Dates Syrup transformation potential I: Study on the Phenomenon of Dates Syrup Crystallization

Abstract

Crystallization of date’s syrup is considered as one of the major industrial problems especially when it is stored at low temperature for a long time. We have studied some factors related to phenomenon such as storing dates syrup at low temperature, type of container used, type of dates and the technology used. The  results demonstrated that 70% of the dates syrup were crystallized when it was stored at temperature around 6-7°C for  a period of 90 days. The percentage was decreased to 2% at 25 °C. The result also confirmed that dates syrup obtained from Barhi Dates is  more susceptible to crystallize than other varieties of dates. On the other hand Container Jars were less affected by crystallization than plastic container. Similar results were noticed on non filtered date’s syrup.

Key words: Dates syrup, crystallization, extraction

Introduction                                                  
Date syrup is probably the most common derived date product, produced by extraction and boiling down of the date juice (Barreveld, 1994. FAO, 1989). The phenomenon of dates syrup crystallization is considered as a big issue while it is stored for a long time at low temperature. In this study we have tried to follow up this phenomenon according to storage temperature, type of dates used, method of sugar extraction and type of container.

Materials and methods

• We used three types of dates -season 2003 - Lulu, Berhi, and mixed dates. The three kind of dates syrups were stored in a cold storage (8-10degres centigrades).
• Dates syrup production was established according to  an industrial standard (HACCP manual 2005) in two ways.  First using a micro filter and in a second step without using micro filtration at a brix ranging between 76 to 78.
•  Different types  of containers were used such as Plastic containers and jar containers (1.5 , 3 kg )
• syrup  were stored in cold store at 3 different kind of tempretures (6, 15, and 25   degres Centgrades)
• Determination of dates syrup concentration was carried by refractometer (At ago PR - 301).
• pH by pH meter (Hanna pH 211).
• Viscosity by (Bohlin visco 88).
• aw Water activity meter (Decagon).
• Protein by Kheldal method
• Sugar by GlC according to (Sahi, 1986. AOAC, 1995)
• Ash by muffle furnace according to (Sahi, 1986. AOAC, 1995)

Results and Discussion
Table (1) shows the physical and chemical analysis of micro filtered (MF) and non micro filtered (nonMF) dates syrup. The results did not detect any significant  differences  between  MF and nonMF  except the value of the viscosity. This value increased when the brix  reached 78%, further more the percentage of dates syrup crystallization was increased  to 70%  when dates syrup was stored at 6ºC fig.1  .
The result shows also that Berhi dates syrup was more susceptible of crystallization than other varieties of dates fig. 2.  Moreover, the Jar container were less affected to crystallization  than the plastic container  fig. 3. Similar results were noticed on non filtered dates syrup. This is due to the low brix and viscosity. However, this study is still in progress and more samples and conditions will be analyzed. 
Our conclusions are:

• Room storage at 25 Cْ   has shown a significant reduction of crystallization.
• The date syrup obtained from Berhi date was more susceptible to crystallization than other dates.
• Jar containers and non filtered date syrup were less affected to crystallization than plastic containers and filtered date syrup.

Table 1. Physical and Chemical analysis of micro filter (MF) and non micro filter (non MF) Dates Syrup

   Fig. 1. Effect of storage temperature on dates syrup crystallization during 9 months                                  
Fig.2.Effects of the type of dates on dates syrup crystallization during 9 months

Fig. 3. Effect of manufacturing method on dates syrup crystallization during 9 months
Fig. 4. Effect of the type of container on date’s syrup crystallization during 9 months

                              
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