WO1995030027A1

WO1995030027A1 - Date process apparatus and product

Info

Publication number: WO1995030027A1
Application number: PCT/GB1995/001012
Authority: WO
Inventors: John Karkalas; Robert Marshall
Original assignee: Ashbrough Limited
Priority date: 1994-05-03
Filing date: 1995-05-03
Publication date: 1995-11-09
Also published as: AU2350095A; GB9408749D0; GB9622959D0; GB2302099A

Abstract

There is provided a process for producing a date extract, the process comprising extracting sugar from dates to produce a extract in the form of a residue and concentrating the extract into a syrup. Apparatus for carrying out the process is also provided, as well as the product itself.

Description

DATE PROCESS APPARATUS AND PRODUCT

Dates are an important food commodity in many countries of the near and Middle East. Egypt, Saudi Arabia, Iran, Iraq and Sudan are major producers of the nutritionally valuable and attractive fruit. Local dates are consumed fresh early in the harvesting season, but they are best known to the western world in the partially dried form which is particularly popular during Christmas and New Year.

Dried dates do not require refrigeration because their high sugar content preserves them naturally. Dried de- stoned dates consist approximately of 70% sugars, 80% dietary fibre, 2.5% protein, 1.5% mineral matter and 18% water. Dates are often dipped in honey or glucose syrup to make them shiny and, when not suitable for packaging, accidentally damaged or deformed dates are sold in block form which are mainly used in baking.

According to a first aspect of the present invention there is provided a process comprising extracting sugar from dates to produce an extract and leaving a residue, and concentrating the extract into a syrup. Preferably, the residue is dried.

Preferably, the extraction of sugar from the dates is by means of heating the dates to at least 80°C and supplying a quantity of water to the dates .

Preferably, the extract is filtered by means of a filter press.

Preferably, the extract is concentrated by means of a falling film evaporator.

Preferably, the water evaporated from the extract is used in the extraction of the sugar.

Preferably, the dates will be prepared, for example are dried and de-stoned, before entering the process. The dates may also be chopped or sliced before entering the process.

According to a second aspect of the present invention there is provided an apparatus for processing dates, said apparatus comprising a sugar extractor which produces a date extract, and a concentrator for concentrating the date extract.

Preferably, the sugar extractor is a two-staged extractor maintaining the temperature at over 80°C and supplying water in controlled jets to the dates.

Preferably, the sugar extractor produces a residue and an extract. A drier may be provided to dry the wet residue.

Preferably, a conveyor is provided to transport the wet residue to the drier.

Preferably, the drier is in the form of a tunnel through which the wet residue passes on a conveyor.

Preferably, there is provided a filter means for the extract.

An evaporator is preferably provided for condensing the filtered extract. Preferably, the evaporator is in the form of a falling film evaporator.

A surface condenser may be provided in the evaporator to recirculate water to the sugar extractor.

Preferably, the resulting extract, in the form of a syrup, is maintained at a temperature of approximately 80° centigrade.

According to a third aspect of the present invention there is provided a product comprising a syrup of condensed sugar extract, wherein the extract is produced from dates by heating said dates and supplying water thereto.

Preferably, the syrup produced is comprised of approximately 70% solids and 30% water.

Preferably, the syrup is comprised of approximately 60% combined glucose and fructose.

Preferably, the heating is to a temperature greater than 80°C.

Preferably, the water supplied is at a temperature of approximately 80°C.

According to a fourth aspect of the present invention there is provided a product comprising a dried date residue from which some of the sugar has been extracted. Preferably the sugar is extracted by heating the dates (preferably de-stoned and coarsely cut) and providing the dates with water to remove sugars therefrom. The residue may then be dried.

Preferably, the residue is approximately 40% fibre.

Preferably, the residue is approximately 50% combined glucose and fructose.

