Abstract:
The invention is directed to a continuous process for the production of rice flour and dough. Rice flour and dough is made by hydrating rice flour or a blend of rice flour and other cereal components, tempering, and then cooking to partially gelatinize the starch in the flour.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the making of dough from rice flour. More particularly, this invention is directed to the production of partially gelatinized flour and dough which is made by blending the flour with water, hydrating the flour, tempering the hydrated flour and cooking the tempered flour to partially gelatinize the starch in the flour. 
     BACKGROUND OF THE INVENTION 
     Flour and Dough 
     Using and completely cooking rice flour limits flexibility for any process where food products are customized snack foods and the like which require a combination of rice flour or dough with other types of flour and dough, such as masa dough or wheat dough. Providing partially gelatinized rice flour using the process of the invention described herein permits customization of a dough which includes rice dough to a particular product using a continuous process without extensive shut down times. 
     An object of this invention is to provide a new flexible process for the production of partially gelatinized rice flour and dough. 
     These and other objects, advantages, features and characteristics of the present invention will become more apparent upon consideration of the following description and claims. 
     SUMMARY OF THE INVENTION 
     This invention is directed to a continuous process for the production of partially gelatinized rice flour and dough. In the process, rice flour or a blend of rice flour with other components of one or more other cereal grains is hydrated to provide a hydrated rice flour (or blend of rice flour and one or more additional cereal components) which has a moisture content of at least 20 weight percent. The additional cereal components may include flour from other cereals, such as wheat flour and oat flour. 
     In an important aspect, during hydration, the rice flour is mixed with water having a temperature of at least about 10° C., but not at a temperature that would substantially gelatinize the starch in the flour. Generally the temperature of the water/flour blend should not exceed about 60° C. The mixing of the water/flour blend should be effective to substantially, uniformly distribute water throughout the blend to the moisture level of the at least about 20 weight percent. In another important aspect, the hydrated rice flour blend has a moisture content of from about 26 to about 30 weight percent water, based upon the weight of the rice flour and water. 
     After hydration, the hydrated rice flour is tempered for a time to equally distribute moisture throughout the flour. Generally, tempering times range from about 30 seconds to about 12 minutes, depending upon the type and the particle size of the flour in the hydrated flour. 
     After tempering, the tempered flour enters a cooker to cook it in a cooking process which utilizes direct and indirect heat. The indirect heat keeps the cooker and dough at an elevated temperature which is effective for keeping the cooker clean of partially cooked residual dough. The direct heat, such as from the injection of steam into the tempered product, cooks the dough in combination with the indirect heat. The combination of indirect and direct heat brings the temperature of the tempered product to a temperature of at least about 165° F. as it leaves the cooker and partially gelatinizes the starch in the flour and starch in any other cereal components with which the rice flour may be blended or mixed. After the partial gelatinization not more than about 90 weight percent of the starch in the rice flour or rice flour blend is gelatinized, and in an important aspect, not more than about 70 weight percent of the starch in the rice flour or blend is gelatinized. The tempered product is directly exposed to steam for about 1 to about 10 minutes, and preferably from about 1 to about 2 minutes, with the cooking temperature also potentially being affected by a subsequent drying step. 
     After cooking the cooked rice flour or rice flour blend, the rice flour may be dried to a moisture content of not more than about 15 weight percent at a temperature which is effective for not heat damaging or burning the product. Generally, during drying the product temperature should not exceed 95° F. After drying the dried rice flour or blend is sized, such as by milling and sifting to a particle size of from about 16 to about 65 mesh, depending upon what type of food product will be made with the component blend. The process of the invention is effective for hydrating, tempering and cooking the rice flour or component blend, such that waste water is not created and process may be carried out without water being removed from the rice flour or component blend after hydrating, tempering or cooking. Moreover, the process is effective for providing a product which does not require washing after the hydration or cooking steps. 
    
