ORIGINAL PAPER

Physical properties of barley and oats cultivars grown in highaltitude Himalayan regions of India

Afshan Hamdani • Sajad A. Rather •

Asima Shah • Adil Gani • S. M. Wani •

F. A. Masoodi • Asir Gani

Received: 7 January 2014 / Accepted: 28 April 2014

� Springer Science+Business Media New York 2014

Abstract In this study, some selected physical properties

of oats and barley viz seed size, shape, gravimetric prop-

erties, density characteristics, angle of repose, static coef-

ficient of friction and terminal velocity were determined at

a constant moisture content of 8.0 %. These properties are

often required for designing of food processing appliances.

The average of the principle diameters was found to be

4.96 ± 0.50, 5.34 ± 0.31, 6.00 ± 0.26 and 5.41 ±

0.44 mm and 1,000-grain weight was 41.9 ± 0.2, 40.06 ±

0.02, 36.66 ± 0.01 and 36.51 ± 0.02 g for hulled barley,

hulless barley, Sabzaar oats and SkO-20 oats, respectively.

The grains were narrow and elongated having an average

sphericity of 50.55 ± 3.7, 47.923 ± 1.8, 32.578 ± 1.3 and

35.69 ± 2.1 %, respectively. The physical properties of the

flours like angle of repose, flowability, bulk and true den-

sity were also determined. The value of angle of repose

was found to be 50.44 ± 0.270, 63.45 ± 0.340, 46.86 ±

0.250 and 44.49 ± 0.100 for the flour of hulled barley,

hulless barley, oats Sabzaar and SKO-20, respectively. The

flours had poor flowability having a compressibility index

of 33.69 ± 0.12, 34.32 ± 0.87, 27.94 ± 1.23 and 27.5 ±

0.74 and Hausner’s ratio 1.58, 1.52, 1.38 and 1.37,

respectively.

Keywords Oats � Barley � Physical properties � Flour

Abbreviations

L Length, (mm)

W Width (mm)

T Thickness (mm)

Dg Geometric mean diameter (mm)

De0 Equivalent sphere diameter (mm)

Da Arithmetic mean diameter (mm)

S Surface area (mm2)

V Volume of the seed (mm3)

Ra Aspect ratio

W1000 Thousand seed weight (g)

qb Bulk density (Kg/m3)

qt True/tapped density (kg/m3)

e Porosity (%)

l Static coefficient of friction

h Angle of repose �(degree)

A Sphericity (%)