Embodiments of the present invention will now be described as means of example only with reference to the accompanying tables and figures in which:

Table 1 gives the composition of de-stoned dry dates before being processed in accordance with the present invention; Table 2 gives an analysis of the product in accordance with the third aspect of the present invention which is the product of the process and apparatus in accordance with the present invention; Table 3 gives an analysis of the product in accordance with the fourth aspect of the present invention, which is a product of the apparatus and process in accordance with the present invention; Fig 1 is a simplified schematic flow diagram of one embodiment of the process and apparatus in accordance with the present invention; Fig 2 is a schematic flow diagram of the process and apparatus in accordance with the present invention; and Fig 3 is a diagrammatic perspective view of the apparatus in accordance with the present invention. Fig 4 is a schematic flow chart of one embodiment of the process and apparatus of the present invention.

Figure 1 is a flow-sheet illustrating schematically one embodiment of the present invention. In the apparatus and process shown stage A involves date preparation which would normally include removal of the date stones as well as sorting the dates to remove any of sub- standard quality. Stage B is a further stage of date preparation in which the dates are roughly chopped by machine. Stage C indicates generally the process of sugar removal, wherein the dates heated to approximately 80°C are provided with heated water into which the date sugars are extracted. In the flow sheet of Figure 1 two tanks having rotating screw conveyors are illustrated, but this part of the process may be adapted as required.

The treated residue moves on to the final sugar extraction stage, shown generally at D. Once the processed dates have passed through this stage separation of the extract and residue occurs. The residue is gathered into a hop Dl and undergoes drying by means of a drying apparatus D2 , in the form of a tunnel with a fan dryer. The date extract is pumped to a collecting tank E provided with a stirrer or agitator. The extract is then filtered in stage F, and the filtered extract is collected to Collecting Tank G. From there the extract is concentrated through a concentrating apparatus H to produce the final syrup, which is collected in Storage Tank J.

Referring to the Figures 2 and 3 in which, a bucket elevator 1 with an electric driving motor and a capacity of 1667 kg per hour leads to a cutting device 2 in the form of a rotating knife with a driving electric motor and starter switch for chopping the dates at the rate at which they are delivered by the bucket elevator 1. The cutting device 2 has a rotameter for manual control of added hot water.

The cutting device 2 is adjacent to a two-stage extraction system 3 for extracting date sugars . The extraction system 3 also has a capacity of 1667 kg of de-stoned dates per hour. The extraction system 3 comprises two stainless steel screw conveyors with stainless steel troughs and a stainless steel screw press for the partial de-watering of the date fibre. Each of these items has a variable speed motor. Troughs are provided in the extraction system 3 which are provided with steam jackets to maintain the contents of the troughs at a temperature of not less than 80°C. The screw press is capable of handling approximately 1200 kg per hour of wet date fibre residue. Hot water jets with water at 80°C are situated above the two troughs for the supply of controlled quantities of water which provides the extraction of the sugars. Two rotameter type flow meters accurately control the water input. A hand held refractometer is also used with a sugar scale of 0-30% for the monitoring of the sugar content (c. 18-21°Bx) of the extract. The extract resulting from the extraction system 3 contains approximately 1% insoluble suspended solids. The flow rate of the liquid extract is approximately 5166.7 kg per hour (density approximately 1.080 kg per litre at approximately 20°Brix) .

A screw conveyor with an electric motor and starter switch transports the wet fibre residue at a rate of 1200 kg per hour to a tunnel drier 11. The tunnel drier 11 is a hot air drier with a countercurrent with endless mesh conveyors which are anti-stick PTFE-coated. The tunnel drier 11 dries the date fibre residue at a rate of 1200 kg per hour. The tunnel drier 11 has a drying capacity of 835 kg per hour of water. The dry product resulting from the tunnel drier 11 is approximately 300 kg per hour of date fibre flakes of 5% water content maximum. Two electric motors and starter switches one for a hot air fan and the other for the conveyor belt are provided in the tunnel drier 11. The conveyor belt is of variable speed to vary the drying capacity of the tunnel drier. The date fibre flakes have a bulk density of approximately 0.15 kg per litre and the volume of flakes is about 50 m³ per 24 hours.

A holding tank 5 of stainless steel is provided for the sugar extract as extracted by the sugar extraction system 3. The holding tank 5 has a capacity of 10,000 metres with a slow speed paddle agitator at approximately 15 rpm. The holding tank 5 provides a steady supply of sugar extract to two plate and frame filter presses 7.

