Effect of pre-harvest practices on physical and colorimetric characteristics of date fruit (cv. ‘Aziza Bouzid’) in Figuig oasis

Dates represent a very important energy source that contains a wide range of functional, nutritional, bioactive, and aromatic components. Dates characteristics have been widely studied but none has been conducted on the pre-harvest factors responsible for the quality variation. The aim of this study is to evaluate the effect of pre-harvest practices on physical and colorimetric characteristics. The analyses were conducted on twelve samples of ‘Aziza Bouzid’ cultivar and collected at Tmar stage from Figuig oasis. Results obtained for physical parameters show a significant variation between different samples. Weight of ‘Aziza Bouzid’ varied from 5.44 g to 9.04 g. Geometric mean diameter and Porosity varied from 13.08 mm to 17.01 mm and 31.88 % to 42.3 % respectively for ‘Aziza Bouzid’. Highest Chroma and hue values registered for ‘Aziza Bouzid’ were 38.14 and 83.22 and the lowest were 21.1 and 67.15. This study contributes to develop good agricultural practices, help improve the quality and increase the quantity of Moroccan date production.


Introduction
Date palm (Phoenix dactylifera L.) is one of the oldest fruit trees grown in arid regions of Arabian Peninsula, North Africa and the Middle East [1]. It has been cultivated for ecological, economical and social purposes. Dates fruit are considered as a good source of sugars (fructose, glucose and sucrose) and fibers, important vitamins and minerals [2].
Total date production in the Figuig oasis for the 2012-2013 campaign is estimated at 3384 tones. It is dominated by the Assiane cultivar, followed by Boufeggous and Khalts. However 'Aziza Bouzid', which is the flagship profile of this region is only 39 T and therefore only represents 3.2% [7].
Fruits quality may be affected by different factors, they are classified in three groups; preharvest, harvest and post-harvest processes .Pre-harvest including firstly Climatic condition like temperature light rains winds and humidity [8].Secondly Tree condition as variety tree age, fruit positioning [9] and finally Cultural practices (Irrigation , use of fertilizers etc). Harvest factors relating at maturity at harvest and method and harvest time [8] .As for postharvest factors, Washing, Pre-cooling, Grading, Packaging, Transportation, Cold storage, Marketing can also affect fruit quality by modifying physiology, chemical composition, and morphology of fruits [9].
Knowledge of physical properties of agricultural produce and the parameters, which affected these characteristics, is a critical aspect to formulate the proper design standards of harvesting, handling, processing, and storing equipment [10]. The mass, size and shape are important for sorting, sizing and various separation. Density, surface areas and porosity of fruit solids must be known for accurate modelling of heat and mass transfer during drying and Colling [11].
Numerous studies have been carried out on the physical parameters of dates fruits. But none have been studied for the design, development of machinery and equipment for handling, processing, transporting and storing Moroccan cultivars. [12] Reported that the length, width and thickness of 'Zahidi' cultivars were 33.65mm, 22.12mm, 20.02mm respectively. GMD and AMD were 23.51-25.96mm and 24.29-26.59mm, respectively. The Sphericity value ranged from 0.73 to 0.737. [13] Investigated the physical parameters of dates fruit, and discovered that the values of axial dimensions and weight of cultivar Medjool were significantly higher than those of variety 'Khadrawy'. According to [14] the linear measurements of cultivar 'Mazafati' ranged from 32.10 to 43.50 mm in length, 20.50 to 28.20 mm in width and the average weight was 8.39 g. The density of the fruits was 0.82 g / cm3 and the density of the pitted fruits was 1.25 g / cm3, respectively. Bulk density and porosity were 0.44 g / cm3 and 44.90%. GMD, Sphericity and area were calculated to be 27.87mm, 0.73mm 2 and 2446.70 mm 2 correspondingly.
The effect of pre-harvest practices on the physical characteristics of dates has been discussed by some authors. [15] found out that thinning the center of the bunch by removing 15-30% of the total number of sprigs improved various physical and chemical aspects of the fruits of the "Khadrawi" date palm. According to research by [16], Bagging fruit bunches increased the weight of date bunches, accelerated ripening, and improved fruit quality compared to unbagged bunches. [17] found that irrigation systems can also alter the physical qualities of fruits.
The aims of this study are to determine physical properties for 'Aziza Bouzid' cultivar and to evaluate interaction between pre-harvest factors and these properties .To facilitate the design of some machines for its processing.