Introduction

Physical properties of the agricultural grains include their

geometric properties like linear dimensions (length,

breadth and thickness), geometric and arithmetic mean

diameter, surface area, seed volume, sphericity and aspect

ratio, gravimetric properties like 1,000-seed mass, true

and bulk density and porosity, frictional properties like

angle of repose and static coefficient of friction and

aerodynamic properties like terminal velocity. Study of

such physical properties is required for designing of the

equipment for handling, harvesting, processing, sorting

and conveying of these grains [12]. A similar kind of

study can be conducted with the flour obtained from these

A. Hamdani � S. A. Rather � A. Shah � A. Gani (&) �S. M. Wani � F. A. Masoodi

Department of Food Science and Technology, University of

Kashmir, Srinagar, India

e-mail: adil.gani@gmail.com

A. Gani

Department of Food Engineering and Technology, SLIET,

Punjab, India

123

Food Measure

DOI 10.1007/s11694-014-9188-1

grains, which includes the study of the parameters like

bulk density, tapped density, compressibility index,

Hausner’s ratio, mass flow rate, angle of repose and the

static co-efficient of friction against different test surfaces,

like glass, cardboard etc. Such properties are important in

determining the flow behavior of the flour. In theoretical

calculations agricultural seeds are assumed to be sphere or

ellipse because of their irregular shapes [24, 25]. Bulk

density, true density and porosity affect the structures and

loads and in the sizing of container tanks. The angle of

repose is important in designing of storage and trans-

porting structures, like the hoppers. This is because the

inclination angle of hopper walls should be always greater

than the angle of repose to ensure the continuous flow of

the grains (i.e. gravity flow). The static coefficient of

friction of the grain, determined against the various sur-

faces is important in the designing of conveyors, for

example, the rougher surface like rubber can create the

friction necessary to hold the grains or flour on the con-

veying surface preventing them to slip or slide backward,

thus useful in material handling, and the smoother surface

like fiberglass can be useful in material conveying. Sim-

ilarly, the terminal velocity is an important aerodynamic

property at which the particles are suspended stationary in

vertical air stream should be known for pneumatic con-

veying, separation, cleaning, harvesting and drying of

agricultural products. It can be determined mathematically

as well as by the laboratory studies. The powder prop-

erties of the flours on the other hand help us to know

about their flow behavior which is helpful in their proper

handling during the conveying, processing and their

storage. In recent years, physical properties have been

studied for various crops including fruits, grains and

seeds, such as; faba beans [14], pumpkin seeds [21], lentil

seeds [10], pearl millet i.e. Pennisetum gambiense [20],

white lupin [26], sunflower seeds [17], bambara ground-

nuts [9], sea buckthorn [13], hackberry [13], apricot pit

[15], chickpea seeds [22], hemp seed [30], groundnut

kernel [27], almond nut and kernel [8], lentil seed [5],

edible squash seed [29], Juniperus drupacea fruits [3],

garlic [19] and funnel seed [1] but, no detailed study of

such properties has been conducted on oats and barley.

The physical properties of barley and oats cultivars are

essential for the design of equipment for handling, har-

vesting, processing and storing the grain, or determining

the behaviour of the grain for its handling. Various types

of cleaning, grading and separation equipment are

designed on the basis of the physical properties of grains

or seeds [9]. The objective of this study was therefore to

determine the physical properties of oats and barley as

whole grains, and some of the physical properties of the

flour obtained upon their milling.

Materials and methods

Materials

Two varieties of oats i.e. Sabzaar (OSb) and SKO-20 (OSk)

and that of barley i.e., Hulled (BH) and Hulless (BHL)

(Fig. 1) were obtained in the month of June from

SKAUST-K. The grains were harvested separately, cleaned

manually to remove all foreign matter such as dust, dirt,

stones and chaff as well as immature, broken grains.

1,000-grain weight

To determine thousand grain mass (M1000), 1,000 randomly

selected grains were weighed in an electronic balance

reading to 0.001 g [7].

Geometrical properties

In order to determine the dimensions of the grain 100

individual grains were randomly selected and their three

principal linear dimensions namely length (L), width

(W) and thickness (T) were measured by a digital caliper

reading to an accuracy of 0.01 mm.

According to [31, 33], the geometric mean diameter

(Dg) is calculated as:

Dg ¼ LWTð Þ1=3: ð1Þ

The arithmetic mean diameter is determined according

to formula given by [23] as:

Da ¼ LþWþ Tð Þ=3: ð2Þ

According to [20], seed volume (V) and sphericity (u)

were calculated by using the following formulae:

V ¼ pB2L2= 6 2L� Bð Þ½ �; ð3Þ

u ¼ Dg=L� �

� 100; ð4Þ

where B = (WT) 0.5

The surface area, S in mm2 was found using the formula

given as under, using the method analogous to one used by

[30, 37, 4] as:

S ¼ D2g � p. ð5Þ

The aspect ratio (Ra) of grains was calculated as follows

[28].

Ra ¼ W=Lð Þ � 100: ð6Þ

The diameter of equivalent sphere was determined by

using the formula as given below, according to [16].

ð7Þ

A. Hamdani et al.

123

where De is the diameter of equivalent sphere in mm; Wt is

weight of seed in kg; ct is true density of seed, in kg/m3.

Gravimetrical properties

Bulk density was measured by dividing the weight of a

quantity of seeds of each variety on its volume, which is

measured by using graduate cylinder [6], using the formula

as follows:

qb ¼ M=Vb ð8Þ

where qb is the bulk density of the bulk seeds, kg/m3; Vb is

bulk volume of the weight sample of bulk seeds, m3

The toluene (C7H8) displacement method was used to

determine true density. Toluene (C7H8) was used in place

of water because it is absorbed by seeds to lesser extend.

