Patent Publication Number: US-2005142277-A1

Title: Method of producing a soya bean product

Description:
THIS INVENTION relates to a method of producing a soya bean product and to a soya bean product produced in accordance with the method.  
      Soya beans, also called soybeans, are widely used as a source of protein. The main products derived from soya beans are soya milk, soya oil, soya protein and soya bean meal.  
      According to a first aspect of the invention, there is provided a method of producing a soya bean product, the method including the step of exposing soya beans to an aqueous solution having a pH of between about 2.0 and 5.5.  
      The soya beans may be whole beans i.e. soya beans which have not been de-hulled.  
      The method may include the prior step of dissolving an organic acid in water to produce the aqueous solution having a pH of between about 2.0 and 5.5.  
      The organic acid may be citric acid or ascorbic acid.  
      A pH of between about 2.0 and 5.5 inhibits the lipoxygenase reaction which generally causes off flavours and off colours in soya products such as soya milk. In prior art processes, soya beans have generally been processed by a wet method which involves de-hulling of the beans. Because the lipoxygenase enzyme is concentrated in the hull of the bean, it is believed that, when de-hulling and wet processing takes place, the biological activity of the enzyme is increased when it comes into contact with oxygen and water when the hull is ruptured. The enzyme then oxidizes lipids in the bean. This is believed to lead to the formation of “grassy”, “beany” or “paint-like” off flavours and off odours in the soya product and particularly in the soya milk which is produced. The method of the invention requires no prior de-hulling of the beans and substantially reduces the problem of off flavours and off odours to the extent that they present little or no problem.  
      The method may include the prior step of dissolving both an organic acid and a sugar in the water to produce the aqueous solution having a pH of between about 2.0 and 5.5. The method may thus include the step of dissolving a sugar in the water.  
      The method may, instead, include the prior step of combining the organic acid and the sugar to form an additive and dissolving the additive in water to produce the aqueous solution. The sugar may be selected from dextrose, glucose and sucrose. In particular, the sugar may be dextrose.  
      The soya beans may be exposed to the acidic aqueous solution by soaking the beans in the acidic aqueous solution for a period of between about 4 and 12 hours. The soya beans may be exposed to the acidic aqueous solution by soaking the beans in the acidic aqueous solution at a temperature of between about 2 and 16° C.  
      The mass ratio of the organic acid to the sugar in the acidic aqueous solution may be between about 100:0 and 1:1. Preferably, the mass ratio will be about 1:1. The mass ratio of the combined organic acid and sugar to the soya beans may be between about 0.1:100 and 2:100.  
      The method may include the further step of separating the soya beans from the aqueous solution and then blanching the soaked beans. The blanching step may be conducted at a temperature of between about 95 and 100° C. It may be conducted for a period of between about 2 and 6 minutes. Separating the soaked soya beans may be by draining and rinsing the soaked beans.  
      The method may include the subsequent step of milling the blanched soya beans to produce a slurry comprising a soya milk fraction and a soya solids fraction and separating the soya milk fraction from the soya solids fraction. The milling step may be a wet milling step and may be conducted at a temperature of between about 65 and 98° C. Preferably, the successive steps of soaking, separating, blanching and milling are conducted without any substantial delays between the steps. The time interval between each of the successive steps of soaking, separating, blanching and milling will preferably be as short as possible and is preferably between about 15 and 30 minutes.  
      The method may include spray-drying the soya milk to produce a spray-dried powder.  
      According to a second aspect of the invention, there is provided a method of producing a soya bean product by processing soya beans, the method including the step of at least partially decreasing the biological activity of oxidizing enzymes in the soya beans.  
      The soya beans may have hulls and the oxidising enzymes may largely be contained in the hulls. The enzymes may be lipoxygenase enzymes or trypsin inhibitors.  
      The biological activity of the oxidizing enzymes may be at least partially decreased by exposing the soya beans to an acidic aqueous solution.  
      The acidic aqueous solution may have a pH of between about 2.0 and 5.5 The method may include the prior step of dissolving an organic acid in water to produce the aqueous acidic solution.  
      The organic acid may be citric acid or ascorbic acid.  
      The method may include the prior step of dissolving a sugar in the water.  
      Instead, the method may include the prior step of combining the organic acid and the sugar to form an additive and dissolving the additive in the water.  
      The sugar may be selected from dextrose, glucose and sucrose.  
      The soya beans may be exposed to the acidic aqueous solution by soaking the beans in the acidic aqueous solution for a period of between about 4 and 12 hours. The soya beans may be exposed to the acidic aqueous solution by soaking the beans in the acidic aqueous solution at a temperature of between about 2 and 16° C.  
      The mass ratio of the organic acid to the sugar in the acidic aqueous solution may be between about 100:0 and 1:1. Preferably, the mass ratio is about 1:1.  
      The mass ratio of the combined organic acid and sugar to the soya beans may be between about 0.1:100 and 2:100.  
      The method may include the further step of separating the soya beans from the aqueous solution and then blanching the separated beans.  
      The blanching step may be conducted at a temperature of between about 95 and 100° C. The blanching step may be conducted for a period of between about 2 and 6 minutes.  
      The method may include the step of milling the blanched soya beans to produce a slurry comprising a soya milk fraction and a soya solids fraction and separating the soya milk fraction from the soya solids fraction.  
      The milling step may be a wet milling step. The wet milling step may be conducted at a temperature of between about 65 and 98° C.  
      The time interval between each of the successive steps of soaking, separating, blanching and milling will be as short as possible and is preferably between about 15 and 30 minutes.  
      The method may include spray-drying the soya milk to produce a spray-dried powder.  
      According to a third aspect of the invention there is provided a soya bean product produced in accordance with a method as hereinbefore described.  
      The soya bean product may be soya milk.  
      The invention extends to an additive comprising an organic acid and a sugar for use in a method as hereinbefore described. 
    
