**4. Result**

#### **4.1 Descriptives**

The total TP entries was 583, from 74 studies collected from 18 countries, consisting of 102 (17.9%), 118 (20.7), and 350 (61%) entries for Khalal, Rutab, and Tamer stages, respectively. More than 50% of the entries came from five countries (n, %): Pakistan (126, 21.61), KSA (125, 21.44), Tunisia (59, 10.12), Iran (47, 8.06), and Algeria (35, 6). The apparent number of included cultivars was 250, with Khalas (5.5%), Khadhrawi (4.3%), Barhi (3.1%), Hallawi (2.7%), Deglet Nour (2.4%), and Medjool (2%) being the most represented. Descriptive statistics, including estimates of centrality and dispersion, are presented in **Table 4** for data with and without outliers. The proportion of detected outliers was 1.96, 8.5, and 6.3% for the three maturation stages, respectively. As expected, the mean and median of TP content were higher in Khalal stage than the final maturation stage, Tamer. Removing outliers greatly improved the statistics of dispersion (SD, SEM, range, variance) as well as the kurtosis, skewness, and CL.

**109**

**Figure 2.**

*included, n = 360 and (B) outliers removed, n = 339.*

*Antioxidants in Date Fruits and the Extent of the Variability of the Total Phenolic Content…*

Count 104 102 119 108 360 339 Mean 994.92 935.98 368.67 228.62 446.97 240.93 SEM 111.83 105.85 38.74 18.05 59.00 10.18 Median 791.37 777.28 247.98 177.71 232.05 217.65 SD 1140.46 1068.99 422.65 182.33 1119.40 187.45 Variance 1300651.78 1142745.95 178630.03 33244.77 1253049.41 35137.96 Kurtosis 34.75 46.91 5.59 −0.71 47.66 −0.12 Skewness 4.95 5.85 2.21 0.55 6.55 0.71 Range 9785.41 9785.41 2228.61 663.80 10303.70 858.83 Minimum 9.59 9.59 4.33 4.33 0.14 0.14 Maximum 9795.00 9795.00 2232.94 668.13 10303.85 858.97

**Khalal Rutab Tamer WO NO WO NO WO NO**

221.79 209.97 76.72 35.81 116.02 20.03

Khalal stage exhibited higher variation than Rutab and Tamer. The distribution of the TP values was not normal and rightly skewed for the three stages. **Figure 2** depicts the frequency and cumulative frequency density (CFD) of the TP values of the Tamer stage. Similar patterns are also seen for the Khalal and Rutab stages (not shown). More

*Estimates of centrality and variability of the values of TP content (expressed as mg GAE/100 g DM) recruited* 

CV 114.63 114.21 114.64 79.75 250.44 77.80 Q1 343.18 336.73 102.54 87.72 93.89 84.90 Q2 791.37 777.28 247.98 233.64 233.33 217.65 Q3 1298.02 1281.76 470.23 440.04 388.64 351.12

**Figure 3A** and **B** depicts the spread of numerical values of the TP content in dates at Tamer stages against the country of origin of dates and cultivar, respectively. These figures, as well as data given in **Table 2**, provide clear evidence against claims and misconceptions of the antioxidant superiority of a particular date cultivar due to its country of origin or cultivar. Low and high values of TP content

*Histogram and cumulative frequency density (CFD) of the TP content of the Tamer stage. (A) With outliers* 

than 50% of the values of TP content were below 260 mg GAE/100 g DM.

can be found for a specific date cultivar in a single country.

*DOI: http://dx.doi.org/10.5772/intechopen.83851*

*WO = with outliers included, NO = outliers not included.*

*in this work and obtained from studies listed on* **Table 2***.*

CL (95.0%)

**Table 4.**

*Antioxidants in Date Fruits and the Extent of the Variability of the Total Phenolic Content… DOI: http://dx.doi.org/10.5772/intechopen.83851*


#### **Table 4.**

*Antioxidants*

**Country Author** 

Tunisia El-Arem et al.,

USA Al-Turki et al.,

**Table 2.**

2010 (10)

*Information are alphabetically arranged based on country.*

**(no. cultivar)**

2017 (3)