True density was calculated as the ratio of sample mass to

the volume of the sample [32, 34].

qt ¼ M=Vt; ð9Þ

where qt is the true density of seeds, kg/m3; Vt is the

volume of toluene displaced by the mass of grains, m3

The bulk and true densities tests were repeated three

times. The porosity (e) was calculated by the equation

given by [24]:

e ¼ 1� qb=qtð Þ½ � � 100: ð10Þ

Frictional properties

Static coefficient of friction of the grains was determined

against surfaces of corrugated board, fiber glass and ply

wood. A wooden table provided with an adjustable tilting

plate on its top, that could be faced with the test surface

was used for the purpose. The sample was placed on an

adjustable plate on top of the table and the inclination of

the test surface was increased gradually so that the grains

start to slide down and until about 75 % of the sample

slided down. The equipment and the angle of tilt were

calculated as:

l ¼ tan a. ð11Þ

The angle of repose is the angle compared to the hori-

zontal at which the material (sample grains) will stand

when piled. It was determined by using software Digimizer

version 4.2.1.

Fig. 1 Images of different

varieties of grains: a Sabzaar

(OSb); b SKO-20 (OSk);

c Hulled barley (BH) and

d Hulless barley (BHL)

Properties of barley and oats

123

Aerodynamic properties

Theoretically, the terminal velocity can be calculated by

using the formula as suggested by [16]. For this purpose,

the diameter of equivalent sphere and shape factor were

calculated by using the following formula.

Vkrtð Þ2¼ 4:g:de:ct: 6Z� pð Þ½ �= 3:ca 0:44ð Þ½ � ð12Þ

where Vkrt is the theoretical terminal velocity in m/s, g is

the Gravitational acceleration in m/s2, Z is the Shape fac-

tor, which is given by: !a is Density of air (1.225 kg/m3), Z

is (p/6) (De/Dg)3 9 u

Determination of powder properties of the flour

Bulk and tapped density

The bulk density was calculated as the ratio of mass of

contents to volume of container occupied and determined

according to [6]. The results were expressed in kg/m3.

To determine the tapped density of the flours, the similar

procedure was repeated, but the tapping of the sample was

done in the measuring cylinder, very carefully until no fur-

ther decrease in the level of flour was observed at the grad-

uation mark. The results were again expressed in kg/m3.

Compressibility index and Hausner ratio

In recent years the compressibility index and the closely

related Hausner ratio have become the simple, fast, and

popular methods of predicting powder flow characteristics.

The compressibility index has been proposed as an indirect

measure of bulk density, size and shape, surface area,

moisture content, and cohesiveness of materials because all

of these can influence the observed compressibility index.

The compressibility index and Hausner ratio was calcu-

lated using measured values for bulk density (qb) and

tapped density (qt) as per the formula given by [11]:

CI ¼ 100� qt�qbð Þ=qt½ �; ð13ÞHausner Ratio HRð Þ ¼ qt=qb: ð14Þ

In a variation of these methods, the rate of consolidation

is sometimes measured rather than, or in addition to, the

change in volume that occurs on tapping. For the com-

pressibility index and the Hausner ratio, the generally

accepted scale of flow ability is given in Table 1.

Angle of repose

The angle of repose is very important in characterization of

the flow properties of powders. It is a characteristic related

to inter particulate friction or resistance to movement

between particles. It is the constant, three-dimensional

angle assumed by a cone-like pile of flour formed relative

to the horizontal base. Angle of repose test results are

reported to be very dependent upon the method used. In our

study, it was determined by the method of image analysis,

using software Digimizer version 4.2.1. (Table 2)

Flow through an orifice

Monitoring the rate of flow of material through an orifice is

an important measure of powder flowability. It can be

determined using either mass flow rate or volume flow rate

basis as per [11]. In our experiment, it was determined on

mass flow rate basis, using a half cut PET bottle, with its

necked mouth with a diameter of 21 mm as an orifice. The

weight of flour that flowed through the orifice for a period

of 30 s was measured using a digital balance correct up

to ±0.001 g, and the results were expressed as g/30 s. The

flow rate was measured making the system subjected to

some constant vibrations, to make the constant flow of the

flour possible which is otherwise pulsating in nature.