    
     DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic illustration of a cooker used in the process of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The process includes hydrating rice flour and/or hydrating rice flour with other components, such as components from other cereals, such as corn. In the case of corn, these components include (1) corn germ, or (2) corn grits and corn germ, or (3) corn grits, corn germ and corn bran, or (4) corn germ and corn bran, or (5) corn bran, or (6) corn grits and corn bran, or (7) ground whole corn to provide a rice flour or a rice flour component blend. The rice flour or component blend may be mixed dry and then mixed with water for hydration of the blend or may be separately mixed into water for hydration of the blend. Thereafter, the rice flour or component blend is hydrated with water to provide a hydrated corn component blend which has a moisture content of at least about 20 weight percent. After hydration the process includes tempering the hydrated rice flour or component blend to provide a tempered rice flour or component blend, cooking the tempered rice flour or component blend with indirect heat and direct steam. After cooking, the cooked product with the partially gelatinized starch may be used as a dough. In an important aspect, however, this cooked product is dried and optionally milled and sized. 
     Hydration Step 
     The rice flour or rice flour component blend is mixed with water in a high-speed mixer. The temperature of the hydrating water varies between about 10° C. to about 60° C. The temperature of the hydrating water depends on the time required for full hydration, and also on the size of the particles in the blend. The time for the hydration can vary between 5 minutes and 4 hours. 
     The temperature of the hydrating water varies between about 10° C. and about 60° C., and preferably from about 25° C. to about 60° C. Higher temperatures can be used, but they are not advisable because during the mixing, heating can occur. Any heating which results in substantial gelatinization of the starch in the flour or in any component of the blend should be avoided because such gelatinization will not provide a uniform final product for the cooking step. In this respect, substantial gelatinization means the starch granule structure is not disrupted and there is no loss of bifringency prior to cooking, such as more than about 5 percent weight percent of the starch in the flour or blend is gelatinized. 
     The preferred mixer for the process is a turbulizer as supplied by Hosokawa Bepex, but other high-speed mixers available can be used. Mixing during hydration is important to substantially uniformly distribute water throughout the whole raw mix. Time is not critical as long as the moisture is substantially evenly distributed throughout the rice flour or component blend to a moisture level of at least about 20 weight percent, in an important aspect, in a range of from about 23 to about 34 weight percent, and preferably about 26 to about 30 weight percent, based upon the weight of the hydrated blend. 
     Tempering 
     After hydration, the hydrated rice flour or component blend is kept or tempered for a few minutes to make sure the moisture is equally distributed throughout all of the flour or component particles. This can be done by methods including the use of a standard transport screw or a tempering vessel. It is not essential, but advisable, to maintain a constant temperature during that process. Tempering times can vary between about 30 seconds and about 12 minutes. Long tempering times are not advisable as microbial growth can occur. Long tempering times are not required as the rice flour particles are small enough to make sure all the water is equally distributed throughout the product and a uniform mixture is obtained for the cooking. 
     Cooking 
     The cooker cooks with indirect and direct heat, such as a screw-type cooker and partially gelatinizes the starch in the rice flour or component blend. This cooker, as shown in FIG. 1, is a elongated heating device which has a heat jacket surrounding a channel through which the tempered product is conveyed. The hydrated and tempered product is moved forward down the cooker by means of paddles on a hollow rotor in the device. The rotor is connected to a steam source to transmit steam to the paddles which are hollow and are open to receive steam from the rotor. Steam enters the rotor and is conveyed therethrough into the paddles which have one or more holes from which the steam is injected into the tempered product. The paddles uniformly distribute the steam in the product being cooked. Indirect heat is applied from the jacket of the device. The direct heat brings the tempered product to temperature, partially gelatinizing starch while the indirect heat keeps the cooker and dough at an elevated temperature which is effective for keeping the cooker clean of partially cooked residual dough. Cooking conditions are controlled through selection of a specific length for the device, the number of open steam holes in the paddles, the amount of indirect heat being applied and the rate the tempered product is conveyed through the cooker. 