**108**

**4. Result**

**Table 3.**

**4.1 Descriptives**

The total TP entries was 583, from 74 studies collected from 18 countries, consisting of 102 (17.9%), 118 (20.7), and 350 (61%) entries for Khalal, Rutab, and Tamer stages, respectively. More than 50% of the entries came from five countries (n, %): Pakistan (126, 21.61), KSA (125, 21.44), Tunisia (59, 10.12), Iran (47, 8.06), and Algeria (35, 6). The apparent number of included cultivars was 250, with Khalas (5.5%), Khadhrawi (4.3%), Barhi (3.1%), Hallawi (2.7%), Deglet Nour (2.4%), and Medjool (2%) being the most represented. Descriptive statistics, including estimates of centrality and dispersion, are presented in **Table 4** for data with and without outliers. The proportion of detected outliers was 1.96, 8.5, and 6.3% for the three maturation stages, respectively. As expected, the mean and median of TP content were higher in Khalal stage than the final maturation stage, Tamer. Removing outliers greatly improved the statistics of dispersion (SD, SEM, range, variance) as well as the kurtosis, skewness, and CL.

*Countries and number of recruited studies used to collect and analyze data points of TP content in date fruits.*

**Parameter Stg. Mean** 

ABTS (mmol TE/100 g FW) K 1.36 (0.03,

DPPH (AE = 1/EC50) K 3.54 (0.63,

TP (mg GAE/100 g FW) T 318.19 (61.75,

*Mean, SD, and range of selected parameters of antioxidant constituency (TP, TF, CT) and antioxidant activity (ABTS, DPPH, FRAP) extracted from selected published studies demonstrating the large reported variability.*

**Country References No. Country References No.** Algeria [22, 23, 39, 40] 4 Morocco [30, 31, 65–68] 5 Bahrain [41, 42] 2 Oman [32, 33, 69, 70] 4 Egypt [24, 43–45] 4 Palestine [74] 1 Iran [25, 26, 46–49] 6 Pakistan [34, 35, 71–73] 5 Iraq [50] 1 Spain [75–77] 3 Israel [51] 1 Sudan [78] 1 KSA [11, 27–29, 52–62] 14 Tunisia [36–38, 78–86] 13 Malaysia [63] 1 USA [28, 87] 2 Mauritania [64] 1 Yemen [89] 1

**(SD, range)**

1.3–1.4)

2.7–4.1)

22.7–491.3)

R 1.26 (0.07, 1.2–1.4)

T 1.13 (0.10, 1.0–1.3)

R 2.54 (0.36, 2.1–2.7)

T 1.76 (0.42, 1.4–2.4)

**References**

[38]

[28]

*Estimates of centrality and variability of the values of TP content (expressed as mg GAE/100 g DM) recruited in this work and obtained from studies listed on* **Table 2***.*

Khalal stage exhibited higher variation than Rutab and Tamer. The distribution of the TP values was not normal and rightly skewed for the three stages. **Figure 2** depicts the frequency and cumulative frequency density (CFD) of the TP values of the Tamer stage. Similar patterns are also seen for the Khalal and Rutab stages (not shown). More than 50% of the values of TP content were below 260 mg GAE/100 g DM.

**Figure 3A** and **B** depicts the spread of numerical values of the TP content in dates at Tamer stages against the country of origin of dates and cultivar, respectively. These figures, as well as data given in **Table 2**, provide clear evidence against claims and misconceptions of the antioxidant superiority of a particular date cultivar due to its country of origin or cultivar. Low and high values of TP content can be found for a specific date cultivar in a single country.

#### **Figure 2.**

*Histogram and cumulative frequency density (CFD) of the TP content of the Tamer stage. (A) With outliers included, n = 360 and (B) outliers removed, n = 339.*


#### **Table 5.**

*Estimates of centrality and variability of reported TP values (expressed as mg GAE/100 g DM) of selected date cultivars from different countries.*

**111**

**Ajwa (KSA)**

> Count

Mean

SEM Median

SD Variance

Range Minimum Maximum

CL

218.423

261.89

121.35

95.47

170.31

251.73

189.85

170.31

95.47

218.423

(95.0%)

CV (%)

**Table 6.**

120.81

74.45

64.40

106.67

125.80 *Statistics of centrality and variability of reported TP values (expressed as mg GAE/100 g DM) of selected date cultivars taken from different studies from two countries (KSA and Oman).*