Statistical analysis

Mean values, standard deviation, analysis of variance

(ANOVA) were computed using a commercial statistical

package SPSS 10.1 (USA). These data were then compared

using Duncan’s multiple range tests at 5 % significance

level.

Table 1 Table of flowability

Compressibility index (%) Flow characteristics Hausner ratio

10 Excellent 1.00–1.11

11–15 Good 1.12–1.18

16–20 Fair 1.19–1.25

21–25 Passable 1.26–1.34

26–31 Poor 1.35–1.45

32–37 Very poor 1.46–1.59

[38 Very, very poor [1.60

Table 2 Flow property and corresponding angle of reposes

Angle of repose (degrees) Flow properties

25–30 Excellent

31–35 Good

36–40 Fair-aid not needed.

41–45 Passable

46–55 Poor

56–65 Very poor

[66 Very, very poor

A. Hamdani et al.

123

Results and discussions

Geometric properties of grains

The average values of different geometric parameters are

shown in Table 3. There were not much inter-varietal

differences between barley and oat varieties, considering

their dimensional features, but the oats seeds were in

average found to be longer and narrower than barley seeds.

The knowledge of these dimensions is very useful in

determining aperture sizes in the design of grain handling

machineries, e.g. the major axis (L) being indicative of the

natural rest position of the seed, and will be useful in the

application of compressive force to induce mechanical

rupture of the hull. The geometric mean diameter was

found to be 4.33 ± 0.27, 4.53 ± 0.24, 4.22 ± 0.21 and

4.01 ± 0.24 mm for hulled barley, hulless barley, Sabzaar

oats and SKO-20 oats respectively. The results were found

to be similar to those found by [18] in case of barley

(Sahin-91 and Sur-93). Geometric mean diameter was

found to vary significantly except between the two oats

varieties where it varied non-significantly. The geometric

mean of the axial dimensions is useful in the estimation of

the projected area of the seeds which is generally indicative

of its pattern of behavior in a flowing fluid such as air, for

example during air classification as well as the ease of

separating extraneous materials from the particle during

cleaning by pneumatic means. The values of equivalent

diameter were found to be 0.0259 ± 0.1, 0.0244 ± 0.1 m

for hulled and hulless barley, respectively and 0.0259 ±

0.1 m for both varieties of oats when it was estimated for a

sample of 10 g of grains with their own respective values

of true density. And the values of arithmetic mean diameter

were found to be 4.96 ± 0.50 mm for hulled barley,

5.34 ± 0.31 mm for hulless barley, 6.00 ± 0.26 mm for

Sabzaar oats and 5.41 ± 0.44 mm for SKO-20 oats. It was

found to vary significantly among the varieties except the

SKO-20 oats and hulless barley. The sphericity of all the

grain varieties varied significantly and was found to be

50.55 ± 3.7 and 47.92 ± 1.8 % for hulled and hulless

barley and 32.578 ± 1.3 and 35.69 ± 2.1 %, for Sabzaar

and SKO-20 oats respectively. It implies that the grains all-

in-all have lesser sphericity i.e. these are less resembling to

a sphere [35, 16] and are elongated. However, compara-

tively the sphericity of barley seeds was found to be more

than that of the oats. Similarly the aspect ratio of the grains

was found to be 43.52 ± 4.4 and 39.13 ± 1.6 % for hulled

and hulless barley respectively and 21.03 ± 1.3 and

23.92 ± 1.8 % for Sabzaar and SKO-20 oats respectively.

