat, ash and acidity ranged 1.01-2.41%,
23.75-26.64%, 27.86-29.82% and 0.1-029%, respectively. The results show the importance of optimizing the drying process,
in order to obtain products with better functional and physicochemical properties.
Keywords Spray drying, Solubility, Flowability, Bulk density, Hygroscopicity
1. Introduction
According to FAO[1] there were 19 million camels in the
world, out of which 15 million in Africa, 4 million in Asia.
According to FAO[1] statistics, the annual camel milk
production was around 1.300.000 tons. The camel milk is a
potentially important source of food to nomads. In some
countries, camel milk is one of the main components of
human diet. The present knowledge about camel's milk
production potential is very limited. In traditional pastoral
systems, camel milk is used for feeding calves and human
consumption, two quarters of the udder are usually selected
for milking and segregated with ropes while the calf suckles
the other two quarters[2].
Camel milk differs from cow milk in its chemical
composition, however, it contains all essential nutrients as
cow milk[3] (Elagamy, 1988). Camel milk is highly
nutritious, contains lower fat and lactose, higher levels of
potassium, iron and vitamin C and large amounts of insulin
like protein. It has high contents of whey proteins such as
lactoferrin and immunoglobulin confer to it the high
antimicrobial properties. In average, camel milk contains
more proteins and whey protein than cow milk[4][5] (Farah,
* Corresponding author:
abuelhadi@hotmail.com (Abdel Moneim E. Sulieman)
Published online at http://journal.sapub.org/food
Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved
Z. 1993; Walstra et al., 1999). It is rich in essential amino
acids, which explain the health benefit of camel milk for
human nutrition.
Carmel's milk have been consumed for thousands of
years in Africa and the Middle East, it's medical benefits
toward modern diseases were not known until recently.
Spray drying is a method of producing a dry powder from
a liquid or slurry by rapidly drying with a hot gas. This is the
preferred method of drying of many thermally-sensitive
materials such as foods and pharmaceuticals. A consistent
particle size distribution is a reason for spray drying some
industrial products such as catalysts. Air is the heated drying
medium; however, if the liquid is a flammable solvent such
as ethanol or the product is oxygen-sensitive then nitrogen is
used[6].
Spray drying is the most used commercial method for
drying milk, because the very short time of heat contact and
the high rate of evaporation that give a high quality product
with a relatively low cost[7].
A dry powder product is highly desirable since it possess
long shelf life, requires relatively low transportation cost and
storage capacity and the product can be distributed over a
wide area, thus a process for producing a dried camel's milk
powder that is soluble and without loss of nutritive value is
highly desirable. A spray drying system for cow milk powder
has been characterized by various factors such as inlet air
temperature, feed rate, atomizer speed, out let air
temperature product temperature, thermal and evaporative
16 Abdel Moneim E. Sulieman et al.: Comparison of Physicochemical Properties
of Spray-dried Camel’s Milk and Cow's Milk Powder
efficiencies[8].
The production of milk powder based on the cow milk
powder quality standards such as solubility, flowability,
color and moisture content, process development must be
conducted using the various parameters such as set
temperature, inlet temperature, outlet temperature, product
flow rate, and the direction of the product versus the drying
air. Based on these processing parameters, the best
conditions could be selected for the production of excellent
milk powder.
The major reason for production of milk powder is to
prolong shelf life and to facilitate storage and handling.
When stored in appropriate storage conditions under dry and
cool condition, whole milk powder has a shelf life of 12
months and skim milk powder in excess of 2 years. The shelf
life of milk powder is generally established to warrant
microbiological safety and to keep acceptable sensory
characteristics such as color and flavor. Although milk
powder is microbiologically stable and acceptable, many
physicochemical changes, such as lactose crystallization,
particle caking, oxidation of fat, maillard and enzymatic
reactions, may occur during storage and these modify
physical and functional properties such as flowability,
reconstitution properties, emulsifying and foaming
properties of the powder[9]. The extent of these changes is
strongly dependent on the storage condition such as
temperature, relative humidity and time. Therefore an
understanding of the physicochemical changes that occur
under storage conditions will be very useful to predict the
behavior of powder during its end use[9].
The objectives of the present study were to compare the
physicochemical and functional properties of spray dried
camel's milk powder with spray-dried cow's milk powder.
2. Materials and Methods
2.1. Materials
Fresh camel’s milk and cow’s milk were supplied by Al
Ain Dairy Company during the year (2008). In addition,
commercial cow milk powder samples were bought from a
local supermarket in Alain, United Arab Emirates to be used
in the study.
