Abstract:
A process for the production of liquid sugar by forming a sugar solution of water and natural sugar containing juice, adjusting the pH of a sugar solution to the range of from 1.0 to 2.0 to obtain an inverted juice, filtering the inverted juice, decolorizing the inverted juice to obtain sugar syrup, demineralizing the sugar syrup, evaporating the demineralized sugar syrup, and cooling the sugar syrup to form the liquid sugar.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is related to Mexican patent application NL/9/2001/000011, filed Apr. 18, 2001, the subject matter of which is incorporated by reference herein.  
         FIELD OF THE INVENTION  
         [0002]    The present invention is related to processes for the production of liquid sugar, and more particularly to a process for the production of liquid sugar which avoids the need of producing final sugar and other waste materials commonly produced in the traditional sugar production processes, and reduces the thermal and electrical energy consumption compared to conventional processes for the production of crystal sugar that ordinarily need a great amount of vapor and electricity for its production.  
         DESCRIPTION OF RELATED ART  
         [0003]    There is currently an over-supply and an over-production of crystal sugar, which causes a low selling price that affects the financial health of the sugar industry. In addition, there is a tendency in the food industry to substitute corn syrup, which is fructose rich, for crystal sugar, especially in the beverage industry. This causes an additional depression of crystal sugar prices in the worldwide market.  
           [0004]    The conventional process for the production of crystal sugar from sugar cane comprises the following steps:  
           [0005]    reducing the cane size by means of a grinding machine. Normally such machines have a cutting blade rotating at a velocity of between about 400 to 500 rpm in order to extract the juice of the sugar cane by extrusion;  
           [0006]    adding from 25 to 35% in weight of “imbibition” water to the raw sugar cane juice at a temperature of 75 to 85° C. to assure an efficient sucrose extraction of from 95 to 98.5%.  
           [0007]    submitting the juice obtained in the last step to a purification proceeds known as defecation consisting in the addition of 0.5 Kgs of calcium hydroxide by each ton of cane, to raise the pH of the juice to a pH of from 7.5 to 8.5;  
           [0008]    feeding the juice to a heat interchanger to raise the temperature to 90-105° C., to precipitate the resin gum serums and albuminoidal substances;  
           [0009]    feeding the obtained juice to a continuous clarifier and evaporator to separate the liquid from the solids, called sedimentation sludge. The sedimentation sludge is passed to a continuous rotary filter in which a sugar solution is recovered. The obtained precipitation product has a sugar content of from 0.8 to 1.2% in weight;  
           [0010]    pumping the sugar solution having a sucrose content of from 12 to 15% to a multiple effect evaporator (from two to three effects), wherein a solid concentration of from 60 to 65% is achieved;  
           [0011]    crystallizing the solids obtained in the last step inside a one effect intermittent evaporator until obtaining a solid concentration of from 85 to 90% to obtain a boiled mass containing crystal sugar. This is the most expensive step since a bad crystallization may provoke an increase of the production of non-crystallizable product (molasses), which is a by product that consumes as much as from 10 to 15% of the total cane sugar content;  
           [0012]    centrifuging the boiled mass inside cans rotating at 1000 to 1800 RPM to separate the sugar crystals from the mass;  
           [0013]    washing the sugar crystals with atomized water in order to separate the molasses from the sugar crystals; and  
           [0014]    drying the sugar crystals by means of a rotary dryer to obtain raw sugar ready for a refining process.  
           [0015]    The refining process comprise the following steps:  
           [0016]    mixing raw sugar with syrup having a solid content of from 72 to 75° Brix inside a mixer having a rotary agitator for eliminating the molasses from the sugar crystals;  
           [0017]    centrifuging the mixture of syrup and raw sugar to separate the clean sugar crystals from the syrup; and  
           [0018]    dissolving the crystals in water to obtain a solution having a concentration of from 55 to 60° Brix.  
           [0019]    The purification of the solution comprises the steps of:  
           [0020]    clarification;  
           [0021]    filtration; and  
           [0022]    de-coloration in order to obtain a de-colored (clear) solution. The clarification is carried out by carbon phosphate, whitewashing, filtration and discoloration;  
           [0023]    crystallization: the de-colored solution is evaporated to obtain a solid concentration of form 85 to 90° Brix and then it is sent to an agitated tank; where it is centrifuged for separating refined sugar crystals form the solution;  
           [0024]    washing: the refined sugar crystals are washed with hot water and the washing water is recycled to the crystallization step;  
           [0025]    drying: the washed refined sugar crystals are dried with a countercurrent hot air stream inside a rotary drier until obtaining a water content of 0.05% in weight.  
           [0026]    The main disadvantage of the above process is the production of a final solution and molasses having a high content of non-processed sugar. Moreover, in order to carry out the crystallization of the sugar, the traditional process consumes a great amount of energy (vapor and electricity).  
           [0027]    Furthermore, the traditional process needs the crest of the cane to be cut, since this part of the cane contains no crystallizable monosaccharide sugars that would raise the weight of the recollected cane for as much as 20 to 25%.  
           [0028]    In view of the above-referred disadvantages and of the need of the food industry for alternative to the corn syrup, applicants developed a process for the production of liquid sugar.  
           [0029]    The process of the present invention obtains a final product comprising liquid sugar having a fructose content of 50% in weight and a high efficiency of extraction sugar solids content of from 69 to 75% in weight.  
           [0030]    The process of the present invention is able to treat the crest of the cane thus using all the cane and reducing the amount of waste material.  
           [0031]    Furthermore, the process of the present invention has fewer steps compared with the traditional process thus reducing the quantity of needed equipment.  