    
      The invention is now described, by way of example, with reference to the accompanying diagrammatic drawings and Tables, in which  
       FIG. 1  is a schematic diagram of a first part of a soya bean processing plant;  
       FIG. 2  is a schematic diagram of a second part of the soya bean processing plant of  FIG. 1 ; and  
       FIG. 3  is a schematic diagram of a third part of the soya bean processing plant of  FIG. 1 .  
    
    
      Referring to  FIG. 1 , reference numeral  10  generally indicates, schematically, a first part of a soya bean processing plant for the production of soya milk in accordance with the method of the invention.  
      The part  10  of the processing plant includes two 200 litre plastics soaking tanks  11 ,  12  in which soya beans are soaked in baskets of which one is shown schematically at  14 . The soaking tanks  11 ,  12  are kept in a cold room represented schematically by the rectangle  13  which maintains the tanks at a temperature of about 8° C. The part  10  further includes a container  16  in which the drained beans are held prior to being weighed on a scale  18 . The part  10  further includes two blanching vessels  20 ,  22  and two blanching baskets  24 ,  26  in which, in use, the soya beans are blanched. Each of the blanching vessels  20 ,  22  has a capacity of about 120 litres and each is provided with a heating jacket  28 ,  30  heated respectively by a steam-inlet conduit  32 ,  34  respectively. The blanching vessels  22 ,  24  are provided with drainage outlets schematically represented by the arrows  36 ,  38  and with expansion boxes and steam traps indicated by reference numerals  39 ,  41 .  
      Referring to  FIG. 2 , the second part of the processing plant, generally indicated by reference numeral  50 , includes a colloid mill  51  which is fed from a 200 litre holding tank  52  via a conduit  54  which includes a slurry pump  56 , a valve  58  downstream of the holding tank  52  and upstream of the slurry pump  56  and a three-way valve  60  downstream of the slurry pump  56  and upstream of the colloid mill  51 . A recycle flow line  62  extends from the colloid mill back to the holding tank  52  and includes a three-way valve  64  from where a feedline  66  extends back to the colloid mill. The holding tank  52  is fed with warm water via a feedline  68  from a warm water vessel  70  which is provided with a steam jacket  72  heated by a steam inlet schematically indicated by the arrow  74  and an expansion box and steam trap generally indicated by reference numeral  71 . The feedline  68  includes a valve  69 . A slurry feedline  76  extends from the three-way valve  60  to a decanter  78  from where a feedline  80  extends to a soya milk reservoir  82 . Solid material in the form of wet meal or okara is collected, as is shown schematically by the arrow  84 , in a holding tank  86 . In the Figure the blanched beans are shown being added to the colloid mill  51 , as indicated schematically by the arrow  88 , from one of the blanching baskets  24 .  
      Referring now to  FIG. 3 , the third part of the soya bean processing plant, generally indicated by reference numeral  100 , includes a blending tank  101  which is connected via a feedline  102 , which includes a valve  104 , to a homogeniser  106 . A feedline  108  connects the homogeniser  106  to an ultra high temperature (UHT) pasteurising unit  110  from which a flowline  112  extends via a cooler  114  to a soya milk storage vessel  116 . The refrigerating unit which cools the cooler  114  is shown schematically by the rectangle  118  and flowlines  120 .  