The two plate and frame filter presses 7 are of stainless steel construction. The presses 7 are manually operated hydraulic closing mechanisms. Inlet and outlet pressure gauges are provided on the presses 7. One inlet and outlet stand-pipe and four vent points are provided on the press 7. Drain trays are situated below the press 7 to collect the filtrate. The length of each press is about three metres and the width one metre. The filter medium of the presses 7 is cotton-twill or man-made fibre. The presses 7 have an operation time of about two hour cycles.

A receiving tank for the filtrate is provided made of stainless steel with a capacity of 10,000 litres. No agitator is required for this receiving tank 13. A lobe pump 14 is provided to supply the filtrate via a rotameter 15 to the evaporator system 16.

The evaporator system 16 is a double effect falling film evaporator system. The shell diameter for each evaporator 16 is about 45 centimetres with a height of about 9 metres. Each evaporator 16 is provided with a vapour liquid separator with sufficient capacity to prevent loss of syrup through entrainment (estimated diameter x height approximately 1 x 1.5 metres). A surface condenser 19 (plate heat exchanger) is an iatrical part of the evaporator system 16. The surface condenser 19 saves considerable quantities of processed water which can be used in the sugar extraction system 3. A vacuum pump 20 is provided in the second effect of the evaporator 16 to generate an absolute pressure of not more than 12 kPa ( ie approximately 93 mm Hg, or 93 torr) . A cooling water pump 21 is provided in cast iron with a rate of 30 m³ per hour. Each evaporator system 16 is provided with a condensate pump 22, 23, 24 for the extraction of condensate under reduced pressure (about 2500 litres per hour). A syrup pump is provided for the extraction of the final product from the vapour liquid separator of the second effect of the evaporator system 16, for example a mono-pump with variable speed motor with a rate of approximately 1500 litres per hour. A hand-held refractometer can be used which is calibrated in the range of 30-80% sugar to monitor the concentration of the final date syrup product. A closed tank 18 with a slow speed agitator is provided for the finished date syrup product with a capacity of approximately 15 m³. The density of the final syrup product is 1.34 kg per litre.

A hot water tank 25 is provided for the collection of condensate. The tank 25 has a capacity of 5000 litres with a steam-heated coil to maintain the temperature at about 80° centigrade. A pump 26 with a capacity of 6000 litres per hour supplies the hot water to the sugar extraction system 3.

In use dry de-stoned dates are supplied by the bucket elevator 1 to the cutting device 2 where they are chopped up and washed by the water supply of the cutting device 2. The chopped dates then enter the sugar extraction system 3 in which some of the sugar is extracted from the dates by means of heating to over 80°C and pressing the dates whilst hot water jets at 80°C are directed at the date product.

At this point the date becomes two products, firstly an extract and secondly a residue. The residue is transferred to a receiver tank 9 after having been through a de-watering system 4. A conveyor 8 then conveys the residue to a hot air tunnel drier 11. On exiting the tunnel drier 11, the dried date residue is deposited in a hopper 12 which has a lid.

This dried residue is a product with a composition as shown in Table 3 including a fibre content of approximately 40%. This product would be suitable as an alternative breakfast supplement as it is 100% natural with some of the sugars, proteins and minerals of the natural date fruit. It also contains a higher fibre content than many other breakfast foods .

The sugar extract is collect from the extraction system 3 into a tank with a panel agitator 5 and a steam- heating coil. The extract is transferred to the filter presses 7 and the filtrate produced by the filter presses 7 is collected in a holding tank 13. A pump 14 pumps the filtrate from the tank 13 via a rotameter 15 to the evaporator system 16 which is a double effect falling film evaporator system. A syrup pump is provided for the extraction of the final product from a vapour liquid separator in the evaporator system 16 and hand-held refractometer calibrated in the range of 30-80% sugar, monitors the concentration of the final date syrup. A stainless steel tank 18 with an agitator and a lid collects the finished product.