2.2. Methods
Production of milk powder was completed in two stages
evaporation and spray drying, as follows:
Raw camel’s milk and cow’s milk was concentrated to
20% - 30% total solids using rotary evaporator (Rotavapor R
II, Buchi , Switzerland ) at 80°C. The camel milk concentrate
was dried using a spray dryer (FT 80 Tall from Spray Dryer,
Arm field Ltd., UK). Different drying conditions were
employed. Air inlet temperature was set at (200°C – 220°C),
air outlet temperature was between (98°C -105°C), pump
speed was set at (3 - 5) arbitrary units and the outlet air
relative humidity ranged between (1.2 - 5.8) percent.
2.3. Effect of Direction of Feed on Physicochemical
Properties Camel Milk Powders
The effect of direction of feed on physicochemical
properties of camel milk were determined as follows:
Water activities of spray dried powders were measured
using a water activity analyzer (Rotronic SW with hydrolyte
VD sensor, Rotronic Instrument Corp., Huntington, NY).
The flowability (Hausner ratio) is the ratio of un-tapped
bulk density and tapped bulk density. Un-tapped bulk
density was determined by sifting milk powder into a 100
ml cylinder and then weighing. Tapped bulk density was
determined by reading the volume after tapping the cylinder
100 times[10].
For determination of solubility, 10 g of whole milk
powder was mixed with 100 ml of water at approx 24 °C in
mixer at high speed for 90s.The milk then was left for 15 min.
After which it is stirred with a spatula. 50ml was filled in to a
graduated 50 ml centrifuge glass with conically graduated
bottom. The glass was spun in a centrifuge for 5 min, the
sediment free liquid is sucked off, the glass was filled up
again with water and the content is stirred up. Then the glass
was put in to the centrifuge and spun for 5 min after which
the sediment was read. The sediment was expressed in ml
and is termed insolubility index. It usually below 0.2 ml in
powder from good quality milk dried in designed dryers.
Process yield was calculated as the relation between total
solids content in the resulting powder and total solids content
in the feed mixture.
Hygroscopicity (determined by moisture gain by two
grams of powder samples) were measured under saturation
solution of Na2SO4. After 1 week, hygroscopic moisture was
expressed as g of moisture per100 g dry solids (g/100g) to
determine hygroscopicity.
Hygroscopicity (g/100g) = ( Wf – Wi )X100)/(Wi
X(100-moisture/100)
Where:
Wf = final weight .
Wi = initial weight.
2.4. Colour Determination
The color of different samples was measured using a
colorimeter (Hunter lab).The results were expressed in the
CIE L, a, b. which determined the degree of lightness,
redness and yellowness characteristics of the various milk
powder samples
Where
L = is an indication of lightness.
A = is an indication of redness.
B = is an indication of yellowness.
2.5. Chemical Analyses
The contents of moisture, ash, protein, total soluble solids,
fat and titratable acidity were determined according to
AOAC[11] methods. The pH value was determined using a
pH meter (model HANNA pH 211 micro processor)
according to AOAC[12] method. The ascorbic acid (vitamin
International Journal of Food Science and Nutrition Engineering 2014, 4(1): 15-19 17
C) content was determined in spray dried milk powder
samples according to the AOAC[12].
3. Results and Discussion
3.1. Effect of Direction of Feed on Physicochemical
Properties of Camel Milk Powders
The data in Table (1) show the water activity values of
different spray-dried camel's milk (SDC), spray-dried cow's
milk (SDW) and commercial milk powder (CDM). The
water activity (AW) was influenced by type of milk, such
that water activity was less in spray-dried camel milk
samples (0.154 to 0.208), while AW of SDW ranged
between 0.229 - to 0.255 and CDM contained the highest
value (0.326). The concentration, temperature, direction of
feed and type of milk did not affect water activity of
spray-dried milk powder, but it gave different results for
spray dried cow milk and commercial milk powder samples.
The data in Table (1) show untapped bulk density of
different spray-dried camel's milk, cow milk and commercial
powder milk. The untapped bulk density was affected by the
type of drying, spray-drying produced heavier powder with
higher bulk density (0.46- 0.53). Commercial samples had
density similar to spray dried powder (0.38). It was found
that the direction of feeding did not affect the untapped bulk
density of spray-dried camel milk powders. However,
commercial samples had less density than the powder that
produced co-current feeding.
The tapped density of different spray-dried camel's milk,
spray-dried cow milk and commercial milk powder is
indicated in Table (1). The tapped density was affected by
type of milk, the spray-dried powder (0.43- 0.43) and
commercial samples (0.50) had better results. Drying
temperature, direction of feed, type of milk and
concentration did not affect the tapped density of spray-dried,
freeze-dried and commercial milk powders.
The Hausner ratio (flowability) was affected by the
direction of feeding; it was found that the co-current gave a
lower Hausner ratio (1.27) than counter current (1.37). This
shows that powder produced by co- current drying was more
flowable. Concentration, temperature of drying, type of
drying and type of milk did not affect Hausner ratio. The
Hausner ratio is the untapped divided by the tapped bulk
density. A hausner ratio of 1 to 1.25 indication the powder
had free flowing, hausner ratio of 1.25 to 1.4 indicate fairly
free flowing powder, and powder with hausner ratios greater
than 1.4 are cohesive and do not flow well.