           [0032]    Finally thanks to the process of the present invention there is produced more sugar by using the same amount of energy and cane compared with the traditional process and eliminates the production of molasses.  
         SUMMARY OF THE INVENTION  
         [0033]    It is therefore an object of the present invention to provide a process for the production of liquid sugar by which is produced a liquid sugar containing 50% of fructose and from 69% to 75% of high efficiency process of extraction sugar cane solids.  
           [0034]    It is another object of the present invention to provide a process of the above referred nature by which is produced more sugar by using the same amount of energy and cane compared with the traditional process.  
           [0035]    It is still another object of the present invention to provide a process of the above referred nature which is able to treat the crest of the cane thus using all the cane and reducing the amount of waste material.  
           [0036]    It is a further object of the present invention to provide a process of the above referred nature that has less steps compared with the traditional process thus reducing the quantity of needed equipment.  
           [0037]    It is an additional object of the present invention to provide a process of the above referred nature that produces more sugar by using the same amount of energy and cane compared with the traditional process and eliminates the production of molasses.  
           [0038]    Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]    The invention will now be described in accordance with a preferred embodiment thereof and to an specific example of the results of the process of the present invention.  
         [0040]    The process for the production of liquid sugar of the present invention may include the following steps:  
         [0041]    grinding the cane by means of a grinding machine having a cutting blade rotating at a velocity of between about 400 to 500 rpm in order to break the cane&#39;s bark and reduce the cane&#39;s size;  
         [0042]    mixing the grinded cane with imbibition water in an amount of from 25% to 35% in weight inside an diffusion-extraction unit comprised by a five stages four masses mill inside of which the grinded cane is mixed with a countercurrent stream of imbibition water at a temperature of from 60 to 75° C.;  
         [0043]    extracting the juice from the cane mixed with imbibition water by means of an extractor mill capable of exerting a pressure of from 120 to 150 kgs/cm2 by which is extracted the 55% of the diluted solution from the cane which equals to the extraction of the 98.50% of the total sugar content thus obtaining a solution of cane juice mixed with imbibition water having a concentration of from 12 to 15° Brix;  
         [0044]    adjusting the pH of the solution obtained in the last step at 1.0 to 2.0 by pre-heating it until a temperature of approximately from 90 to 100° C. inside a heat interchanger and then discharging the solution into an agitated reactor made of stainless steel and adding mineral acids such as sulfuric acid, phosphoric acid and hydrochloric acid. They may be used organic acids such as acetic, propionic, tartaric, sucinic, citric and invertase enzyme. The residence time of the solution inside the reactor must be of from 45 to 75 minutes by which is obtained an inverted juice at a 100%; purifying the inverted juice by firstly adjusting its pH at 5.5 to 6.5 by adding a lime slurry inside a tank type agitated neutralizer reactor inside of which the temperature is maintained at between about 90 to 100° C., and then discharging the juice to a continuous clarifier at the bottom of which a precipitated is settled which is filtered from the juice by means of a rotary filter in order to mix the juice filtered at the bottom of the clarifier with the clarified juice that is discharged by the continuous clarifier&#39;s superior end to a balance tank inside of which the temperature is maintained at a temperature of between about 70-80° C. in order to obtain a purified inverted juice; decolorizing the purified inverted juice in order to obtain a discolored syrup by feeding it to a tandem of decolorizing activated carbon columns of mineral or vegetal origin and then feeding the decolorized syrup to a balance tank into which the temperature of the syrup is reduced at between about 40 to 50° C. for continuously feeding it to the next step;  
         [0045]    demineralizating thee syrup by feeding it to a demineralization tandem comprised by: a weak basic macro reticular and micro porous anionic resin column, a highly acidic resin column and a week basic anionic resin and controlling the exit pH between a range of from 5.5 to 6.5 for subsequently discharging the demineralized syrup to a balance tank wherein the temperature is raised at between about 70 to 80° C.; evaporating the demineralized syrup by means of an evaporator of triple effect descending film and five specific fruit juice bodies for avoiding the overheating of the sugar solution and the formation of colored substances that reduce the quality of the final product operating at a vacuum negative pressure of 26 inches of Hg at a temperature of between about 110 to 120° C. in order to obtain a final syrup having a final concentration of 75° Brix having fructose content of 50% in weight; and lowering the syrup temperature by means of a heat interchanger at a temperature of between about 30 to 35° C.; sending the cooled syrup to a storage tank.  
         [0046]    The storage tank should be made of stainless steel sanitary grade having an inert gas pressure of between about 0.05 to 0.1 atm. The inert gas may be nitrogen, carbonic anhydride or a mix thereof.  
       EXAMPLE  
       [0047]    In order to exemplify and comparing the performance of the process for producing liquid sugar of the present invention, the following operational data from the “Plan de Ayala” traditional sugar refinery located in Cd. Valles-S.L.P México, was obtained from the “Manual Azucarero Mexicano” of the year 2000, taking as comparison parameters a ton of refined sugar versus a ton of liquid sugar having a concentration of 75° Brix.  
                                                                                                     Comparison parameters from the traditional process for the production       of refined sugar compared with the process of the present invention.                Comparison base                    1000   1000           Kgs of crystalline sugar   Kgs of liquid                            Comparison parameter                        Process of the present           Traditional process   invention                        cane sugar   9.4561   6.0374       Tons of molasses   0.3405   Non produced       Tons of cachaza   0.3044   Non produced       Tons of vapor   3.3159   2.020                   
 
         [0048]    Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.