Fruit Materiel:
Fruit material is composed of the most appreciated cultivar in the oasis of Figuig. Twelve samples of 'Aziza Bouzid' cultivar were collected at Tmar stage from twelve plots chosen randomly in Figuig oasis. Each sample was carried out according to a factorial schemas 20 x 5 x 1 (dates x trees x plot). Date palm trees used in this study were identified as homogeneous (same age, height and intact). Dates samples were transported in isotherm bags to the laboratory, then stored at -20 °C until further analysis.

Field investigation
Field investigation on each plot was reposed mainly on tree characteristics (Age and height of tree), and also on cultural practices used such as (limitation, thinning and bagging of bunches, irrigation and fertilization technics, method of pollination, presence or not of intercropping)

Size and weight measurements
Dimensions measurements were realized on 100 fruits per samples. Width (W), Length (L), and thickness (T) are carried out using a digital caliper. Dates, seed, and pulp weight (Wt) were determined by weighing samples with precision balance (RADWAG PS 360.R2). The percentage of seed and pulp on the whole fruit was calculated using formulas (1) and (2) respectively; (2)

Geometric and arithmetic mean diameter, Sphericity, aspect ratio and surface area
Geometric and arithmetic mean diameter (GMD, AMD) obtained from the measured geometric dimensions of Width (W) , length (L) and thickness (T) as (3) and (4) formulas [17][18].
Sphericity expresses solid object shape relative to that sphere of same volume [18]. It is a relevant property to calculate fluid flow, heat and mass transfer. Sphericity was calculated by using the equations (5) Surface area is an important physical parameter that is related to size and shape. It is found by using relation reported by [19]; Aspect ratio of fruit indicates its tendency to be an oblong shape during handling and processing. It is calculate by equation (7) described by [19] R = W/L ×100 (7)

Bulk and true density and porosity
The true density (ρT) is determined by the water displacement method [20] which the volume of water displaced was estimated by immersing the weighed quantity of fruits in water. Whereas Bulk density ρ b is the mass (M) of a group of individual fruit occupied a box of known volume (V) [21]. Fruits were poured into a standard container without compaction and afterward the content was weighed. The bulk density is calculated as the ratio of fruits mass only to container volume.
Bulk and true density respectively were expressed on (g cm -3 ) and calculated as (8)  equation Porosity is the percentage of air between the fruits compared to a unit volume of fruit [21]; it was calculated using equation (9) P = ((ρ T − ρ b )/ ρ T )* 100 (9)

Color measurement
Fruits color properties were measured using a Chroma Meter CR 400 and were expressed according to the CIELAB color space system defined by International Commission on Illumination (CIE) in 1976. Coordinates L* define to lightness a* correspond a red and green ratio and b* indicate ratio yellow and blue. The chroma C* and Hue H* were defined according to the mathematical functions (10,11).

Statistical analysis
Data analysis was performed using SPSS Statistics 19.0 package (SPSS Inc., Chicago, USA). One-way analysis of variance (ANOVA) and Duncan's multiple-range test were applied to determine significant differences between means and to separate groups of means with a probability p≤0.05 according to their physical and colorimetric characteristics. Values were expressed as an average of four determinations ± standard deviation. Principal component analysis (PCA) was performed on the physical data set in order to verify whether it was possible to differentiate the samples according to their soil condition and pre-harvest practices and to obtain information of variable that influence physical parameters of 'Aziza Bouzid' and Assiane cultivars 3 Results and discussion