     Referring to FIG. 1 for more detail, the tempered product is fed into a elongated heating device 4 shown in FIG. 1. The tempered product is fed into the heating device feed aperture 8 into channel 10. The tempered product is conveyed down channel 10 in the y direction. Channel 10 is surrounded by a steam jacket 12 through which steam is circulated. A hollow rod 14 extends longitudinally down the center of the channel. A plurality of paddles 16 are mounted on the rod 14 down its longitudinal length. The rod 14 is rotated and the paddles are angled such that as the rod rotates the paddles, mix the tempered product and push the product down channel 10. The paddles have openings 18 which extend through the paddles to the hollow center of rod 14. These openings are to transmit steam going through the rod and paddles so that the steam may be injected into the particulate food product being transmitted down channel 10. As the rod rotates the paddles push product down the conduit to exit aperture 20 through which the cooked dough flows. The openings in the paddles may be opened or closed to control steam injection into the product being transmitted down the channel. The amount of steam injected is effective for heating and cooking the product such that a product with partially gelatinized starch is obtained. Additional indirect heating of the tempered product and the cooking channel is done by using indirect heat from the jacket of the device. Enough steam is injected to cook the tempered product and gelatinize the starch therein and to provide the cooked product with a temperature of at least about 165° F. A device which can be used to cook the tempered product as described herein is available as a Solidaire Model SJCS 8-4 from the Hosokawa Bepex Corporation, 333 N.E. Taft Street, Minneapolis, Minn. 55413. 
     The direct heat, such as from the injection of steam into the tempered product, cooks the dough in combination with the indirect heat. The indirect heat may be provided by steam or oil. The combination of indirect and direct heat brings the temperature of the tempered product to a temperature of at least about 165° F. as it leaves the cooker. The tempered product is directly exposed to steam for about 1 to about 10 minutes, and preferably from about 1 to about 2 minutes, with the cooking time and temperature also potentially being affected by the temperature in the subsequent drying step. When lower temperatures are used during drying, higher temperatures are used during cooking and vice versa. 
     The cooking temperature as measured by the temperature of the product as it leaves the cooker is a function of the type of the product that is desired and the drying temperatures which are subsequent to the cooking step. When lower drying temperatures are used, such as when the inlet temperature of the drier is 370° F., significant cooking in the dryer does not occur. When lower drying temperatures are used, the temperature of the cooked product as it leaves the cooker is in the higher end of the range of from about 185° F. to about 210° F. When higher temperatures are used, such as about 500° F. for inlet air temperature, and the temperature of the dried product exceeds 85° C., the cooked product leaves the cooker at the lower end of the latter range, about 160° F. to about 200° F. Overcooking will result in a sticky dough when further processing it. In an important aspect, cooked product may be used directly in further processing and cooking, such as in snack foods. In a very important aspect, cooked product is dried to provide a product with partially gelatinized starch. 
     Drying 
     Conventional techniques, such as a flashdryer or belt dryer, can be used for drying the cooked mixture to provide a product with partially gelatinized starch and a product with a moisture level of not more than about 15 weight percent. Alternatively, a Micron dryer, as supplied by Hosokawa Bepex, or a flash dryer may be used. In this system there is also a classifier system which mills the cooked product in such a manner that the right final granulation of the dried flour is obtained for specific applications. For applications where a coarser granulation is required, this air-classification system can be reduced to a minimal level to make sure that still the required coarse particles are present. 
     The temperatures used during the drying depend upon the temperatures and moisture used during cooking stage. If a high temperature is used during the cooking, a lower temperature can be used during the drying process. If lower temperature and lower moisture levels are used during the cooking, higher temperatures are used during the drying stage to make sure that some cooking is obtained during the drying step. However, a fine balance is kept to prevent the product from heat damage during the drying process. Such heat damage will result in a masa which does not form a proper cohesive dough and which is discolored. 
     Sizing of the Dried Product 
     The dried rice product is sifted on a standard sieve to obtain the right granulation. Coarse fractions can be removed and milled to a smaller granulation. Too fine product can be removed if necessary. 
     The follow examples describe and illustrate the process of the invention and the rice flour prepared by the process of the invention. 
     EXAMPLE I 
     Rice flour is hydrated by mixing with water using a turbulizer. 
     The hydrated product then is heated in a Solidaire 6 from Hosokawa Bepex Corporation, paddles open for steam injection. The cooked product then is dried. 
     