Solubility is an important feature in judging the physical
characteristics of milk powder. It refers to the ability of
desiccated milk when mixed with water to form a solution,
suspension or emulsion which will simulate the physical
characteristics of natural milk, which is measured as
in-solubility index[13]. The insolubility index of the
different spray-dried milk powder samples is presented in
Table (1). It was found that the concentration of 20% and
30% total solid did not affect the insolubility index. However,
spray-dried had relatively lower insolubility index (0.4). On
the other hand, the commercial milk powder was found to
has less insolubility index than that of both spray-dried
camel milk and spray dried cow’s milk, this may be due to
additions of certain addaitives to facilitate the solubility.
Milk powder has to be soluble in water, however, not all of
components in the powder are soluble when reconstituted in
water. In powder produced in modern dryers, this amount is
very small and approaching 100% solubility. Nevertheless,
powder with a bad solubility is still produced. Dryer can be
mal-operated resulting in powder with bad solubility.
It was found that the yield of dried powder was affected by
type of drying. The yield of spray-dried milk samples ranged
between (68.84 -88.20). The type of milk had no effect on
yield of powder.
The data in Table (1) also show the hygroscopicity of
different spray- dried milk powder samples. It was found that
the hygoscopicity of different powder milk was not affected
by type of milk, it ranged between 18.8 - 21.26, with the low
values in commercial milk powder.
Table 1. Physicochemical properties of spray-dried camel milk (SDC), spray-dried cow’s milk (SDW) and commercial milk (CDM)
Run No. Aw
Utapped bulk
density
Tapped
bulk density
Haunser ratio
Insolubility
Index
Yield
Hygrocop--ic
ity
SDC 1 0.178 0.40 0.49 1.21 0.50 88.20 20.43
SDC 2 0.176 0.37 0.50 1.37 0.40 8766 20.47
SDC 3 0.193 0.41 0.53 1.22 0.40 86.90 21.26
SDC 4 0.204 0.38 0.49 1.27 0.45 76.13 20.43
SDC 5 0.154 0.34 0.45 1.33 0.35 75.62 20.45
SDC 6 0.210 0.40 0.52 1.3 0.45 78.00 20.11
SDC 7 0.208 0.39 0.50 1.29 0.50 76.69 20.52
SDW1 0.229 0.29 0.43 1.46 0.50 84.87 20.81
SDW2 0.255 0.18 0.46 1.48 0.70 85.22 20.12
SDW3 0.290 0.21 0.51 1.47 0.80 68.84 21.0
CDM 0.326 0.18 0.50 1.28 0.10 ND 18.8
ND = Not determined
18 Abdel Moneim E. Sulieman et al.: Comparison of Physicochemical Properties
of Spray-dried Camel’s Milk and Cow's Milk Powder
3.2. Colour of Spray Dried Milk
L value is an indication of lightness and blackness. If the
value is 100 the color is white, and if the value is 0 the color
is black. The data in Table (2) and Fig 1 show the lightness of
different milk powder samples. The lightness of spray dried
camel milk (SDC) and spray-dried cow milk (SDC) ranged
between was and Commercial milk powder (CDM) ranged
between 90.24- 97.73 and 94.70-95.78, respectively (Table
1). On the other hand, the lightness of the milk powder was
affected by the direction of feeding, when the direction of
feeding was co-current, it produced lighter color, while, the
lightness of milk powder was less when the direction of
feeding was counter current. It was also found that if high
temperature was used in the spray dryer, the lightness of the
milk was less as compared to low temperature. Lightness of
the milk powder was not greatly affected by the type of milk.
Table 2. The colour of spray dried camel milk (SDC), spray-dried cow
milk (SDW) and Commercial milk powder (CDM) samples
Run No.
Lightness
Redness Yellowness
SDC 1
97.73
-1.08
7.9
SDC 2
96.73
-0.77
8.54
SDC 3
94.37
0.11
11.05
SDC 4
90.24
2.93
17.99
SDC 5
91.40
2.23
17.61
SDC 6
93.82
1.06
12.93
SDC 7
94.03
0.88
13.36
SDW1
94.70
0.82
17.19
SDW 2
95.78
-0.26
10.29
SDW 3
95.64
-0.58
10.54
CDM 94.77 -2.28 21.84
The A value is an indication of redness and greenness of
the product. If the A value is positive, it indicates redness, if
A value is negative, it indicates greenness. The data in Table
(2) (2) show redness of different milk powder samples.
