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Effect of Storage on the Dates Quality
Abstract
 
Twelve varieties of dates namely (Fardh, Jabri, Dabass, Nbutsaif, Barhi, Naghal, Khalas, Khniazi, Shishi, Lulu, Bumaan, Razize) were studied for determining the physical changes during the storage for a period of 6 months.
Washed and non washed dates were used and stored in cold stores (8-10 ° C) and relative humidity (35%-45%).
The results showed that the unwashed dates were physically effected. For the washed dates it was noticed an increase of moisture content because of higher water activity (aw) and subsequently resulted in growth of mold in Barhi. It also showed flaking characteristics in Khalas, Bumman ,Barhi, and Neghal.
 
Introduction
 
Storing of dates in cold stores is considered as a better way to maintain the quality, as well as their nutritious value by decreasing the following factors:
• Microbial growth.
• Enzymatic and bio-reactions during storage.
• Respiration and ethylene production (Abboudi, A., 2000).
• Dryness and hardness of dates (peeling) (Barreved, H.W., 1994).
• Infection by insect.
The effects of these changes depend upon many factors such as dates varieties, maturity, temperature, relative humidity and method of storage (Nickrson & Ronsivallil, 1990, عبالعظيم الحمادي, 2000).
This study was designed to determine the effect of temperature and relative humidity on storage of 12 varieties of washed and non washed dates in Emirates Dates Factory –Al Saad, and is an attempt to explain the changes of moisture content and water activity (aw), in addition to find explanation in physical changes.
 
Material and methods
 

12 varieties of dates were used (Bumaan, Naghal, Lulu, Nabtat saif, Shishi, Razeez, khanaizi, Jabri, Khalas, Dabas, Barhi, and Fardh).

  • Washing of received dates was done by using chlorinated water (1-2 ml/L CL2 ) in stainless steel tank. Water removed from Dates surface is carried out by compressed air; the dry dates received were arranged in crates of 15-18 Kg. ( HACCP manual 2005 )
  • Dates were stored in cold stores (capacity is 800-1000 tones) at temperature range from 8-10 ْC and relative humidity 35-45 %.
Measuring the moisture of dates was determined by using a moisture  balance model AMB50 and the water activity (aw) by water activity meter (Decagon).
 

Result and Discussion

 
Fig. 1 and 2 shows the evaluation of moisture and water activity of twelve varieties of dates before and after washing. We noted that the levels of moisture content and water activity were increased to 15-25% after dates were washed clearly in Khalas and Bumman dates. Table 1 shows the physical changes for dates after six months of storing at
8-10 ºC and relative humidity 35-45%, certain varieties such as Barhi, Nighal, Bumman were physically changed. Flaking of the outer skin
was noticed as well as additional mold growth was observed in Khanaizi dates. The remaining varieties of dates (Fardh, Jabri, Dabas, Nabtat saif, Shishi, Lulu and Razaiz) were observed without any physical changes before and after washing. The results have shown that unwashed dates have the ability to store for long term and no physical changes has been noted. The washed dates helps in peeling the outer skin of dates, with
an increased water activity aw which leads to mould growth.
 
References
 
  • Abboudi, A.  2000.  Controlled atmosphere storage of dates at the Rutab stage.  The international Date palm Abu Dhabi- UAE
  • Barreved, H.W.  1994. Date palm products F.A.O. United nations.
  • Nickrson & Ronsivallil, 1990.  Elementary Food science.  Second print. The AVI publishing company.
  • عبدالعظيم محمد مصطفى الحمادي، 2000 ، اعداد وتداول التمور، الدورة التدريبية حول تقانات ما بعد  جني الثمار .  
  • HACCP manual 2005 Emirates Dates Factory – Al Saad
 
Table 1. Physical changes for Dates after 6 months of storage
 
  Type Physical changes
before Washing		 Physical changes
after Washing
 
1 Fardh No change No change
2 Jabri No change No change
3 Dabas No change No change
4 Nabtat saif No change No change
5 Barhi No change Flaking
6 Naghal No change Flaking
7 Khalas No change Flaking
8 Khanaizi No change Moulds
9 Shishi No change No change
10 Lulu No change No change
11 Bumaan No change Flaking
12 Razeez No change No change
 
 
 
  Fig. 1. Moisture% of different types of dates
     
  a)

Before washing
  b)

After washing

 
 
 
  Fig. 2. Aw of different type of dates
     
  a)

Before washing
  b)

After washing

 

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