         ______________________________________Product Run   1       2       3    4    5    6     7______________________________________Cooker Feed   300     300     300  300  300  300   300Rate lb/hrIndirect        215     215  215  215  215   215Steam Temp° F.Direct          259     259  259  259  259   259Steam Temp° F.Tempering       8 min   8 min                        8 min                             8 min                                  8 min 8 minTimeHydration   26.02% H20% Moisture      30.54        30.24                             29.83aftercookingCooking         207.1   208.5                        208.7                             208.4                                  208.5 208.5Temp ° F.% Finished                   13.9      10.43 10.68ProductMoistureRVA 25% d.s.5 min.                                       91010 min.                                      91012.5 min.                                    901______________________________________ RVA: rapid visco analyzer. Equipment to measure the viscosity. We make a solution of varying % of dry solids solutions and measure over a period o 12.5 minutes the viscosity. Viscosity is expressed in cPoise. 
    
     EXAMPLE II 
     
         ______________________________________Product Run   1       2       3    4    5    6     7______________________________________Cooker Feed   300     300     300  300  300  300   300Rate lb/hrIndirect   215     215     215  215  215  215   215Steam Temp° F.Direct  259     259     259  259  259  259   259Steam Temp° F.Tempering   8 min   8 min   8 min                        8 min                             8 min                                  8 min 8 minTimeHydration       26.72% H20% Moisture   29.56                28.51     28.56aftercookingCooking 208.1   208.3   208.5     209.1                                  209.3 209.5Temp ° F.% Finished   10.68                11.53                             10.65                                  9      9.8ProductMoistureRVA (d.s.)      30%     30%       25%  30%   30%5 min           3042    1080      1081 1916  163610 min          4023    1307      1273 2483  205612.5 min        4278    1371      1364 2694  2211______________________________________ 
    
     EXAMPLE III 
     
         ______________________________________Product Run   1       2       3    4    5    6     7______________________________________Cooked Feed   300     300     300  300  300  300   300Rate lb/hrIndirect   215     234     234  285  285  285   260Steam Temp° F.Direct  259     256     256  259  259  259   259Steam Temp° F.Tempering   8 min   8 min   8 min                        8 min                             8 min                                  8 min 8 minTimeHydration                              28.91% H20% Moisture      27.75   27.78                        211.1                             211.4                                  212.1 210.1aftercookingCooking         210.9   212Temp% Finished   9.85    8.89ProductMoistureRVA (d.s.)   30%     25%     30%  25%  25%  25%5 min   2035    &lt;100    1376 149  761  117210 min  2696    &lt;100    1265  56  898  141412.5 min   2976    &lt;100    1138 165  931  1563______________________________________ 
    
     EXAMPLE IV 
     
         ______________________________________Product Run   1       2       3    4    5    6     7______________________________________Cooked Feed   300     300     300  300  300Rate lb/hrIndirect   260     260     260  260  260Steam Temp° F.Direct Steam   259     259     259  259  259Temp ° F.Tempering   8 min   8 min   8 min                        8 min                             8 minTimeHydration   29.01% H20% Moisture      30.05             30after cookingCooking 210.5   210.2   210.2                        210.7                             210.7Temp.% Finished      6.71ProductMoistureRVA (d.s.)   25%     25%5 min   7055    627110 min  8259    717712.5 min   8555    7434______________________________________ 
    
     EXAMPLE V 
     
         ______________________________________    Free                     StarchAsh      Fat     Protein   Starch Damage H20______________________________________S1   0.44    0.62    8.21    78     4.5    11.94S2   0.46    0.23    8.33    79.5   13.4   10.78S3   0.46    0.28    8.32    79.16  15.7   10.95S5   0.4     0.37    8.18    78.1   2.5    12.89S6   0.4     0.47    8.13    80     10.9   11.94S7   0.4     0.23    8.27    79.26  15.7   11.77______________________________________ S1 and S5 are plain flour, not treated according to the invention. S2, S3 S6, and S7 are partially cooked rice flour processed in accordance with the invention. 
    
     EXAMPLE VI 
     
         ______________________________________RVA Viscosity 50° C. Profile, 35% d.s.5 min.            12.5 min.                      Differ.______________________________________S1      233            245      239S2      7639           9312     9870S3     12295          13502    13845S5      118            105      112S6     24650          26204    26185S7     n.a.           n.a.     n.a.______________________________________ 
    
     EXAMPLE VII 
     
         ______________________________________5 min.            10 min. 12.5 min.______________________________________RVA Viscosity 50° C. Profile, 25% d.s.S5     &lt;100           &lt;100    &lt;100S6      287            276     265S7      460            467     506RVA Viscosity 50° C. Profile, 30% d.s.S1     &lt;100           &lt;100    &lt;100S2     1082           1164    1191S3     3256           4130    4480______________________________________ 
    
     EXAMPLE VIII 
     
         ______________________________________Granulation (%)Mesh Size    S1      S2      S3    S5    S6    S7______________________________________&gt;325     13.2    2.3200      10.6    3.2     4.3100      43.6    8.6     23.2  25.5  11.6  7.880       17      43.6    17.9  7.7   6.7   560       14.3    31      34.6  3.2   10    9.840       1.3     11.3    17.5  28.2  28.5  28.620       0       0       0     35.4  43.2  46.316       0       0       0     0     0     0    100     100     100   100   100   100______________________________________ 
    
     EXAMPLE IX 
     
         ______________________________________Partially cooked coarse Rice FlourRVA: 20% d.s.RVA Viscosity      Coarse        Flour   50 Deg.______________________________________20% d.s.    5            12.5    12.5-5S8         411           390      -21S9          74            66      -8 S10        52            59       7RVA Viscosity, 25% d.s.S8         10808         14792   3984S9         313           318       5 S10       214           219       5RVA Viscosity, 30% d.s.S8         &gt;16,000       n.a.    n.a.S9         4739          5939    1200 S10       3113          4266    1153______________________________________