When high temperature and high concentration were applied,
the spray dried milk powder showed increasing in redness,
while low temperature and low concentration were applied
as process parameters, the spray dried milk powder showed
less redness. On the other hand, it was found that the green
color was produced when the direction of feeding was
co-current. But in comparison to the counter current feeding,
the color produced was red and the degree of redness was
(1.19). In the spray dried milk powder samples form the three
types of milk, the A value for the milk powder was positive
indicating the redness.
The B value is an indication of yellowness and blueness of
the product. If the B value is positive, it indicates yellowness,
if B value is negative, it indicates blueness. The data in Table
(2) show yellowness of different milk powder samples. The
yellowness was affected by the direction of feeding, when
co-current direction of feeding was used, the yellowness was
less in the range of (7.90 -17.99). When counter current
direction of feeding was used, the yellowness was more in
the range of (12.93 – 17.61). It was found that the drying
temperature affected the yellowness, low temperature
produced less yellowness in comparison to high temperature.
However yellowness was not affected by type of milk.
3.3. Chemical Composition of Spray-dried Milk Powder
The data in Table (3) indicate some of the chemical
components of different spray-dried camel's milk (SDC),
spray-dried cow milk (SDW) and commercial powder milk
(CDM). The moisture content ranged between (1.01-2.41).
When drying temperature increased, the moisture of the
spray dried milk powders decreased. The moisture content of
the commercial sample (1.70) was closely related to those of
spray dried camel's milk and cow milk samples. These values
are within the recommended standards of powder milk in the
Sudan[9] and USA[10] which are <3% and <5%,
respectively.
The fat content of different samples ranged between
(27.86-29.82%). The drying temperature affected the fat
content of spray-dried powder, with production of high fat
content at low temperature in the powder if compared to high
temperature. Using high temperature in spray drying may
result in adhesion occurrence or overlap between the lipid
and protein molecules. However, the fat content was not
affected by concentration and, type of milk, but it is known
that cow milk naturally contains more fat than camel milk.
The data in Table (3) show the protein content of different
spray-dried camel's milk and cow milk which ranged
(23.75-26.64%) while that of commercial sample was
25.02%. However, these values were in agreement to those
of the Sudanese Standard value[9] and the USA Standard
value[10] which were <27% and <28%; respectively. The
protein concentration levels had an inverse effect on protein,
when high concentration was used protein level decreased.
The direction feeding was another factor that affects protein
content, such the co-current it was produced high protein
levels than counter-current mode of direction feeding.
Table 3. Chemical composition of spray-dried camel milk (SDC),
spray-dried cow’s milk (SDW) and commercial milk (CDM)
Run No. Moisture
(%)
Protein
(%) Fat (%) Ash
(%)
Aci
dly
(%)
SDC 1
1.62
26.07
28.15
7.69
0.20
SDC 2
1.21
26.73
27.86
7.51
0.27
SDC 3 1.24 24.12 28.50 7.63 0.29
SDC 4
1.94
24.10
28.41
6.69
0.27
SDC 5
1.01
25.26
27.88
6.93
0.25
SDC 6 2.23 26.64 28.52 7.46 0.24
SDC 7
2.41
25.99
29.24
7.28
0.24
SDW1
1.59
23.75
28.82
5.71
0.20
SDW2
2.15
25.66
29.82
5.83
0.17
SDW3
1.73
25.30
29.55
5.78
0.17
CDM 1.70 25.02 29.75. 5.84 0.15
Camel's milk had higher ash content than that of cow’s
milk. Ash content of the spray dried camel milk powders and
spray-dried cow’s milk powders were between (6.93 -7.69)
and (5.71 – 5.83)%, respectively. Increase in the ash content
International Journal of Food Science and Nutrition Engineering 2014, 4(1): 15-19 19
of camel's milk was due to its large amount of minerals and
vitamins, as compared with milk cow. The acidity was
affected by concentration and type of milk; it was found that
the acidity was directly proportional to the concentration, an
increased in concentration increased acidity and vice versa.
Acidity was influenced by the type of milk. It was observed
that camel milk had a higher acidity, 0.24%, than cow’s milk,
0.18%.
4. Conclusions
With an increase in temperature a decrease in % water
activity was observed in the spray-dried camel's milk
samples to as low as 0.18%, indicating the possibility of a
longer shelf life. It was also observed that an increase in
temperature resulted in higher values of insolubility index
mainly due to denaturation of proteins; this irreversible
change can limit the usage of these camels' milk powders in
the form of re constituted milk. The flowability of all camel's
milk powder were below 50°C thus promoting a fairly good
flow, however this trend was also observed in spray-dried
cow's milk powders, but the color of spray dried camel's milk
powders was lighter yellow. Further investigations are
required to validate the prospects of camel milk powder on
an industrial scale and to encourage usage of camel's milk
powder as food ingredients in snacks, chocolates, ice cream
and infant formulae.
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