The aspect ratio relates the width to the length of the fruit

which is an indicative of its tendency towards being oblong

in shape. Thus the values of the aspect ratio and sphericity

generally indicate a likely difficulty in getting the grains to

roll. The grain sphericity was found to be 50.55 ± 3.7 %

for hulled barley, 47.923 ± 1.8 % for hulless barley,

32.578 ± 1.3 % for Sabzaar oats and 35.69 ± 2.1 % for

SKO-20 oats. The relatively low sphericity and aspect ratio

of the seeds indicate that there may be some difficulty in

getting the seeds to roll. The seeds may therefore be

expected to slide on their flat surfaces like the oilbean seed

[28], a property which is quite important in the design of

hoppers and other processing equipment. The aspect ratio

was found to be 43.521 ± 4.4 % for hulled barley,

39.131 ± 1.6 % for hulless barley, 21.03 ± 1.3 % for

Sabzaar oats and 23.923 ± 1.8 % for SKO-20 oats. Since

aspect ratio of oats varieties is very less than that of barley

varieties, it implies that their rolling tendency will also be

comparatively lesser. The different values of surface area

Table 3 Geometric and

gravimetrical properties of

grains

Values are mean ± standard

deviation of three

determinations (n = 3)

Values followed by different

superscript letter in a row are

significantly different

(p B 0.05)

BH BHL Osb OSK

L 8.569 ± 1.2a 9.485 ± 0.69b 13.026 ± 0.59d 11.313 ± 1.1c

W 3.683 ± 0.23b 3.704 ± 0.18b 2.742 ± 0.23a 2.697 ± 0.24a

T 2.643 ± 0.23c 2.85 ± 0.16d 2.256 ± 0.28a 2.236 ± 0.09a

Da 4.331 ± 0.27bc 4.538 ± 0.24c 4.244 ± 0.21b 4.018 ± 0.24a

U 50.55 ± 3.7d 47.923 ± 1.8c 32.578 ± 1.3a 35.69 ± 2.1b

S 58.468 ± 8.6b 65.654 ± 6.2c 56.683 ± 5.6b 50.124 ± 6.6a

Ra 43.521 ± 4.4d 39.131 ± 1.6c 21.03 ± 1.3a 23.923 ± 1.8b

V 26.954 ± 5.3b 31.807 ± 4.8c 23.347 ± 3.5ab 20.127 ± 3.4a

Da 4.9646 ± 0.50a 5.3458 ± 0.31b 6.0077 ± 0.26c 5.415 ± 0.44b

De 0.0259 ± 0.1b 0.0244 ± 0.1a 0.0259 ± 0.1b 0.0259 ± 0.1b

Vkrt 0.02757 ± 0.1d 0.02419 ± 0.1b 0.02273 ± 0.1a 0.02583 ± 0.1c

W1000 41.9 ± 0.2d 40.06 ± 0.02c 36.66 ± 0.01b 36.51 ± 0.02a

qb 690 ± 0.5d 530 ± 0.1c 410 ± 0.1b 399 ± 0.2a

qt 1112 ± 0.1b 1333 ± 0.2a 1112 ± 0.3b 1112 ± 0.2b

e 37.95 ± 0.01a 60.24 ± 0.02b 63.12 ± 0.01c 64.11 ± 0.01d

Properties of barley and oats

123

were examined to be 58.46 ± 8.6, 65.65 ± 6.2,

56.68 ± 5.6 and 50.12 ± 6.6 mm2 respectively for hulled

barley, hulless barley, Sabzaar oats and SKO-20 oats. The

surface area of the grains was found to vary significantly

among the grains except in hulled barley and Sabzaar oats

where it varied non significantly. It is studied that this will

actually be an indication of the way the grains will behave

on oscillating surfaces during processing. The seed volume

was found to be 26.95 ± 5.3 mm3 for hulled barley,

31.80 ± 4.8 mm3for hulless barley, 23.34 ± 3.5 mm3 for

Sabzaar oats and 20.12 ± 3.4 mm3 for SKO-20 oats.

Terminal velocity of grains

Terminal velocity of grains is given in Table 3. Between the

two barley varieties, the hulless has lower terminal velocity i.e.

0.02757 ± 0.1 m/s compared to hulled which has 0.02419 ±

0.1 m/s. This is because of their different seed mass, projected

areas and sphere values. Same is true for Sabzaar oats which

has the lower terminal velocity of 0.02273 ± 0.1 m/s com-

pared to SK-20 oats which has 0.02583 ± 0.1 m/s. The dif-

ferences in terminal velocity of these grains can prove to be

very useful in their air classification.