      In separate runs using 40 kg each of a USA grade yellow  2  soya bean, about 140 litres of soaking water comprising an aqueous solution of citric acid (1.4 kg) and dextrose (1.4 kg) was cooled to 8° C. in the soaking tanks  11 ,  12  and the soya beans were added to the tanks  11 ,  12  and left to soak overnight. The batches of beans were then withdrawn from the soaking tanks  11 ,  12 , drained and weighed on the scale  18 . The respective batches of beans were then transferred to the blanching baskets  24 ,  26  which were submerged in the blanching pots  20 ,  22 . Each blanching pot  20 ,  22  contained about 120 litres of water at a temperature of about 98° C. The beans were blanched for 5 minutes and were then transferred to the colloid mill  51  where the blanched beans were milled. The blanching pots  20 ,  22  were half drained via the drainage outlets  36 ,  38  and topped up with water. The water in the blanching vessels contained lime at a pH of 9.  
      Warm water at a temperature of 85° C. was transferred in 120 litre batches from the warm water vessel  70  via the feedline  68  to the holding tank  52 . Circulation of water through the colloid mill  51  via the flowlines  54 ,  62  and back to the holding tank  52  was started before the batches of beans were added to the colloid mill  51 . The blanched beans were slowly introduced via a hopper located above the colloid mill  51 . The slurry formed in the colloid mill  51  was transferred via the line  62  back to the holding tank  52 . Once all of the beans had been added to the mill  51 , the setting of the mill  51  was adjusted to produce a smaller particle size and the milling process was continued for 15 minutes.  
      The slurry was then fed via the valve  60  and the flowline  76  to the decanter  78  and the desludged soya filtrate was collected in the reservoir  82 . It was then weighed and transferred to a holding tank (not shown). The wet meal (okara) was collected in the holding tank  86  and weighed. The raw soya milk which collected in the reservoir  82  was transferred to the blending tank  101  and weighed amounts of salt (50 g/200 l) and sugar (50 g/200 l) were blended into the milk in the blending tank  101 . The resulting blend was then pumped from the blending tank  101  at a rate of 60 litres per hour via the feedline  102  to the homogeniser  106 . The homogeniser  106  was maintained at a pressure of 200 kg/cm 2  gauge. From the homogeniser  106  the milk was pumped via the feedline  108  to the UHT pasteurising unit  110  where it was heated to a temperature of 140° C. for 3 seconds. The heated milk was then passed through the feedline  112  to the cooler  114  where it was cooled to a temperature of 10° C. The cooled milk was then allowed to flow into the soya milk storage vessel  116 .  
      The results of 5 further batches of USA Yellow No. 2 beans processed in accordance with the method described above are set out in Table 1.  
                                   TABLE 1                       DESCRIPTION   BATCH 1   BATCH 2   BATCH 3   BATCH 4   BATCH 5                                                        BLANCHING:                           RINSED SOAKED BEANS (KG)   39.5   40.5   39.8   40.6   40.5       CALCULATED DRY BEANS (KG)   19.75   20.25   19.9   20.3   20.25       WATER pH BEFORE BLANCHING   10.3   10.5   10.1   9.5   10.2       BLANCH TIME (MINUTES)   5   5   5   5   5       WATER pH AFTER BLANCHING   7.1   7.2   7   6.9   7.1       EXTRACTION:       EXTRACTION WATER LOADED (L)   108   125   120   120   120       EXTRACTION WATER TEMP (° C.)   83   85   78   89   81       MILLING ROUGH SETTING (MIN)   10   10   10   10   10       MILLING FINE SETTING (MIN)   12   15   13   15   15       DECANTER:       FEED RATE (L/H)   240   260   240   240   240       MILK YIELDED (L)   97   118.6   109   118.5   FAILURE       ACCUM. OKARA WEIGHED (KG)   36   68   103   135       DEAD VOLUMES &amp; RETAINED   14.5   14.9   15.8   10.1       MASS IN DECANTER (KG)       BLENDING:       SUGAR ADDED (GRAMS)   1,500   2,500   2,720   2,900       SALT ADDED (GRAMS)   50   215   220   230       HOMOGENISATION:       PRESSURE (kg/cm 3 )   200   200   200   200       FLOW RATE (L/HR)   160   160   160   160       UHT TREATMENT:       TEMPERATURE (° C.)   140   140   140   140       HOLDING TIME (SEC)   3   3   3   3       OUTLET TEMP (° C.)   10   14   16   22                  
 