130.32

166.46

125.80

106.67

120.81

584.46

217.65

565.53

458.32

296.15

439.74

248.72

296.15

458.32

584.46

6.8

21.26

8.44

7.85

0.20

0.23

0.14

0.20

7.85

6.8

577.66

196.39

557.09

450.47

295.96

439.52

248.57

295.96

450.47

577.66

55776.74

11114.00

32625.96

24961.62

18814.52

41102.45

14235.21

18814.52

24961.62

55776.74

236.17

105.42

180.63

157.99

137.17

202.74

119.31

137.17

157.99

236.17

28.35

185.90

327.06

26.12

33.94

35.63

18.92

33.94

26.12

28.35

89.26

60.87

54.46

43.82

61.34

90.67

59.66

61.34

43.82

89.26

195.48

141.60

280.46

148.11

109.03

155.57

71.68

109.03

148.11

195.48

7

3

11

13

5

5

4

5

13

7

**Rashoudiah (KSA)**

**Sukkari (KSA)**

**Khalas (KSA)**

**Khalas (Oman)**

**Faradh (Oman)**

**Khasab (Oman)**

**Khalas (Oman)**

**Khalas (KSA)**

*Antioxidants in Date Fruits and the Extent of the Variability of the Total Phenolic Content…*

*DOI: http://dx.doi.org/10.5772/intechopen.83851*

**Ajwa (KSA)**


*Antioxidants in Date Fruits and the Extent of the Variability of the Total Phenolic Content… DOI: http://dx.doi.org/10.5772/intechopen.83851*

 *Statistics of centrality and variability of reported TP values (expressed as mg GAE/100 g DM) of selected date cultivars taken from different studies from two countries (KSA and Oman).*

*Antioxidants*

**110**

**Table 5.**

**Figure 3.**

*(A) and cultivar (B). Outliers were removed.*

*cultivars from different countries.*

**Ajwa Barhi Khadhrawi Khalas Mejdool Zahidi Deglet** 

Count 9 4 10 20 7 7 13 10 Mean 178.48 254.50 274.79 158.10 265.45 251.96 159.52 220 SEM 70.05 89.86 61.51 34.75 61.84 64.58 34.47 60 Median 49.94 253.26 266.58 112.48 289.46 153.12 108.55 176 SD 210.15 179.71 194.50 155.39 163.62 170.87 124.28 171 Variance 44162.2 32295.9 37829.8 24145.3 26772.8 29195.4 15445.5 29,978 Range 577.66 319.39 477.41 458.12 468.4 407.66 363.74 439 Minimum 6.80 96.05 50.28 0.20 3.33 72.11 3.33 33 Maximum 584.46 415.44 527.69 458.32 471.72 479.77 367.07 472 CL (95.0%) 161.53 285.96 139.14 72.72 151.32 158.02 75.10 149 CV (%) 117.74 70.61 70.78 98.28 61.64 67.82 77.91 81 Country 2 5 7 4 5 5 5 5

*Distribution of the values of TP content in Tamer stage arranged ascendingly according to the country of origin* 

*Estimates of centrality and variability of reported TP values (expressed as mg GAE/100 g DM) of selected date* 

**Nour**

**Average**

## **4.2 Variability of TP values of selected date cultivars from different countries**

**Table 5** presents estimates of variability and central tendency of TP content of selected date cultivars reported from different countries. Normally, in nutritional epidemiology, the variance represents the true variability of nutrient content. The variability of continuous type of results produced experimentally by some assays is evaluated by the CV rather than SD, since the CV is a standardization of the SD (CV = SD/mean \* 100). Using CV allows for direct comparison of estimates of variability regardless of the magnitude of the level of analyte under investigation. In many biological fields, a twofold difference in measurements of the same sample can be acceptable as the upper limit of variability. Furthermore, a CV of 40% can be tolerated in nutrient estimation for food labeling and nutrient intake calculation [90]. Since there is no reference value or a benchmark for the variability of TP content in dates to compare with, the above recommendation may be used to facilitate comparison. The variance and CV, as well as other estimates of dispersion, are very large. The largest variance was found for Ajwa, whereas Deglet Nour exhibited the lowest variance. The CV was even more pronounced as an evidence of the vast variability, with some cultivar possessing CV values of more than 100%. Estimates presented on **Table 5** demonstrate the extent of variability of the TP content values regardless of the country.

**Table 6** presents similar statistics based on data obtained from studies originated from a single country for a particular date cultivar. This table illustrates the extent of variability of the TP content within a country. For example, TP values of Khalas cultivar from two countries (Saudi Arabia and Oman) showed large variation within cultivar and between the two countries, while the TP values of selected date cultivars taken from different studies carried out within that country are similar. Again, all estimates of variability are indicative of the large disparity of the published TP values. Notably, Ajwa cultivar of Saudi Arabia, which is grown almost exclusively in the holy city, Al-Madina Al-Munawara, possessed the largest CV (%) among the listed four cultivars.
