11 jzs-chem 18-final

 
Table 5. Physical parameters (weight, volume, true density, percentage yield, moisture content and ash contents) of 
Kurdistan’s walnut kernels. 
 
3.2. Total oil content 
The extracted oil of walnut kernels was yellowish color [17]. The physicochemical properties of extracted 
oil are given in table 6. Fat was the highest constitute in all samples, ranging from 36.07% in sikat (sample 
number 03) to 70.24% in akre (sample number 15). These values were similar to the results reported in 
Amaral et al., [18] and Yang et al., [19]. Oil contents of this study were lower than those reported by other 
Ash content 
%
Moisture 
content %
Yield of kernel 
(%) 
True density ( 
kg/m
3
) 
Volume of 
kernel (cm
3
) 
Weight of 
kernel (g) 
Sample 
2.01
4.36
47.16 
1259.44 
4.367 
5.50 
K1 
1.28
5.23
50.92 
1425.81 
5.19 
7.40 
K2
1.43
4.28
53.49 
1248.27 
4.35 
5.43 
K3
2.03
3.68
43.51 
1136.10 
3.60 
4.09 
K4
2.08
5.62
63.42 
1472.42 
5.44 
8.01 
K5
2.20
4.44
47.79 
1261.95 
4.39 
5.54 
K6
2.05
4.67
46.47 
1354.29 
4.77 
6.46 
K7
2.03
3.87
43.99 
1178.37 
3.70 
4.36 
K8
1.85
4.59
54.45 
1288.24 
4.51 
5.81 
K9
0.94
4.73
63.79 
1381.14 
4.88 
6.74 
K10
1.72
3.93
41.59 
1198.41 
3.78 
4.53 
K11
2.12
4.21
44.38 
1246.54 
4.34 
5.41 
K12
1.61
3.79
52.21 
1168.04 
3.63 
4.24 
K13
1.32
4.69
46.95 
1353.55 
4.78 
6.47 
K14
1.45
3.74
41.56 
1156.42 
3.58 
4.14 
K15
1.74 
4.38 
49.44 
1275.26 
4.35 
5.60 
mean

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JZS-A Volume 22, Issue 2, December 2020
116
[16]. Pereira et al., 2008, reported total oil contents from 78.83 to 82.4%. Variation of total oil % in the walnut 
samples is presented in table number 6.
Refractive index was determined between 1.4734 (sample number 07 i.e. Qaladze) and 1.4767 (sample 
number 13 i.e. Ballakayati). In addition, pH-values of kernel oils were measured between 6.23 (sample 
number 04 i.e. Sharbazher) and 7.02 (sample number 12 i.e. Walzi). The relative density was determined 
between 0.9746 (sample number 04 i.e. Sharbazher) and 0.9801 (sample number 05 i.e. Sharazur), the result 
of relative density of all samples was higher than the value reported by Ozcan et al., 2003 [17] for the peanut 
oil of kernels (0.954-0.955) and also by Ozcan et al., 2004 [20], for terebinth fruit oil (0.9742). Differences 
between the values of walnut varieties are due to the growing conditions, climatic, environmental conditions 
and analytic conditions [13].
Table 6. Physical parameter (total oil content, pH, refractive index and relative density of the oils) of walnut kernels.
Relative 
density
RI
pH
Total oil 
content 
(%)
W t. of sample (g) 
(after extraction) 
Wt. of sample (g) 
(before extraction) 
Sample 
0.9764
1.4750
6.35
63.37 
40.35 
63.67 
K1 
0.9787
1.4751
6.40
45.89 
35.74 
77.88 
K2
0.9798
1.4758
6.38
36.07 
27.14 
75.23 
K3
0.9746
1.4759
6.23
55.10 
35.27 
64.00 
K4
0.9801
1.4754
6.67
45.05 
25.58 
56.78 
K5
0.9753
1.4757
6.61
59.97 
35.00 
58.36 
K6
0.9747
1.4734
6.61
59.26 
29.29 
49.42 
K7
0.9762
1.4754
6.45
66.92 
32.45 
48.49 
K8
0.9775
1.4745
6.50
53.79 
31.89 
59.28 
K9
------
------
------
----- 
----- 
----- 
K10
------
------
------
----- 
----- 
----- 
K11
0.9753
1.4748
7.02
51.04 
25.57 
50.09 
K12
0.9786
1.4767
6.95
54.39 
29.08 
53.46 
K13
0.9749
1.4756
6.60
59.85 
25.58 
42.74 
K14
0.9773
1.4738
6.97
70.24 
40.99 
58.35 
K15
0.9768 
1.4751 
6.59 
55.45 
31.84 
58.28 
mean

4. Conclusions

The study aimed to investigate and evaluate a physicochemical characterization of different walnut samples 

from different locations to confirm its economical and nutritional quality. There are no significant differences 
in most of the physicochemical parameters between all studied walnut samples. All investigated types of 
walnut were acidic and were within the standard limit that indicates freshness of all investigated samples. The 
differences in physical properties of walnut fruits having about the same size were probably due to the 
conditions of environmental in conjunction with analytical methods that used [21]. In addition, the moisture 
content, the ash content and the crude oil contents of walnut fruits are affected mainly by variety and the 
growth conditions [15]. Finally the present study concludes that the quality and physicochemical properties of 
walnut shells and kernels in Kurdistan region did not show any considerable significant variations with 
reference to their physical and chemical properties.