The finished product of date syrup has a composition as given in Table 2 and is a 100% natural product with no additives which can provide a valuable source of energy as well as having a delicious flavour. The syrup has a content of approximately 32% glucose and 31.4% fructose and would provide a good substitute for molasses, honey or maple syrup.

Water is collected from the evaporator system and maintained at approximately 80°C for reuse in the extractor system 3.

In the process illustrated in Figure 4, the dates undergo sorting and are then de-stoned by machine. At the de-stoning stage water is added. The de-stoned dates plus water are heated to 80°C or above in order to extract sugars from the dates into the water. The mixture may be agitated to aid sugar removal. Once sugar extraction is complete, the mixture is filtered to separate the date residue from the extract, which is comprised of the water and date sugars removed from the date starting material. The extract is concentrated by evaporation, which may be conducted at elevated temperatures and/or at pressures below atmospheric pressure. Following the evaporation process a date syrup is produced according to the third aspect of the present invention. The date residue is treated separately by drying, which may be conducted using conventional techniques, to produce a dried date residue according to the fourth aspect of the present invention.

Improvements and modifications can be made to the process, apparatus and products without departing from the scope of this invention.

Claims

1. A process comprising extracting sugar from dates to produce an extract and leaving a residue, and concentrating the extract into a syrup.

2. A process as claimed in Claim 1, wherein the residue is dried.

3. A process as claimed in either preceding Claim, wherein the extraction of sugar from the dates is by means of heating the dates to at least 80°C and supplying a quantity of water to the dates.

4. A process as claimed in any preceding Claim, wherein the extract is filtered by means of a filter press.

5. A process as claimed in any preceding Claim, wherein the extract is concentrated by means of a falling film evaporator.

6. A process as claimed in any preceding Claim, wherein the water evaporated from the extract is used in the extraction of the sugar.

7. A process as claimed in any preceding Claim, wherein the dates are subjected to pre-preparation, for example, are dried, de-stoned, chopped or sliced before entering the process.

8. A process as claimed in any one of Claims 1 to 7, wherein the resulting extract, in the form of a syrup, is maintained at a temperature of approximately 80° centigrade.

9. Apparatus for processing dates, said apparatus comprising a sugar extractor which produces a date extract, and a concentrator for concentrating the date extract.

10. Apparatus as claimed in Claim 9, wherein the sugar extractor is a two-staged extractor maintaining the temperature at over 80°C and supplying water in controlled jets to the dates.

11. Apparatus as claimed in Claims 9 or 10, wherein the sugar extractor produces a residue and an extract.

12. Apparatus as claimed in Claim 11, and including a drier to dry the wet residue.

13. Apparatus as claimed in Claim 12, wherein a conveyor is provided to transport the wet residue to the drier.

14. Apparatus as claimed in Claims 12 or 13, wherein the drier is in the form of a tunnel through which the wet residue passes on a conveyor.

15. Apparatus as claimed in Claims 9 to 14, wherein there is provided a filter means for the extract.

16. Apparatus as claimed in Claims 9 to 15, wherein an evaporator is provided for condensing the filtered extract.

17. Apparatus as claimed in Claim 16, wherein the evaporator is in the form of a falling film evaporator.

18. Apparatus as claimed in Claims 16 or 17, wherein a surface condenser is provided in the evaporator to recirculate water to the sugar extractor.

19. A product comprising a syrup of condensed sugar extract, wherein the extract is produced from dates by heating said dates and supplying water thereto.

20. A product as claimed in Claim 19, wherein the syrup produced is comprised of approximately 70% solids and 30% water.

21. A product as claimed in Claims 19 or 20, wherein the syrup is comprised of approximately 60% combined glucose and fructose.

22. A product comprising a dried date residue from which some of the sugar has been extracted.

23. A product as claimed in Claim 22, wherein the sugar is extracted by heating the dates and providing the dates with water to remove sugars therefrom.

24. A product as claimed in Claims 22 or 23, wherein the residue is approximately 40% fibre.

25. A product as claimed in Claims 22 to 24, wherein the residue is approximately 50% combined glucose and fructose.