Physical analysis
Size measurements (width, length, weigh and thickness) are presented in Table2  Values are average (n=100) ± standard deviation. Different litters (a-g) show significant differences in the same row Pulp thickness was ranging between 3.58 mm for Loudaghir (Lg), Oulad Lmaiz 2 (OM.2) and 4.59g, 4.54g respectively for Hamam Tahtani (Ht) and Znaga 1(Zng.1). Percentage of seed per date is ranging between 13.52% for 'Aziza bouzid' of Zng.4 to 20.72% of Lg. These findings corroborate with [22] results for Tunisian cultivar has indicate an important differences between dates of different varieties, but also within same varieties.
[23] Also revealed that morphological analysis of cultivar grown in Saudi showed a high level of diversity in length-width ratio, color, shape of the fruit, fruit-base and in the percentage of area covered by the fruit cap. Great variability was also reported between Pakistani cultivars by [24].
The study revealed an important variability from different 'Aziza Bouzid' samples. Highest quality of dates samples was from the Hamam Tahtani (Ht), Aarja (Arj) and cooperative Aziz (Cop.A) plot may be due to the good practices used. The lowest quality registered for Oulad lmaiz and Loudaghir (Lg) owed to the use of traditional cultural practices. The investigation revealed that Hamam Tahtani, Aarja and cooperative Aziza (Good 'Aziza Bouzid' fruits quality) are the recent date palm plantations that adapt good cultural practices, such as respect of regular plantation and use of drips irrigation, use organic and mineral fertilizer. In addition to developed pre-harvest practices as cleaning trees and limitation, thinning, protecting fruit bunches .However, Oulad lmaiz and Loudaghir ( low 'Aziza Bouzid') fruits quality plots belong to the ancient palm grove which is characterized by irregular planting, heterogeneous varietal profile, and use of ancestral practices. In the fact, according to [26], thinning of bunches induces to increase in fruit volume, weight, diameter, and length; along with seed and flesh weight in the 'Succary' cultivar. An irrigation system can also affect the physical properties of fruits; Findings given from the North African and Middle East countries marked that irrigation systems have an important influence on dates quality [17].
Variation interval of physical parameters raised in this study for 'Aziza Bouzid' allows to elaborate standards for machines designs. Dimensions are important physical parameters for drying, storing and are also useful to determinate the shape of the fruits. Arithmetic mean diameter and geometric mean diameter values are used to design of separating, harvesting, sizing and grinding machine. Determined Sphericity values serving to concept handling equipment of fruits. The porosity of dates fruits is important because it shows fruits resistance to air flow during, drying process and storage process.

Color measurement
Color results are presented in table 4. No significant variation was unregistered for Fruits color properties (a*, b*, C* and H*) except luminosity L* that values varied from 36.99 for Laabidate (Lb) to 44.18 for Hamam Tahtani (Ht) .Light colored dates are considered better mentioned. 'Aziza Bouzid' from Hamam Tahtani plot showed a better color with higher values unlike Laabidate plot which is the lowest one. [9] Indicate that climatic condition is responsible for color variability as temperature, light and humidity. Cultural factors as thinning, grading, and Bunching can also affect color.   3). Actually, the first group is correlated with Pulp weight, dates, weight, Geometric mean diameter, width of dates, Surface, Aritmetique mean diameter, dates length, Bulk density, true density, Ratio P/D and thickness. The second group is the opposite of the first one with respect to PC1. For principal component 2, the most distinct variables, were Aspect ratio R and Sphericity. According to the PC1, the effect of Pre-harvest practices is mainly manifested. In fact, Morphological 'Aziza Bouzid' samples from plot using good practices were opposed to those using traditional practices. 'Aziza Bouzid' sampled in Hamam Tahtani (Ht), Cooperative Aziza (Cop.A), Aarja (Arj) characterized by high morphological quality (high weight, high length and width dates, hand low seed percentage). In opposition, samples collected from Loudaghir (Lg), present a low quality with low size and high portion of seed. In addition, the results of this statistical analysis allow us to highlight a clear variability between studied 'Aziza Bouzid' dates samples according to morphological quality characteristics. PCA analysis exposed clearly the effects of the preharvest practices on dates quality.

Conclusion
This study revealed the effect of pre-harvest factors on the physical and colorimetric characteristics of the cultivar 'Aziza Bouzid. The interaction between physical quality and pre-harvest practices showed that the highest physical quality was recorded in the plots for which farmers' adapted adequate pre-harvest practices. However, a low quality of the cultivar 'Aziza Bouzid' was observed especially in the plots where ancestral practices are still used.
The obtained results can be exploited for the raise yield of dates and also for the improvement of Moroccan dates quality. Firstly the study raised adequate pre-harvest