      Results of Sample Analysis  
      A summary of the analyses of four batches of soya milk and okara from five batches is shown in Table 2. The adjusted values representing the sample prior to the addition of sugar are shown in Table 3.  
               TABLE 2                          Summary of Analysis                                                 Sample       Total           Dietary           Energy       No.   Description   Protein   Fat/Oil   Carbohydrates   Fibre   Ash   Moisture   (Kj/100 g)                                                         227   Okara,   10.23%   5.59%   0.40%   7.07%   0.84%   75.87%   387           Batch 1 &amp; 2       228   Milk Batch 2,   2.43%   1.78%   3.57%   0.30%   0.46%   91.46%   164           After           UHT       229   Milk Batch 2,   2.55%   1.83%   3.46%   0.70%   0.38%   91.08%   166           Before UHT       230   Milk Batch 4,   2.47%   1.04%   4.15%   0.31%   0.35%   91.68%   147           After UHT                  
 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                   
               
               
                 Values with and without Sugar 
               
            
           
           
               
               
               
            
               
                   
                 BATCH 2 
                 BATCH 4 
               
               
                   
                 SAMPLE NO. 229 
                 SAMPLE NO. 230 
               
            
           
           
               
               
               
               
               
            
               
                   
                 WITH 
                   
                 WITH 
                   
               
               
                 ITEM 
                 SUGAR 
                 WITHOUT 
                 SUGAR 
                 WITHOUT 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 SUGAR ADDED 
                 2.06% 
                   
                 2.39% 
                   
               
               
                 Protein (%) 
                 2.55 
                 2.60 
                 2.47 
                 2.53 
               
               
                 Fat/Oil (%) 
                 1.83 
                 1.87 
                 1.04 
                 1.07 
               
               
                 Carbohydrates (%) 
                 3.46 
                 1.43 
                 4.15 
                 1.80 
               
               
                 Dietary Fibre (%) 
                 0.70 
                 0.71 
                 0.31 
                 0.32 
               
               
                 Ash (%) 
                 0.38 
                 0.39 
                 0.35 
                 0.36 
               
               
                 Moisture (%) 
                 91.08 
                 93.00 
                 91.68 
                 93.92 
               
               
                   
                 100.00 
                 100.00 
                 100.00 
                 100.00 
               
               
                 Solids Content (%) 
                 8.92 
                 7.00 
                 8.32 
                 6.08 
               
               
                   
               
            
           
         
       
     
      It is an advantage of the invention illustrated that the method of the invention produces a soya bean product, in particular a soya bean milk, which does not have the “grassy”, “beany” or “paint-like” taste which is associated with the product produced by the traditional Chinese method of water extraction. Generally, the relative abundance of animal protein and the off flavours of soya products have resulted in a lack of interest in soya products despite the excellent nutritional value of soya milk and related products. A great deal of research has, in the past, concentrated on solving the problem of enzyme activity. This research has, for example, resulted in processes which incorporate deodorisation steps downstream of the de-hulling step. With one exception, prior art processes of which the Applicant is aware, incorporate de-hulling in the production of soya milk. In addition to the production of off flavours and off odours, another problem associated with de-hulling is that the process is seldom achieved with 100% effectiveness. This generally results in the loss of about 10% of the mass of the bean with associated loss of protein and bland tasting fibre. The only whole bean process known to the Applicant, i.e. the only process known to the Applicant which does not involve de-hulling of the beans, is an expensive oxygen starvation process in which the processing of the bean takes place in a deoxygenated atmosphere. However, the process is expensive and requires specialised equipment and operating procedures to achieve an oxygen-free environment. It is a particular advantage of the invention illustrated that the soya milk production process of the invention does not require de-hulling of the bean. The pre-treatment process of the invention is simple and inexpensive when compared with prior art processes of which the Applicant is aware and the extraction process of the invention produces a product which does not have the off flavours or off odours associated with prior art products. The product is an excellent tasting, highly digestible soya milk.