The 1,000-grain weight, bulk density, true density

and porosity of grains

The 1,000-grain weight, bulk density, true density and

porosity of oats and barley are given in Table 3. The 1,000

seed mass was found to be 41.9 ± 0.2, 40.06 ± 0.02,

36.66 ± 0.01 and 36.51 ± 0.02 g for hulled barley, hulless

barley, Sabzaar oats and SKO-20 oats respectively. The

bulk density of hulled and hulless barley was found to be

690 ± 0.5 and 530 ± 0.1 kg/m3 respectively and that of

Sabzaar and SKO-20 oats cultivars was found to be

410 ± 0.1 and 399 ± 0.2 kg/m3 respectively. The value of

the true density was found to be 1,112 ± 0.1 and

1,333 ± 0.2 kg/m3 for hulled and hulless barley respec-

tively and was 1,112 ± 0.3 and 1,112 ± 0.2 kg/m3 for oats

varieties. The values of porosity were 37.95 ± 0.01,

60.24 ± 0.02, 63.12 ± 0.01 and 64.11 ± 0.01 % respec-

tively for hulled barley, hulless barley, Sabzaar oats and

SKO-20 oats.

The static co-efficient of friction and angle of repose

of grains

The static coefficient of friction of the grains against dif-

ferent surfaces is given in Table 5. It was found to be

0.0067 ± 0.0003, 0.0066 ± 0.0001 and 0.0071 ± 0.0002

for hulled barley and 0.0071 ± 0.00, 0.0071 ± 0.0002 and

0.0076 ± 0.0002 for hulless barley when sun-mica, glass

and corrugated board were used as the test materials

respectively. For oats varieties, the static co-efficient of

friction was found to be similar for sunmica i.e. 0.0066 ±

0.002, it was almost similar for glass i.e. 0.0062 ± 0.0002

for Sabzaar and 0.0064 ± 0.0001 for SKO-20, but was

slightly different in case of corrugated board i.e. 0.0067 ±

0.0002 for Sabzaar and 0.0076 ± 0.0003 for SKO-20. The

friction co-efficient was highest for corrugated board, fol-

lowed by sunmica and glass. This is probably due to

increased surface area and force of adhesion between the

grain and the test surface which leads to higher value of co-

efficient of friction. The values of angle of repose varied as

given in Table 5. It was found to be 34.350 ± 0.0050 and

34.320 ± 0.0320 for hulled and hulless barley and

30.500 ± 0.430 and 40.470 ± 0.50 for Sabzaar and SKO-

20 oats respectively. Angle of repose gives us the indica-

tion of the internal friction between the grains providing

the maximum slope at which the grains are stable and

different angles of the heap that lead to slope failures.

However, the value of angle of repose is greater for

cohesive materials because of the growing cohesion forces

between them and smaller for non-cohesive materials [36].

The results indicate that the grains of hulless barley and

SKO-20 oats are more cohesive than the grains of hulled

barley and Sabzaar oats respectively, because the moisture

content which is one of the main factors affecting the inter-

granular friction and ultimately the value of angle of repose

was maintained to be constant in all the varieties used.

Table 4 Density and flow properties of flour

Bulk density (Kg/m3) Tapped density (Kg/m3) Mass flow rate (g/30 s) Compressibility index (CI) Hausner ratio (HR)

BH 340.36 ± 1.38b 513.33 ± 1.15c 7.6 ± 0.26c 33.69 ± 0.12c 1.58 ± 0.43c

BHL 340 ± 2.00b 517.67 ± 2.51d 7.76 ± 0.15c 34.32 ± 0.87d 1.52 ± 0.96b

OSb 339.5 ± 3.59a 471.16 ± 2.3b 7.1 ± 0.26b 27.94 ± 1.23a 1.38 ± 1.6a

OSk 335.6 ± 2.72c 462.93 ± 2.10a 6.83 ± 0.35a 27.5 ± 0.74a 1.37 ± 0.05a

Values are mean ± standard deviation of three determinations (n = 3)

Values followed by different superscript letter in a column are significantly different (p B 0.05)

A. Hamdani et al.

123

Compressibility index and Hausner ratio of flour

The compressibility index of hulled and hulless barley flour

was found to be 33.69 ± 0.12 and 34.32 ± 0.87, respec-

tively. According to the scale of flowability given in

Table 1, the flour of both varieties has very poor flow

properties, which is also implied by the scale of Hausner’s

ratio, the value of which is 1.58 ± 0.43 for hulled barley

and 1.52 ± 0.96 for hulless barley. The flour obtained from

the oats varieties was found to have comparable values of

both the parameters. The compressibility index was

27.94 ± 1.23 and 27.5 ± 0.74, and the Hausner ratio was

1.38 ± 1.6 and 1.37 ± 0.05, respectively for Sabzaar and

SKO–20. Again from the scale of flowability, the flour

obtained from oats was found to have Poor flow properties.

Comparing the two, the flowability of oat flours was better

than that of barley which fell in the range of very poor flow

properties.

Bulk density and tapped density of flour

Bulk density and true density of the samples are given in

Table 4. The two varieties of barley were found to have

comparable bulk densities i.e. 340.36 ± 1.38 kg/m3 for

hulled and 340.00 ± 2.00 kg/m3 for hulless, but the values

of tapped densities were found to vary appreciably, being

513.33 ± 1.15 and 517.65 ± 2.51 kg/m3, for hulled and

hulless, respectively. In case of oats, the bulk density was

339.5 ± 3.59 and 335.6 ± 2.72 kg/m3 and the tapped

density was 471.16 ± 2.3 and 462.93 ± 2.10 kg/m3 for

Sabzaar and SkO-20, respectively.

Flow through an orifice (Mass flow rate of flour)

The average mass flow rate was found to be 7.6 ± 0.26 g/

30 and 7.76 ± 0.15 g/30 s for hulled and hulless barley

and 7.1 ± 0.26 g/30 and 6.83 ± 0.35 g/30 s for Sabzaar

oats and SKO-20 oats, respectively (Table 4). The flow rate

of a material depends upon many factors, some of which

are particle-related and some related to the process, i.e. the

methodology used. Since, the methodology and the factors

like diameter and shape of the orifice, type of container

material (PET) and height of the powder bed were main-

tained to be constant during the study, the difference in

particle size and the particle density were presumably

responsible for the differences in the mass flow rates of the

flour samples. So, the possible reason of higher mass flow

rate of barley flour is its higher density compared to the

oats flour. Further, the mass flow rate basis of determining

the flow rate of powders also biases the results in favor of

high-density materials to a certain extent.

Static co-efficient of friction and Angle of repose

of flour

The static coefficient of friction of the flour of sample grains

against different surfaces is given in Table 5. It was found

to be 0.0144 ± 0.0001, 0.0204 ± 0.0002 and 0.0290 ±

0.001 for the flour of hulled barley and 0.0144 ± 0.002,

0.0203 ± 0.0001 and 0.0290 ± 0.001 for hulless barley,

respectively, when sun-mica, glass and corrugated board

were used as the test materials. For the flour of oats varie-

ties, again the static co-efficient of friction was found to be

similar for sunmica i.e. 0.0142 ± 0.0001, almost similar for

glass i.e. 0.0213 ± 0.0001 for the flour of Sabzaar oats and

0.0209 ± 0.0002 for the flour of SKO-20 oats, but was

slightly different in case of corrugated board, i.e. 0.0307 ±

0.0001 in case of Sabzaar and 0.0296 ± 0.0001 in case of

SKO-20. The value of angle of repose found for the flours

(Table 5) was found to be 50.44 ± 0.270, 63.45 ± 0.340,

46.86 ± 0.250 and 44.49 ± 0.100 for barley hulled, hulless,

Sabzaar oats and SKO-20, respectively. It is very important

in characterization of the flow properties of flours as it is a

characteristic related to inter-particulate friction or resis-

tance to movement between particles. According to the

Table 1, which gives the scale of flowability, it can be

concluded that the flowability of the barley flour is very less

than oats flour. The flowability of the flour from hulled

barley was poor, such that it needed to be agitated or

vibrated for obtaining a consistent flow, and the flowability

Table 5 Frictional properties

of grains and flour

Values are mean ± standard

deviation of three

determinations (n = 3)

Values followed by different

superscript letter in a row are

significantly different

(p B 0.05)

Static co-efficient of friction of grains and flour

Sun-mica Glass Corrugated board Angle of repose

BH 0.0067 ± 0.0003b 0.0066 ± 0.0001c 0.0071 ± 0.0002b 34.35 ± 0.005b

BHL 0.0071 ± 0.00c 0.0071 ± 0.0002d 0.0076 ± 0.0002c 34.32 ± 0.032b

OSb 0.0066 ± 0.0001a 0.0062 ± 0.0002a 0.0067 ± 0.0002a 30.50 ± 0.43a

OSk 0.0066 ± 0.002a 0.0064 ± 0.0001b 0.0076 ± 0.0003c 40.47 ± 0.5c

BH Flour 0.0144 ± 0.0001b 0.0204 ± 0.0002a 0.0290 ± 0.001a 50.44 ± 0.27c

BHL Flour 0.0144 ± 0.002b 0.0203 ± 0.0001a 0.0290 ± 0.001a 63.45 ± 0.34d

OSb Flour 0.0142 ± 0.0001a 0.0213 ± 0.0001d 0.0307 ± 0.0001c 46.86 ± 0.25b

OSk Flour 0.0142 ± 0.0001a 0.0209 ± 0.0002b 0.0296 ± 0.0001b 44.49 ± 0.10a

Properties of barley and oats

123

of the flour obtained from hulless barley was even poorer

falling in the category of very poor flow properties. In case

of oats flour, the flowability was poor and passable

respectively for Sabzaar oats and SKO-20.

Conclusion

The geometric mean diameter was found to be 4.33 ± 0.27,

4.53 ± 0.24, 4.22 ± 0.21 and 4.01 ± 0.24 mm and arith-

metic mean diameter was found to be 4.96 ± 0.50,

5.34 ± 0.31, 6.00 ± 0.26 and 5.41 ± 0.44 mm for hulled

barley, hulless barley, Sabzaar oats and SKO-20 oats,

respectively. The sphericity of barley seeds was found to be

more than that of the oats. The surface area of seeds was

58.46 ± 8.6, 65.65 ± 6.2, 56.68 ± 5.6 and 50.12 ±

6.6 mm2 and the seed volume was 26.95 ± 5.3, 31.80 ± 4.8,

23.347 ± 3.5 and 20.127 ± 3.4 mm3, respectively. The

1,000 seed mass was found to be maximum for hulled barley

i.e. 41.9 ± 0.2 g, and minimum for SKO-20 oats i.e.

36.51 ± 0.02 g. Porosity of grains was found to be lesser for

hulled barley 37.95 ± 0.01 % compared to hulless barley

60.24 ± 0.02 % and more in SKO-20 oats 64.11 ± 0.01 %

compared to Sabzaar 63.12 ± 0.01 %. The value of co-

efficient of friction was calculated to be highest for corru-

gated board, followed by sunmica and glass for both varieties

of oats as well as barley grains. Same was true for the flours of

these varieties. Hulless barley and SKO-20 oats were found

to have more angle of repose than hulled barley and Sabzaar

oats. The terminal velocity of hulless barley was lower

0.02419 ± 0.1 m/s compared to hulled 0.02757 ± 0.1 m/s.

Sabzaar oats had the lower terminal velocity of 0.02273 ±

0.1 m/s compared to SKO-20 oats 0.02583 ± 0.1 m/s. The

values of tapped densities were found to vary appreciably,

being 513.33 ± 1.15 and 517.67 ± 2.51 kg/m3 for hulled

and hulless barley respectively. In case of oats, the bulk

density was 339.5 ± 3.59 and 335.6 ± 2.72 kg/m3 and the

tapped density was 471.16 ± 2.3 and 462.93 ± 2.10 kg/m3

for Sabzaar and SkO-20, respectively. The flowability of the

barley flour was poor. On the other hand, the mass flow rate

of barley flour was more than the oats flour because of its

higher density.

Acknowledgments Authors are thankful to Department of Bio-

technology, Government of India, for their financial support.

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